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Chromatophores of the Human Eye*
JOHN CHENAULT LONG
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enough to preserve detail. Fortunately, it is! usually possible to place the illuminating; beam in the pupillary area so that points of':' interest are avoided. The photographs' shown in Figures 4 through 12 are illustra-
tive of the type of records obtainable by this method. 227 16th Street (2). ACKNOWLEDGMENT
The engineering assistance of Mr. Richard Raper is gratefully acknowledged.
REFERENCES
1. Douvas, N., and Allen, L.: Anterior segment photography. Am. J. Ophth., 33:291, 19S0. 2. Lubkin, V.: Photography of the red reflex. Arch. Ophth., 43:718, 1950. 3. Fincham, E. F.: Photographic recording of opacities of the ocular media. Brit. J. Ophth., 39:85,1955. 4. Ogg, A. J.: Photography of lens opacities by trans-scleral illumination. Brit. J. Ophth., 44:374, 1960.
CHROMATOPHORES O F T H E HUMAN EYE* M.
I. KACZUROWSKI,
M.D.
Philadelphia, Pennsylvania INTRODUCTION
Although the results of many investi gators have been published on the choroid of the eye 1-6 ' 11 very little data are available concerning its pigment elements, particu larly the chromatophores.î Our knowledge of the melanoblasts in general is sufficiently extensive7-10·12 but no one has paid any at tention to a systematic study of the mor phology of the pigment cells of the eye, probably because this requires a special technique of investigation, and suitable ma terial which had been difficult to obtain in thejpast. Previous investigations on this subject were generally performed using low magnifica tion2 and were related to histologie (mi crotomy and staining) techniques. Recent work has been based on electron micros copy.^'5·11 In·the first case (low magnifica tion) it was impossible to obtain any mor^ * From the Wills Eye Hospital. This study was supported hy grant No. 2B-S076 from the National Institute of Neurological Diseases and Blindness, National Institutes of Health, United States Public Health Service. t Chromatophores: "Melanoblasts," "pigment cells," "melanocells" will be used as synonyms.
phologic details of the structure of pig ment elements which densely populated the choroidal spaces. The illegible picture of the choroid's content was complicated by struc tures not related to the pigment, which were manifested by staining. The technique of electron magnification does not deal with the outward appearances of the chromatophores. With electron microscopy the shape of the cells and outstanding parts generally disap pear from the field of view and only the inner structures are shown. Therefore, one can ,say that little has been added to ex ternal morphology of the pigment elements of the human choroid, in recent times. Wolter 2 indicates that these cells have at tracted little attention from physiologic, as well as the morphologic, consideration. From the viewpoint that form determines function and; on the other hand, that func tion explains form, it is obviously useful to have more detailed knowledge about the morphology of the chromatophores of the human choroid. It is no longer possible to hold the opinion that chromatophores are just cellular structures filling out the cho roidal space among the vessels and nerves.
CHROMATOPHORES OF THE HUMAN EYE
This study was designed to describe the microanatomic shape of melanocells and to determine the possible role of the chromatophores and their pigment granules. Existing histologie data on these cells include a few morphologic types 1 and an intricate relation ship between melanoblasts and other struc tures of the choroid.2 The latter observa tion has led Wolter to postulate that a spe cial relationship exists between chromatophores and blood vessels and nerves of the choroid. However, the physiologic role of these elements has never been interpreted. This situation probably existed because in vestigators for a long time disregarded the method of flat preparation. The flat prepara tion method is primarily effective for study ing such tissues as pigment epithelium, cho roid, iris and so forth. The technique of flat preparations together with recently per fected techniques of light microscopy can yield information not obtainable by other histologie procedures. MATERIAL
This work is based on a relatively large amount of material, 119 human eyes being used. All eyes were obtained from the EyeBank of the Wills Eye Hospital and no eye had any signs of abnormality. The age dis tribution of eyes is as follows : AGE GROUPS
N U M B E R OF CASES
Year 1-10 10-20 20-30 30-40 40-50 S0-60 60-70 70-80 80-90 90-100
4 4 7 10 12 26 20 25 10 1 METHODS
PREPARATION OF T H E EYE
All eyes received from the Eye-Bank were injected with four-percent formalin through the optic nerve and then immersed
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Fig. 1 (Kaczurowski). (1) Applicator; (2) soli tary granules remaining after removal of pigment epithelium; (3) pigment epithelium (P. E.) ; (4) Bruch's membrane (lamina vitrea) ; (5) vitreous part of choroid; (6) chromatophores; (7) line of cleavage of the choroid; (8) scierai part of the choroid; (9) thin remnants of sciera after cutting most of it away; (10) removed part of sciera.
in the same solution. After a few days, when the distended eyeball hardened, the sciera was removed with a razor blade. The eyes were then cut frontally at the level of the ora serrata. The open eyeballs (poste rior portion) were dissected meridionally through the optic nerve into eight separate identical parts. Following removal of the vitreous body and the retina, the pigment epithelium was brushed off by a cotton ap plicator and rinsed briefly in distilled water. No microtomy or staining was used. Sub sequently when the choroid was gently stripped from the sciera, two separate fine sheets of it were obtained: one connected with Bruch's membrane (vitreous part) and the second, somewhat thinner sheet, attached to remnants of the sciera (scierai part) (fig. 1). The prepared specimens were dehydrated with alcohol (70 to 95 percent), cleared in carbo-xylene, then xylene and were finally mounted with harleco synthetic resin. After clearing the preparation of remnants of scierai tissue, there was no obstacle to mi-
M. I. KACZUROWSKI
768
croscopic observation. Therefore, the two flat sheets of the choroid were observed from: (a) Bruch's membrane, (b) the sur face of cleavage, (c) the sciera (fig. 2). To avoid the complication of the very confusing picture of densely distributed melanoblasts, no stain was used and the natural color of melanin was observed. OBSERVATION
The areas of observation and method of measurements have been described else where.13 It will be useful here to communi cate some details about the microscopic tech nique working with the flat prepared speci mens. Since flat preparations have consider able thickness, deep vertical focusing is nec essary. To avoid erroneous conclusions in appraising microscopic objects, one must be certain that the body, the processes or other structures of the observed chromatophores are not damaged or changed during the elaboration of the tissue. Usually a division occurs in the blood vessel layer in the process of separating the choroid from the sciera. Some chromato phores may tear into two portions with re
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sulting loss of the processes and intensity of pigmentation. For observation, only un damaged cells and structures were used. An important criterion for determining the in tact state of the cells or other structures being examined, is to note the state of struc tures in the planes of the tissue above and below it. If these were intact, the cells in question were considered to be well pre served between these two planes. If, on the other hand, the structures above or below could not be well defined, this object was re jected for study. Thus, measurement and defi nition of intensity of pigmentation of chro matophores and their shape were determined only on "untouched cells." Figure 2 presents a clearer understanding of these points. RESULTS A. GENERAL DESCRIPTION OF A CHROMATO. PHORE
The general morphologic characteristic of the chromatophore may be determined within the limits of light microscopy as follows: Body. The bodies of the cells vary greatly in size and shape. Variability of the chro matophores evidently depends on their loca-
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Fig. 2 (Kaczurowski). (I) Vit reous part of the choroid observed from Bruch's membrane; (II) vit reous part of the choroid observed from surface of cleavage; (III) scierai part of the choroid observed from sciera; (IV) scierai part of the choroid observed from surface of cleavage. (1) Bruch's mem brane; (2) pigment epithelium; (3) surface of cleavage of the cho roid; (4) remnant of the sciera.
CHROMATOPHORES OF THE HUMAN EYE
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tion in the choroid and also on such struc tures as vessels and nerves surrounding it. The shapes of the cells change from round and elongated, to star-shaped and vermi form. The body of the chromatophore is usually flat, although many cells are bulky. The relation of the length to the thickness is defined by the ratios 2:1, 5:1, 10:1. Cells with a ratio 5:1 or 10:1, are usually ob served. Within the chromatophore (often not in the center) a large elongated nucleus is located, ordinarily covered from the pe riphery with either two, three or many layers of melanogranules. The unstained nucleus seems structureless and transparent, being similar to cytoplasm which evidently does not contain many melanogranules in the middle of cells. In some preparations, using high magnifications, it is possible to see highly refractive "fibers" located above or below the nucleus (fig. 33). Processes. The body of the chromato phores has from two to six processes which exist in three forms: (a) plasmatic, rela tively thick and medium length, covered
with innumerable tiny granules (fig. 30), (b) long consisting of one row of granules (punctiforme processes) (fig. 20) and (c) short and coarse processes (fig. 26). The relation between the length of the processes and their diameter varied from 5:1 to 25:1 and more. The ratio of the length of the processes to the diameter of the chromato phore body varied from 1:1 to 1:30. Channels. It was possible to mark inside of some processes refractive spaces directed within the length. At times these spaces begin outside of the processes in close prox imity to the cell body. At other times chan nel-like formations originate in the middle of the processes. Often the "space" begins imperceptibly from the body of the chroma tophore. These structures could be inter preted as "channels" among the granules containing a cytoplasm or fibrillar structures (fig. 6 ) . Protrusions. On the periphery of the chromatophores, an immense number of very thin melanogranules, sized from 0.2 μ to 0.6 μ, are dispersed. Some chromatophores
M. I. KACZUROWSKI
770
have spherical shaped accumulations ("pro trusions") of the melanogranules on the surface (figs. 3 and 23). The outer shape of the granules is nearly oval, but a more detailed determination of external granular shape is impossible even with high magnifi cation ( X 2,000). At times, the granules may form spherical protrusions on the body and on the process (fig. 5). Globes. The distal ends of the processes are rarely sharp-pointed. Frequently, the ends have knotlike thickenings or spherical globes (figs. 3, 7, 8, 21 and 22). The proc esses enter into the lower pole of the globe. On the opposite pole, mostly one, rarely two and very seldom three apertures can be ob served as very refractive spots. The size of the globes is measured from 2.0 μ to 12 μ in
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diameter. Sometimes, under the influence of unknown causes, the globes indicate frag mentations of many particles or separated granules (figs. 3 and 12). As a rule, the globes are more intensely pigmented than the supporting processes. B.
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The chromatophores are scattered throughout the choroid in a definite order and form nine to 12 horizontal layers. Close to the vessels some pigment cells are elon gated and arranged lengthwise and crossways. Close to the sciera the chromatophores are branching and star-shaped but near the lamina vitrea they are clusterlike with a multitude of processes and globes (figs. 22
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Fig. 4 (Kaczurowski). The names "vitreocapillary" and "sclerochoroid" layers will be used in this scheme to distinguish the area and location of some typical melanocells more definitely. 1. Subtle type—forms I, II, III 6. Irregular type 2. Flowered type—forms I, II 7. Paving-stone type 3. Round type 8. Impressed type 4. Elongated type 9. Lacunated type—forms I, II 5. Star-shaped type—forms I, II, III 10. Vermiform type
CHROMATOPHORES OF THE HUMAN EYE
771
and 28). In the blood vessel layer, the chromatophores are more voluminous compared with those in the scierai and Bruch's mem brane areas. Usually two or three layers of chromatophores accompany the vessels and nerves, by passing through the sciera. C. ADDITIONAL MELANOSTRUCTURES OF THE CHOROID
"Dust" or powdery granules. In the study of flat preparations of choroidal specimens, a significant number of solitary randomly scattered granules or accumulations of them are seen. In many cases of observation above and below (between two "untouched layers" of chromatophores), "dust" (ac cumulations of the granules) was observed,
Fig. 6 (Kaczurowski). Flat preparation of the human choroid of a 55-year-old man. Two processes connected by a fiber. Note easily visible channels in side the processes (arrows) occupied by connecting fiber. Location: equator, suprachoroid. (XlOOO.)
Fig. 5 (Kaczurowski). Flat preparation of the human choroid of a 57-year-old man. Note the pro trusions on the process (arrows). Location: between the equator and ora serrata, supracapillary layer. (X900.) M// r
Fig. 7 (Kaczurowski). Flat preparation of the human choroid of an 11-year-old child. Three globes are located on the end of a process. Location: equator, supracapillary layer. (X900.)
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M. I. KACZUROWSKI Fig. 8 (Kaczurowski). Flat preparation of the human choroid of a 54-year-old man. A globe with aperture is seen (arrow). Location: optic nerve area, supracapillary layer. (χ900.)
indicating that the extracellular accumula tions of the granules were not the result of artefact, but rather a phenomenon of physio logic function of melanoblasts of the choroid. That is to say the melanogranules are a product of "secretion" of the chromatophores, which could be interpreted as sui generis microglands (figs. 2, 3, 9, 10 and 36). The accumulation of granules in the inter cellular media. Occasionally, large particles of melanin were observed. The conglomer ates resembled coalesced granules of multishaped particles, at times completely round and measuring from 1.0 μ to 6.0 μ in di ameter. Both structures were found on all
Fig. 9 (Kaczurowski). Flat preparation of the human choroid of a 40-year-old man. Arrow 1 indi cates "dust" or the extracellular accumulation of the pigment granules extruded from the lacunated chro ma tophore (indicated by arrows 2). Location: equator, blood vessel layer. (χ900.)
Fig. 10 (Kaczurowski). Flat preparation of the human choroid of a 10-year-old child. Note the ex tracellular accumulation of melanogranules (ar rows). Location: between equator and optic nerve areas, blood vessel layer. (χ900.)
CHROMATOPHORES OF THE HUMAN EYE
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Fig. 12 (Kaczurowski). Flat preparation of human choroid of an 11-year-old child. A globe in fragmen tation phase. Optic nerve area, supracapillary layer. (X900.)
extensions of the choroid (figs. 9, 10, 12 and 13). A correlation with the topographi cal location of the choroid was not estab lished. Filaments. The most interesting of struc tures occurring in the choroid are thread like refractive formations covered with pig ment granules. "Filament" structures can be seen in parts of the choroid adjacent to the sciera, primarily in the area of the ora serrata, equator and occasionally in the optic nerve area (figs. 3, 14, 15, 16 and 17). D. TYPES OF CHROMATOPHORES
The chromatophores are distributed in rows of from nine to 12, parallel to the
Fig. 11 (Kaczurowski). A flat preparation of the human choroid of a four-year-old child. The picture shows two processes with channels. Location: equator, choriocapillary layer. (X2000.)
Fig. 13 (Kaczurowski). Flat preparation of the human choroid of a 78-year-old man. Fragmentation of a chromatophore. Location: equator, blood vessel layer. (X2000.)
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M. I. KACZUROWSKI
Fig. 14 (Kaczurowski). Flat preparation of the human choroid of a 54-year-old man. In the center of the field are seen in straight-line arrangement many melanogranules forming "filaments" (arrows). Location: equator, suprachoroid layer. (X2000.)
sciera. The distance between the layers is on the average 3.0 μ to 5.0 μ. Ten types of chromatophores were established, showing a gradual variation from one to another (fig. 4). 1. Subtle type, form I. Two or four μ below Bruch's membrane, in the vitreocapillary layer, the "subtle type" of the chromatophore was typically found. These cells have a semitransparent body with an insignificant quantity of melanin. The gran ules, as a rule, are seen on the outside edge of the body. Some granules are very dark and comparatively enlarged. The "subtle" chromatophore has two or three short proc esses, usually without the legible formed globes (fig. 18). Such types of chromato phores have been found every place in the choroid, frequently in the optic nerve area 2.0 μ to 4.0 μ below Bruch's membrane. They are seen in each third or fourth mi croscopic field at 900 magnification. The
body and processes are located mostly in one flat plane. The dimensions of cells is 10 μ to 20 μ in diameter. Deeper, from Bruch's membrane (5.0 μ to 6.0 μ), the subtle type form II of chro matophore continues to exist with a modifi cation: the cells look more pigmented, the processes are thicker and one can often see the small globes on top (fig. 19). In the sclerochoroid layer the third, form III of subtle type is found. The typical outline of these cells, trigonal-shaped body, very thin processes (sometimes punctiform) and low pigmentation, occurs mostly in the sclerocho roid of the ora serrata and equator areas (fig. 20). 2. The "flowered" type. The "flowered" types of chromatophores are typical of the capillary and supracapillary layers of the choroid (figs. 21, 22 and 23). There are two forms: The first form has short processes oc casionally bearing globes (fig. 21).
Fig. 15 (Kaczurowski). Flat preparation of the human choroid of a four-year-old child. The "fila ment" is located vertically in the middle of the pic ture. Location: optic nerve area, sclerochoroid layer. (X1000.)
CHROMATOPHORES OF THE HUMAN EYE The second form possesses long processes crowned with many globes. Both forms also have protrusions on the body (fig. 22). The "flowered" type of melanoblasts is dis tributed everywhere in the choroid, 7.0 μ to 10 μ below the Bruch's membrane (capil lary and supracapillary layer). This type of chromatophore is relatively small and inten sively pigmented. The body of these cells is 10 μ to 20 μ in diameter. 3. The round type. The round type of chromatophores can be observed in the blood vessel layer and only occasionally in the supracapillary or suprachoroidal layer. The basic pattern of this chromatophore is spher ical or approximately so. Occasionally, small processes or traces of them can be observed. They range in size from 8.0 μ to 40 μ in diameter (fig. 24). At times, in the round type of cell, the nucleus is not clearly visible.
Fig. 16 (Kaczurowski). Flat preparation of the human choroid of a 55-year-old man. The picture shows two vertically located "filaments." Location: ora, capillary layer. (X900.)
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Fig. 17 (Kaczurowski). Flat preparation of the human choroid of a 35-year-old man. "Filaments" are seen (arrows). Location: ora serra ta, suprachoroid layer. (X°00.)
4. The "elongated" type. The elongated type of chromatophores belongs mostly to the blood vessel layer. These cells are observed in the neighborhood of medium and large sized vessels. The ratio of the major to minor axis is approximately 12:1. The major axis is oriented parallel to the vessels and nerves and sometimes to the choroidal folds, or fol low the fibers. Under low magnification this kind of cell often forms a criss-crossing net. These chromatophores have a good visible bulk, are intensely pigmented, do not have processes and possess an oval nucleus (fig. 25). 5. The star-shaped chromatophores. The star-shaped chromatophores have been ob served in the blood-vessel layer, suprachoroid and supracapillary layers. Three forms of star-shaped chromatophores occur: Form I has short (3.0 to 5.0 μ) pyram idal processes, with irregular edges and without globes. The cells are very flat and large (measuring 20 to 60 μ in diameter) with an oval nucleus (from 5.0 to 8.0 μ ) .
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M. I. KACZUROWSKI
Fig. 18 (Kaczurowski). Flat preparation of the human choroid of a 50-year-old man. This picture represents a subtle type (form I) of chromatophore. Note the semitransparent body and short, relatively thin processes. Location: optic nerve area, vitreocapillary layer (3.0 μ below the Bruch's membrane). (X900.)
Fig. 19 (Kaczurowski). Flat preparation of the human choroid of a 50-year-old man. A subtle type (form II) is located in the capillary layer, 6.0 μ be low the Bruch's membrane. This deeply situated modification of a subtle cell is intensely pigmented and the processes are thick with one or two globes on the end. This cell was observed between the equator and optic nerve area as shown in this photo graph. (X900.)
The first form is usually located in the blood vessel and suprachoroid layers extending from the optic nerve area to the ora serrata (fig. 26). Form II has a relatively large body (20 to 30 μ) and processes of medium length (fig. 27). The processes may or may not have globes. The second form is scattered from the optic nerve area to the ora serrata in the supracapillary and suprachoroid layer. Form III of the star-shaped chromato phore possesses a polygonal body and very long processes, often with globes. This form is also typical for suprachoroid, supracapil lary layers and the adjacent area of blood vessel layers. They are scattered in great numbers from the optic nerve area to the ora serrata. The size of the body ranges from 10 to 20 μ, the processes from 20 μ ίο40μ (figs. 28, 29 and 30). 6. The irregular type. Resembling clumps,
Fig. 20 (Kaczurowski). Flat preparation of the human choroid of a 55-year-old man. Subtle type, form III, is scattered in sclerochoroid from ora ser rata to optic nerve area. Note trigonal transparent body and filamentlike processes. (X900.)
CHROMATOPHORES OF T H E HUMAN EYE
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Fig. 22 (Kaczurowski). Flat preparation of the human choroid of a 55-year-old man. A flowered type (form II) of chromatophore. Location: equa tor, supracapillary layer 7.0 μ below Bruch's mem brane. The long processes with many globes are typical. Many additional protrusions are seen on the processes.
this type occupies the medium part of the blood vessel layer, especially in the optic nerve and equator areas. The body of these chromatophores is relatively large, being from 25 to 50 μ. These cells have an intense brown color and occasional chromatophores of this type have short, coarse processes (fig. 31). 7. The paving-stone type. This type of chromatophore is very flat and never has processes or globes. The intensity of pig mentation is variable. These large sized cells, measuring from 30 to 50 μ, are scattered from the optic nerve to the ora serrata in
Fig. 21 (Kaczurowski). Flat preparation of the human choroid of a 57-year-old man. A flowered type (form I) of chromatophore possessing short processes with two, three or four globes. Location: ora serrata area, supracapillary layer, 8.0 μ-9.0 μ be low the Bruch's membrane. ( X900.)
Fig. 23 (Kaczurowski). A flat preparation of the human eye of a five-year-old child. This flowered type form I was found between the ora serrata and equator 5.0 or 6.0 μ below Bruch's membrane in the capillary layer. (XlOOO.) Note many protrusions (arrows).
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M. I. KACZUROWSKI
Fig. 24 (Kaczurowski). Flat preparation of the human choroid of a 57-year-old man. This is a round type of chromatophore. Note absence of proc esses, pigmentation is intensive. Location : blood ves sel layer close to the suprachoroid, equator area. (X2000.)
the blood vessel and suprachoroid layers (fig. 32). 8. Impressed type. Cells, aggregated in large groups, usually have been found at the equator, in the optic nerve area deep in the blood vessel, and in the suprachoroid layers. "Impressed" cells seem to possess very legi ble impressions on the bodies and the proc esses, hence the name. The size of these cells is 25 to 50 μ in diameter. They are not greatly pigmented and no globes are seen (figs. 33 and 34). 9. The lacunated type. Two forms of this type occur. The first or macrolacunated forms are not numerous, but they are a very interesting kind of melanocell (figs. 35, 36 and 37). They are from 30 to 50 μ in size and, for the most part, are without proc esses. Macrolacunated chromatophores are elongated or irregular shaped with round lacunae in the bodies and at times in the processes. The lacunae are from 2.0 to 8.0 μ
in diameter. These chromatophores are scat tered throughout all areas of the choroid, but mostly in the blood vessel layer near to the suprachoroid. The number of lacunae varies considerably from a few to 50. Using high magnification, it is clearly evident that the lacunae are not as smooth as they appear in low-power observations. The lacunae probably are the results of fragmentation of the protrusions. The edges of the lacunae are framed with melanogranules of differ ent size and intensity of pigmentation. At the depth of lacunae, the transparent cyto plasm is usually seen. The second or microlacunated form of the chromatophores is very numerous and polymorphic (fig. 37). Practically all types of chromatophores, particularly the flat type (paving stone, starshaped, impressed types) often possess very fine lacunae on the body or processes. The diameter of the small lacunae is usually identical to the size of the granules. The average number of these lacunae varies from
Fig. 25 (Kaczurowski). Flat preparation of the human choroid of a 27-year-old man. This is an elongated type of chromatophore. Note absence of the processes. The pigmentation is intensive. Loca tion: equator area. (χΙΟΟΟ.)
CHROMATOPHORES OF THE HUMAN EYE
779
10 to 100, measuring from 0.1 to 0.6 μ in diameter. 10. Vermiform type. Finally, one must note a very remarkable type of chromatophore, termed vermiform. This type has a small elongated body from 5.0 to 10 μ in length and usually two very long processes. The relation between the size of the body and the length of the processes can be char acterized by the ratio 1 : 30. The vermiform type of chromatophores is scattered in the sclerochoroid and capillary layer from the optic nerve area to the ora serrata. The average quantity of cells is negligible (fig. 38). DISCUSSION
In the present investigation such peculi arities of choroidal tissue as thinness, ease of separation of the choroid from the retina and sciera and transparency of the cho roidal stroma were utilized. For better obFig. 27 (Kaczurowski). Flat preparation of the human choroid of a 40-year-old woman. The picture represents a star-shaped type of the chromatophore form II—star-shaped body and medium sized proc esses. Location: ora serrata, suprachoroid. (XlOOO.) serration of the chromatophores, a method for extension of the choroid was used by injecting formalin into the eyeball. By this manipulation the thickness of the choroid was reduced by approximately one-tenth, but the multilayered arrangement of the chromatophores was not affected. Besides the stretched chromatophores and reduction of the thickness of the choroid, some changes in the measurements of different objects of lesser importance were made. It is quite possible that some chromatophores were en larged and the distance between them made a little greater. These changes can be ig nored, however, because they occur within the limits of normal variation. Fig. 26 (Kaczurowski). Flat preparation of the human choroid of an 11-year-old boy. Star-shaped type of chromatophores (form I). Note the short pitted processes without globes. The processes are connected with fibers (arrow). Location: equator, blood vessel layer near the suprachoroid. (X900.)
In addition to a complete description of the melano-elements of the choroid, an at tempt was also made to estimate the pos sible function and role of the melano-ele ments. We were keenly aware of the possi-
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M. I. KACZUROWSKI Fig. 28 (Kaczurowski). Flat preparation of the human choroid of a 37-year-old man. A star-shaped type of chromatophore (form III). This kind of cell possesses the long processes with globes. Location: ora serrata between sclerochoroid and suprachoroid layers. (X900.)
bility of artefacts being present. Therefore, during the work, a special method of micro scopic selection of the objects was elaborated (see Methods). Although chromatophores are extremely polymorphous, it was possible to allot the cells to definite locations and constant shapes. Ten basic types with typi cal outlines and some variations of chroma tophores were established (fig. 4 ) . Besides the types of melanoblasts, a series of adnexal melanin-formations and organella such as "channels," "globes," "filaments" and so forth were noted. The formation of the basic mass of visi ble melanin in the choroid occurs after birth. The fetal and newborn eyes are poorly pro vided with melanogranules in the choroid.3 The formation of melanin from its pre-
Fig. 29 (Kaczurowski). Flat preparation of the human choroid of a 95-year-old man. A star-shaped type of chromatophore (form III) with extremely long processes. Location: ora serrata between cap illary and supracapillary layers. (χ900.)
Fig. 30 (Kaczurowski). Flat preparation of the human choroid of the five-year-old child. A starshaped chromatophore (form I I I ) . Equator, supra choroid layer. (X900.)
CHROMATOPHORES OF THE HUMAN EYE
cursors (dihydroxyphenylalanine [Dopa] or tyrosine) by the action of dopa-oxidase or tyrosinase, is a complex process and de pends on many surrounding chemical and physical factors, particularly ultraviolet rays. Melanin synthesis evidently occurs in cyto plasm of the melanoblast and its processes and also on the ends of these processes. The appearance of a new mass of melanin and the increase in the number of granules lead to development of so-called "protru sions." They are located on the surface of the cell and its processes. On the endings of the processes protrusions appear as globes. No structural difference between globes and protrusions exists because both are spherical melano-structures. In the case of advanced production of melanin, it is possible to observe secondary protrusions on the globes and on the protrusions them selves. With increasing age the average quantity of melanogranules in the choroid increases, but is gradually reduced in aged persons. Under the influence of light and other unknown causes melanogranules are able to migrate from the cells into the intercellular
Fig. 31 (Kaczurowski). Flat preparation of the human choroid of a 45-year-old woman. An irregular type of the chromatophore. Equator, blood vessel layer. (χ900.)
781
Fig. 32 (Kaczurowski). Flat preparation of the human choroid of an 11-year-old boy. A pavingstone type of chromatophore. Note absence of the processes and flat compressed-like bodies. Equator, bloodvessel layer. (χ900.)
Fig. 33 (Kaczurowski). Flat preparation of the human choroid of a 27-year-old man. An impressed type of chromatophore. Note a fiber crossing nu cleus (arrow). Location: between equator and optic nerve area, suprachoroid layer. (X900.)
782
M. I. KACZUROWSKI
Fig. 34 (Kaczurowski). Flat preparation of the human choroid of a 27-year-old man. An impressed type of chromatophore. Location: between equator and ora serrata, blood vessel layer. (χ900.)
Fig. 35 (Kaczurowski). Flat preparation of the human choroid of a 10-year-old child. A macrolacunated type of chromatophore (form I ) . Location: equator, blood vessel layer. (X2000.)
space forming "dust" visible everywhere in the choroid. The migration occurs by differ ent ways: (1) via fragmentation of the globes (fig. 12) ; (2) in some cases by frag mentation of melanocells (fig. 13); (3) oc casionally protrusions separate from cells and thereupon disperse into solitary gran ules (figs. 9 and 10). The so-called "macrolacunated chromatophores" could very well be the result of the latter type of "secre tion." However, the most important and constant form of "secretion" of melanogranules is the excretion of many solitary granules from the body and processes of chromatophores (fig. 37), resulting in the presence of "microlacunated chromato phores" in the choroid. The shape of the chromatophores in the choroid depends also upon phototropic prop erties of melanin and upon the quantity and location of nerve fibers, passing in proximity
Fig. 36 (Kaczurowski). Flat preparation of the human choroid of a 28-year-old woman. A macrolacunated type of chromatophore (form I ) . Optic nerve area, blood vessel layer. Note extracellular "dust" (arrows). (X900.)
CHROMATOPHORES OF THE HUMAN EYE to the given chromatophore. In the areas of choroid, where the chromatophores are rela tively seldom distributed but are located close to the nerve fibers (capillary, supracapillary layers), the pigment cells have a branching appearance. Formation of the processes occurs via ad sorption of melanogranules by nerve fibers, from the nearest pigment cell. Depending on the number of nerve fibers in contact with the chromatophore, a similar number of processes appears. When the chromato phores are located in a relatively thick stratum (suprachoroid layer), the nerves and elastic fibers, compressed between melanocells formed on the bodies of chromato phores, are well-observed impressions (im pressed type of chromatophores). In such conditions nerve fibers appear fully insulated by flat bodies of melanocells. The forma tion of the processes in this case does not
Fig. 37 (Kaczurowski). Flat preparation of the human choroid of a 27-year-old man. A microlacunated type of chromatophore (form I I ) . Many mi nute lacunae are seen among the granules (arrow 1 ). "Dust" (extruded solitary granules outside of the cells) is indicated by arrow 2.
783
Fig. 38 (Kaczurowski). Flat preparation of the human choroid of a 55-year-old man. A vermiforme type of chromatophore (arrow). Note extremely small body and two long processes. Location: ora serrata between the sclerochoroid and suprachoroid layers. (χ900.)
take place. Also, if a distance between nerve fibers and melanocells is relatively large, no formation of the processes occurs and "fila ments" appear. The phototropic ability of melanogran ules probably is not limited only to reaction to light but could be classified as "tropism" to any kind of radiant energy, for example, to bio-electrical impulses conducted through the nerves and their fibers. If the nervous excitations are transmitted through nonmedullated fibers they can adsorb melano granules from the intercellular spaces. The adsorbed melanogranules probably create an isolating sheet which has a dual purpose: to prevent the current impulses from diffuse losses into the surrounding tissues and to pre vent centripetal or centrifugal excitation from outside light influences. The mechanism of the insulating func tion of melanin in the uveal tract may be outlined as follows: melanogranules located on the periphery of the nerve fiber absorb
784
M. I. KACZUROWSKI
and hold superfluous impulses in the eye, independent of their point of origin. There fore, the direct rays of the light penetrating through the optic system into the eye may be absorbed by melanogranules, thus exces sive light irritation is limited in this way. With this, the reaction of the uveal tract is automatically regulated and kept on a phys iologically "normal" level. On the other hand, if centripetal or centrifugal excitation passes in some nerve to any area of the uvea, the attached granules form protection from loss of these given impulses or from contamination from outside light. On the basis of the results obtained by us and from data of other authors con cerning the choroid of the eye, its struc ture,1"6 the nature of the melanin 9 · 12 ' 15-17 and finally our knowledge about the role of myelin23·24 in the nerve system, the fol lowing hypothesis would appear to have a plausible foundation: 1. Subtle type I chromatophores may pos sibly be interpreted as being sympathetic gan glion cells with adsorbed superficial melano granules (fig. 18). 2. The chromatophores of the choroid play the role of sui generis microglands, producing a specific "secretion" as melano
granules, which are extruded into the inter cellular space of the choroid. 3. The melanogranules in the choroid play the role of an isolation material for nerve fibers, on which the myelin sheets are ab sent. 4. The insulating ability of the melanin finally aids in the achievement of accurate and sharp vision because it protects im pulses from diffuse dispersion in surround ing tissues. SUMMARY
1. A method of flat preparation and ob servation of the human choroid have been described. 2. Ten types of chromatophores have been found in the human choroid. 3. It is suggested that melanin serves as an insulator for radiant energy impulses. 4. The role of chromatophores as regulat ors of uveal function in the human eye is pos tulated. 1601 Spring Garden Street (30). ACKNOWLEDGMENT
I wish to acknowledge gratefully the assistance of Theodore W. Sery, Ph.D. I am also indebted to Miss Ada Padgett for her co-operation in obtaining the material.
REFERENCES
1. Arey, L. B.: Retina, choroid and sciera. Cowdry Spec. Cytology V, III, New York, Hoeber, 1932, pp. 1266-1275. 2. Wolter, J. R.: Melanoblasts of the normal human choroid. AMA Arch. Ophth., 53:211-214, 1955. 3. Yoshihisa, I.: Histological studies on ocular structures of fetuses: Observation on the development of pigmented cells of the choroid and sciera. Japanese J. Ophth., 1:124-130, 1957. 4. Moyer, F. H.: Electron microscope observations on the origin, development and genetic variation of melanin granules in the eye. New York, Academic Press, 1961, pp. 469-486. 5. Feeney, L. B., and Hogan, M. J.: Electron microscopy of the human choroid. Am. J. Ophth., 51: 1057/185-1083/211, 1961 6. Kobayashi, S., and Amino, N.: Tissue culture of the choroid. Acta Soc. Ophth. Jap., 64:1811-1817, 1960. 7. Willys, K. S.: Genes and the pigment cells of mammals. Science, 134:368-373, 1961. 8. Birbeck, M. S. C, Mercer, E. H., and Barnicot, N. A.: The structure and formation of pigment granules in human hair. Exper Cell Res., 10:505-514, 1956. 9. Szabo, G.: Pigment Cell Biology. (Ed. Myron Gordon). New York, Academic Press, 1959. 10. Charles, A., and Ingram, T.: Electron microscope observations of the melanocyte of the human epidermis. J. Biophys. & Biochem. Cytol., 6:41-44, 1959. 11. Hogan, M. J., and Feeney, L.: Electron microscopy of the human choroid: III. The blood vessels. Am. J. Ophth., 51:1084/212-1097/225,1961. 12. Hu, F.: Cytological studies of human pigment cells in tissue culture in pigment cell biology. New York, Academic Press, 1959, pp. 147-158. 13. Kaczurowski, M. I.: The pigment epithelium of the human eye. Am. J. Ophth., 53:79-92, 1962.
CHROMATOPHORES OF THE HUMAN EYE
785
14. Duke-Elder, W. S.: Textbook of Ophthalmology. St. Louis, Mosby, 1939, v. 1. 15. Lignac, G. O. E.: Melanogenesis. J. Pathol. & Bact., 68:273-276, 1954. 16. Fitzpatrick, T. B., and Bunsen, L. A.: Biochemical basis of human melanin pigmentation. AMA Arch. Dermat. & Syphil, 69:133-149, 1954. 17. Hill and Whittingham : Photosynthesis. London, Wiley, 1955. 18. Adler, F.: Physiology of the Eye. St. Louis, Mosby, 1959, ed. 3. 19. Lauber, M.: Das Auge in von Moltendorf, W.: Handbuch der Microscopischen Anatomie des Menschen, Berlin, Springer-Verlag, 1936, Band III, Teil 2. 20. Rosenberg, S. A., Kodani, M., and Rosenberg, J. C : The malignant melanoma of hamsters: II. Growth and morphology of a transplanted melanotic and amelanotic tumor in tissue culture. Cancer Re search, 21:632-635, 1961. 21. Lerner, A. B., and McGuire, J. S.: Effect of alpha- and beta-melanocyte stimulating hormones on the skin color of man. Nature, 189:176-179, 1961. 22. Friedenwald, J., et al.: Ophthalmic Pathology. Philadelphia, Saunders, 1952. 23. Maximow, A. A.: Text-Book of Histology. Philadelphia and London, Saunders, 1938. 24. Hamm, A. W.: Histology. Philadelphia, Lippincott, 1957, ed. 3. 25. Lerner, A. B., and Fitzpatrick, T. B.: Biochemistry of melanin formation. Physiol. Rev., 30:91, 1950.
COUP-CONTRECOUP MECHANISM OF OCULAR J.
REIMER WOLTER,
INJURIES*
M.D.
Ann Arbor, Michigan T h e term contrecoup is commonly used in ophthalmology to explain contusion damage of the eye at a point opposite to the site of the impact of a blow. This type of distant injury was first observed in the brain by Fallopius in the latter part of the 16th century and by Valsalva in 1700. 1 T h e term of contrecoup was introduced for such brain injuries by a group of French surgeons in the latter half of the 18th century. 1 T h e original explana tion of this type of damage in the brain was that oscillations of the brain tissue starting at the point of impact traverse the head and injure the brain by local vibrations against the inner table of the skull. Later theories of other authors included deformation of the whole head, as well as the complicated reflections of concussion waves in the skull, and resulted in confusion of the first simple theory. V e r y recently Courville 1 ' 2 has cleared the confusion about the mechanism of contre coup in the brain by dividing contrecoup in* From the Department of Ophthalmic Surgery, University Hospital. This study was supported by Grant No. B-2873 of the U.S. Department of Health, Education, and Welfare.
juries of the head in two groups: ( 1 ) those cases in which the head is in motion and in which the brain gets hurt by a sudden stop of this motion (fall or car accident) and ( 2 ) those cases in which a moving object hits the resting head. Courville has shown that, in this second group, the direct blow to a quiescent head usually produces some local (coup) damage and that a direct line of force traverses the brain to the opposite wall of the skull. In the brain, foci of dam age are found along this direct line of force at all interfaces, due to differences in density of brain tissue, dura, skull and ventricles. T h e use of the term of contrecoup in eye injuries had started long before the reveal ing studies of Courville. 1 ' 2 T h e new views of this author on the mechanism of contre coup in the brain can be applied to eye in juries and allow for a better explanation of contrecoup in the eye. I n the ophthalmologic literature most studies on contrecoup damage of the eye have been limited to the retina. After a few re ports before 1900 of macular changes fol lowing contusion of the eye, great interest in this type of damage suddenly resulted in
766
enough to preserve detail. Fortunately, it is! usually possible to place the illuminating; beam in the pupillary area so that points of':' interest are avoided. The photographs' shown in Figures 4 through 12 are illustra-
tive of the type of records obtainable by this method. 227 16th Street (2). ACKNOWLEDGMENT
The engineering assistance of Mr. Richard Raper is gratefully acknowledged.
REFERENCES
1. Douvas, N., and Allen, L.: Anterior segment photography. Am. J. Ophth., 33:291, 19S0. 2. Lubkin, V.: Photography of the red reflex. Arch. Ophth., 43:718, 1950. 3. Fincham, E. F.: Photographic recording of opacities of the ocular media. Brit. J. Ophth., 39:85,1955. 4. Ogg, A. J.: Photography of lens opacities by trans-scleral illumination. Brit. J. Ophth., 44:374, 1960.
CHROMATOPHORES O F T H E HUMAN EYE* M.
I. KACZUROWSKI,
M.D.
Philadelphia, Pennsylvania INTRODUCTION
Although the results of many investi gators have been published on the choroid of the eye 1-6 ' 11 very little data are available concerning its pigment elements, particu larly the chromatophores.î Our knowledge of the melanoblasts in general is sufficiently extensive7-10·12 but no one has paid any at tention to a systematic study of the mor phology of the pigment cells of the eye, probably because this requires a special technique of investigation, and suitable ma terial which had been difficult to obtain in thejpast. Previous investigations on this subject were generally performed using low magnifica tion2 and were related to histologie (mi crotomy and staining) techniques. Recent work has been based on electron micros copy.^'5·11 In·the first case (low magnifica tion) it was impossible to obtain any mor^ * From the Wills Eye Hospital. This study was supported hy grant No. 2B-S076 from the National Institute of Neurological Diseases and Blindness, National Institutes of Health, United States Public Health Service. t Chromatophores: "Melanoblasts," "pigment cells," "melanocells" will be used as synonyms.
phologic details of the structure of pig ment elements which densely populated the choroidal spaces. The illegible picture of the choroid's content was complicated by struc tures not related to the pigment, which were manifested by staining. The technique of electron magnification does not deal with the outward appearances of the chromatophores. With electron microscopy the shape of the cells and outstanding parts generally disap pear from the field of view and only the inner structures are shown. Therefore, one can ,say that little has been added to ex ternal morphology of the pigment elements of the human choroid, in recent times. Wolter 2 indicates that these cells have at tracted little attention from physiologic, as well as the morphologic, consideration. From the viewpoint that form determines function and; on the other hand, that func tion explains form, it is obviously useful to have more detailed knowledge about the morphology of the chromatophores of the human choroid. It is no longer possible to hold the opinion that chromatophores are just cellular structures filling out the cho roidal space among the vessels and nerves.
CHROMATOPHORES OF THE HUMAN EYE
This study was designed to describe the microanatomic shape of melanocells and to determine the possible role of the chromatophores and their pigment granules. Existing histologie data on these cells include a few morphologic types 1 and an intricate relation ship between melanoblasts and other struc tures of the choroid.2 The latter observa tion has led Wolter to postulate that a spe cial relationship exists between chromatophores and blood vessels and nerves of the choroid. However, the physiologic role of these elements has never been interpreted. This situation probably existed because in vestigators for a long time disregarded the method of flat preparation. The flat prepara tion method is primarily effective for study ing such tissues as pigment epithelium, cho roid, iris and so forth. The technique of flat preparations together with recently per fected techniques of light microscopy can yield information not obtainable by other histologie procedures. MATERIAL
This work is based on a relatively large amount of material, 119 human eyes being used. All eyes were obtained from the EyeBank of the Wills Eye Hospital and no eye had any signs of abnormality. The age dis tribution of eyes is as follows : AGE GROUPS
N U M B E R OF CASES
Year 1-10 10-20 20-30 30-40 40-50 S0-60 60-70 70-80 80-90 90-100
4 4 7 10 12 26 20 25 10 1 METHODS
PREPARATION OF T H E EYE
All eyes received from the Eye-Bank were injected with four-percent formalin through the optic nerve and then immersed
767
Fig. 1 (Kaczurowski). (1) Applicator; (2) soli tary granules remaining after removal of pigment epithelium; (3) pigment epithelium (P. E.) ; (4) Bruch's membrane (lamina vitrea) ; (5) vitreous part of choroid; (6) chromatophores; (7) line of cleavage of the choroid; (8) scierai part of the choroid; (9) thin remnants of sciera after cutting most of it away; (10) removed part of sciera.
in the same solution. After a few days, when the distended eyeball hardened, the sciera was removed with a razor blade. The eyes were then cut frontally at the level of the ora serrata. The open eyeballs (poste rior portion) were dissected meridionally through the optic nerve into eight separate identical parts. Following removal of the vitreous body and the retina, the pigment epithelium was brushed off by a cotton ap plicator and rinsed briefly in distilled water. No microtomy or staining was used. Sub sequently when the choroid was gently stripped from the sciera, two separate fine sheets of it were obtained: one connected with Bruch's membrane (vitreous part) and the second, somewhat thinner sheet, attached to remnants of the sciera (scierai part) (fig. 1). The prepared specimens were dehydrated with alcohol (70 to 95 percent), cleared in carbo-xylene, then xylene and were finally mounted with harleco synthetic resin. After clearing the preparation of remnants of scierai tissue, there was no obstacle to mi-
M. I. KACZUROWSKI
768
croscopic observation. Therefore, the two flat sheets of the choroid were observed from: (a) Bruch's membrane, (b) the sur face of cleavage, (c) the sciera (fig. 2). To avoid the complication of the very confusing picture of densely distributed melanoblasts, no stain was used and the natural color of melanin was observed. OBSERVATION
The areas of observation and method of measurements have been described else where.13 It will be useful here to communi cate some details about the microscopic tech nique working with the flat prepared speci mens. Since flat preparations have consider able thickness, deep vertical focusing is nec essary. To avoid erroneous conclusions in appraising microscopic objects, one must be certain that the body, the processes or other structures of the observed chromatophores are not damaged or changed during the elaboration of the tissue. Usually a division occurs in the blood vessel layer in the process of separating the choroid from the sciera. Some chromato phores may tear into two portions with re
rw
sulting loss of the processes and intensity of pigmentation. For observation, only un damaged cells and structures were used. An important criterion for determining the in tact state of the cells or other structures being examined, is to note the state of struc tures in the planes of the tissue above and below it. If these were intact, the cells in question were considered to be well pre served between these two planes. If, on the other hand, the structures above or below could not be well defined, this object was re jected for study. Thus, measurement and defi nition of intensity of pigmentation of chro matophores and their shape were determined only on "untouched cells." Figure 2 presents a clearer understanding of these points. RESULTS A. GENERAL DESCRIPTION OF A CHROMATO. PHORE
The general morphologic characteristic of the chromatophore may be determined within the limits of light microscopy as follows: Body. The bodies of the cells vary greatly in size and shape. Variability of the chro matophores evidently depends on their loca-
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Fig. 2 (Kaczurowski). (I) Vit reous part of the choroid observed from Bruch's membrane; (II) vit reous part of the choroid observed from surface of cleavage; (III) scierai part of the choroid observed from sciera; (IV) scierai part of the choroid observed from surface of cleavage. (1) Bruch's mem brane; (2) pigment epithelium; (3) surface of cleavage of the cho roid; (4) remnant of the sciera.
CHROMATOPHORES OF THE HUMAN EYE
PROTRUSIONS
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769 FIBER
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LACUNAE AT SITE OF PREVIOUS PROTRUSIONS
Fig. 3 (Kaczurowski). Forms of chromatophores.
tion in the choroid and also on such struc tures as vessels and nerves surrounding it. The shapes of the cells change from round and elongated, to star-shaped and vermi form. The body of the chromatophore is usually flat, although many cells are bulky. The relation of the length to the thickness is defined by the ratios 2:1, 5:1, 10:1. Cells with a ratio 5:1 or 10:1, are usually ob served. Within the chromatophore (often not in the center) a large elongated nucleus is located, ordinarily covered from the pe riphery with either two, three or many layers of melanogranules. The unstained nucleus seems structureless and transparent, being similar to cytoplasm which evidently does not contain many melanogranules in the middle of cells. In some preparations, using high magnifications, it is possible to see highly refractive "fibers" located above or below the nucleus (fig. 33). Processes. The body of the chromato phores has from two to six processes which exist in three forms: (a) plasmatic, rela tively thick and medium length, covered
with innumerable tiny granules (fig. 30), (b) long consisting of one row of granules (punctiforme processes) (fig. 20) and (c) short and coarse processes (fig. 26). The relation between the length of the processes and their diameter varied from 5:1 to 25:1 and more. The ratio of the length of the processes to the diameter of the chromato phore body varied from 1:1 to 1:30. Channels. It was possible to mark inside of some processes refractive spaces directed within the length. At times these spaces begin outside of the processes in close prox imity to the cell body. At other times chan nel-like formations originate in the middle of the processes. Often the "space" begins imperceptibly from the body of the chroma tophore. These structures could be inter preted as "channels" among the granules containing a cytoplasm or fibrillar structures (fig. 6 ) . Protrusions. On the periphery of the chromatophores, an immense number of very thin melanogranules, sized from 0.2 μ to 0.6 μ, are dispersed. Some chromatophores
M. I. KACZUROWSKI
770
have spherical shaped accumulations ("pro trusions") of the melanogranules on the surface (figs. 3 and 23). The outer shape of the granules is nearly oval, but a more detailed determination of external granular shape is impossible even with high magnifi cation ( X 2,000). At times, the granules may form spherical protrusions on the body and on the process (fig. 5). Globes. The distal ends of the processes are rarely sharp-pointed. Frequently, the ends have knotlike thickenings or spherical globes (figs. 3, 7, 8, 21 and 22). The proc esses enter into the lower pole of the globe. On the opposite pole, mostly one, rarely two and very seldom three apertures can be ob served as very refractive spots. The size of the globes is measured from 2.0 μ to 12 μ in
ΤΠΓ 1
diameter. Sometimes, under the influence of unknown causes, the globes indicate frag mentations of many particles or separated granules (figs. 3 and 12). As a rule, the globes are more intensely pigmented than the supporting processes. B.
GENERAL
DATA
ABOUT
CHROMATOPHOEES
IN
THE
LOCATION
OF
CHOROID
The chromatophores are scattered throughout the choroid in a definite order and form nine to 12 horizontal layers. Close to the vessels some pigment cells are elon gated and arranged lengthwise and crossways. Close to the sciera the chromatophores are branching and star-shaped but near the lamina vitrea they are clusterlike with a multitude of processes and globes (figs. 22
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Fig. 4 (Kaczurowski). The names "vitreocapillary" and "sclerochoroid" layers will be used in this scheme to distinguish the area and location of some typical melanocells more definitely. 1. Subtle type—forms I, II, III 6. Irregular type 2. Flowered type—forms I, II 7. Paving-stone type 3. Round type 8. Impressed type 4. Elongated type 9. Lacunated type—forms I, II 5. Star-shaped type—forms I, II, III 10. Vermiform type
CHROMATOPHORES OF THE HUMAN EYE
771
and 28). In the blood vessel layer, the chromatophores are more voluminous compared with those in the scierai and Bruch's mem brane areas. Usually two or three layers of chromatophores accompany the vessels and nerves, by passing through the sciera. C. ADDITIONAL MELANOSTRUCTURES OF THE CHOROID
"Dust" or powdery granules. In the study of flat preparations of choroidal specimens, a significant number of solitary randomly scattered granules or accumulations of them are seen. In many cases of observation above and below (between two "untouched layers" of chromatophores), "dust" (ac cumulations of the granules) was observed,
Fig. 6 (Kaczurowski). Flat preparation of the human choroid of a 55-year-old man. Two processes connected by a fiber. Note easily visible channels in side the processes (arrows) occupied by connecting fiber. Location: equator, suprachoroid. (XlOOO.)
Fig. 5 (Kaczurowski). Flat preparation of the human choroid of a 57-year-old man. Note the pro trusions on the process (arrows). Location: between the equator and ora serrata, supracapillary layer. (X900.) M// r
Fig. 7 (Kaczurowski). Flat preparation of the human choroid of an 11-year-old child. Three globes are located on the end of a process. Location: equator, supracapillary layer. (X900.)
772
M. I. KACZUROWSKI Fig. 8 (Kaczurowski). Flat preparation of the human choroid of a 54-year-old man. A globe with aperture is seen (arrow). Location: optic nerve area, supracapillary layer. (χ900.)
indicating that the extracellular accumula tions of the granules were not the result of artefact, but rather a phenomenon of physio logic function of melanoblasts of the choroid. That is to say the melanogranules are a product of "secretion" of the chromatophores, which could be interpreted as sui generis microglands (figs. 2, 3, 9, 10 and 36). The accumulation of granules in the inter cellular media. Occasionally, large particles of melanin were observed. The conglomer ates resembled coalesced granules of multishaped particles, at times completely round and measuring from 1.0 μ to 6.0 μ in di ameter. Both structures were found on all
Fig. 9 (Kaczurowski). Flat preparation of the human choroid of a 40-year-old man. Arrow 1 indi cates "dust" or the extracellular accumulation of the pigment granules extruded from the lacunated chro ma tophore (indicated by arrows 2). Location: equator, blood vessel layer. (χ900.)
Fig. 10 (Kaczurowski). Flat preparation of the human choroid of a 10-year-old child. Note the ex tracellular accumulation of melanogranules (ar rows). Location: between equator and optic nerve areas, blood vessel layer. (χ900.)
CHROMATOPHORES OF THE HUMAN EYE
773
Fig. 12 (Kaczurowski). Flat preparation of human choroid of an 11-year-old child. A globe in fragmen tation phase. Optic nerve area, supracapillary layer. (X900.)
extensions of the choroid (figs. 9, 10, 12 and 13). A correlation with the topographi cal location of the choroid was not estab lished. Filaments. The most interesting of struc tures occurring in the choroid are thread like refractive formations covered with pig ment granules. "Filament" structures can be seen in parts of the choroid adjacent to the sciera, primarily in the area of the ora serrata, equator and occasionally in the optic nerve area (figs. 3, 14, 15, 16 and 17). D. TYPES OF CHROMATOPHORES
The chromatophores are distributed in rows of from nine to 12, parallel to the
Fig. 11 (Kaczurowski). A flat preparation of the human choroid of a four-year-old child. The picture shows two processes with channels. Location: equator, choriocapillary layer. (X2000.)
Fig. 13 (Kaczurowski). Flat preparation of the human choroid of a 78-year-old man. Fragmentation of a chromatophore. Location: equator, blood vessel layer. (X2000.)
774
M. I. KACZUROWSKI
Fig. 14 (Kaczurowski). Flat preparation of the human choroid of a 54-year-old man. In the center of the field are seen in straight-line arrangement many melanogranules forming "filaments" (arrows). Location: equator, suprachoroid layer. (X2000.)
sciera. The distance between the layers is on the average 3.0 μ to 5.0 μ. Ten types of chromatophores were established, showing a gradual variation from one to another (fig. 4). 1. Subtle type, form I. Two or four μ below Bruch's membrane, in the vitreocapillary layer, the "subtle type" of the chromatophore was typically found. These cells have a semitransparent body with an insignificant quantity of melanin. The gran ules, as a rule, are seen on the outside edge of the body. Some granules are very dark and comparatively enlarged. The "subtle" chromatophore has two or three short proc esses, usually without the legible formed globes (fig. 18). Such types of chromato phores have been found every place in the choroid, frequently in the optic nerve area 2.0 μ to 4.0 μ below Bruch's membrane. They are seen in each third or fourth mi croscopic field at 900 magnification. The
body and processes are located mostly in one flat plane. The dimensions of cells is 10 μ to 20 μ in diameter. Deeper, from Bruch's membrane (5.0 μ to 6.0 μ), the subtle type form II of chro matophore continues to exist with a modifi cation: the cells look more pigmented, the processes are thicker and one can often see the small globes on top (fig. 19). In the sclerochoroid layer the third, form III of subtle type is found. The typical outline of these cells, trigonal-shaped body, very thin processes (sometimes punctiform) and low pigmentation, occurs mostly in the sclerocho roid of the ora serrata and equator areas (fig. 20). 2. The "flowered" type. The "flowered" types of chromatophores are typical of the capillary and supracapillary layers of the choroid (figs. 21, 22 and 23). There are two forms: The first form has short processes oc casionally bearing globes (fig. 21).
Fig. 15 (Kaczurowski). Flat preparation of the human choroid of a four-year-old child. The "fila ment" is located vertically in the middle of the pic ture. Location: optic nerve area, sclerochoroid layer. (X1000.)
CHROMATOPHORES OF THE HUMAN EYE The second form possesses long processes crowned with many globes. Both forms also have protrusions on the body (fig. 22). The "flowered" type of melanoblasts is dis tributed everywhere in the choroid, 7.0 μ to 10 μ below the Bruch's membrane (capil lary and supracapillary layer). This type of chromatophore is relatively small and inten sively pigmented. The body of these cells is 10 μ to 20 μ in diameter. 3. The round type. The round type of chromatophores can be observed in the blood vessel layer and only occasionally in the supracapillary or suprachoroidal layer. The basic pattern of this chromatophore is spher ical or approximately so. Occasionally, small processes or traces of them can be observed. They range in size from 8.0 μ to 40 μ in diameter (fig. 24). At times, in the round type of cell, the nucleus is not clearly visible.
Fig. 16 (Kaczurowski). Flat preparation of the human choroid of a 55-year-old man. The picture shows two vertically located "filaments." Location: ora, capillary layer. (X900.)
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Fig. 17 (Kaczurowski). Flat preparation of the human choroid of a 35-year-old man. "Filaments" are seen (arrows). Location: ora serra ta, suprachoroid layer. (X°00.)
4. The "elongated" type. The elongated type of chromatophores belongs mostly to the blood vessel layer. These cells are observed in the neighborhood of medium and large sized vessels. The ratio of the major to minor axis is approximately 12:1. The major axis is oriented parallel to the vessels and nerves and sometimes to the choroidal folds, or fol low the fibers. Under low magnification this kind of cell often forms a criss-crossing net. These chromatophores have a good visible bulk, are intensely pigmented, do not have processes and possess an oval nucleus (fig. 25). 5. The star-shaped chromatophores. The star-shaped chromatophores have been ob served in the blood-vessel layer, suprachoroid and supracapillary layers. Three forms of star-shaped chromatophores occur: Form I has short (3.0 to 5.0 μ) pyram idal processes, with irregular edges and without globes. The cells are very flat and large (measuring 20 to 60 μ in diameter) with an oval nucleus (from 5.0 to 8.0 μ ) .
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Fig. 18 (Kaczurowski). Flat preparation of the human choroid of a 50-year-old man. This picture represents a subtle type (form I) of chromatophore. Note the semitransparent body and short, relatively thin processes. Location: optic nerve area, vitreocapillary layer (3.0 μ below the Bruch's membrane). (X900.)
Fig. 19 (Kaczurowski). Flat preparation of the human choroid of a 50-year-old man. A subtle type (form II) is located in the capillary layer, 6.0 μ be low the Bruch's membrane. This deeply situated modification of a subtle cell is intensely pigmented and the processes are thick with one or two globes on the end. This cell was observed between the equator and optic nerve area as shown in this photo graph. (X900.)
The first form is usually located in the blood vessel and suprachoroid layers extending from the optic nerve area to the ora serrata (fig. 26). Form II has a relatively large body (20 to 30 μ) and processes of medium length (fig. 27). The processes may or may not have globes. The second form is scattered from the optic nerve area to the ora serrata in the supracapillary and suprachoroid layer. Form III of the star-shaped chromato phore possesses a polygonal body and very long processes, often with globes. This form is also typical for suprachoroid, supracapil lary layers and the adjacent area of blood vessel layers. They are scattered in great numbers from the optic nerve area to the ora serrata. The size of the body ranges from 10 to 20 μ, the processes from 20 μ ίο40μ (figs. 28, 29 and 30). 6. The irregular type. Resembling clumps,
Fig. 20 (Kaczurowski). Flat preparation of the human choroid of a 55-year-old man. Subtle type, form III, is scattered in sclerochoroid from ora ser rata to optic nerve area. Note trigonal transparent body and filamentlike processes. (X900.)
CHROMATOPHORES OF T H E HUMAN EYE
m
Fig. 22 (Kaczurowski). Flat preparation of the human choroid of a 55-year-old man. A flowered type (form II) of chromatophore. Location: equa tor, supracapillary layer 7.0 μ below Bruch's mem brane. The long processes with many globes are typical. Many additional protrusions are seen on the processes.
this type occupies the medium part of the blood vessel layer, especially in the optic nerve and equator areas. The body of these chromatophores is relatively large, being from 25 to 50 μ. These cells have an intense brown color and occasional chromatophores of this type have short, coarse processes (fig. 31). 7. The paving-stone type. This type of chromatophore is very flat and never has processes or globes. The intensity of pig mentation is variable. These large sized cells, measuring from 30 to 50 μ, are scattered from the optic nerve to the ora serrata in
Fig. 21 (Kaczurowski). Flat preparation of the human choroid of a 57-year-old man. A flowered type (form I) of chromatophore possessing short processes with two, three or four globes. Location: ora serrata area, supracapillary layer, 8.0 μ-9.0 μ be low the Bruch's membrane. ( X900.)
Fig. 23 (Kaczurowski). A flat preparation of the human eye of a five-year-old child. This flowered type form I was found between the ora serrata and equator 5.0 or 6.0 μ below Bruch's membrane in the capillary layer. (XlOOO.) Note many protrusions (arrows).
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Fig. 24 (Kaczurowski). Flat preparation of the human choroid of a 57-year-old man. This is a round type of chromatophore. Note absence of proc esses, pigmentation is intensive. Location : blood ves sel layer close to the suprachoroid, equator area. (X2000.)
the blood vessel and suprachoroid layers (fig. 32). 8. Impressed type. Cells, aggregated in large groups, usually have been found at the equator, in the optic nerve area deep in the blood vessel, and in the suprachoroid layers. "Impressed" cells seem to possess very legi ble impressions on the bodies and the proc esses, hence the name. The size of these cells is 25 to 50 μ in diameter. They are not greatly pigmented and no globes are seen (figs. 33 and 34). 9. The lacunated type. Two forms of this type occur. The first or macrolacunated forms are not numerous, but they are a very interesting kind of melanocell (figs. 35, 36 and 37). They are from 30 to 50 μ in size and, for the most part, are without proc esses. Macrolacunated chromatophores are elongated or irregular shaped with round lacunae in the bodies and at times in the processes. The lacunae are from 2.0 to 8.0 μ
in diameter. These chromatophores are scat tered throughout all areas of the choroid, but mostly in the blood vessel layer near to the suprachoroid. The number of lacunae varies considerably from a few to 50. Using high magnification, it is clearly evident that the lacunae are not as smooth as they appear in low-power observations. The lacunae probably are the results of fragmentation of the protrusions. The edges of the lacunae are framed with melanogranules of differ ent size and intensity of pigmentation. At the depth of lacunae, the transparent cyto plasm is usually seen. The second or microlacunated form of the chromatophores is very numerous and polymorphic (fig. 37). Practically all types of chromatophores, particularly the flat type (paving stone, starshaped, impressed types) often possess very fine lacunae on the body or processes. The diameter of the small lacunae is usually identical to the size of the granules. The average number of these lacunae varies from
Fig. 25 (Kaczurowski). Flat preparation of the human choroid of a 27-year-old man. This is an elongated type of chromatophore. Note absence of the processes. The pigmentation is intensive. Loca tion: equator area. (χΙΟΟΟ.)
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10 to 100, measuring from 0.1 to 0.6 μ in diameter. 10. Vermiform type. Finally, one must note a very remarkable type of chromatophore, termed vermiform. This type has a small elongated body from 5.0 to 10 μ in length and usually two very long processes. The relation between the size of the body and the length of the processes can be char acterized by the ratio 1 : 30. The vermiform type of chromatophores is scattered in the sclerochoroid and capillary layer from the optic nerve area to the ora serrata. The average quantity of cells is negligible (fig. 38). DISCUSSION
In the present investigation such peculi arities of choroidal tissue as thinness, ease of separation of the choroid from the retina and sciera and transparency of the cho roidal stroma were utilized. For better obFig. 27 (Kaczurowski). Flat preparation of the human choroid of a 40-year-old woman. The picture represents a star-shaped type of the chromatophore form II—star-shaped body and medium sized proc esses. Location: ora serrata, suprachoroid. (XlOOO.) serration of the chromatophores, a method for extension of the choroid was used by injecting formalin into the eyeball. By this manipulation the thickness of the choroid was reduced by approximately one-tenth, but the multilayered arrangement of the chromatophores was not affected. Besides the stretched chromatophores and reduction of the thickness of the choroid, some changes in the measurements of different objects of lesser importance were made. It is quite possible that some chromatophores were en larged and the distance between them made a little greater. These changes can be ig nored, however, because they occur within the limits of normal variation. Fig. 26 (Kaczurowski). Flat preparation of the human choroid of an 11-year-old boy. Star-shaped type of chromatophores (form I). Note the short pitted processes without globes. The processes are connected with fibers (arrow). Location: equator, blood vessel layer near the suprachoroid. (X900.)
In addition to a complete description of the melano-elements of the choroid, an at tempt was also made to estimate the pos sible function and role of the melano-ele ments. We were keenly aware of the possi-
780
M. I. KACZUROWSKI Fig. 28 (Kaczurowski). Flat preparation of the human choroid of a 37-year-old man. A star-shaped type of chromatophore (form III). This kind of cell possesses the long processes with globes. Location: ora serrata between sclerochoroid and suprachoroid layers. (X900.)
bility of artefacts being present. Therefore, during the work, a special method of micro scopic selection of the objects was elaborated (see Methods). Although chromatophores are extremely polymorphous, it was possible to allot the cells to definite locations and constant shapes. Ten basic types with typi cal outlines and some variations of chroma tophores were established (fig. 4 ) . Besides the types of melanoblasts, a series of adnexal melanin-formations and organella such as "channels," "globes," "filaments" and so forth were noted. The formation of the basic mass of visi ble melanin in the choroid occurs after birth. The fetal and newborn eyes are poorly pro vided with melanogranules in the choroid.3 The formation of melanin from its pre-
Fig. 29 (Kaczurowski). Flat preparation of the human choroid of a 95-year-old man. A star-shaped type of chromatophore (form III) with extremely long processes. Location: ora serrata between cap illary and supracapillary layers. (χ900.)
Fig. 30 (Kaczurowski). Flat preparation of the human choroid of the five-year-old child. A starshaped chromatophore (form I I I ) . Equator, supra choroid layer. (X900.)
CHROMATOPHORES OF THE HUMAN EYE
cursors (dihydroxyphenylalanine [Dopa] or tyrosine) by the action of dopa-oxidase or tyrosinase, is a complex process and de pends on many surrounding chemical and physical factors, particularly ultraviolet rays. Melanin synthesis evidently occurs in cyto plasm of the melanoblast and its processes and also on the ends of these processes. The appearance of a new mass of melanin and the increase in the number of granules lead to development of so-called "protru sions." They are located on the surface of the cell and its processes. On the endings of the processes protrusions appear as globes. No structural difference between globes and protrusions exists because both are spherical melano-structures. In the case of advanced production of melanin, it is possible to observe secondary protrusions on the globes and on the protrusions them selves. With increasing age the average quantity of melanogranules in the choroid increases, but is gradually reduced in aged persons. Under the influence of light and other unknown causes melanogranules are able to migrate from the cells into the intercellular
Fig. 31 (Kaczurowski). Flat preparation of the human choroid of a 45-year-old woman. An irregular type of the chromatophore. Equator, blood vessel layer. (χ900.)
781
Fig. 32 (Kaczurowski). Flat preparation of the human choroid of an 11-year-old boy. A pavingstone type of chromatophore. Note absence of the processes and flat compressed-like bodies. Equator, bloodvessel layer. (χ900.)
Fig. 33 (Kaczurowski). Flat preparation of the human choroid of a 27-year-old man. An impressed type of chromatophore. Note a fiber crossing nu cleus (arrow). Location: between equator and optic nerve area, suprachoroid layer. (X900.)
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Fig. 34 (Kaczurowski). Flat preparation of the human choroid of a 27-year-old man. An impressed type of chromatophore. Location: between equator and ora serrata, blood vessel layer. (χ900.)
Fig. 35 (Kaczurowski). Flat preparation of the human choroid of a 10-year-old child. A macrolacunated type of chromatophore (form I ) . Location: equator, blood vessel layer. (X2000.)
space forming "dust" visible everywhere in the choroid. The migration occurs by differ ent ways: (1) via fragmentation of the globes (fig. 12) ; (2) in some cases by frag mentation of melanocells (fig. 13); (3) oc casionally protrusions separate from cells and thereupon disperse into solitary gran ules (figs. 9 and 10). The so-called "macrolacunated chromatophores" could very well be the result of the latter type of "secre tion." However, the most important and constant form of "secretion" of melanogranules is the excretion of many solitary granules from the body and processes of chromatophores (fig. 37), resulting in the presence of "microlacunated chromato phores" in the choroid. The shape of the chromatophores in the choroid depends also upon phototropic prop erties of melanin and upon the quantity and location of nerve fibers, passing in proximity
Fig. 36 (Kaczurowski). Flat preparation of the human choroid of a 28-year-old woman. A macrolacunated type of chromatophore (form I ) . Optic nerve area, blood vessel layer. Note extracellular "dust" (arrows). (X900.)
CHROMATOPHORES OF THE HUMAN EYE to the given chromatophore. In the areas of choroid, where the chromatophores are rela tively seldom distributed but are located close to the nerve fibers (capillary, supracapillary layers), the pigment cells have a branching appearance. Formation of the processes occurs via ad sorption of melanogranules by nerve fibers, from the nearest pigment cell. Depending on the number of nerve fibers in contact with the chromatophore, a similar number of processes appears. When the chromato phores are located in a relatively thick stratum (suprachoroid layer), the nerves and elastic fibers, compressed between melanocells formed on the bodies of chromato phores, are well-observed impressions (im pressed type of chromatophores). In such conditions nerve fibers appear fully insulated by flat bodies of melanocells. The forma tion of the processes in this case does not
Fig. 37 (Kaczurowski). Flat preparation of the human choroid of a 27-year-old man. A microlacunated type of chromatophore (form I I ) . Many mi nute lacunae are seen among the granules (arrow 1 ). "Dust" (extruded solitary granules outside of the cells) is indicated by arrow 2.
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Fig. 38 (Kaczurowski). Flat preparation of the human choroid of a 55-year-old man. A vermiforme type of chromatophore (arrow). Note extremely small body and two long processes. Location: ora serrata between the sclerochoroid and suprachoroid layers. (χ900.)
take place. Also, if a distance between nerve fibers and melanocells is relatively large, no formation of the processes occurs and "fila ments" appear. The phototropic ability of melanogran ules probably is not limited only to reaction to light but could be classified as "tropism" to any kind of radiant energy, for example, to bio-electrical impulses conducted through the nerves and their fibers. If the nervous excitations are transmitted through nonmedullated fibers they can adsorb melano granules from the intercellular spaces. The adsorbed melanogranules probably create an isolating sheet which has a dual purpose: to prevent the current impulses from diffuse losses into the surrounding tissues and to pre vent centripetal or centrifugal excitation from outside light influences. The mechanism of the insulating func tion of melanin in the uveal tract may be outlined as follows: melanogranules located on the periphery of the nerve fiber absorb
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and hold superfluous impulses in the eye, independent of their point of origin. There fore, the direct rays of the light penetrating through the optic system into the eye may be absorbed by melanogranules, thus exces sive light irritation is limited in this way. With this, the reaction of the uveal tract is automatically regulated and kept on a phys iologically "normal" level. On the other hand, if centripetal or centrifugal excitation passes in some nerve to any area of the uvea, the attached granules form protection from loss of these given impulses or from contamination from outside light. On the basis of the results obtained by us and from data of other authors con cerning the choroid of the eye, its struc ture,1"6 the nature of the melanin 9 · 12 ' 15-17 and finally our knowledge about the role of myelin23·24 in the nerve system, the fol lowing hypothesis would appear to have a plausible foundation: 1. Subtle type I chromatophores may pos sibly be interpreted as being sympathetic gan glion cells with adsorbed superficial melano granules (fig. 18). 2. The chromatophores of the choroid play the role of sui generis microglands, producing a specific "secretion" as melano
granules, which are extruded into the inter cellular space of the choroid. 3. The melanogranules in the choroid play the role of an isolation material for nerve fibers, on which the myelin sheets are ab sent. 4. The insulating ability of the melanin finally aids in the achievement of accurate and sharp vision because it protects im pulses from diffuse dispersion in surround ing tissues. SUMMARY
1. A method of flat preparation and ob servation of the human choroid have been described. 2. Ten types of chromatophores have been found in the human choroid. 3. It is suggested that melanin serves as an insulator for radiant energy impulses. 4. The role of chromatophores as regulat ors of uveal function in the human eye is pos tulated. 1601 Spring Garden Street (30). ACKNOWLEDGMENT
I wish to acknowledge gratefully the assistance of Theodore W. Sery, Ph.D. I am also indebted to Miss Ada Padgett for her co-operation in obtaining the material.
REFERENCES
1. Arey, L. B.: Retina, choroid and sciera. Cowdry Spec. Cytology V, III, New York, Hoeber, 1932, pp. 1266-1275. 2. Wolter, J. R.: Melanoblasts of the normal human choroid. AMA Arch. Ophth., 53:211-214, 1955. 3. Yoshihisa, I.: Histological studies on ocular structures of fetuses: Observation on the development of pigmented cells of the choroid and sciera. Japanese J. Ophth., 1:124-130, 1957. 4. Moyer, F. H.: Electron microscope observations on the origin, development and genetic variation of melanin granules in the eye. New York, Academic Press, 1961, pp. 469-486. 5. Feeney, L. B., and Hogan, M. J.: Electron microscopy of the human choroid. Am. J. Ophth., 51: 1057/185-1083/211, 1961 6. Kobayashi, S., and Amino, N.: Tissue culture of the choroid. Acta Soc. Ophth. Jap., 64:1811-1817, 1960. 7. Willys, K. S.: Genes and the pigment cells of mammals. Science, 134:368-373, 1961. 8. Birbeck, M. S. C, Mercer, E. H., and Barnicot, N. A.: The structure and formation of pigment granules in human hair. Exper Cell Res., 10:505-514, 1956. 9. Szabo, G.: Pigment Cell Biology. (Ed. Myron Gordon). New York, Academic Press, 1959. 10. Charles, A., and Ingram, T.: Electron microscope observations of the melanocyte of the human epidermis. J. Biophys. & Biochem. Cytol., 6:41-44, 1959. 11. Hogan, M. J., and Feeney, L.: Electron microscopy of the human choroid: III. The blood vessels. Am. J. Ophth., 51:1084/212-1097/225,1961. 12. Hu, F.: Cytological studies of human pigment cells in tissue culture in pigment cell biology. New York, Academic Press, 1959, pp. 147-158. 13. Kaczurowski, M. I.: The pigment epithelium of the human eye. Am. J. Ophth., 53:79-92, 1962.
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14. Duke-Elder, W. S.: Textbook of Ophthalmology. St. Louis, Mosby, 1939, v. 1. 15. Lignac, G. O. E.: Melanogenesis. J. Pathol. & Bact., 68:273-276, 1954. 16. Fitzpatrick, T. B., and Bunsen, L. A.: Biochemical basis of human melanin pigmentation. AMA Arch. Dermat. & Syphil, 69:133-149, 1954. 17. Hill and Whittingham : Photosynthesis. London, Wiley, 1955. 18. Adler, F.: Physiology of the Eye. St. Louis, Mosby, 1959, ed. 3. 19. Lauber, M.: Das Auge in von Moltendorf, W.: Handbuch der Microscopischen Anatomie des Menschen, Berlin, Springer-Verlag, 1936, Band III, Teil 2. 20. Rosenberg, S. A., Kodani, M., and Rosenberg, J. C : The malignant melanoma of hamsters: II. Growth and morphology of a transplanted melanotic and amelanotic tumor in tissue culture. Cancer Re search, 21:632-635, 1961. 21. Lerner, A. B., and McGuire, J. S.: Effect of alpha- and beta-melanocyte stimulating hormones on the skin color of man. Nature, 189:176-179, 1961. 22. Friedenwald, J., et al.: Ophthalmic Pathology. Philadelphia, Saunders, 1952. 23. Maximow, A. A.: Text-Book of Histology. Philadelphia and London, Saunders, 1938. 24. Hamm, A. W.: Histology. Philadelphia, Lippincott, 1957, ed. 3. 25. Lerner, A. B., and Fitzpatrick, T. B.: Biochemistry of melanin formation. Physiol. Rev., 30:91, 1950.
COUP-CONTRECOUP MECHANISM OF OCULAR J.
REIMER WOLTER,
INJURIES*
M.D.
Ann Arbor, Michigan T h e term contrecoup is commonly used in ophthalmology to explain contusion damage of the eye at a point opposite to the site of the impact of a blow. This type of distant injury was first observed in the brain by Fallopius in the latter part of the 16th century and by Valsalva in 1700. 1 T h e term of contrecoup was introduced for such brain injuries by a group of French surgeons in the latter half of the 18th century. 1 T h e original explana tion of this type of damage in the brain was that oscillations of the brain tissue starting at the point of impact traverse the head and injure the brain by local vibrations against the inner table of the skull. Later theories of other authors included deformation of the whole head, as well as the complicated reflections of concussion waves in the skull, and resulted in confusion of the first simple theory. V e r y recently Courville 1 ' 2 has cleared the confusion about the mechanism of contre coup in the brain by dividing contrecoup in* From the Department of Ophthalmic Surgery, University Hospital. This study was supported by Grant No. B-2873 of the U.S. Department of Health, Education, and Welfare.
juries of the head in two groups: ( 1 ) those cases in which the head is in motion and in which the brain gets hurt by a sudden stop of this motion (fall or car accident) and ( 2 ) those cases in which a moving object hits the resting head. Courville has shown that, in this second group, the direct blow to a quiescent head usually produces some local (coup) damage and that a direct line of force traverses the brain to the opposite wall of the skull. In the brain, foci of dam age are found along this direct line of force at all interfaces, due to differences in density of brain tissue, dura, skull and ventricles. T h e use of the term of contrecoup in eye injuries had started long before the reveal ing studies of Courville. 1 ' 2 T h e new views of this author on the mechanism of contre coup in the brain can be applied to eye in juries and allow for a better explanation of contrecoup in the eye. I n the ophthalmologic literature most studies on contrecoup damage of the eye have been limited to the retina. After a few re ports before 1900 of macular changes fol lowing contusion of the eye, great interest in this type of damage suddenly resulted in