- Email: [email protected]
Orbital Volume Following Evisceration, Enucleation, and Exenteration in Rabbits
ORBITAL VOLUME F O L L O W I N G EVISCERATION, ENUCLEATION, AND E X E N T E R A T I O N IN RABBITS BERNARD G. SARNAT, M.D.,
AND P H I L I P D. SHANEDLING,
M.D.
Los Angeles, California
Shape and size of the orbit result from the balance of a number of genetic or environ mental factors which may function on a sys temic, regional, or local basis.1 We were in terested in knowing whether, volumetrically, there was a direct correlation between lack of intraorbital tissue and lack of orbital growth. The imprint method to determine orbital volume was used.2 In three series of young growing rabbits, varying amounts of intraorbital tissue were removed unilaterally. In one group, the in traocular contents were extracted but not the cornea and sciera (evisceration). In a second group, the eye was enucleated. In a third se ries, previously reported but included here for comparison, the contents of the orbit were removed (exenteration). 1 The orbital volumes were determined after different pe riods of postoperative survival. We have found no such report of comparable work in the literature.
face to the outer border of the orbit, the cur vature of the cranium was greater and the cranium was asymmetric on the operated on side. Thomson 4 performed unilateral enucleation in six rabbits at about 20 days of age. Five to eight months later he found that length, height, and depth of the bony orbit were diminished with resulting facial de formity. Wessely5 aspirated the lens in 18 newborn rabbits and two to eight months later noted that both the eye and orbit were smaller. Kennedy 6 enucleated the eyes in growing rabbits and kittens and confirmed earlier reports. These studies were based on linear measurements. Previously, we exenterated the right orbit in rabbits at six weeks of age. 1 After a postoperative survival of eight to nine months, the average volume of the right exenterated orbit (4.2 ml) was less than the average volume of the unoperated left orbit (5.7 ml). MATERIALS AND METHODS
REVIEW OF LITERATURE
Gudden,3 in 1876, reported the postnatal relationship between the eye and size of the orbit in growing mammals. Popow 3 enucle ated the eyeball in the dog, cat, and pig two to three weeks after birth and killed the ani mals two months later. The orbit was signifi cantly smaller on the operated on side and the distance was less from the midline of the From the Departments of Plastic Surgery (Dr. Sarnat), and Ophthalmology (Dr. Shanedling), Division of Surgery and Research Institute, Ce dars-Sinai Medical Center, and Division of Oral Biology, School of Dentistry, University of Califor nia, Los Angeles, California. This study was sup ported in part by Research Grant HD 00179 from the National Institute of Child Health and Human De velopment USPHS Grant RR 05468. Reprint requests to Bernard G. Sarnat, M.D., 435 North Roxbury Drive, Beverly Hills, California 90210. 787
Fifty-one New Zealand albino rabbits were obtained from nine litters (Tables 13). The animals weighed from 100 to 1350 g and ranged in age from seven to 42 days at the time they were operated on. In the seven- to 21-day-old animals, two drops of 0.5% tetracaine HC1 were instilled into the conjunctival sac. Then approxi mately 0.25 ml of a solution of 1% procaine HC1 was injected into the upper and lower eyelids and retrobulbarly for local anesthe sia. In addition, in the 42-day-old animals an injection was given into the marginal ear vein of a 1% aqueous solution of pentobarbital sodium (40mg/kg). Each rabbit was secured on an operating board with the right side of the face ex posed. This was cleansed with an antiseptic solution and the area draped. After injec tion of the local anesthetic agent the eyelids
AMERICAN JOURNAL OF OPHTHALMOLOGY
788
were separated manually. The surgical proce dure was always performed on the right eye. Evisceration—In one group of 22 rabbits, an evisceration of the right globe was done (Table 1). A keratome incision was made at the limbus into the anterior chamber at the 9 o'clock meridian. One 6-0 plain catgut suture was inserted through the anterior and pos terior lips of the incision. The incision was then enlarged circumferentially approxi mately 6.0 mm with corneal scissors. The intraocular contents were completely evacu ated. The incision was then closed with in terrupted 6-0 plain catgut sutures and the eyelids approximated with interrupted 6-0 black silk sutures. Enucleation—In a second group of 23 rabbits, an enucleation of the right eye was done (Table 2 ) . Black silk traction sutures were placed near each margin of the upper and lower eyelids and sometimes through the
NOVEMBER, 1970
nictitating membrane. A peritomy was per formed. The recti muscles were isolated and cut free of the scierai insertions. The bulb was then delivered and the remaining mus cles and extraocular structures were cut and the bulb enucleated. Bleeding was controlled with local pressure. The capsule and con junctiva were closed with mattress sutures of 6-0 plain catgut. Interrupted 6-0 plain catgut sutures were used to reinforce the first row of sutures. The eyelids were ap proximated with 6-0 black silk sutures. Exenteration—In a third group of six rabbits an exenteration of the right orbit was performed (Table 3). The orbit was then packed with petrolatum-impregnated gauze strips and the eyelids sutured with 6-0 black silk. The gauze pack was removed one week later. Controls—In each animal the left orbit was used as a control for the operated on right side.
TABLE 1 APPROXIMATE ORBITAL VOLUMES IN GROWING RABBITS AFTER EVISCERATION OF THE RIGHT EYE WITH A POSTOPERATIVE SURVIVAL OF 15 TO 2 8 3 DAYS
Days
Animal No.
Weight at Surgery (ing)
Age at Surgery
Age at Death
6-11 6-1 6-2 6-15 6-3 6-12 6-9 6-14 6-10 2-3 5-3 2-2 2-1 2-5 2-4 5-7 5-5 5-4 5-6 5-8 5-1 5-2
130 141 120 130 155 120 140 115 150 190 230 205 170 210 190 340 230 340 230 340 230 230
7 7 7 7 7 7 7 7 7 21 19 21 21 21 21 19 19 19 19 19 19 19
22 28 32 37 42 45 158 186 186 248 253 287 287 287 287 299 302 302 302 302 302 302
Volume in ml Postoperative Left Eye Unoperated Survival 15 21 25 30 35 38 151 179 179 227 234 266 266 266 266 280 283 283 283 283 283 283
1.0 1.4 1.3 1.7 2.0 1.6 4.3 7.4 6.4 5.9 6.6 6.2 7.6 6.2 7.8 7.5 6.8 5.9 6.5 6.6 6.8 6.7
Right Eye Eviscerated
Difference (left-right)
0.8 1.1 1.0 1.5 1.8 1.4 3.8 7.1 6.0 5.6 6.2 6.2 7.5 5.8 7.3 6.8 6.8 5.5 6.0 6.0 6.2 5.8
0.2 0.3 0.3 0.2 0.2 0.2 0.5 0.3 0.4 0.3 0.4 0 0.1 0.4 0.5 0.7 0 0.4 0.5 0.6 0.6 0.9
ORBITAL VOLUME
VOL. 70, NO. 5
789
TABLE 2 APPROXIMATE ORBITAL VOLUMES IN GROWING RABBITS AFTER ENUCLEATION OF THE RIGHT EYE WITH A POSTOPERATIVE SURVIVAL OF ONE TO 2 8 3 DAYS
Volume in ml
Days
Animal No.
Weight at Surgery (ing)
Age at Surgery
Age at Death
3-5 4-4 6-21 6-17 6-16 6-4 6-5 6-6 6-7 3-4 4-1 4-5 6-18 6-20 6-22 6-19 6-8 3-3 3-1 3-2 4-6 4-3 4-7
185 225 120 101 130 140 140 140 165 270 340 340 150 115 100 140 130 242 240 230 340 340 340
21 19 7 7 7 7 7 7 7 21 19 19 7 7 7 7 7 21 21 21 19 19 19
22 25 14 19 21 31 31 31 31 52 71 71 168 188 188 188 228 287 287 287 302 302 302
Postoperative Left Eye Unoperated Survival 1 6 7 12 14 24 24 24 24 31 52 52 161 181 181 181 221 266 266 266 283 283 283
0.9 0.8 0.8 0.8 0.9 1.2 1.3 1.4 1.4 1.9 3.3 3.1 5.1 6.0 5.8 6.9 6.8 7.3 8.0 7.4 6.8 7.8 6.5
Right Eye Enucleated 0.8 0.9 0.7 0.7 0.7 1.0 1.1 1.0 0.9 1.4 2.6 2.6 5.0 4.8 4.3 5.2 6.7 6.9 6.4 4.7 6.1 6.9 5.3
Difference (left-right) 0.1 —0.1 0.1 0.1 0.2 0.2 0.2 0.4 0.5 0.5 0.7 1.1 0.1 1.2 1.5 1.7 0.1 0.4 1.6 2.7 0.7 0.9 1.2
TABLE 3 APPROXIMATE ORBITAL VOLUMES IN GROWING RABBITS AFTER EXENTERATION OF THE RIGHT ORBIT WITH A POSTOPERATIVE SURVIVAL OF 177 TO 2 7 4 DAYS
Animal No. 1-7 1-10 1-9 1-5 1-3 1-1
Weight at Age at Surgery Surgery (ing) 1250 1100 1250 1350 1100 1100
42 42 42 42 42 42
Days Age at Death
Volume in ml Postoperative Left Orbit Unoperated Survival
219 288 288 316 316 316
During the postoperative period, the ani mals were observed periodically. They were weaned at six to eight weeks of age. The postoperative survival ranged from one to 283 days. Immediately after death, the head was severed from the body and a portion of
177 246 246 274 274 274
5.1 6.0 6.0 5.6 5.5 5.9
Right Orbit Exenterated 4.3 4.0 3.9 4.6 4.4 4.2
Difference (left-right) 0.8 2.0 2.1 1.0 1.1 1.7
the soft tissues was resected. In selected in stances, the contents of orbits that had been previously operated on were removed and fixed in 10% formalin for histologie study. The heads were then fixed in 70% ethyl al cohol. Subsequently, the skulls were cleaned
790
AMERICAN JOURNAL OF OPHTHALMOLOGY
NOVEMBER, 1970
by boiling in water to which a detergent had been added. Lateral, frontal and dorsal view photo graphs of the heads were taken prior to death (Fig. 1) and anterior, posterior, dorsal and ventral views were taken of the skulls (Fig. 2 ) , the waxed orbits (Fig. 3) and the orbits with the imprints (Fig. 4 ) . Dorsoventral and posteroanterior (Fig. 2-E) roentgenographic views were taken of representa tive skulls. Although an attempt was made to obtain comparable views, this was not always possible. After the skulls were thoroughly cleaned, the openings of the orbital walls and rims were sealed with wax to simulate the intact orbit in the living rabbit (Fig. 3). Elastic rubber-base material (Permlastic) was used to make imprints of the orbit. The orbital volume was determined from the net weight and specific gravity of the imprint. RESULTS GROSS OBSERVATIONS
Living animals—Immediately after evis ceration, enucleation, or exenteration the orbital region on the operated side was noted to be flatter than the intact side (Fig. 1-C). Frequently, the eyelids cohered and at times there were various amounts of mucoid secre tion. Dissected skulls—The findings on the dis sected skulls were more apparent than those seen on the living animals and were limited to the orbital and periorbital regions. Gener ally, the right orbit (evisceration, enucle-
Fig. 1. (Sarnat and Shanedling). Antemortem photographs of face of rabbit number 1-9 which was killed after a postoperative survival of 246 days. (A) Left lateral view. Unoperated left orbit had a postmortem volume of 6.0 ml. (B) Right lateral view. The right orbit which was exenterated at 42 days of age and had a postmortem volume of 3.9 ml. (C) Frontal view. Note the lesser fullness of the right orbital and periorbital areas as com pared to the unoperated left side.
VOL. 70, NO. 5
ORBITAL VOLUME
791
Fig. 2 (Sarnat and Shanedling). Photographs and roentgenograph of skull of rabbit number 3-1 which was killed after a postoperative survival of 266 days. (A) Left lateral view. Unoperated left orbit has a volume of 8.0 ml. (B) Right lateral view. The right orbit from which the eye was enucleated at 21 days of age has a volume of 6.4 ml. Note in comparing the unoperated left orbit and the operated right orbit, that the former is larger, the circumference of the orbital rim is greater, the supraorbital process is larger and higher, and the zygomatic arch is longer. (C and D) Anterior and posterior views. (E) Posteroanterior view roentgenograph. Note that the supraorbital process, S, is higher and larger on the unoperated side. (F) Dorsal and (G) ventral views. The snout deviates toward the operated on right side. (F) Frontal bone. FN, frontonasal suture; L, lacrimal bone; 1, lateral lamina of pterygoid bone; M, maxilla; Mo, premolars and molars; MR, molar root area; O, optic foramen; OF, orbital part of frontal bone; OM, orbital process of maxilla; PSA, anterior and PSP, posterior supraorbital processes of frontal bone; PZ, zygomatic process of squamosal; PZM, zygomatic process of maxilla; S, supraorbital process of frontal bone; T, temporal fossa; Z, zygomatic arch.
792
AMERICAN JOURNAL OF OPHTHALMOLOGY
NOVEMBER, 1970
Fig. 3 (Sarnat and Shanedling). Photographs of dissected skull of rabbit number 4-5 which had a postoperative survival of 52 days. The openings of the orbital walls and orbital rim were sealed with wax and the periorbital areas were reinforced with wax. Plastic rubber-base imprints were made of the orbits and the volumes determined. Note that the left unoperated orbit (volume 3.7 ml) in A is larger than the right orbit (volume 2.6 ml) in B which had the eye enucleated at 19 days of age. (C) Dorsal and (D) ventral views. (W) waxed areas.
VOL. 70, NO. 5
ORBITAL VOLUME
ation, exenteration) was smaller, the supraorbital process was less developed and not as high, and the zygomatic arch was shorter than the left (unoperated) orbit (Figs. 2, 3, and 4). In several animals there was a devia tion of the snout toward the side of the oper ated orbit (Figs. 2-F and G). Histologie findings—Microscopic exam ination showed that tissue removed from the exenterated orbit was composed principally of fibrous and fatty tissue, as well as lesser amounts of muscle, lacrimal gland, and lymphoid tissue. The tissues in the orbits in which an enucleation had been done were similar to those from the exenterated orbits except for the presence of extraocular mus cle and a marked hyperplasia of the lacrimal glands. The tissues in the orbit in which an evisceration had been done showed the cor nea and sciera with mural fibrosis and a thin lining of degenerated tissue, no intraocular tissue, an atrophie optic nerve, slightly atrophie and fibrotic extraocular muscles, minimal chronic conjunctivitis and foci of chronic interstitial inflammation of the lacri mal glands. VOLUMETRIC DETERMINATIONS
Evisceration—The volumes of the orbits after evisceration of the right eyes (Table 1) ranged from 0.8 ml at 22 days of age with a 15-day postoperative survival (animal No. 611) to 7.5 ml at 287 days of age with a 266day postoperative survival (animal No. 2-1). The volumes of the orbits of the intact eye (left) ranged from 1.0 ml at 22 days of age (animal No. 6-11) to 7.8 ml at 287 days of age (animal No. 2-4). Of greater interest
J
793
was that in each animal the volume of the right orbit (evisceration) was always less than the left orbit (no surgical procedure) with two exceptions (animal Nos. 2-2, 5-5) in which there were no differences. Gener ally, the difference in orbital volumes was greater in the animals with a longer postop erative survival. Enucleation—The volumes of the orbits after enucleation of the right eyes (Table 2) ranged from 0.7 ml at 14 days of age with a seven-day postoperative survival (animal No. 6-21) to 6.9 ml at 302 days of age with a 283-day postoperative survival (animal No. 4-3). The volumes of the orbits of the intact eye (left) ranged from 0.8 ml at 14 days of age (animal No. 6-21) to 8.0 ml at 287 days of age (animal No. 3-1). Of greater interest was that in each animal the volume of the right orbit (enucleation), with one exception (animal No. 4-4), was always less than on the left orbit (no surgical procedure). Gen erally, the difference in orbital volumes was greater in the animals with a longer postop erative survival. Exenteration—The volumes of the right orbits after exenteration (Table 3) ranged from 3.9 ml at 288 days of age with a 246day postoperative survival (animal No. 1-9) to 4.6 ml at 316 days of age with a 274-day postoperative survival (animal No. 1-5). The volumes of the orbits in which the con tents (left) had not been disturbed ranged from 5.1 ml at 219 days of age (animal No. 1-7) to 6.0 ml at 288 days of age (animal Nos. 1-9, 1-10). The difference in orbital volumes between the intact and operated on sides was greatest at 288 days of age.
//fit
Fig. 4 (Sarnat and Shanedling). Photographs of dissected skull and orbital imprints of rabbit number 3-1 which was killed after a postoperative survival of 266 days. The right eye was enucleated at 21 days of age. The approximate orbital volumes were 6.4 ml for the right eye (the eye enucleated), and 8.0 ml for the left (unoperated). Elastic rubber-base imprints in place in A, left orbit, and B, right orbit. Paper clip facilitates removal of the imprint. (C) Imprints of the left and right orbits from the depth view. (D) Imprints of the left and right orbits from the superior view. Note difference in size, some small bubbles on the surface, b, where the imprint was trimmed. L, left; R, right; P, posterior; A, anterior (photographs C-left and D-left are reprinted from Sarnat 2 ).
794
AMERICAN JOURNAL OF OPHTHALMOLOGY
NOVEMBER, 1970
TABLE 4 AVERAGE OF RIGHT (OPERATED) ORBITAL VOLUMES AFTER EVISCERATION, ENUCLEATION AND EXENTERATION GROUPED ACCORDING TO POSTOPERATIVE SURVIVAL
(in ml)
Evisceration Post operative Survival (in days)
Enucleation
Average Average of Age at No. Right Opera- Animals Orbital tion Volumes (in days)
1-50 151-1 151-250 251-350
1.27 — 5.74 6.35
7
Average Average Average of Age at No. No. Ave-age Age at Right Opera- Animals of Right Opera Animals Orbital tion Orbital tion Volumes (in days) Volumes (in days) 0.92 2.35 5.20 6.05
6 0 5 11
12 20
Statistical evaluation—Figures 5-A and B show the relationship of orbital volumes to survival times of eviscerated right eye and paired unoperated left eye for the 22 rabbits (Table 1 ) . The equations of least square regression lines and correlation coefficients were determined. Eviscerated right eye orbi tal volumes = 4.83 + 0.0203 (time - 190.), r — 0.94. Unoperated left eye orbital vol umes = 5.19 + 0.0210 ( t i m e - 1 9 0 . ) , r = 0.94. Figure 5-C shows the differences beTABLE 5 AVERAGE OF LEFT (UNOPERATED) ORBITAL VOLUMES AFTER EVISCERATION, ENUCLEATION, AND EXENTERATION GROUPED ACCORDING TO POSTOPERATIVE SURVIVAL (IN ML)
Postoperative Survival (in days)
Evis ceration
Enu cleation
Exenter ation
1-50 51-150 151-250 251-350
1.50
1.14 3.50 6.12 7.30
— —
—
6.12 6.78
Exenteration
5.70 5.66
11 19 7 20
10 2 5 6
.—
4.07 4.40
42 42
0 0 3 3
tween the orbital volumes of unoperated left eye and eviscerated right eye plotted against survival time (Table 1 ) . Similarly, Figures 6-A and B shows the relationship of orbital volumes to survival times of enucleated right eye and paired un operated left eye for the 23 rabbits (Table 2 ) . T h e equations of least square regression lines and correlation coefficients were deter mined. Enucleated right eye orbital vol umes = 3.33 + 0.020S (time - 124.), r = 0.96. Unoperated left eye orbital volume = 4.03 + 0.0242 (time - 124.), r = 0.97). Figure 6-C shows the difference between orbital volumes of unoperated left eye and enucleated right eye plotted against survival time (Table 2 ) . I n addition, the tabular material on orbital volume after evisceration, enucleation, and exenteration (Tables 1-3) was treated ac cording to four age groups with a progres sively longer postoperative survival. There was a marked deceleration of orbital growth after 250 days of age (Tables 4 and 5 ) . T h e
Fig. 5 (Sarnat and Shanedling). (A) Volume of right orbit after evisceration of eye in 22 rabbits plotted against postoperative survival time. (B) Volume of paired left orbit (unoperated eye) of 22 rabbits in A plotted against postoperative survival time. (C) Difference of orbital volumes (left-right) of unoperated left eye and eviscerated right eye in 22 rabbits of A and B plotted against postoperative survival time.
795
ORBITAL VOLUME
VOL. 70, NO. S
8.0 r o υ
RIGHT EYE EVISCERATED 7 DAYS OF AGE - o l9(or)2l DAYS OF AGE- ·
-
^6.0
o
•
o
•·
:
•
f
§
g4.0 h 00 DC O
1 (3
o
2.0 -
o
°o
DC i
8.0
1
I
1
LEFT EYE UNOPERATED ON RIGHT EYE EVISCERATED 7-21 DAYS OF AGE
o ^6.0
»
·
i ^4.0 o μ.2.0
fei
J
1.0 r
I
L
LEFT EYE UNOPERATED ON RIGHT EYE EVISCERATED 7-21 DAYS OF AGE
-
•
-
•
-
···
^-^0.5
• •
-
fco
-
•
··
- ·
• •
•
·
•
·
· · • .
1
1
1
1
1
"
I
'
60 120 180 240 POSTOPERATIVE SURVIVAL (DAYS)
•1
·
1
300
796
AMERICAN JOURNAL OF OPHTHALMOLOGY
8.0
-
6 0
I·
iJ 4 . 0
51 O
RIGHT EYE ENUCLEATED 7 DAYS OF AGE - o I9for)2l DAYS OF AGE - ·
• •
0
o
o o
· • •
•
o
• •
2.0 -
1
8.0
NOVEMBER, 1970
1
t
1
1
'
'
I
'
LEFT EYE UNOPERATED ON RIGHT EYE ENUCLEATED 7-21 DAYS OF AGE
Uj 6.0
1 É 4.0
5
2.0
Ü3 J_
3.0 r
ë$£
_i_
_i_
LEFT EYE UNOPERATED ON RIGHT EYE ENUCLEATED 7 - 2 1 DAYS OF AGE
^ 2 . 0
11
1.0 -
u. o QO
60 120 180 240 POSTOPERATIVE SURVIVAL (DAYS)
300
797
ORBITAL VOLUME
VOL. 70, NO. S
average right (operated) orbital volumes af ter evisceration, enucleation, and exentera tion all increased with age (Table 4 ) . The 251 to 350-day postoperative survival group was operated on at an average age of 20-42 days. Their average orbital volumes would probably have been less had they been oper ated on at an earlier average age such as 7-19 days as were the animals with a shorter aver age postoperative survival of 1-250 days. This statement is based on the premise that younger animals have more rapid orbital growth. Consequently, removal of orbital mass at an earlier age would have a greater decelerating effect upon orbital growth. In a similar analysis it was found that the average orbital volumes of the unoperated left side increased directly with age in the exenteration group (Table 5). The one ex ception was not believed to be significant. The average orbital volumes of the unoper ated left sides were always larger than the average orbital volumes of the operated on right sides. The average of the differences of orbital volumes between the left (unoperated) and right (operated) sides after evisceration, enucleation, and exenteration were also de termined according to postoperative survival (Table 6 ) . The findings were comparable to those above. DISCUSSION ANTEMORTEM OBSERVATIONS
In the rabbit, the bony orbit does not cover a considerable portion of the superior surface of the eyeball which projects about 12 mm beyond the rim of the supraorbital crest.7 The middle of the cornea, however,
TABLE 6 AVERAGE OF DIFFERENCES OF ORBITAL VOLUMES (UNOPERATED, LEFT, AND OPERATED, RIGHT) AFTER EVISCERATION, ENUCLEATION, AND EXENTERATION GROUPED ACCORDING TO POSTOPERATIVE SURVIVAL (IN ML)
Postoperative Survival (in days) 1-50 51-150 151-250 251-350
Evis ceration
Enu cleation
Exen teration
0.23
0.22 0.90 0.92 1.25
1.63 1.27
0.38 0.43
projects only 5 mm beyond the edge of the zygomatic arch. After evisceration, enucle ation, or exenteration the orbital area was flatter than that of the unoperated side. We could not differentiate with any degree of ac curacy the type of surgical procedure on the basis of the flatness. POSTMORTEM OBSERVATIONS
Evisceration—In this group of animals the difference in orbital volumes between the unoperated left eye side and the eviscerated right eye side generally became greater with a longer postoperative survival (Table 1). This was particularly apparent in those ani mals with a 280 to 283-day postoperative survival. There were, however, a number of varia tions. For instance, in a group of seven ani mals of the same litter, the right eyes were eviscerated at 19 days of age and the animals were killed at 299 or 302 days of age. The difference in volumes between the left and right orbits ranged from 0 to 0.9 ml. In ani mals Nos. 2-2 and 5-5 with postoperative survivals of 266 and 283 days, respectively,
Fig. 6 (Sarnat and Shanedling). (A) Volume of right orbit after enucleation of eye in 23 rabbits plotted against postoperative survival time. (B) Volume of paired left orbit (unoperated eye) of 23 rabbits in A plotted against postoperative survival time. (C) Difference of orbital volumes (left-right) of unoperated left eye and enucleated right eye in 23 rabbits of A and B plotted against postoperative survival time.
798
AMERICAN JOURNAL OF OPHTHALMOLOGY
after evisceration of the right eye, surpris ingly there was no difference between the volumes of the left and right orbits. In ani mal No. 6-9, with a postoperative survival of 151 days, the difference in volumes between the left and right orbits was 0.5 ml. This dif ference was equal to or greater than that in 11 out of 15 animals with a postoperative survival as long as 283 days. Enucleation—In this group of animals, the difference in orbital volumes between the unoperated left eye side and the enucleated right side generally became greater with a longer postoperative survival (Table 2). This was particularly apparent in those ani mals with a postoperative survival of 181 days or longer. There were, however, a number of varia tions. For instance, in one group of three an imals of the same litter (Nos. 3-3, 3-1, and 32) the right eye was enucleated at 21 days of age and the animals were killed at 287 days of age. The difference in volumes between the left and right orbits ranged from 0.4 to 2.7 ml. In another group of three animals of the same litter (Nos. 4-6, 4-3, and 4-7) the right eyes were enucleated at 19 days of age and the animals were killed at 302 days of age. Although these animals were operated on earlier and survived longer than the previous group, the difference in volumes between the left and right orbits ranged from 0.7 to only 1.2 ml. In animal No. 6-8, with a postoper ative survival of 221 days after enucleation of the right eye, the volume of the left orbit was 6.8 ml and the right orbit was 6.7 ml. By contrast, in animal No. 4-5, with a postoper ative survival of only 52 days, the difference in volumes between the left and right orbits was 1.1 ml. This was greater than that in five of 11 animals with a postoperative survival ranging from 161 to 283 days. In two of these five animals (Nos. 6-20 and 4-7) the difference in volumes was greater by only 0.1ml. ,,.,"■ Exenteration—In this group of animals, the difference in volumes between the unop-
NOVEMBER, 1970
erated left orbit and the exenterated right or bit ranged from 0.8 ml in animal No. 1-7, with a postoperative survival of 177 days, to 2.1 ml in animal No. 1-9, with a postopera tive survival of 246 days (Table 3). Ani mals with a postoperative survival of 274 days had a lesser difference in orbital volumes than those with a postoperative of 246 days. The explanation for this may be found after ex perimentation with a larger series. The petro latum-impregnated gauze strip which was removed one week postoperatively may have altered orbital growth in this group. The evis ceration and enucleation series did not have a gauze strip inserted. Comparison of orbital volumes—A com parison of the data of the orbital volumes af ter evisceration, enucleation, and exentera tion suggested a direct relationship between the lack of orbital mass and the subsequent lack of development of the orbit. There were, however, a number of individual ex ceptions and a certain amount of overlapping between the groups. Postoperative intraorbi tal scar tissue may have influenced orbital growth. Validity of volumetric determinations— The disadvantages and advantages of this method have been considered.2 The possibil ity of error is lessened when there are less or bital openings to be sealed, such as in the primate. The same person waxed the orbital openings and made the orbital imprints. He had no knowledge of the history of the ani mals. If any errors were made in sealing the orbital openings, such as at varying levels, they should have been comparable. Highly accurate measurements are not as much of an issue, however, as lack of bias between the right and left orbital measure ments. In the entire group of 51 experimen tal animals in which surgery was done on ei ther the right eye or orbit, this orbit, with three exceptions, was always smaller than the unoperated left orbit. In an unoperated group of 14 animals, the left orbit was larger than the right in four instances, equal to the right in three instances, and smaller than the
VOL. 70, NO. S
799
ORBITAL VOLUME
right in seven instances.2 Validity of unoperated orbit as control— The left unoperated side was used as a con trol for the right orbit in which an eviscera tion, enucleation, or exenteration was done. This was preferred to a comparison with lit ter-mates because of the variation in body weight and orbital size.2 With lessened orbital contents on the right side however, and with continued growth of the normal orbital contents (and pressure) on the left side, the interorbital septum might be expected to shift toward the operated right side. This is of particular interest since, in the rabbit, the eye not only fits closely in the orbit but also the adult volume is 15 times that of the newborn.8 Coulombre and Crelin9 found, after operating unilat erally on eyes of embryonic chicks, that the cartilaginous interorbital septum deviated toward the operated side. Even though the left orbit may be larger partly at the expense of the operated right orbit, and even though the left orbit may not be a true control, the findings do reflect the effects of unilateral surgical procedures in animals with a com mon interorbital septum. Orbital and facial growth—In this experi ment, postnatal increase in the volume of the orbit was decelerated after removal of vary ing amounts of the contents. Other local changes noted were a smaller and less ele vated supraorbital process and a shorter zy goma. Deviation of the facial skeleton to ward the side of the operated orbit was noted in several animals. This has been reported previously.3·5'9 Pfeiffer10 stated that "removal of the eye arrests the development of the orbit, and in deed leads to a contraction of it, or to a re duction of its capacity." Our findings were to the contrary. The orbital size, although smaller than on the unoperated side, became progressively larger in growing animals with a longer postoperative survival period. In other words, the orbit is not smaller, actu ally, but is smaller relatively to the unoper ated orbit.
SUMMARY
Postnatal volumetric growth of the orbit was studied in 51 New Zealand albino rab bits after evisceration, enucleation, or exen teration of the right orbit at seven to 42 days of age. The unoperated left side was used as a control. The postoperative survival time ranged from one to 283 days. A removable permanent elastic rubber-base imprint was made of the clean orbit. The volume was cal culated from the weight and specific gravity of the orbital imprint. After excision of orbital tissue, the orbit continued to increase in size but at a slower rate than the unoperated fellow orbit. Gener ally, there was a direct correlation between lack of intraorbital mass and lack of orbital growth. ACKNOWLEDGMENTS
We thank Dr. Frank J. Massey, Jr., School of Public Health, University of California Medical Center, Los Angeles, for his assistance in the statis tical evaluation and Dr. Irving Gault for developing the orbital imprints. REFERENCES
1. Sarnat, B. G., and Shanedling, P. D. : Postna tal growth of the orbit and upper face in rabbits after exenteration of the orbit. Arch. Ophth. 73: 829, 1965. 2. Sarnat, B. G. : The imprint method to deter mine orbital volume in the rabbit. Ophthalmologica 160:142, 1970. 3. Lesshaft, P. : Grundlagen der Theoretischen Anatomie. Leipzig, W. Hartmann, 1892, p. 99. 4. Thomson, W. E. : The determination of the in fluence of the eyeball on the growth of the orbit by experimental enucleation of one eye in young ani mals. Tr. Ophth. Soc. U. K. 21:258, 1901. 5. Wessely, K. : Über korrelationen des Wach stums (nach versuchen am auge). Zschr. Augenheilk. 43:654, 1920. 6. Kennedy, R. E. : The effect of early enucle ation on the orbit in animals and humans. Tr. Am. Ophth. Soc. 62:459, 1964. 7. Prince, J. H. (ed.) : The rabbit in eye re search. Springfield, 111., Charles C Thomas, 1964, p. xi. 8. Washburn, S. L., and Detwiler, S. R. : An ex periment bearing on the problems of physical an thropology. Am. J. Phys. Anthrop. 1:171t 1943. 9. Coulombre, A. J., and Crelin, E. S. : Role of the developing eye in the morphogenesis of the avian skull. Am. J. Phys. Anthrop. 16:25, 1958. 10. Pfeiffer, R. L. : The effect of -enucleation on the orbit Tr. Am. Acad. Ophth. 49:236, 1945.
AND P H I L I P D. SHANEDLING,
M.D.
Los Angeles, California
Shape and size of the orbit result from the balance of a number of genetic or environ mental factors which may function on a sys temic, regional, or local basis.1 We were in terested in knowing whether, volumetrically, there was a direct correlation between lack of intraorbital tissue and lack of orbital growth. The imprint method to determine orbital volume was used.2 In three series of young growing rabbits, varying amounts of intraorbital tissue were removed unilaterally. In one group, the in traocular contents were extracted but not the cornea and sciera (evisceration). In a second group, the eye was enucleated. In a third se ries, previously reported but included here for comparison, the contents of the orbit were removed (exenteration). 1 The orbital volumes were determined after different pe riods of postoperative survival. We have found no such report of comparable work in the literature.
face to the outer border of the orbit, the cur vature of the cranium was greater and the cranium was asymmetric on the operated on side. Thomson 4 performed unilateral enucleation in six rabbits at about 20 days of age. Five to eight months later he found that length, height, and depth of the bony orbit were diminished with resulting facial de formity. Wessely5 aspirated the lens in 18 newborn rabbits and two to eight months later noted that both the eye and orbit were smaller. Kennedy 6 enucleated the eyes in growing rabbits and kittens and confirmed earlier reports. These studies were based on linear measurements. Previously, we exenterated the right orbit in rabbits at six weeks of age. 1 After a postoperative survival of eight to nine months, the average volume of the right exenterated orbit (4.2 ml) was less than the average volume of the unoperated left orbit (5.7 ml). MATERIALS AND METHODS
REVIEW OF LITERATURE
Gudden,3 in 1876, reported the postnatal relationship between the eye and size of the orbit in growing mammals. Popow 3 enucle ated the eyeball in the dog, cat, and pig two to three weeks after birth and killed the ani mals two months later. The orbit was signifi cantly smaller on the operated on side and the distance was less from the midline of the From the Departments of Plastic Surgery (Dr. Sarnat), and Ophthalmology (Dr. Shanedling), Division of Surgery and Research Institute, Ce dars-Sinai Medical Center, and Division of Oral Biology, School of Dentistry, University of Califor nia, Los Angeles, California. This study was sup ported in part by Research Grant HD 00179 from the National Institute of Child Health and Human De velopment USPHS Grant RR 05468. Reprint requests to Bernard G. Sarnat, M.D., 435 North Roxbury Drive, Beverly Hills, California 90210. 787
Fifty-one New Zealand albino rabbits were obtained from nine litters (Tables 13). The animals weighed from 100 to 1350 g and ranged in age from seven to 42 days at the time they were operated on. In the seven- to 21-day-old animals, two drops of 0.5% tetracaine HC1 were instilled into the conjunctival sac. Then approxi mately 0.25 ml of a solution of 1% procaine HC1 was injected into the upper and lower eyelids and retrobulbarly for local anesthe sia. In addition, in the 42-day-old animals an injection was given into the marginal ear vein of a 1% aqueous solution of pentobarbital sodium (40mg/kg). Each rabbit was secured on an operating board with the right side of the face ex posed. This was cleansed with an antiseptic solution and the area draped. After injec tion of the local anesthetic agent the eyelids
AMERICAN JOURNAL OF OPHTHALMOLOGY
788
were separated manually. The surgical proce dure was always performed on the right eye. Evisceration—In one group of 22 rabbits, an evisceration of the right globe was done (Table 1). A keratome incision was made at the limbus into the anterior chamber at the 9 o'clock meridian. One 6-0 plain catgut suture was inserted through the anterior and pos terior lips of the incision. The incision was then enlarged circumferentially approxi mately 6.0 mm with corneal scissors. The intraocular contents were completely evacu ated. The incision was then closed with in terrupted 6-0 plain catgut sutures and the eyelids approximated with interrupted 6-0 black silk sutures. Enucleation—In a second group of 23 rabbits, an enucleation of the right eye was done (Table 2 ) . Black silk traction sutures were placed near each margin of the upper and lower eyelids and sometimes through the
NOVEMBER, 1970
nictitating membrane. A peritomy was per formed. The recti muscles were isolated and cut free of the scierai insertions. The bulb was then delivered and the remaining mus cles and extraocular structures were cut and the bulb enucleated. Bleeding was controlled with local pressure. The capsule and con junctiva were closed with mattress sutures of 6-0 plain catgut. Interrupted 6-0 plain catgut sutures were used to reinforce the first row of sutures. The eyelids were ap proximated with 6-0 black silk sutures. Exenteration—In a third group of six rabbits an exenteration of the right orbit was performed (Table 3). The orbit was then packed with petrolatum-impregnated gauze strips and the eyelids sutured with 6-0 black silk. The gauze pack was removed one week later. Controls—In each animal the left orbit was used as a control for the operated on right side.
TABLE 1 APPROXIMATE ORBITAL VOLUMES IN GROWING RABBITS AFTER EVISCERATION OF THE RIGHT EYE WITH A POSTOPERATIVE SURVIVAL OF 15 TO 2 8 3 DAYS
Days
Animal No.
Weight at Surgery (ing)
Age at Surgery
Age at Death
6-11 6-1 6-2 6-15 6-3 6-12 6-9 6-14 6-10 2-3 5-3 2-2 2-1 2-5 2-4 5-7 5-5 5-4 5-6 5-8 5-1 5-2
130 141 120 130 155 120 140 115 150 190 230 205 170 210 190 340 230 340 230 340 230 230
7 7 7 7 7 7 7 7 7 21 19 21 21 21 21 19 19 19 19 19 19 19
22 28 32 37 42 45 158 186 186 248 253 287 287 287 287 299 302 302 302 302 302 302
Volume in ml Postoperative Left Eye Unoperated Survival 15 21 25 30 35 38 151 179 179 227 234 266 266 266 266 280 283 283 283 283 283 283
1.0 1.4 1.3 1.7 2.0 1.6 4.3 7.4 6.4 5.9 6.6 6.2 7.6 6.2 7.8 7.5 6.8 5.9 6.5 6.6 6.8 6.7
Right Eye Eviscerated
Difference (left-right)
0.8 1.1 1.0 1.5 1.8 1.4 3.8 7.1 6.0 5.6 6.2 6.2 7.5 5.8 7.3 6.8 6.8 5.5 6.0 6.0 6.2 5.8
0.2 0.3 0.3 0.2 0.2 0.2 0.5 0.3 0.4 0.3 0.4 0 0.1 0.4 0.5 0.7 0 0.4 0.5 0.6 0.6 0.9
ORBITAL VOLUME
VOL. 70, NO. 5
789
TABLE 2 APPROXIMATE ORBITAL VOLUMES IN GROWING RABBITS AFTER ENUCLEATION OF THE RIGHT EYE WITH A POSTOPERATIVE SURVIVAL OF ONE TO 2 8 3 DAYS
Volume in ml
Days
Animal No.
Weight at Surgery (ing)
Age at Surgery
Age at Death
3-5 4-4 6-21 6-17 6-16 6-4 6-5 6-6 6-7 3-4 4-1 4-5 6-18 6-20 6-22 6-19 6-8 3-3 3-1 3-2 4-6 4-3 4-7
185 225 120 101 130 140 140 140 165 270 340 340 150 115 100 140 130 242 240 230 340 340 340
21 19 7 7 7 7 7 7 7 21 19 19 7 7 7 7 7 21 21 21 19 19 19
22 25 14 19 21 31 31 31 31 52 71 71 168 188 188 188 228 287 287 287 302 302 302
Postoperative Left Eye Unoperated Survival 1 6 7 12 14 24 24 24 24 31 52 52 161 181 181 181 221 266 266 266 283 283 283
0.9 0.8 0.8 0.8 0.9 1.2 1.3 1.4 1.4 1.9 3.3 3.1 5.1 6.0 5.8 6.9 6.8 7.3 8.0 7.4 6.8 7.8 6.5
Right Eye Enucleated 0.8 0.9 0.7 0.7 0.7 1.0 1.1 1.0 0.9 1.4 2.6 2.6 5.0 4.8 4.3 5.2 6.7 6.9 6.4 4.7 6.1 6.9 5.3
Difference (left-right) 0.1 —0.1 0.1 0.1 0.2 0.2 0.2 0.4 0.5 0.5 0.7 1.1 0.1 1.2 1.5 1.7 0.1 0.4 1.6 2.7 0.7 0.9 1.2
TABLE 3 APPROXIMATE ORBITAL VOLUMES IN GROWING RABBITS AFTER EXENTERATION OF THE RIGHT ORBIT WITH A POSTOPERATIVE SURVIVAL OF 177 TO 2 7 4 DAYS
Animal No. 1-7 1-10 1-9 1-5 1-3 1-1
Weight at Age at Surgery Surgery (ing) 1250 1100 1250 1350 1100 1100
42 42 42 42 42 42
Days Age at Death
Volume in ml Postoperative Left Orbit Unoperated Survival
219 288 288 316 316 316
During the postoperative period, the ani mals were observed periodically. They were weaned at six to eight weeks of age. The postoperative survival ranged from one to 283 days. Immediately after death, the head was severed from the body and a portion of
177 246 246 274 274 274
5.1 6.0 6.0 5.6 5.5 5.9
Right Orbit Exenterated 4.3 4.0 3.9 4.6 4.4 4.2
Difference (left-right) 0.8 2.0 2.1 1.0 1.1 1.7
the soft tissues was resected. In selected in stances, the contents of orbits that had been previously operated on were removed and fixed in 10% formalin for histologie study. The heads were then fixed in 70% ethyl al cohol. Subsequently, the skulls were cleaned
790
AMERICAN JOURNAL OF OPHTHALMOLOGY
NOVEMBER, 1970
by boiling in water to which a detergent had been added. Lateral, frontal and dorsal view photo graphs of the heads were taken prior to death (Fig. 1) and anterior, posterior, dorsal and ventral views were taken of the skulls (Fig. 2 ) , the waxed orbits (Fig. 3) and the orbits with the imprints (Fig. 4 ) . Dorsoventral and posteroanterior (Fig. 2-E) roentgenographic views were taken of representa tive skulls. Although an attempt was made to obtain comparable views, this was not always possible. After the skulls were thoroughly cleaned, the openings of the orbital walls and rims were sealed with wax to simulate the intact orbit in the living rabbit (Fig. 3). Elastic rubber-base material (Permlastic) was used to make imprints of the orbit. The orbital volume was determined from the net weight and specific gravity of the imprint. RESULTS GROSS OBSERVATIONS
Living animals—Immediately after evis ceration, enucleation, or exenteration the orbital region on the operated side was noted to be flatter than the intact side (Fig. 1-C). Frequently, the eyelids cohered and at times there were various amounts of mucoid secre tion. Dissected skulls—The findings on the dis sected skulls were more apparent than those seen on the living animals and were limited to the orbital and periorbital regions. Gener ally, the right orbit (evisceration, enucle-
Fig. 1. (Sarnat and Shanedling). Antemortem photographs of face of rabbit number 1-9 which was killed after a postoperative survival of 246 days. (A) Left lateral view. Unoperated left orbit had a postmortem volume of 6.0 ml. (B) Right lateral view. The right orbit which was exenterated at 42 days of age and had a postmortem volume of 3.9 ml. (C) Frontal view. Note the lesser fullness of the right orbital and periorbital areas as com pared to the unoperated left side.
VOL. 70, NO. 5
ORBITAL VOLUME
791
Fig. 2 (Sarnat and Shanedling). Photographs and roentgenograph of skull of rabbit number 3-1 which was killed after a postoperative survival of 266 days. (A) Left lateral view. Unoperated left orbit has a volume of 8.0 ml. (B) Right lateral view. The right orbit from which the eye was enucleated at 21 days of age has a volume of 6.4 ml. Note in comparing the unoperated left orbit and the operated right orbit, that the former is larger, the circumference of the orbital rim is greater, the supraorbital process is larger and higher, and the zygomatic arch is longer. (C and D) Anterior and posterior views. (E) Posteroanterior view roentgenograph. Note that the supraorbital process, S, is higher and larger on the unoperated side. (F) Dorsal and (G) ventral views. The snout deviates toward the operated on right side. (F) Frontal bone. FN, frontonasal suture; L, lacrimal bone; 1, lateral lamina of pterygoid bone; M, maxilla; Mo, premolars and molars; MR, molar root area; O, optic foramen; OF, orbital part of frontal bone; OM, orbital process of maxilla; PSA, anterior and PSP, posterior supraorbital processes of frontal bone; PZ, zygomatic process of squamosal; PZM, zygomatic process of maxilla; S, supraorbital process of frontal bone; T, temporal fossa; Z, zygomatic arch.
792
AMERICAN JOURNAL OF OPHTHALMOLOGY
NOVEMBER, 1970
Fig. 3 (Sarnat and Shanedling). Photographs of dissected skull of rabbit number 4-5 which had a postoperative survival of 52 days. The openings of the orbital walls and orbital rim were sealed with wax and the periorbital areas were reinforced with wax. Plastic rubber-base imprints were made of the orbits and the volumes determined. Note that the left unoperated orbit (volume 3.7 ml) in A is larger than the right orbit (volume 2.6 ml) in B which had the eye enucleated at 19 days of age. (C) Dorsal and (D) ventral views. (W) waxed areas.
VOL. 70, NO. 5
ORBITAL VOLUME
ation, exenteration) was smaller, the supraorbital process was less developed and not as high, and the zygomatic arch was shorter than the left (unoperated) orbit (Figs. 2, 3, and 4). In several animals there was a devia tion of the snout toward the side of the oper ated orbit (Figs. 2-F and G). Histologie findings—Microscopic exam ination showed that tissue removed from the exenterated orbit was composed principally of fibrous and fatty tissue, as well as lesser amounts of muscle, lacrimal gland, and lymphoid tissue. The tissues in the orbits in which an enucleation had been done were similar to those from the exenterated orbits except for the presence of extraocular mus cle and a marked hyperplasia of the lacrimal glands. The tissues in the orbit in which an evisceration had been done showed the cor nea and sciera with mural fibrosis and a thin lining of degenerated tissue, no intraocular tissue, an atrophie optic nerve, slightly atrophie and fibrotic extraocular muscles, minimal chronic conjunctivitis and foci of chronic interstitial inflammation of the lacri mal glands. VOLUMETRIC DETERMINATIONS
Evisceration—The volumes of the orbits after evisceration of the right eyes (Table 1) ranged from 0.8 ml at 22 days of age with a 15-day postoperative survival (animal No. 611) to 7.5 ml at 287 days of age with a 266day postoperative survival (animal No. 2-1). The volumes of the orbits of the intact eye (left) ranged from 1.0 ml at 22 days of age (animal No. 6-11) to 7.8 ml at 287 days of age (animal No. 2-4). Of greater interest
J
793
was that in each animal the volume of the right orbit (evisceration) was always less than the left orbit (no surgical procedure) with two exceptions (animal Nos. 2-2, 5-5) in which there were no differences. Gener ally, the difference in orbital volumes was greater in the animals with a longer postop erative survival. Enucleation—The volumes of the orbits after enucleation of the right eyes (Table 2) ranged from 0.7 ml at 14 days of age with a seven-day postoperative survival (animal No. 6-21) to 6.9 ml at 302 days of age with a 283-day postoperative survival (animal No. 4-3). The volumes of the orbits of the intact eye (left) ranged from 0.8 ml at 14 days of age (animal No. 6-21) to 8.0 ml at 287 days of age (animal No. 3-1). Of greater interest was that in each animal the volume of the right orbit (enucleation), with one exception (animal No. 4-4), was always less than on the left orbit (no surgical procedure). Gen erally, the difference in orbital volumes was greater in the animals with a longer postop erative survival. Exenteration—The volumes of the right orbits after exenteration (Table 3) ranged from 3.9 ml at 288 days of age with a 246day postoperative survival (animal No. 1-9) to 4.6 ml at 316 days of age with a 274-day postoperative survival (animal No. 1-5). The volumes of the orbits in which the con tents (left) had not been disturbed ranged from 5.1 ml at 219 days of age (animal No. 1-7) to 6.0 ml at 288 days of age (animal Nos. 1-9, 1-10). The difference in orbital volumes between the intact and operated on sides was greatest at 288 days of age.
//fit
Fig. 4 (Sarnat and Shanedling). Photographs of dissected skull and orbital imprints of rabbit number 3-1 which was killed after a postoperative survival of 266 days. The right eye was enucleated at 21 days of age. The approximate orbital volumes were 6.4 ml for the right eye (the eye enucleated), and 8.0 ml for the left (unoperated). Elastic rubber-base imprints in place in A, left orbit, and B, right orbit. Paper clip facilitates removal of the imprint. (C) Imprints of the left and right orbits from the depth view. (D) Imprints of the left and right orbits from the superior view. Note difference in size, some small bubbles on the surface, b, where the imprint was trimmed. L, left; R, right; P, posterior; A, anterior (photographs C-left and D-left are reprinted from Sarnat 2 ).
794
AMERICAN JOURNAL OF OPHTHALMOLOGY
NOVEMBER, 1970
TABLE 4 AVERAGE OF RIGHT (OPERATED) ORBITAL VOLUMES AFTER EVISCERATION, ENUCLEATION AND EXENTERATION GROUPED ACCORDING TO POSTOPERATIVE SURVIVAL
(in ml)
Evisceration Post operative Survival (in days)
Enucleation
Average Average of Age at No. Right Opera- Animals Orbital tion Volumes (in days)
1-50 151-1 151-250 251-350
1.27 — 5.74 6.35
7
Average Average Average of Age at No. No. Ave-age Age at Right Opera- Animals of Right Opera Animals Orbital tion Orbital tion Volumes (in days) Volumes (in days) 0.92 2.35 5.20 6.05
6 0 5 11
12 20
Statistical evaluation—Figures 5-A and B show the relationship of orbital volumes to survival times of eviscerated right eye and paired unoperated left eye for the 22 rabbits (Table 1 ) . The equations of least square regression lines and correlation coefficients were determined. Eviscerated right eye orbi tal volumes = 4.83 + 0.0203 (time - 190.), r — 0.94. Unoperated left eye orbital vol umes = 5.19 + 0.0210 ( t i m e - 1 9 0 . ) , r = 0.94. Figure 5-C shows the differences beTABLE 5 AVERAGE OF LEFT (UNOPERATED) ORBITAL VOLUMES AFTER EVISCERATION, ENUCLEATION, AND EXENTERATION GROUPED ACCORDING TO POSTOPERATIVE SURVIVAL (IN ML)
Postoperative Survival (in days)
Evis ceration
Enu cleation
Exenter ation
1-50 51-150 151-250 251-350
1.50
1.14 3.50 6.12 7.30
— —
—
6.12 6.78
Exenteration
5.70 5.66
11 19 7 20
10 2 5 6
.—
4.07 4.40
42 42
0 0 3 3
tween the orbital volumes of unoperated left eye and eviscerated right eye plotted against survival time (Table 1 ) . Similarly, Figures 6-A and B shows the relationship of orbital volumes to survival times of enucleated right eye and paired un operated left eye for the 23 rabbits (Table 2 ) . T h e equations of least square regression lines and correlation coefficients were deter mined. Enucleated right eye orbital vol umes = 3.33 + 0.020S (time - 124.), r = 0.96. Unoperated left eye orbital volume = 4.03 + 0.0242 (time - 124.), r = 0.97). Figure 6-C shows the difference between orbital volumes of unoperated left eye and enucleated right eye plotted against survival time (Table 2 ) . I n addition, the tabular material on orbital volume after evisceration, enucleation, and exenteration (Tables 1-3) was treated ac cording to four age groups with a progres sively longer postoperative survival. There was a marked deceleration of orbital growth after 250 days of age (Tables 4 and 5 ) . T h e
Fig. 5 (Sarnat and Shanedling). (A) Volume of right orbit after evisceration of eye in 22 rabbits plotted against postoperative survival time. (B) Volume of paired left orbit (unoperated eye) of 22 rabbits in A plotted against postoperative survival time. (C) Difference of orbital volumes (left-right) of unoperated left eye and eviscerated right eye in 22 rabbits of A and B plotted against postoperative survival time.
795
ORBITAL VOLUME
VOL. 70, NO. S
8.0 r o υ
RIGHT EYE EVISCERATED 7 DAYS OF AGE - o l9(or)2l DAYS OF AGE- ·
-
^6.0
o
•
o
•·
:
•
f
§
g4.0 h 00 DC O
1 (3
o
2.0 -
o
°o
DC i
8.0
1
I
1
LEFT EYE UNOPERATED ON RIGHT EYE EVISCERATED 7-21 DAYS OF AGE
o ^6.0
»
·
i ^4.0 o μ.2.0
fei
J
1.0 r
I
L
LEFT EYE UNOPERATED ON RIGHT EYE EVISCERATED 7-21 DAYS OF AGE
-
•
-
•
-
···
^-^0.5
• •
-
fco
-
•
··
- ·
• •
•
·
•
·
· · • .
1
1
1
1
1
"
I
'
60 120 180 240 POSTOPERATIVE SURVIVAL (DAYS)
•1
·
1
300
796
AMERICAN JOURNAL OF OPHTHALMOLOGY
8.0
-
6 0
I·
iJ 4 . 0
51 O
RIGHT EYE ENUCLEATED 7 DAYS OF AGE - o I9for)2l DAYS OF AGE - ·
• •
0
o
o o
· • •
•
o
• •
2.0 -
1
8.0
NOVEMBER, 1970
1
t
1
1
'
'
I
'
LEFT EYE UNOPERATED ON RIGHT EYE ENUCLEATED 7-21 DAYS OF AGE
Uj 6.0
1 É 4.0
5
2.0
Ü3 J_
3.0 r
ë$£
_i_
_i_
LEFT EYE UNOPERATED ON RIGHT EYE ENUCLEATED 7 - 2 1 DAYS OF AGE
^ 2 . 0
11
1.0 -
u. o QO
60 120 180 240 POSTOPERATIVE SURVIVAL (DAYS)
300
797
ORBITAL VOLUME
VOL. 70, NO. S
average right (operated) orbital volumes af ter evisceration, enucleation, and exentera tion all increased with age (Table 4 ) . The 251 to 350-day postoperative survival group was operated on at an average age of 20-42 days. Their average orbital volumes would probably have been less had they been oper ated on at an earlier average age such as 7-19 days as were the animals with a shorter aver age postoperative survival of 1-250 days. This statement is based on the premise that younger animals have more rapid orbital growth. Consequently, removal of orbital mass at an earlier age would have a greater decelerating effect upon orbital growth. In a similar analysis it was found that the average orbital volumes of the unoperated left side increased directly with age in the exenteration group (Table 5). The one ex ception was not believed to be significant. The average orbital volumes of the unoper ated left sides were always larger than the average orbital volumes of the operated on right sides. The average of the differences of orbital volumes between the left (unoperated) and right (operated) sides after evisceration, enucleation, and exenteration were also de termined according to postoperative survival (Table 6 ) . The findings were comparable to those above. DISCUSSION ANTEMORTEM OBSERVATIONS
In the rabbit, the bony orbit does not cover a considerable portion of the superior surface of the eyeball which projects about 12 mm beyond the rim of the supraorbital crest.7 The middle of the cornea, however,
TABLE 6 AVERAGE OF DIFFERENCES OF ORBITAL VOLUMES (UNOPERATED, LEFT, AND OPERATED, RIGHT) AFTER EVISCERATION, ENUCLEATION, AND EXENTERATION GROUPED ACCORDING TO POSTOPERATIVE SURVIVAL (IN ML)
Postoperative Survival (in days) 1-50 51-150 151-250 251-350
Evis ceration
Enu cleation
Exen teration
0.23
0.22 0.90 0.92 1.25
1.63 1.27
0.38 0.43
projects only 5 mm beyond the edge of the zygomatic arch. After evisceration, enucle ation, or exenteration the orbital area was flatter than that of the unoperated side. We could not differentiate with any degree of ac curacy the type of surgical procedure on the basis of the flatness. POSTMORTEM OBSERVATIONS
Evisceration—In this group of animals the difference in orbital volumes between the unoperated left eye side and the eviscerated right eye side generally became greater with a longer postoperative survival (Table 1). This was particularly apparent in those ani mals with a 280 to 283-day postoperative survival. There were, however, a number of varia tions. For instance, in a group of seven ani mals of the same litter, the right eyes were eviscerated at 19 days of age and the animals were killed at 299 or 302 days of age. The difference in volumes between the left and right orbits ranged from 0 to 0.9 ml. In ani mals Nos. 2-2 and 5-5 with postoperative survivals of 266 and 283 days, respectively,
Fig. 6 (Sarnat and Shanedling). (A) Volume of right orbit after enucleation of eye in 23 rabbits plotted against postoperative survival time. (B) Volume of paired left orbit (unoperated eye) of 23 rabbits in A plotted against postoperative survival time. (C) Difference of orbital volumes (left-right) of unoperated left eye and enucleated right eye in 23 rabbits of A and B plotted against postoperative survival time.
798
AMERICAN JOURNAL OF OPHTHALMOLOGY
after evisceration of the right eye, surpris ingly there was no difference between the volumes of the left and right orbits. In ani mal No. 6-9, with a postoperative survival of 151 days, the difference in volumes between the left and right orbits was 0.5 ml. This dif ference was equal to or greater than that in 11 out of 15 animals with a postoperative survival as long as 283 days. Enucleation—In this group of animals, the difference in orbital volumes between the unoperated left eye side and the enucleated right side generally became greater with a longer postoperative survival (Table 2). This was particularly apparent in those ani mals with a postoperative survival of 181 days or longer. There were, however, a number of varia tions. For instance, in one group of three an imals of the same litter (Nos. 3-3, 3-1, and 32) the right eye was enucleated at 21 days of age and the animals were killed at 287 days of age. The difference in volumes between the left and right orbits ranged from 0.4 to 2.7 ml. In another group of three animals of the same litter (Nos. 4-6, 4-3, and 4-7) the right eyes were enucleated at 19 days of age and the animals were killed at 302 days of age. Although these animals were operated on earlier and survived longer than the previous group, the difference in volumes between the left and right orbits ranged from 0.7 to only 1.2 ml. In animal No. 6-8, with a postoper ative survival of 221 days after enucleation of the right eye, the volume of the left orbit was 6.8 ml and the right orbit was 6.7 ml. By contrast, in animal No. 4-5, with a postoper ative survival of only 52 days, the difference in volumes between the left and right orbits was 1.1 ml. This was greater than that in five of 11 animals with a postoperative survival ranging from 161 to 283 days. In two of these five animals (Nos. 6-20 and 4-7) the difference in volumes was greater by only 0.1ml. ,,.,"■ Exenteration—In this group of animals, the difference in volumes between the unop-
NOVEMBER, 1970
erated left orbit and the exenterated right or bit ranged from 0.8 ml in animal No. 1-7, with a postoperative survival of 177 days, to 2.1 ml in animal No. 1-9, with a postopera tive survival of 246 days (Table 3). Ani mals with a postoperative survival of 274 days had a lesser difference in orbital volumes than those with a postoperative of 246 days. The explanation for this may be found after ex perimentation with a larger series. The petro latum-impregnated gauze strip which was removed one week postoperatively may have altered orbital growth in this group. The evis ceration and enucleation series did not have a gauze strip inserted. Comparison of orbital volumes—A com parison of the data of the orbital volumes af ter evisceration, enucleation, and exentera tion suggested a direct relationship between the lack of orbital mass and the subsequent lack of development of the orbit. There were, however, a number of individual ex ceptions and a certain amount of overlapping between the groups. Postoperative intraorbi tal scar tissue may have influenced orbital growth. Validity of volumetric determinations— The disadvantages and advantages of this method have been considered.2 The possibil ity of error is lessened when there are less or bital openings to be sealed, such as in the primate. The same person waxed the orbital openings and made the orbital imprints. He had no knowledge of the history of the ani mals. If any errors were made in sealing the orbital openings, such as at varying levels, they should have been comparable. Highly accurate measurements are not as much of an issue, however, as lack of bias between the right and left orbital measure ments. In the entire group of 51 experimen tal animals in which surgery was done on ei ther the right eye or orbit, this orbit, with three exceptions, was always smaller than the unoperated left orbit. In an unoperated group of 14 animals, the left orbit was larger than the right in four instances, equal to the right in three instances, and smaller than the
VOL. 70, NO. S
799
ORBITAL VOLUME
right in seven instances.2 Validity of unoperated orbit as control— The left unoperated side was used as a con trol for the right orbit in which an eviscera tion, enucleation, or exenteration was done. This was preferred to a comparison with lit ter-mates because of the variation in body weight and orbital size.2 With lessened orbital contents on the right side however, and with continued growth of the normal orbital contents (and pressure) on the left side, the interorbital septum might be expected to shift toward the operated right side. This is of particular interest since, in the rabbit, the eye not only fits closely in the orbit but also the adult volume is 15 times that of the newborn.8 Coulombre and Crelin9 found, after operating unilat erally on eyes of embryonic chicks, that the cartilaginous interorbital septum deviated toward the operated side. Even though the left orbit may be larger partly at the expense of the operated right orbit, and even though the left orbit may not be a true control, the findings do reflect the effects of unilateral surgical procedures in animals with a com mon interorbital septum. Orbital and facial growth—In this experi ment, postnatal increase in the volume of the orbit was decelerated after removal of vary ing amounts of the contents. Other local changes noted were a smaller and less ele vated supraorbital process and a shorter zy goma. Deviation of the facial skeleton to ward the side of the operated orbit was noted in several animals. This has been reported previously.3·5'9 Pfeiffer10 stated that "removal of the eye arrests the development of the orbit, and in deed leads to a contraction of it, or to a re duction of its capacity." Our findings were to the contrary. The orbital size, although smaller than on the unoperated side, became progressively larger in growing animals with a longer postoperative survival period. In other words, the orbit is not smaller, actu ally, but is smaller relatively to the unoper ated orbit.
SUMMARY
Postnatal volumetric growth of the orbit was studied in 51 New Zealand albino rab bits after evisceration, enucleation, or exen teration of the right orbit at seven to 42 days of age. The unoperated left side was used as a control. The postoperative survival time ranged from one to 283 days. A removable permanent elastic rubber-base imprint was made of the clean orbit. The volume was cal culated from the weight and specific gravity of the orbital imprint. After excision of orbital tissue, the orbit continued to increase in size but at a slower rate than the unoperated fellow orbit. Gener ally, there was a direct correlation between lack of intraorbital mass and lack of orbital growth. ACKNOWLEDGMENTS
We thank Dr. Frank J. Massey, Jr., School of Public Health, University of California Medical Center, Los Angeles, for his assistance in the statis tical evaluation and Dr. Irving Gault for developing the orbital imprints. REFERENCES
1. Sarnat, B. G., and Shanedling, P. D. : Postna tal growth of the orbit and upper face in rabbits after exenteration of the orbit. Arch. Ophth. 73: 829, 1965. 2. Sarnat, B. G. : The imprint method to deter mine orbital volume in the rabbit. Ophthalmologica 160:142, 1970. 3. Lesshaft, P. : Grundlagen der Theoretischen Anatomie. Leipzig, W. Hartmann, 1892, p. 99. 4. Thomson, W. E. : The determination of the in fluence of the eyeball on the growth of the orbit by experimental enucleation of one eye in young ani mals. Tr. Ophth. Soc. U. K. 21:258, 1901. 5. Wessely, K. : Über korrelationen des Wach stums (nach versuchen am auge). Zschr. Augenheilk. 43:654, 1920. 6. Kennedy, R. E. : The effect of early enucle ation on the orbit in animals and humans. Tr. Am. Ophth. Soc. 62:459, 1964. 7. Prince, J. H. (ed.) : The rabbit in eye re search. Springfield, 111., Charles C Thomas, 1964, p. xi. 8. Washburn, S. L., and Detwiler, S. R. : An ex periment bearing on the problems of physical an thropology. Am. J. Phys. Anthrop. 1:171t 1943. 9. Coulombre, A. J., and Crelin, E. S. : Role of the developing eye in the morphogenesis of the avian skull. Am. J. Phys. Anthrop. 16:25, 1958. 10. Pfeiffer, R. L. : The effect of -enucleation on the orbit Tr. Am. Acad. Ophth. 49:236, 1945.