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Argon Laser Photomydriasis
ARGON LASER PHOTOMYDRIASIS WILLIAM A. JAMES, JR., M.D.,
ANDREW I JEROETTH, JR., M.D., MAX FORBES, L'I ISPERANCE, JR., M.D.
M.D.,
AND FRANCIS A.
New York, New York Miotic agents provide the foundation for the medical management of most glaucoma patients. While these agents effectively lower intraocular pressure, the accompanying miosis is not always acceptable and can be debilitating in some patients. Subjective dim ness of vision, accentuation of visual field defects, and a decrease in visual acuity can be produced by a constriction of the pupil. Axial opacities in the ocular media can fur ther exaggerate all these adverse effects of miosis.1'2 Various photocoagulation modalities have been utilizd as an alternative to surgery in treating pupillary abnormalities. These pho tocoagulation sources include the xenon arc,3*6 direct sunlight,7 and the ruby laser.8 Most of these cases, however, occurred in aphakic patients with updrawn pupils. One report described the enlargement of eight miotic pupils with xenon arc photocoagulation.8 Because of complications, the proce dure was recommended only for aphakic pa tients. The argon laser offers an excellent source for iris photocoagulation, with potential advantages over other photocoagulation sources.9"12 We have used the argon laser to enlarge miotic pupils in a series of glaucoma patients, both phakic and aphakic, maintained on a variety of miotic agents. We have termed this procedure photomydriasis. Some of the clinical results have been presented previ ously.12 In addition to the clinical studies, we performed argon laser iris photocoagulation in a small series of rabbits. From the Edward S. Harkness Eye Institute, Columbia-Presbyterian Medical Center, New York, New York. Reprint requests to William A. James, Jr., M.D., Box 55, 635 W. 165th St., New York, NY 10032.
MATERIAL AND METHODS
A Coherent Radiation Laboratories argon laser photocoagulator was used for all stud ies. For each eye treated, power levels were monitored at the cornea with a Coherent Radiation Laboratories power meter. Animal studies—We treated a series of pigmented Dutch and chinchilla rabbits with argon laser photocoagulation. The treat ments consisted of a single-row barrage of contiguous, solitary impacts directed to the region of the iris sphincter around the en tire circumference of the pupillary border. For all treatments, the exposure time was 0.2 seconds and the spot size was 200 μ. The power level, however, was increased by 200-mW increments for each eye treated. Thus, the first eye was treated at 200 mW of power, the second eye at 400 mW, the third eye at 600 mW, and so on. The full power range of our laser was utilized, up t o 1400 mW for the last eye treated. No medications were administered after treat ment. The animals were carefully observed a t weekly intervals for eight weeks in order t o determine any effects on the lens under lying the treatment zone. After eight weeks, the animals were killed. The enucleated globes were fixed in formalin, embedded in paraffin, and appropriate histologie sections were made of the treated irises. Clinical studies—Twenty eyes in 18 pa tients with open-angle glaucoma were treated in our series. Glaucoma medications con sisted of pilocarpine in 15 of the treated eyes, echothiophate iodide (Phospholine Iodide) in four eyes, and carbachol in one eye. Initially, we selected eyes with poor visual potential for treatment to establish the technique. As our studies progressed, we used a trial mydriasis before treatment
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ARGON LASER PHOTOMYDRIASIS
to screen appropriate candidates for photomydriasis. The treatment technique consisted of treating the iris directly, using the slit-lamp delivery system of the argon laser photocoagulator. Neither a contact lens nor a corneal bath were required, and retrobulbar anesthesia was not necessary in most pa tients. Topical anesthesia reduced the fre quency of blinking on the part of the pa tient. Multiple 200-μ impacts were placed in a contiguous manner for 360 degrees, immedi ately adjacent to the pupillary border. The desired effect was an immediate shriveling of the iris, with moderate oozing of iris pig ment and plasmoid aqueous humor, but not a severe explosion. Exposures of 0.2 seconds and power settings in the range of 250 to 500 mW seemed ideal. The power setting must be adjusted to individual iris pigmenta tion. Low-power settings produced some immediate shriveling of the iris, but the re sultant mydriasis was löst once the patient resumed a miotic regimen. Higher power settings, especially with shorter exposures, produced bubbles and pigment explosions, and we found these effects to be excessive. Once the initial 200-μ barrage surrounded the pupillary border, we made an additional 500-μ treatment circle just outside the initial treatment circle. This second row of treat ments reinforced the initial row, and thoroughly covered the region of the iris sphincter, which forms a broad 1-mm band surrounding the pupillary border. As the spot size was increased to 500 μ, the ex posure was kept at 0.2 seconds, and the power was increased to between 350 and 600 mW. The desired effect again was a moderate oozing of pigment and plasmoid aqueous hu mor, not a severe explosion. After the second row of treatments was completed, the pupil usually doubled its original size. Figure 1 schematically summarizes the treatment technique. Some pupils may lose much of the newly acquired mydriasis, once the patient resumes
63
Fig. 1 (James and associates). Photomydriasis technique. Contiguous, solitary laser impacts are placed in a double circle around the pupillary border, directed to the region of the iris sphincter.
topical miotics. If so, retreatment should be instituted. We explored three methods of retreat ment. The first method repeated the original double-circle technique, treating the same area adjacent to the pupillary border. This method enhanced the injury to the sphincter muscle until an appropriate amount of sphincter function was obliterated. This method was most satisfactory. Another method of retreatment treated a more diffuse area of iris, even to the iris periphery. This method produced a sustained amount of mydriasis, but it injured the dilator muscle as well as the sphincter, and the pupil after treatment responded poorly to miotics and mydriatics. Such a diminished response to mydriatics was not advanta geous. We dilated the pupil with mydriatics for the third method of retreatment, and then treated the region of the sphincter, using the same double-circle technique, with the pupil in the dilated state. This method was potent, and may be used not only as a retreatment technique, but as an initial technique for patients receiving stronger miotics. Prior to
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laser treatment, however, the pupil should not be dilated to more than 3 or 4 mm. Further dilatation, followed by photomydriasis, resulted in an excessively large pupil. After treatment, all patients continued on their usual glaucoma medications. In addi tion, one dose of 500 mg of acetazolamide (Diamox) was given orally immediately after treatment, and topical corticosteroids, four times daily, for three to seven days. RESULTS
Animal studies—Each photocoagulation impact produced an immediate shriveling of the iris within the impact zone, pulling the pupil toward the point of impact. Areas of treatment assumed a uniform, muddy colora tion. Power levels of 400 to 600 mW pro duced moderate pigment dispersion and plasmoid aqueous humor. Power levels over 600 mW produced more severe tissue ex plosions and bubbles, often accompanied by an audible noise. Power levels over 1,000 mW produced gross bits of iris tissue torn away into the anterior chamber. All eyes showed some anterior chamber reaction after treatment. A reaction of moderate pigment dispersion and aqueous flare tended to dissipate in two to three hours. More severe reactions, with libera tion of much pigment and even bits of iris tissue, required six to 12 hours to resolve. None of the treated eyes showed any signifi cant ciliary injection or residual anterior chamber reaction after the first 24 hours. No retinal burns were noted. During the eight weeks of observation after treatment, there were no lens changes in any eyes treated within the power range of 200 to 800 mW. Eyes treated at 1,000 to 1,400 mW showed discrete, small opaci ties located at the level of the lens epithelium and the most anterior portion of the cortex. These opacities were faint, some only visu alized by careful retro-illumination. Each opacity was approximately 100 to 200 μ, roughly corresponding to an imprint left by the iris photocoagulation impact. These
JANUARY, 1976
opacities apparently occurred when heat ab sorbed at the level of the iris pigment epi thelium was transmitted directly to the un derlying anterior layers of the lens. None of the opacities progressed during the ob servation period. Hematoxylin and eosin and Masson trichrome preparations were made of the treated irises after the eight-week observa tion period. Power settings from 200 to 400 mW produced disruption of the anterior border layer of the iris, with moderate atro phy of the irfs stroma and the underlying sphincter muscle. The iris pigment epi thelium remained intact. We noted macro phages laden with pigment within the zone of stromal atrophy. Power settings from 400 to 600 mW produced severe and vir tually total atrophy of the anterior border layer and the iris stroma. Atrophy and dis ruption of the sphincter muscle became more severe. The iris pigment epithelium remained intact, although pigment dispersion and mi gration of pigment-laden macrophages were noted. Figure 2 is a Masson trichrome preparation from an iris treated within the 400- to 600-mW range. The impact zone is adjacent to an area of relatively intact sphincter. This power range corresponded to clinically effective human coagulations. Power settings over 800 mW produced severe changes in all the iris layers. The anterior border layer and the iris stroma were obliterated, and there was severe atro phy and disruption öf the sphincter muscle. Disruption of the underlying iris pigment epithelium also occurred, with pigment dis persion. A Masson trichrome preparation from an iris treated in the 800- to 1,000-mW range revealed severe destruction within the impact zone (Fig. 3). We limited the animal observation period in this study to eight weeks. The lens and iris changes noted during this time appeared to be stable, but these changes possibly might be progressive over a longer period of time. Histology of the discrete lens changes was not attempted, because of the difficulty in
Fig. 2 (James and associates). Histologie section of rabbit iris at pupillary border. Laser impact (ar row), 400 to 600 mW power range (Masson trichrome, x 40).
Fig. 3 (James and associates). Histologie section of rabbit iris at pupillary border. leaser impact (ar row), 800 to 1,000 mW power range (Masson trichrome, x 64).
Fig. 4 (James and associates). Miotic pupil of glaucoma patient prior to photomydriasis.
Fig. 5 (James and associates). Same pupil as in Figure 4 following photomydriasis and after six weeks of continued miotic therapy. Additional 4% pilocarpine was administered prior to photograph. Note the lack of significant iris disruption or atrophy.
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locating these faint opacities. Clinical studies—Pupillary measurements were made with a calibrated grid in the oculars of a Zeiss slit lamp. We observed all patients from six weeks to eight months after treatment. Measurements after treat ment were not considered conclusive until the patients had resumed their usual miotic regimen for at least six weeks. In addition, before collecting these measurements after treatment, we instilled four doses of pilocarpine 4% in the laboratory in all treated eyes. The additional pilocarpine challenged the mydriatic effect of the laser treatment and standardized the results. Before treatment, the average pupil in all the treated eyes measured 1.5 mm hori zontally and 1.5 mm vertically. After treat ment, followed for several weeks and chal lenged by pilocarpine 4%, the average pupil measured 3.1 mm horizontally and 3.0 mm vertically. The treatment doubled the size of the average miotic pupil. Figure 4 shows a pupil before treatment and Figure 5 shows the same pupil after treatment, when the patient had resumed miotic therapy for six weeks and received four doses of pilocarpine 4%. Six of the 20 eyes required retreatment to maintain a stable and desired amount of mydriasis. Once the size of the treated pupil was stabilized, by retreatment if necessary, it tended to remain constant over our eightmonth observation period. Our rationale for limiting the treatment to the region of the sphincter muscle was to render the pupil refractory to miotics, yet preserve as much mydriatic function as possible. The average pupil following photomydriasis measured 3.1 mm horizontally and 3.0 mm vertically when challenged by mi otics, and dilated to 4.6 mm horizontally and 4.6 mm vertically when given topical mydriatics. Pupils on chronic miotic medi cations dilated poorly. Nevertheless, when ever we compared the treated eye with the untreated eye in the same patient, with both eyes receiving the same miotic regimen, we
67
found that our technique of photomydriasis had not interfered with mydriasis in the treated eye. All eyes were dilated with the same combination of sympathomimetic and parasympatholytic agents. The visual results in our series were limited because eyes with poor visual po tential were treated early in the series. Despite this limitation, 11 of the 20 treated eyes showed visual improvement of two lines or more on the Snellen chart. A few results were striking. Visual acuity in one woman with advanced nuclear sclerosis improved from hand movements to 20/80. One man had partial pupillary membranes in each eye after surgery as a child for congenital cata racts and subsequent bilateral retinal detach ments. After pilocarpine instillation in each eye, his pupils constricted to less than 2.0 mm and visual acuity was R.E.: 20/200, and L.E.: counting fingers. After photo mydriasis, his pupils were sustained at 3.5 mm, and visual acuity stabilized at 20/80 — in each eye with continued use of the same miotic. There were nine perimetry studies avail able for comparison before and after treat ment. Visual fields improved in six patients consisting of a generalized increase in visual field size and a decrease in the size of rela tive scotomas. Miosis can exaggerate visual field changes in some patients,1'2 and photo mydriasis can be beneficial in this regard if patients are properly selected before treat ment. There were few complications. All treated eyes showed an immediate plasmoid iritis, with moderate pigment dispersion. This re action disappeared spontaneously one to two hours after treatment. Topical corticosteroids for three to seven days after treat ment seemed an ample regimen for the usual postoperative reaction. Three patients noted a delayed iritis that occurred several weeks after the treated eyes were quiescent. These cases of delayed iritis were effectively treated with additional topical corticosteroids. Cycloplegics were not necessary in
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AMERICAN JOURNAL OF OPHTHALMOLOGY
treating these cases of iritis. Chronic iritis did not occur. Most of the treated eyes showed a tran sient increase in intraocular pressure of S to 7 mm Hg after treatment. The duration of this intraocular pressure increase tended to parallel the duration of the iritis noted after treatment, with the intraocular pressure re turning to pretreatment levels as the iritis subsided. A single dose of 500 mg of acetazolamide, orally administered after the laser treatment, was adequate therapy for the transient increase in intraocular pres sure. Patients continued their usual glau coma regimen. The underlying glaucoma in three patients was more severely affected. Two patients had poorly controlled glaucoma at the on set of treatment. Both patients continued to show an increase in intraocular pressure of 7 to 10 mm Hg for several days after treatment. The third patient was treated at high-power levels, with liberation of much pigment. This patient experienced moderate corneal edema and a pressure increase to 64 mm Hg within one hour after treatment. An oral osmotic agent was given, with prompt resolution of the pressure increase. However, these cases emphasize that pa tients with poorly controlled glaucoma should be carefully observed after treatment, and excessive treatment should be avoided. We observed no chronic glaucoma-related problems. The short course of topical corticosteroids given after treatment produced no cases of corticosteroid-induced glaucoma. The reduced miotic response of the treated pupil did not interfere with the effect of the miotic agent on open-angle glaucoma.18 However, patients with narrow angles were not treated since reduced miosis in these cases may have precipitated angle closure. One patient developed a small hemorrhage at an impact site of high intensity (600 m W ) . The bleeding was cauterized by further photocoagulation, and presented no subsequent problem. Photocoagulation burns of the lens did not
JANUARY, 1976
occur, and we did not observe exacerbation of preexisting cataracts during the eight months of clinical observation. We also did not observe progressive atrophy of the treated irises during this period. Such atro phy might occur over a longer period of time, however, and our observations to date have not excluded this possibility. We en countered no retinal photocoagulation in any of the treated eyes, although inadvertent treatment into the macula is a potential prob lem in the absence of retrobulbar anesthesia. The laser beam should be directed away from the visual axis, and any patient unable to maintain a steady direction of gaze should receive a retrobulbar injection. We observed no corneal changes related to the treatment. We excluded from our series any patients with significant endothelial dis ease. DISCUSSION
The standard surgical approach for visual problems related to miotic pupils includes an optical iridectomy, or, when indicated, a cataract extraction. Surgery is the only effec tive approach in some cases, such as eyes with advanced, diffuse cataract formation or pupils with extensive posterior synechiae. Conversely, in properly selected patients, en largement of the pupil with photocoagulation can offer significant visual improve ment, and the procedure is technically easy to accomplish. In these cases, photocoagulation has advantages over surgery in that photocoagulation can be performed as an outpatient procedure, without the risks of intraocular manipulation. Previous reports of xenon arc iris photocoagulation indicated complications including corneal burns, persistent iritis, and lens changes.3"6 Extensive iris atrophy occurred in one patient whose entire pupillary border was treated.6 There is some question as to whether the associated lens changes can be progressive,14 and because of this, xenon arc photocoagulation of the iris has been generally limited to aphakic patients. These
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69
complications and limitations apparently re fields should be carefully evaluated, first with sult from the infrared portion of the xenon the patient's miotic pupil, then with a more arc spectrum, the relatively large xenon arc dilated pupil. We consider the patient's own spot size, and the imprecise focusing poten subjective preference the most important factor in deciding which pupillary size is tial of the xenon arc delivery system. more appropriate. The argon laser, as a source for iris photoOnce a possible candidate for photomy coagulation, does not offer these disad vantages. The argon beam and the slit-lamp driasis has been selected, the patient's glau delivery system afford precise focusing coma therapy should be converted from capability. The argon wavelengths are effi miotics to sympathomimetic agents. This ciently absorbed by the iris pigment epi will enlarge the pupil, and laser treatment thelium, with high-power densities attained will not be necessary. However, based on in small coagulations. Since there is little our experience, most miotic agents must be transmission of energy to the lens or to stopped before a sympathomimetic agent will posterior structures at clinically effective enlarge the pupil. Should the miotic agent power levels, argon laser photocoagulation be continued to control the patient's glau of the iris can be performed in phakic pa coma, the pupil will usually remain small, tients without observable lens changes. Dur and photomydriasis is indicated. ing our observation period, we found mini SUMMARY mal complications, although our results indi Argon laser photomydriasis was used to cate that, following photomydriasis, each pa enlarge 20 miotic pupils in 18 open-angle tient's underlying glaucoma should be care glaucoma patients, with beneficial visual re fully monitored for several days. sults in patients properly selected before The success of photomydriasis for any treatment. During eight months of observa patient will depend largely on the proper tion, significant complications such as per selection of patients. Various factors relat sistent iritis and lens changes did not occur. ing visual acuity to pupillary size are com plex. A small pupil enhances depth of visual An increase in intraocular pressure occasion field and minimizes spheric and chromatic ally occurred shortly after treatment, but aberration of peripheral light rays. Con chronic exacerbation of underlying glaucoma versely, a small pupil permits less illumina was not observed. Argon laser iris photocoagulation in rabbit tion and also increases diffraction at the pupillary border, thus superimposing un eyes showed localized atrophy of the iris focused rays onto the retinal image. These sphincter and stroma within the treatment various physiologic factors reach equi zones. Discrete, anterior lens opacities oc librium, with the "ideal" pupillary diameter curred only at high-power levels, and these appeared to be nonprogressive during the generally calculated to be 2.4 mm.15 Lenticular opacities and visual field eight-week observation period. changes, commonly present in glaucoma pa REFERENCES tients, further complicate the equation for an 1. Day, R. M., and Scheie, H. G. : Simulated pro ideal pupillary diameter. In practical terms, gression of visual field defects of glaucoma. Arch. some glaucoma patients undoubtedly prefer Ophthalmol. 50:418, 1953. 2. Forbes, M. : Influence of miotics on visual a more miotic pupil, while others prefer a fields in glaucoma. Invest. Ophthalmol. 5:139, 1966. more enlarged pupil. A trial mydriasis with 3. Meyer-Schwickerath, G. : Light Coagulation. topical agents should be conducted prior to M. Drance (trans.), St. Louis, C. V. Mosby Co., treatment to select appropriate candidates 1960, pp. 105-111. 4. Pischel, D. K. : Symposium : Photocoagulation. for photomydriasis. Each patient's subjec Trans. Am. Acad. Ophthalmol. Otolaryngol. 66:67, tive symptoms, visual acuity, and visual 1962.
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5. Straatsma, B. R., Allen, R. A., Pettit, T. H., and Hall, M. 0.: Subluxation of the lens treated with iris photocoagulation. Am. J. Ophthalmol. 61 : 1312, 1966. 6. Cleasby, G. W. : Photocoagulation coreplasty. Arch. Ophthalmol. 83:145, 1970. 7. Otiti, J. M. L. : Photocoagulation of the iris using direct sunlight. Br. J. Ophthalmol. 53:574, 1969. 8. Flocks, M., and Zweng, H. C. : Laser coagu lation of ocular tissues. Arch. Ophthalmol. 72:604, 1964. 9. L'Espérance, F. A., Jr.: An ophthalmic argon laser photocoagulation system : Design, construction, and laboratory investigations. Trans. Am. Ophthal mol. Soc. 66:827, 1968. 10. : The ocular histopathologic effect of krypton and argon laser radiation. Am. J. Ophthal
OPHTHALMIC
JANUARY, 1976
mol. 68:263, 1969. 11. : Qinical applications of argon laser photocoagulation. Trans. Ophthalmol. Soc. U.K. 89 : 557, 1969. 12. L'Espérance, F. A., Jr., and James, W. A., Jr. : Argon laser photocoagulation of iris abnor malities. Trans. Am. Acad. Ophthalmol. Otolaryngol. 79:321, 1975. 13. Becker, B., Gage, T., Kolker, A. E., and Gay, A. J. : The effect of phenylephrine hydrochloride on the miotic-treated eye. Am. J. Ophthal mol. 48:313, 1959. 14. McDonald, J. E., and Light, A. : Photocoagu lation of iris and retina. Arch. Ophthalmol. 60:384, 1958. 15. Moses, R. A. : Adler's Physiology of the Eye, 5th ed. St. Louis, C. V. Mosby Co., 1970, p. 566.
MINIATURE
PRO.? LAPSE Prepared by Virginia Howard Louisiana State University Medical Center New Orleans, Louisiana
ANDREW I JEROETTH, JR., M.D., MAX FORBES, L'I ISPERANCE, JR., M.D.
M.D.,
AND FRANCIS A.
New York, New York Miotic agents provide the foundation for the medical management of most glaucoma patients. While these agents effectively lower intraocular pressure, the accompanying miosis is not always acceptable and can be debilitating in some patients. Subjective dim ness of vision, accentuation of visual field defects, and a decrease in visual acuity can be produced by a constriction of the pupil. Axial opacities in the ocular media can fur ther exaggerate all these adverse effects of miosis.1'2 Various photocoagulation modalities have been utilizd as an alternative to surgery in treating pupillary abnormalities. These pho tocoagulation sources include the xenon arc,3*6 direct sunlight,7 and the ruby laser.8 Most of these cases, however, occurred in aphakic patients with updrawn pupils. One report described the enlargement of eight miotic pupils with xenon arc photocoagulation.8 Because of complications, the proce dure was recommended only for aphakic pa tients. The argon laser offers an excellent source for iris photocoagulation, with potential advantages over other photocoagulation sources.9"12 We have used the argon laser to enlarge miotic pupils in a series of glaucoma patients, both phakic and aphakic, maintained on a variety of miotic agents. We have termed this procedure photomydriasis. Some of the clinical results have been presented previ ously.12 In addition to the clinical studies, we performed argon laser iris photocoagulation in a small series of rabbits. From the Edward S. Harkness Eye Institute, Columbia-Presbyterian Medical Center, New York, New York. Reprint requests to William A. James, Jr., M.D., Box 55, 635 W. 165th St., New York, NY 10032.
MATERIAL AND METHODS
A Coherent Radiation Laboratories argon laser photocoagulator was used for all stud ies. For each eye treated, power levels were monitored at the cornea with a Coherent Radiation Laboratories power meter. Animal studies—We treated a series of pigmented Dutch and chinchilla rabbits with argon laser photocoagulation. The treat ments consisted of a single-row barrage of contiguous, solitary impacts directed to the region of the iris sphincter around the en tire circumference of the pupillary border. For all treatments, the exposure time was 0.2 seconds and the spot size was 200 μ. The power level, however, was increased by 200-mW increments for each eye treated. Thus, the first eye was treated at 200 mW of power, the second eye at 400 mW, the third eye at 600 mW, and so on. The full power range of our laser was utilized, up t o 1400 mW for the last eye treated. No medications were administered after treat ment. The animals were carefully observed a t weekly intervals for eight weeks in order t o determine any effects on the lens under lying the treatment zone. After eight weeks, the animals were killed. The enucleated globes were fixed in formalin, embedded in paraffin, and appropriate histologie sections were made of the treated irises. Clinical studies—Twenty eyes in 18 pa tients with open-angle glaucoma were treated in our series. Glaucoma medications con sisted of pilocarpine in 15 of the treated eyes, echothiophate iodide (Phospholine Iodide) in four eyes, and carbachol in one eye. Initially, we selected eyes with poor visual potential for treatment to establish the technique. As our studies progressed, we used a trial mydriasis before treatment
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ARGON LASER PHOTOMYDRIASIS
to screen appropriate candidates for photomydriasis. The treatment technique consisted of treating the iris directly, using the slit-lamp delivery system of the argon laser photocoagulator. Neither a contact lens nor a corneal bath were required, and retrobulbar anesthesia was not necessary in most pa tients. Topical anesthesia reduced the fre quency of blinking on the part of the pa tient. Multiple 200-μ impacts were placed in a contiguous manner for 360 degrees, immedi ately adjacent to the pupillary border. The desired effect was an immediate shriveling of the iris, with moderate oozing of iris pig ment and plasmoid aqueous humor, but not a severe explosion. Exposures of 0.2 seconds and power settings in the range of 250 to 500 mW seemed ideal. The power setting must be adjusted to individual iris pigmenta tion. Low-power settings produced some immediate shriveling of the iris, but the re sultant mydriasis was löst once the patient resumed a miotic regimen. Higher power settings, especially with shorter exposures, produced bubbles and pigment explosions, and we found these effects to be excessive. Once the initial 200-μ barrage surrounded the pupillary border, we made an additional 500-μ treatment circle just outside the initial treatment circle. This second row of treat ments reinforced the initial row, and thoroughly covered the region of the iris sphincter, which forms a broad 1-mm band surrounding the pupillary border. As the spot size was increased to 500 μ, the ex posure was kept at 0.2 seconds, and the power was increased to between 350 and 600 mW. The desired effect again was a moderate oozing of pigment and plasmoid aqueous hu mor, not a severe explosion. After the second row of treatments was completed, the pupil usually doubled its original size. Figure 1 schematically summarizes the treatment technique. Some pupils may lose much of the newly acquired mydriasis, once the patient resumes
63
Fig. 1 (James and associates). Photomydriasis technique. Contiguous, solitary laser impacts are placed in a double circle around the pupillary border, directed to the region of the iris sphincter.
topical miotics. If so, retreatment should be instituted. We explored three methods of retreat ment. The first method repeated the original double-circle technique, treating the same area adjacent to the pupillary border. This method enhanced the injury to the sphincter muscle until an appropriate amount of sphincter function was obliterated. This method was most satisfactory. Another method of retreatment treated a more diffuse area of iris, even to the iris periphery. This method produced a sustained amount of mydriasis, but it injured the dilator muscle as well as the sphincter, and the pupil after treatment responded poorly to miotics and mydriatics. Such a diminished response to mydriatics was not advanta geous. We dilated the pupil with mydriatics for the third method of retreatment, and then treated the region of the sphincter, using the same double-circle technique, with the pupil in the dilated state. This method was potent, and may be used not only as a retreatment technique, but as an initial technique for patients receiving stronger miotics. Prior to
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AMERICAN JOURNAL OF OPHTHALMOLOGY
laser treatment, however, the pupil should not be dilated to more than 3 or 4 mm. Further dilatation, followed by photomydriasis, resulted in an excessively large pupil. After treatment, all patients continued on their usual glaucoma medications. In addi tion, one dose of 500 mg of acetazolamide (Diamox) was given orally immediately after treatment, and topical corticosteroids, four times daily, for three to seven days. RESULTS
Animal studies—Each photocoagulation impact produced an immediate shriveling of the iris within the impact zone, pulling the pupil toward the point of impact. Areas of treatment assumed a uniform, muddy colora tion. Power levels of 400 to 600 mW pro duced moderate pigment dispersion and plasmoid aqueous humor. Power levels over 600 mW produced more severe tissue ex plosions and bubbles, often accompanied by an audible noise. Power levels over 1,000 mW produced gross bits of iris tissue torn away into the anterior chamber. All eyes showed some anterior chamber reaction after treatment. A reaction of moderate pigment dispersion and aqueous flare tended to dissipate in two to three hours. More severe reactions, with libera tion of much pigment and even bits of iris tissue, required six to 12 hours to resolve. None of the treated eyes showed any signifi cant ciliary injection or residual anterior chamber reaction after the first 24 hours. No retinal burns were noted. During the eight weeks of observation after treatment, there were no lens changes in any eyes treated within the power range of 200 to 800 mW. Eyes treated at 1,000 to 1,400 mW showed discrete, small opaci ties located at the level of the lens epithelium and the most anterior portion of the cortex. These opacities were faint, some only visu alized by careful retro-illumination. Each opacity was approximately 100 to 200 μ, roughly corresponding to an imprint left by the iris photocoagulation impact. These
JANUARY, 1976
opacities apparently occurred when heat ab sorbed at the level of the iris pigment epi thelium was transmitted directly to the un derlying anterior layers of the lens. None of the opacities progressed during the ob servation period. Hematoxylin and eosin and Masson trichrome preparations were made of the treated irises after the eight-week observa tion period. Power settings from 200 to 400 mW produced disruption of the anterior border layer of the iris, with moderate atro phy of the irfs stroma and the underlying sphincter muscle. The iris pigment epi thelium remained intact. We noted macro phages laden with pigment within the zone of stromal atrophy. Power settings from 400 to 600 mW produced severe and vir tually total atrophy of the anterior border layer and the iris stroma. Atrophy and dis ruption of the sphincter muscle became more severe. The iris pigment epithelium remained intact, although pigment dispersion and mi gration of pigment-laden macrophages were noted. Figure 2 is a Masson trichrome preparation from an iris treated within the 400- to 600-mW range. The impact zone is adjacent to an area of relatively intact sphincter. This power range corresponded to clinically effective human coagulations. Power settings over 800 mW produced severe changes in all the iris layers. The anterior border layer and the iris stroma were obliterated, and there was severe atro phy and disruption öf the sphincter muscle. Disruption of the underlying iris pigment epithelium also occurred, with pigment dis persion. A Masson trichrome preparation from an iris treated in the 800- to 1,000-mW range revealed severe destruction within the impact zone (Fig. 3). We limited the animal observation period in this study to eight weeks. The lens and iris changes noted during this time appeared to be stable, but these changes possibly might be progressive over a longer period of time. Histology of the discrete lens changes was not attempted, because of the difficulty in
Fig. 2 (James and associates). Histologie section of rabbit iris at pupillary border. Laser impact (ar row), 400 to 600 mW power range (Masson trichrome, x 40).
Fig. 3 (James and associates). Histologie section of rabbit iris at pupillary border. leaser impact (ar row), 800 to 1,000 mW power range (Masson trichrome, x 64).
Fig. 4 (James and associates). Miotic pupil of glaucoma patient prior to photomydriasis.
Fig. 5 (James and associates). Same pupil as in Figure 4 following photomydriasis and after six weeks of continued miotic therapy. Additional 4% pilocarpine was administered prior to photograph. Note the lack of significant iris disruption or atrophy.
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locating these faint opacities. Clinical studies—Pupillary measurements were made with a calibrated grid in the oculars of a Zeiss slit lamp. We observed all patients from six weeks to eight months after treatment. Measurements after treat ment were not considered conclusive until the patients had resumed their usual miotic regimen for at least six weeks. In addition, before collecting these measurements after treatment, we instilled four doses of pilocarpine 4% in the laboratory in all treated eyes. The additional pilocarpine challenged the mydriatic effect of the laser treatment and standardized the results. Before treatment, the average pupil in all the treated eyes measured 1.5 mm hori zontally and 1.5 mm vertically. After treat ment, followed for several weeks and chal lenged by pilocarpine 4%, the average pupil measured 3.1 mm horizontally and 3.0 mm vertically. The treatment doubled the size of the average miotic pupil. Figure 4 shows a pupil before treatment and Figure 5 shows the same pupil after treatment, when the patient had resumed miotic therapy for six weeks and received four doses of pilocarpine 4%. Six of the 20 eyes required retreatment to maintain a stable and desired amount of mydriasis. Once the size of the treated pupil was stabilized, by retreatment if necessary, it tended to remain constant over our eightmonth observation period. Our rationale for limiting the treatment to the region of the sphincter muscle was to render the pupil refractory to miotics, yet preserve as much mydriatic function as possible. The average pupil following photomydriasis measured 3.1 mm horizontally and 3.0 mm vertically when challenged by mi otics, and dilated to 4.6 mm horizontally and 4.6 mm vertically when given topical mydriatics. Pupils on chronic miotic medi cations dilated poorly. Nevertheless, when ever we compared the treated eye with the untreated eye in the same patient, with both eyes receiving the same miotic regimen, we
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found that our technique of photomydriasis had not interfered with mydriasis in the treated eye. All eyes were dilated with the same combination of sympathomimetic and parasympatholytic agents. The visual results in our series were limited because eyes with poor visual po tential were treated early in the series. Despite this limitation, 11 of the 20 treated eyes showed visual improvement of two lines or more on the Snellen chart. A few results were striking. Visual acuity in one woman with advanced nuclear sclerosis improved from hand movements to 20/80. One man had partial pupillary membranes in each eye after surgery as a child for congenital cata racts and subsequent bilateral retinal detach ments. After pilocarpine instillation in each eye, his pupils constricted to less than 2.0 mm and visual acuity was R.E.: 20/200, and L.E.: counting fingers. After photo mydriasis, his pupils were sustained at 3.5 mm, and visual acuity stabilized at 20/80 — in each eye with continued use of the same miotic. There were nine perimetry studies avail able for comparison before and after treat ment. Visual fields improved in six patients consisting of a generalized increase in visual field size and a decrease in the size of rela tive scotomas. Miosis can exaggerate visual field changes in some patients,1'2 and photo mydriasis can be beneficial in this regard if patients are properly selected before treat ment. There were few complications. All treated eyes showed an immediate plasmoid iritis, with moderate pigment dispersion. This re action disappeared spontaneously one to two hours after treatment. Topical corticosteroids for three to seven days after treat ment seemed an ample regimen for the usual postoperative reaction. Three patients noted a delayed iritis that occurred several weeks after the treated eyes were quiescent. These cases of delayed iritis were effectively treated with additional topical corticosteroids. Cycloplegics were not necessary in
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treating these cases of iritis. Chronic iritis did not occur. Most of the treated eyes showed a tran sient increase in intraocular pressure of S to 7 mm Hg after treatment. The duration of this intraocular pressure increase tended to parallel the duration of the iritis noted after treatment, with the intraocular pressure re turning to pretreatment levels as the iritis subsided. A single dose of 500 mg of acetazolamide, orally administered after the laser treatment, was adequate therapy for the transient increase in intraocular pres sure. Patients continued their usual glau coma regimen. The underlying glaucoma in three patients was more severely affected. Two patients had poorly controlled glaucoma at the on set of treatment. Both patients continued to show an increase in intraocular pressure of 7 to 10 mm Hg for several days after treatment. The third patient was treated at high-power levels, with liberation of much pigment. This patient experienced moderate corneal edema and a pressure increase to 64 mm Hg within one hour after treatment. An oral osmotic agent was given, with prompt resolution of the pressure increase. However, these cases emphasize that pa tients with poorly controlled glaucoma should be carefully observed after treatment, and excessive treatment should be avoided. We observed no chronic glaucoma-related problems. The short course of topical corticosteroids given after treatment produced no cases of corticosteroid-induced glaucoma. The reduced miotic response of the treated pupil did not interfere with the effect of the miotic agent on open-angle glaucoma.18 However, patients with narrow angles were not treated since reduced miosis in these cases may have precipitated angle closure. One patient developed a small hemorrhage at an impact site of high intensity (600 m W ) . The bleeding was cauterized by further photocoagulation, and presented no subsequent problem. Photocoagulation burns of the lens did not
JANUARY, 1976
occur, and we did not observe exacerbation of preexisting cataracts during the eight months of clinical observation. We also did not observe progressive atrophy of the treated irises during this period. Such atro phy might occur over a longer period of time, however, and our observations to date have not excluded this possibility. We en countered no retinal photocoagulation in any of the treated eyes, although inadvertent treatment into the macula is a potential prob lem in the absence of retrobulbar anesthesia. The laser beam should be directed away from the visual axis, and any patient unable to maintain a steady direction of gaze should receive a retrobulbar injection. We observed no corneal changes related to the treatment. We excluded from our series any patients with significant endothelial dis ease. DISCUSSION
The standard surgical approach for visual problems related to miotic pupils includes an optical iridectomy, or, when indicated, a cataract extraction. Surgery is the only effec tive approach in some cases, such as eyes with advanced, diffuse cataract formation or pupils with extensive posterior synechiae. Conversely, in properly selected patients, en largement of the pupil with photocoagulation can offer significant visual improve ment, and the procedure is technically easy to accomplish. In these cases, photocoagulation has advantages over surgery in that photocoagulation can be performed as an outpatient procedure, without the risks of intraocular manipulation. Previous reports of xenon arc iris photocoagulation indicated complications including corneal burns, persistent iritis, and lens changes.3"6 Extensive iris atrophy occurred in one patient whose entire pupillary border was treated.6 There is some question as to whether the associated lens changes can be progressive,14 and because of this, xenon arc photocoagulation of the iris has been generally limited to aphakic patients. These
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complications and limitations apparently re fields should be carefully evaluated, first with sult from the infrared portion of the xenon the patient's miotic pupil, then with a more arc spectrum, the relatively large xenon arc dilated pupil. We consider the patient's own spot size, and the imprecise focusing poten subjective preference the most important factor in deciding which pupillary size is tial of the xenon arc delivery system. more appropriate. The argon laser, as a source for iris photoOnce a possible candidate for photomy coagulation, does not offer these disad vantages. The argon beam and the slit-lamp driasis has been selected, the patient's glau delivery system afford precise focusing coma therapy should be converted from capability. The argon wavelengths are effi miotics to sympathomimetic agents. This ciently absorbed by the iris pigment epi will enlarge the pupil, and laser treatment thelium, with high-power densities attained will not be necessary. However, based on in small coagulations. Since there is little our experience, most miotic agents must be transmission of energy to the lens or to stopped before a sympathomimetic agent will posterior structures at clinically effective enlarge the pupil. Should the miotic agent power levels, argon laser photocoagulation be continued to control the patient's glau of the iris can be performed in phakic pa coma, the pupil will usually remain small, tients without observable lens changes. Dur and photomydriasis is indicated. ing our observation period, we found mini SUMMARY mal complications, although our results indi Argon laser photomydriasis was used to cate that, following photomydriasis, each pa enlarge 20 miotic pupils in 18 open-angle tient's underlying glaucoma should be care glaucoma patients, with beneficial visual re fully monitored for several days. sults in patients properly selected before The success of photomydriasis for any treatment. During eight months of observa patient will depend largely on the proper tion, significant complications such as per selection of patients. Various factors relat sistent iritis and lens changes did not occur. ing visual acuity to pupillary size are com plex. A small pupil enhances depth of visual An increase in intraocular pressure occasion field and minimizes spheric and chromatic ally occurred shortly after treatment, but aberration of peripheral light rays. Con chronic exacerbation of underlying glaucoma versely, a small pupil permits less illumina was not observed. Argon laser iris photocoagulation in rabbit tion and also increases diffraction at the pupillary border, thus superimposing un eyes showed localized atrophy of the iris focused rays onto the retinal image. These sphincter and stroma within the treatment various physiologic factors reach equi zones. Discrete, anterior lens opacities oc librium, with the "ideal" pupillary diameter curred only at high-power levels, and these appeared to be nonprogressive during the generally calculated to be 2.4 mm.15 Lenticular opacities and visual field eight-week observation period. changes, commonly present in glaucoma pa REFERENCES tients, further complicate the equation for an 1. Day, R. M., and Scheie, H. G. : Simulated pro ideal pupillary diameter. In practical terms, gression of visual field defects of glaucoma. Arch. some glaucoma patients undoubtedly prefer Ophthalmol. 50:418, 1953. 2. Forbes, M. : Influence of miotics on visual a more miotic pupil, while others prefer a fields in glaucoma. Invest. Ophthalmol. 5:139, 1966. more enlarged pupil. A trial mydriasis with 3. Meyer-Schwickerath, G. : Light Coagulation. topical agents should be conducted prior to M. Drance (trans.), St. Louis, C. V. Mosby Co., treatment to select appropriate candidates 1960, pp. 105-111. 4. Pischel, D. K. : Symposium : Photocoagulation. for photomydriasis. Each patient's subjec Trans. Am. Acad. Ophthalmol. Otolaryngol. 66:67, tive symptoms, visual acuity, and visual 1962.
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5. Straatsma, B. R., Allen, R. A., Pettit, T. H., and Hall, M. 0.: Subluxation of the lens treated with iris photocoagulation. Am. J. Ophthalmol. 61 : 1312, 1966. 6. Cleasby, G. W. : Photocoagulation coreplasty. Arch. Ophthalmol. 83:145, 1970. 7. Otiti, J. M. L. : Photocoagulation of the iris using direct sunlight. Br. J. Ophthalmol. 53:574, 1969. 8. Flocks, M., and Zweng, H. C. : Laser coagu lation of ocular tissues. Arch. Ophthalmol. 72:604, 1964. 9. L'Espérance, F. A., Jr.: An ophthalmic argon laser photocoagulation system : Design, construction, and laboratory investigations. Trans. Am. Ophthal mol. Soc. 66:827, 1968. 10. : The ocular histopathologic effect of krypton and argon laser radiation. Am. J. Ophthal
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mol. 68:263, 1969. 11. : Qinical applications of argon laser photocoagulation. Trans. Ophthalmol. Soc. U.K. 89 : 557, 1969. 12. L'Espérance, F. A., Jr., and James, W. A., Jr. : Argon laser photocoagulation of iris abnor malities. Trans. Am. Acad. Ophthalmol. Otolaryngol. 79:321, 1975. 13. Becker, B., Gage, T., Kolker, A. E., and Gay, A. J. : The effect of phenylephrine hydrochloride on the miotic-treated eye. Am. J. Ophthal mol. 48:313, 1959. 14. McDonald, J. E., and Light, A. : Photocoagu lation of iris and retina. Arch. Ophthalmol. 60:384, 1958. 15. Moses, R. A. : Adler's Physiology of the Eye, 5th ed. St. Louis, C. V. Mosby Co., 1970, p. 566.
MINIATURE
PRO.? LAPSE Prepared by Virginia Howard Louisiana State University Medical Center New Orleans, Louisiana