- Email: [email protected]
Neodymium: YAG laser iridotomy
SURVEY OF OPHTHALMOLOGY@ VOLUME
DIAGNOSTIC
NUMBER 3
l
NOVEMBER-DECEMBER
1987
TECHNIQUES
EDITOR
Neodymium:YAG V. DRAKE,
l
AND SURGICAL
STEVEN G. KRAMER,
MICHAEL
32
Laser Iridotomy
M.D.
Department of Ophthalmology, University of Cabfoonzia at San Francisco, San Francisco, Calzfornia
Abstract. During
the past several years t‘he Neodymium:YAG laser has become increasingly popular for performing peripheral iridotomy. Using energy levels of 2-8 millijoules per shot and 1-3 shots per treatment, most irides can be penetrated in one sitting. Nd:YAG laser iridotomies show very little tendency to close, except in patients with active intraocular inflammation. A small amount of hemorrhage is common following YAG laser iridotomy, but clinically significant hyphema is rare. Significant lenticular or cornea1 damage is extremely rare. Although longterm follow-up of large numbers of patients is lacking, Nd:YAG laser iridotomy appears to be a safe and effective alternative to Argon laser iridotomy in selected patients. (Surv Ophthalmol 32:171-177,
Key words. peripheral
1987)
Abraham iridotomy
lens
l
Argon
laser
*
Soon after laser systems became available for clinical investigation, attempts were made to use them to perform peripheral iridotomy.5J0,3g,g0 Early attempts with pulsed Ruby lasers were abandoned because of inconsistent results and a significant inci6,52,77 The subsequent experidence of complications. ence with continuous wave Argon lasers was much more positive.‘~37~53~56~a0~83 Refinements in technique, as well as innovations such as the Abraham lens, led to increasing popularity of Argon laser iridotomy during the latter part of the 1970s.2J1,55 By the early 1980s Argon laser iridotomy had largely replaced surgical iridectomy as the treatment of choice for patients with angle closure glaucoma or occludable angles. 60,63,66,6* However, Argon laser iridotomy was not appropriate for all patients, and considerable difficulty was encountered in performing iridotomy for patients with light blue irides, dark brown irides, and others.30,62,7gJg Pulsed Neodymium:YAG (Nd:YAG) lasers be-
Neodymium:YAG
laser
l
came available commercially in the United States in 1982.35,82 They deliver intense amounts of energy into a well-focused spot over a period of pica seconds to nano seconds.3*8Ja*0 The extremely high irradiance produced by Nd:YAG lasers strips electrons from atoms, resulting in a high energy electron cloud or plasma. 7,45The local disruptive effect of these instruments is dependent upon the effects of optical breakdown at the focal point of the laser. Optical breakdown is a nonlinear absorptive phenomenon which occurs at an extremely high threshold intensity (on the order of 10’0wIcm2).84 Clinical experience indicates that YAG laser iridotomy may offer significant advantages over Argon laser iridotomy in selected patients.38
I. Technique As with any surgical procedure, is of paramount importance.54@ 171
patient selection Our own experi-
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Surv Ophthalmol 32(3) November-December 1987
ence includes patients with acute angle closure glaucoma, positive provocative tests for angle closure glaucoma, chronic progressive angle closure glaucoma, fellow eyes in which a documented angle closure glaucoma attack occurred in the opposite eye, and patients in whom gonioscopy indicates occludable angles. The patients must be physically and psychologically able to cooperate with the laser procedure and be able to remain seated at the slit-lamp for a period of three to five minutes. The cornea must be sufficiently clear to allow adequate laser energy to reach the iris and to allow the physician to visualize the iris for proper aiming and focusing of the laser beam. Patients who are not already using pilocarpine or similar miotic therapy should probably be treated with pilocarpine preoperatively. Pilocarpine puts the iris on stretch, which may make the procedure easier, as well as perhaps blunting the tendency toward postoperative pressure rise in some eyes.” After the patient is seated at the laser and appropriate topical anesthetic is applied, the angle should be reexamined with a gonioscopy lens. We use the Goldmann or Zeiss indirect methods to examine the angle, because these examinations can be performed effectively with the patient sitting at the slitlamp. Next, an Abraham or similar lens is applied.2,6’,87Although the Abraham lens is not an absolute requirement, it has advantages that enhance the safety and efficacy of the procedure. First, the suction of the lens and coupling agent (e.g., Goniosola) on the eye allows the surgeon to control fuation during the procedure. Second, the construction of the lens prevents inadvertent blinking during the laser treatment. Third, the converging button of the Abraham lens tends to focus the laser beam more sharply on the iris. 2 This results in a higher power density that achieves optical breakdown at lower total energy levels. Further, the increased cone angle is associated with a greater beam divergence distal to the treatment site.45,5g Although energy levels vary widely from machine to machine, and sometimes even within the same machine, the overwhelming majority of clinical iridotomies are made with settings between three and ten millijoules per shot. We find that the minimum settings for an iridotomy in a blue iris using an Abraham lens are approximately three to four millijoules per shot, one to three shots per burst.16 This minimum level corresponds roughly to the energy level required for visible spark formation in air when our machine is fired without using any external focusing device (such as the Abraham lens). Energy levels from 50% to 100% higher are necessary when performing iridotomy on thick, velvety smooth, brown irides.
DRAKE Energy delivery can be increased by using either more power per shot or more shots per burst. Higher energy levels and more shots per burst are associated with a greater degree of success in fewer treatment sessions, but also with a greater degree of intraocular damage. Human and experimental animals studies have shown that anterior lens capsule damage is a frequent complication when relatively central iridotomies are performed using energy settings of greater than seven milhjoules per shot and three or more shots per burst.23,2’,5’,86 These studies probably overestimate the actual incidence of lens damage at such energy settings in practice, because the iridotomies were purposely placed more centrally than usual. A more peripheral treatment site takes advantage of the fact that the iris diameter is greater than the lens diameter and that the lens begins to curve posteriorly toward its periphery. Thus, the anterior lens capsule is not directly adjacent to the posterior surface of the iris and any excess laser energy that penetrates the iris is less likely to damage the lens. In addition to choosing a peripheral treatment site, one can decrease the likelihood of intraocular damage by using fewer shots per burst and by not using the Nd:YAG laser to enlarge an iridotomy opening. 27 A series of five, six, or more shots per burst commits one to delivering the full pulse train with each treatment application. If the first or second shot produces a patent iridotomy, the latter shots in the sequence are delivered unimpeded into the iridotomy hole, potentially damaging intraocular structures. This same rationale applies to the prohibition against using the Nd:YAG laser to enlarge a smaller iridotomy opening. A small fixation shift or focusing error can result in the delivery of laser energy through the iridotomy hole and to deep intraocular structures. If an iridotomy opening is deemed too small, it is probably wisest to choose another means of enlarging the opening (such as an Argon laser) or to create an additional Nd:YAG iridotomy at a separate site. If the initial attempt at an iridotomy fails to produce a through and through hole, one can choose to retreat again at the same site or to move to a separate site, depending on the appearance of the partial thickness crater. The decision to retreat at the same site depends partially on the degree of pigment dispersion and hemorrhage caused by the previous partial treatment. Especially in thick, brown irides, an incomplete treatment may result in a thick cloud of dispersed iris pigment. This cloud makes it difficult to visualize or focus adequately on the base of the previous partial thickness treatment. Repeated applications of laser energy into this pigment cloud may result in increased pigment dispersion and
NEODYMIUM:YAG
hemorrhage rather than a patent iridotomy.** Currently, we either move to another site for our next iridotomy attempt or wait a few minutes until the pigment cloud has dispersed. If we choose to wait until the pigment cloud has dispersed and then attempt to complete the iridotomy at the initial site, we will generally use fewer shots per burst and/or less energy per shot. Conversely, if we move to a separate site for our second attempt, we may increase the energy settings appropriately. Following a successful iridotomy, as evidenced by a gush of pigment debris through the iridotomy site and direct visualization of the through and through opening, patients are examined at 30 minutes and at two to three hours after the procedure. Any immediate postoperative complications are treated. Patients are then discharged and seen at intervals of one day, one week, one month, and three months after the procedure. If.
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LASER IRIDOTOMY
Treatment Results
Using the parameters outlined above, a successful iridotomy is achieved in virtually all patients, usually in one treatment session.‘6,47~50~57~73 This is the case even when prior attempts at Argon laser iridotomy have failed .68The typical YAG laser iridotomy is a small (ZOOto 500 mu), irregularly oval opening oriented radially, with somewhat ragged edges (Fig. 1). The total energy required to produce an iridotomy ranges between seven or eight millijoules and 200 millijoules, depending on the various factors mentioned above. Except in eyes with uveitis or other inflammatory disease, YAG laser iridotomies show very little tendency to close. Overall patency rates as high as 99% have been reported. 73This contrasts to closure rates as high as 30% with Argon laser iridotomy.“~47~“~65~68 Our own results corroborate this. Of our first 51 YAG laser iridotomies, only four closed in the postoperative period. Ail four of these patients had active intraocular inflammation prior to the laser procedure, and a diagnosis of iris bombe. We have found that performing several iridotomies in such patients lessens the chance that the iris bombe will reoccur postoperatively.
III. Complications Minor complications occur with some frequency in YAG laser iridotomy. Most of these have no deleterious sequelae and are probably better termed “side effects.” There have been relatively few serious Complications.
A. CORNEA Cornea1 epithelial burns are seen with some frequency in Argon laser iridotomy, but are rare with
YAG laser iridotomy. I5This is due at least in part to the dramatic decrease in total energy required for a YAG laser iridotomy. In contrast to the 8-200 millijoules (mean: 25-30) required for YAG laser iridotomy, 5-50 joules (5000-50000 millijoules) may be required for Argon laser iridotomy. Furthermore, since the continuous wave Argon laser depends on a thermal effect to produce an iridutomy, energy absorbed by the cornea can result in local burns. The plasma formation associated with optical breakdown propagates back toward the laser delivery source, thereby directing a substantial amount of the energy used to perform a YAG laser iridotomy back toward the cornea1 endothelium. This is of particular concern when performing iridotomies in extremely shallow or flat anterior chambers. Experimental studies have shown a local denuding of cornea1 endothelial tissue when the YAG laser is focused 1 mm or less posterior to the endothelial surface.36+a4g Clinically, one may observe linear nonprogressive cracks at the level of Descemet’s membrane directly over the iridotomy site. Generally these cracks are approximately 500 mu in length and may be seen best by retroillumination. Spectromicroscopy has shown central endothelial cell loss to be minimal in patients who have undergone YAG laser iridotomy, compared to 8 or 10% with Argon laser iridotomy.‘j’j B. ANTERIOR
CHAMBER
Laser iridotomy results in a measurable breakdown in the blood-aqueous barrier. This is aimost assuredly a prostaglandin mediated response, as is seen following iris trauma from any number of sources.7o However, clinically significant uveitis is seen less often with YAG laser iridotomy than with In our patients treated Argon laser iridotomy. ‘3,73,76 with the YAG laser, antiinflammatory medications were required postoperatively only for patients with preoperative uveitis or other ocular inflammations. In contrast, Argon laser iridotomy produced significant uveitis in approximately 10% of our patients. C. INTRAOCULAR
PRESSURE
Postoperative intraocular pressure rise has been a serious concern with YAG laser iridotomy.72 This transient acute pressure rise has its peak incidence between one and three hours after the procedure. In some cases, severe pressure rises (up to 50 or 60 mm Hg) have been reported. 28~”There has not been a consistent relationship between the amount of energy required for the iridotomy and the increase in intraocular pressure following the procedure. Although it seems intuitively obvious that pigment
Surv Ophthalmol
Fig. I. Neodymium:YAG ragged-edged, irregularly
32(3) November-December
laser iridotomy oval appearance.
FROM
THE IRIDOTOMY
DRAKE
with typical
and iris stroma debris liberated by the procedure have the potential to clog the trabecular outflow system, other factors may also play an important role.26~44~45,67 The shock wave associated with YAG iridotomy may affect trabecular function or may lead to changes in the aqueous or vitreous that affect the intraocular pressure. A postoperative pressure rise is seen in 25120% of patients undergoing YAG laser iridotomy. This percentage is similar to that seen in patients undergoing Argon laser iridotomy or YAG laser capsulotFor this reason, all patients should be omy. 17,26,35,81,85 followed carefully for several hours after the procedure. Particular attention should be given to individuals who have severe glaucoma and in whom a transient severe pressure spike may have particularly disastrous results. 85We treat significant pressure spikes aggressively, using systemic carbonic anhydrase inhibitors and oral hyperosmotic agents as necessary. As with Argon laser iridotomy, the pressure spikes following YAG iridotomy are transient and resolve within the first several days postoperatively. D. BLEEDING
1987
SITE
A frequent and sometimes troubling side effect of YAG laser iridotomy is bleeding from the iridotomy site.‘6*64Some degree of hemorrhage may be found in over half of the patients treated. Most often this is a microhemorrhage visible either just around the edges of the iridotomy or visible as a thin hemorrhage cascade coursing a few millimeters over the surface of the iris (Fig. 2). Most of these hemorrhages are entirely self-limited, resolving spontaneously within a few seconds. Occasionally the hemorrhage is more active and the cascade continues for some time after the treatment has been given. In
Fig. 2. Self-limited hemorrhage cascade photographed fifteen minutes after Neodymium:YAG laser iridotomy. The hemorrhage is often visible for several hours after the procedure, but is usually gone by the next day.
such cases we use digital pressure on the Abraham lens for several seconds to a few minutes, until the hemorrhage stops. This procedure has successfully arrested the hemorrhage before hyphema formation occurred in all but one of our cases. In that one case, despite digital pressure for a period of several minutes, a pulsatile stream of hemorrhage issued forth from the iridotomy site and layered out, forming a 20% hyphema. This hemorrhage was associated with an immediate postoperative intraocular pressure rise from 2 1 to 37 mm Hg. The patient was not hospitalized and the hyphema resolved spontaneously overnight. Hyphema has been reported by others as a rare but potentially serious complication of YAG laser iridotomy.24 In an attempt to prevent hyphema formation, some have suggested pretreating iridotomy sites with the Argon laser before attempting a YAG laser iridotomy. 6g We do not advocate this for two reasons. First, in an unpublished series, we pretreated irides in anesthetized rabbits with Argon laser spots of various intensities before attempting YAG laser iridotomy. Unless the Argon laser iridotomy was made through and through, iris vessels deep to the Argon crater would bleed routinely when the YAG iridotomy was made. Others have noted similar findings. 42Further, the one patient in our experience who had a significant hyphema had been previously treated with an Argon laser. The YAG laser treatment in this case was delivered at the base of the
NEODYMIUM:YAG
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LASER IRIDOTOMY
previous Argon crater, but significant hemorrhage. Although the reported resolved spontaneously, it some cases have occurred permanent damage results.
nevertheless
resulted
in a
cases of hyphema have is certainly possible that or will occur in which
E. LENS Inadvertent damage to the anterior lens capsule has been a major concern of ophthalmologists perConcern stems from forming YAG iridotomy. 23,27,78 the fact that YAG lasers have been used for years to perform posterior capsulotomy at energy levels that average approximately 5% to 20% of the levels used for iridotomy. Clinically, however, major lens complications have not been reported. There are several reasons why lens damage may not have been seen. First, iridotomies are routinely attempted in the far iris periphery. This is done both to insure free communication between the anterior and posterior chambers, and to avoid damaging the lens with any throughput of laser energy. The additional prismatic effect gained by using an Abraham lens often allows one to place the iridotomy site so far out under the peripheral arcus that it may be difficult to visualize directly. An iridotomy in this position is peripheral to the outer edge of the lens. Second, when the threshold for optical breakdown is reached, the resultant plasma shield prevents any further throughput of energy and the energy propagates back toward the delivery source rather than continuing on posteriorly. This phenomenon serves to protect the anterior lens capsule during iridotomy; however, it probably accounts for some of the intraocular lens damage seen when performing posterior capsulotomy, and for the linear cracks in Descemet’s membrane se& after performing iridotomy in eyes where there is close iridocorneal opposition. Third, the iris itself absorbs the bulk of the energy delivered during iridotomy and thus works as a protective barrier for the anterior lens capsule. Fourth, experimental animal and human studies in which iridotomy was performed in a way that would increase the chances for lens damage have shown that the YAG laser can produce small, nonprogressive pits on the anterior lens capsule. Therefore, it is possible that subclinical anterior lens capsule damage has occurred in some cases. However, the peripheral location of these lesions, their minute size, and their lack of progression have rendered them inconsequential. We reexamined 50 phakic patients 3-16 months after they had undergone YAG iridotomy. We found no focal or progressive lenticular opacities that we could attribute to the YAG laser. This
agrees with other reported series, and is in contrast to the 8-10% of patients who show small focal lens opacities, similar to lesions seen following Argon laser panretinal photocoagulation, after Argon laser iridotomy.41,47,48,50,57,75
Because the potential exists for creating an inadvertent and serious anterior capsular rent, the safe performance of iridotomies requires meticulous attention to detail. Patient positioning, fixation, and laser focus must be controlled precisely, and the lowest energy settings compatible with successful results should be used.
F. CILIARY
BODY AND RETINA
Ciliary body detachment has been reported after an attempt to reopen a sclerotic trabeculectomy site with the YAG laser.58 Retinal holes and subsequent detachment have been reported after YAG capsulotomy and vitreous band lysis.21~32 In all of these instances, deep intraocular damage occurred at a site distal to the intended treatment site. This is most likely due to a throughput of direct laser energy, the effects of the shockwave accompanying plasma formation, or a combination of the two. Bilateral nonrhegmatogenous retinal detachment has been reported following successful YAG iridotomy.33 By comparison direct retinal burns, choroidal and retinal detachment, hyphema, cystoid macular edema, and visual loss have been reported following Argon laser iridotomy.4,9.12,14.29,34
IV. Conclusions The initial experience with using the YAG laser for peripheral iridotomy has been generally positive. The YAG laser is more effective in producing iridotomies in one sitting than the Argon laser, while damage to the cornea1 epithelium, central corneal endothelium, and the anterior lens capsule are less frequent with the YAG laser than with the Argon laser. The incidence of post-laser intraocular pressure increase is approximately the same with YAG and Argon lasers. Although hemorrhage from the iridotomy site is seen more frequently with the YAG laser than the Argon laser, the hemorrhage is self-limited in the vast majority of cases and can usually be stopped with mild digital pressure in those rare cases where bleeding continues. Our patients and other patients4’s5’ who have had both YAG laser and an Argon laser iridotomy procedure generally prefer the YAG laser procedure. Most patients who are good candidates for YAG laser iridotomy are good candidates for Argon laser iridotomy as well; however, there are rare patients who are not suitable for the Argon laser but can be treated successfully with the YAG laser. We have
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32(3) November-December
DRAKE
1987
recently treated such a patient who was suffering from tardive dyskinesia after decades of phenothyrazine treatment. The patient’s constant dysrhythmic upper body movements and lip smacking made it impossible for him to hold his head still for treatment. Fortunately, the Abraham lens and YAG laser allowed treatment to be applied effectively in a split ‘second. Perhaps as a natural consequence of the ease and apparent safety of performing laser iridotomies, the indications for iridotomy have broadened in most centers. We have performed several times more iridotomies in the past five years than we performed in the prior decade, even though the longterm safety of YAG laser iridotomy has yet to be established. As was the case with surgical iridectomy, we may find that there are late visual acuity changes that are undetected during the first one to two years of followup.22~25~~~43~“~74J’* The ultimate position of YAG laser iridotomy in our .therapeutic armamentarium depends on further refinement in technique and on longterm follow-up studies of our patient populations.
References Argon laser iridectomy 1. Abraham RK, Miller CC: Outpatient for angle closure glaucoma: A two year study. Tram Am Acad OphthalmolOtolaryngol79:529-538, 1975 RK, Munnerlyn C: Laser iridotomy - Improved 2. Abraham methodology with a new iridotomy lens. Ophthalmology86: 126, 1979 M, Thyzel R: Use of the 3. Aron-Rosa D, Aron JJ, Griesemann Neodymium YAG laser to open the posterior capsule after lens implant surgery: A preliminary report. Am Intra-OculImplant SOC J 6:352-354, 1980 TJ, Hease RJ, Steigner B: Loss of 4. Balkan RJ, Zimmerman central visual acuity after lens peripheral iridectomy. Arm Ophthalmol I4:721-723, 1982 Beckman H, Barraco R, et al: Laser iridotomies. Am J Ophthalmol72:393-402, 1971 Beckman H, Sugar HS: Laser iridotomy therapy of glaucoma. Arch Ophthalmol!W:453-455, 1973 Belcher CD, Mainster MA, Buzney SM: Current status of neodymium YAG laser photodisruptors in ophthalmology: Part I. Ann OphthalmolL5:997-999, 1983 8. Belcher CD, Mainster MA, Buzney SM: Current status of Neodymium YAG laser photodisruptors in ophthalmology: Part II. Ann Ophthalmol15:1097-1099, 1983 from laser iridotomy. Oph9. Berger B: Fovea1 photocoagulation thalmolou 91:1029-1033, 1984 DE: Low energy Q-switched Ruby 10. Bonney CH, Gaasterland laser iridotomies in macaca mulatta. Invest Ophthalmol Vis Sci l&278-287, 1979 11. Brainard JO, Landers JH, Shark P: Recurrent angle closure following a patent 75 micron laser iridotomy: A case report. OphthalmicSurg 13:103C-1032, 1982 12. Chopin NT, Bene CH: Cystoid macular edema following laser iridotomy. Ann Ophthalmol15:172-l 73, 1983 13. Cohen JS, Bibler L, Tucker D: Hypopyon following laser iridotomy. OphthalmicSurg 15:604-606, 1984 14. Corrineau LA, Nasr Y, Fanous S: Choroidal and retinal detachment following Argon laser iridotomy. Can J Ophthalmol21: 107-108, 1986 YAG laser iridot15. Dragon DM, Robin AC, et al: Neodymium: omy in the cynmolgus monkey. Invest Ophthalmol Vis Sci 26: 789-796, 1985
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intraocular following Neodymium YAG laser iridectomy. Arch Ophthalmol104:178, 1986 Hodes BL, Bentrwega JF, Weyer N.1: Hyphema complicating laser iridotomy. Arch O~hthalmk 100:92&~25, 1982 _ Hoskins HD. Mialiazzo CV: Laser iridectomv - A techniaue for blue irises. Oihthalmic Surg 15:488-190, 1984 Iacobs IH, Krohn DL: Central anterior chamber depth after ‘iaser iridectomy. Am J Ophthalmol89:865-867, 1980 lamnol LM. Goldbere NF. Iedrick N: Retinal damage from a YQ-switched YAG lasel. Ai> 0phthalmo196:326-329,y1983 Karjalainen K, Laatikainen L, Raitta C: Bilateral nonrhegmatogenous retinal detachment following Neodymium YAG laser iridectomies. Arch Ophthalmol104:1134, 1986 Karmon G, Savin H: Retinal damage after Argon laser iridotomy. Am J Ophthalmol101:554-560, 1986 Katzen LA, Fleischman JA, Trahel SL: The YAG laser: An American experience. Am Intra-Oc Implant Sot J 9: 151, 1983 Ken Muir MC, Sherrard ES: Damage to the cornea1 endotbeliurn during Nd:YAG photodisruption. Br J Ophthalmof69:77-85, 1985 Khuri CH: Argon laser iridotomies. Am J Ophthalmol76:490pressure
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in the
NEODYMIUM:YAG
LASER IRIDOTOMY
M, Sliney D, Belcher CD III, Buzney SM: Laser 45. Mainster photodisruptors. Ophtkalmology 90:973-99 1, 1983 46. Martin NF, Gaasterland DE, et al: Damage thresholds for retinocorneal Nd:YAG pulses. Invest Ophthalol Vis Sci (Suppl) 25:330, 1984 47. McAllister JA, Schwartz W, Moster MM, Spaeth GL: Laser peripheral iridotomy comparing Q-switched Neodymium YAG with Argon. Trum Ophthalmol Sot UK 10#:67-69, 1984 48. McCanna P, Chandion S R, et al: Argon laser induced cataract as a complication of retinal photocoagulation. Arch Ophthafmol 100:1071-1073, 1982 49. Meyer KT, Petitt TA, Straatsma BR: Cornea1 endothelial damage with Neodymium YAG laser. Ophthalmology 92:1022-1028, 1984 50. Moster MM, Schwartz CW, et al: Laser iridotomy: A controlled study comparing Argon and Neodymium:YAG. Ophthalmolou 93:20-24, 1986 51. Master MR, Schwartz CW, et al: The effect of Nd:YAG laser iridotomy on the rabbit lens. Invest Ophthalmol Vis Sci (Suppf) 25r1419, 1984 52. Perkins ES, Brown NAP: Iridotomy with a Ruby laser. Br J Ophthalmol57:487-498, 1973 53. Podos SM, Kels BD, et al: Continuous wave Argon laser iridotomy in angle closure glaucoma. Am J Ophthalmol #:83&842, 1979 54. Pollack IP: Chronic angle closure glaucoma: Diagnosis and treatment in patients with angles that appear open. Arch Ophthalmol85:67&-689, 1971 55. Poliack JP: Use of Argon laser energy to produce iridotomies. Ophthalmic Surg 11:506-545, 1980 56. Pollack JP, Patz A: Argon laser iridotomy. An experimental and clinical study. Ophthalmic Surg 7:22-30, 1976 57. Pollack JP, Robin AL, et al: Use of the Neodymium: YAG laser to create iridotomies in monkeys and humans. 7’ras.s Am Ophthal Sot 82:307-328, 1984 58. Prywes AS, LoPinto RJ: Temporary visual loss with ciliary body detachment and hypotony after attempted YAG laser repair of failed filtering surgery. Am J Ophthalmol 101:305-307, 1986 59. Puliatito CA, Steinert R: Laser surgery ofthe lens. Ophthalmology 90:1007-1012. 1983 60. Quigley H: Long term followup of laser iridotomy. Ophthalmology 88:218-224, 1981 F, Lijtsden H: Contact glasses for use 61. Riquin D, Frankhauser with high power lasers. Int Ophthalmol 6: 191-200, 1983 62. Ritch R, Palmberg P: Argon laser iridectomy in densely pigmented irides. Am J 0phtha1mo193:800-801, 1982 63. Ritch R: Argon laser treatment for medically unresponsive attacks of angle closure glaucoma. Am J Ophthalmol 94: 197-204, 1982 64. Robin A, Arkell S, et al: Q-switched Neodymium YAG laser iridotomy. A field trial with a portable laser system. Arch Ophthalmol 104:526-530, 1986 65 Robin A, Pollack IR: A comparison of Neodymium YAG and Argon laser iridotomies. Ophthalmology 91:1011-1016, 1984 66. Robin A, Pollack JP: Argon laser peripheral iridotomies in the treatment of primary angle closure glaucoma: Longterm followup. Arch Ophthalmol 100:919-923, 1982 67. Robin AL, Pollack JP, et al: Histologic studies of angle structures after laser iridotomy in primates. Arch Ophthalmol 100: 16651670, 1982 68. Robin A, PoHack J: Q-switched Neodymium YAG laser iridotomy in patients in whom the Argon laser fails. Arch Ophthalmol 104:531-535, 1986
177 69. Rockwood EJ, Meters SM, et al: Treatment of selected cases of papillary block with YAG laser iridotomies. Ophthulmic Surg 15.968, 1984 70. Schrems W, Dorp HP, Wendel M, Kreigelstein GK: The effect of YAG laser iridotomy on the blood aqueous barrier in the rabbitt. Craefcs Arch Clin Exp Ophthdmd 221:179-181, 1984 7 1. Schrems W, Eichelbronner 0, Kreigelstein GK: The immediate IOP response of Nd:YAG laser iridotomy and its prophylactic treatability. Acta Ophthalmd (Copd) 620:673-680, 1984 72. Schubert HD: A history of intraocular pressure rise with reference to the Nd:YAG laser. Sun, O$hthalmol30:168-172, 1985 73. Schwartz LW, Moster MR, et al: Neodymium YAG laser iridectomies in glaucoma associated with closed or occludable angles. Am J Ophthdmol1QZ:4 l-44, I986 74. Shaffer RN, Rosenthal C: Comparison of cataract incidence in the normal and glaucomatous population. Am J Ophthalmol 69368-370, 1970 75. Shapiro A, Tso MO, Goldberg MF: Argon laser induced cataract. Arch Ophthahol 102:579-383, 1984 76. Shin DH: Another hypopyon following laser iridotomy. Ophthulmic Surg 15:968, 1984 77. Snyder WB: Laser coagulation of the anterior segment. Arch Ophthalmol 77:93-98, 1967 78. Spaeth GL: Discussioh of Gaasterland, et al: Threshold for lens damage during YAG laser iridectomy. OphthdmologV 922:1623, 1985 79. Stez D, Smith H Jr., Ritch R: A simplified technique for laser iridectomy in blue irides. Am J Ophthalmol %:249-251, 1983 80. Schwartz LW, Rodrigues MM, et al: Argon laser iridotomy in the treatment of patients with primary angle closure or pupillary block glaucoma. A clinicopathologic study. Tranr Am Acad Ophthalmol Otolarynpof 8.5:294-309, 1978 81. Terry AC, Stark WJ, Maumenee AE, Fagadau W: Neodymium YAG laser for posterior capsulotomy. Am J Ophthalmol 96: 716-720, 1983 82. Trokel SL (ed): YAC Laser Ophthalmic Microsurgery. Norwalk CT, Appleton-Century, 1983 83. Van der Zypen E, Fankhauser F, Bebie H: On the effects of different laser energy sources upon the iris of the pigmented and the albino eye. Int Ophthalmol 1:39-48, 1978 84. Vogel A, Hentschel W, Holzfuss J, Lauterborn W: Cavitation bubble dynamics and acoustic transient generation in ocular surgery with pulsed Neodymium:YAG lasers. Ophthalmology 93:1259-1269, 1986 85. Weinreb RN,. Rudenerman J, Juster R, Zweig K: Immediate intraocular pressure response to Argon laser trabeculoplasty. Am J Ophthalmol95:279-286, 1983 86. Welch DB, Apple DJ, Mendelsohn AD, et al: Lens injury following iridotomy with a Q-switched Neodymium YAG laser. Arch Ophthalmol 104: 123-125, 1986 87. Wise JB, Munnerlyn CR, Erickson PJ: A high efftciency laser iridotomy-sphincterotomy lens. Am J Ophthalmol 101:546--553, 1986 88. Wollensak J, Zeisberg B: Pathophysiology, treatment, and prophylaxis of angle closure glaucoma. Glaucoma 8:3011, 1986 89. Yassur Y, Melamed S, Cohen S, Ben-Sira I: Laser iridectomy in closed angle glaucoma. Arch Ophthalmol 97: 1920-I 92 1, 1979 90. Zweng H, Flocks M, et al: Experimental laser photocoaguiation. Am J Ophthalmol 58:353-352, 1964 Reprint requests should be addressed to Michael V. Drake, M.D., Ophthalmology, U490, School of Medicine, University of California, San Francisco, CA 94143.
DIAGNOSTIC
NUMBER 3
l
NOVEMBER-DECEMBER
1987
TECHNIQUES
EDITOR
Neodymium:YAG V. DRAKE,
l
AND SURGICAL
STEVEN G. KRAMER,
MICHAEL
32
Laser Iridotomy
M.D.
Department of Ophthalmology, University of Cabfoonzia at San Francisco, San Francisco, Calzfornia
Abstract. During
the past several years t‘he Neodymium:YAG laser has become increasingly popular for performing peripheral iridotomy. Using energy levels of 2-8 millijoules per shot and 1-3 shots per treatment, most irides can be penetrated in one sitting. Nd:YAG laser iridotomies show very little tendency to close, except in patients with active intraocular inflammation. A small amount of hemorrhage is common following YAG laser iridotomy, but clinically significant hyphema is rare. Significant lenticular or cornea1 damage is extremely rare. Although longterm follow-up of large numbers of patients is lacking, Nd:YAG laser iridotomy appears to be a safe and effective alternative to Argon laser iridotomy in selected patients. (Surv Ophthalmol 32:171-177,
Key words. peripheral
1987)
Abraham iridotomy
lens
l
Argon
laser
*
Soon after laser systems became available for clinical investigation, attempts were made to use them to perform peripheral iridotomy.5J0,3g,g0 Early attempts with pulsed Ruby lasers were abandoned because of inconsistent results and a significant inci6,52,77 The subsequent experidence of complications. ence with continuous wave Argon lasers was much more positive.‘~37~53~56~a0~83 Refinements in technique, as well as innovations such as the Abraham lens, led to increasing popularity of Argon laser iridotomy during the latter part of the 1970s.2J1,55 By the early 1980s Argon laser iridotomy had largely replaced surgical iridectomy as the treatment of choice for patients with angle closure glaucoma or occludable angles. 60,63,66,6* However, Argon laser iridotomy was not appropriate for all patients, and considerable difficulty was encountered in performing iridotomy for patients with light blue irides, dark brown irides, and others.30,62,7gJg Pulsed Neodymium:YAG (Nd:YAG) lasers be-
Neodymium:YAG
laser
l
came available commercially in the United States in 1982.35,82 They deliver intense amounts of energy into a well-focused spot over a period of pica seconds to nano seconds.3*8Ja*0 The extremely high irradiance produced by Nd:YAG lasers strips electrons from atoms, resulting in a high energy electron cloud or plasma. 7,45The local disruptive effect of these instruments is dependent upon the effects of optical breakdown at the focal point of the laser. Optical breakdown is a nonlinear absorptive phenomenon which occurs at an extremely high threshold intensity (on the order of 10’0wIcm2).84 Clinical experience indicates that YAG laser iridotomy may offer significant advantages over Argon laser iridotomy in selected patients.38
I. Technique As with any surgical procedure, is of paramount importance.54@ 171
patient selection Our own experi-
172
Surv Ophthalmol 32(3) November-December 1987
ence includes patients with acute angle closure glaucoma, positive provocative tests for angle closure glaucoma, chronic progressive angle closure glaucoma, fellow eyes in which a documented angle closure glaucoma attack occurred in the opposite eye, and patients in whom gonioscopy indicates occludable angles. The patients must be physically and psychologically able to cooperate with the laser procedure and be able to remain seated at the slit-lamp for a period of three to five minutes. The cornea must be sufficiently clear to allow adequate laser energy to reach the iris and to allow the physician to visualize the iris for proper aiming and focusing of the laser beam. Patients who are not already using pilocarpine or similar miotic therapy should probably be treated with pilocarpine preoperatively. Pilocarpine puts the iris on stretch, which may make the procedure easier, as well as perhaps blunting the tendency toward postoperative pressure rise in some eyes.” After the patient is seated at the laser and appropriate topical anesthetic is applied, the angle should be reexamined with a gonioscopy lens. We use the Goldmann or Zeiss indirect methods to examine the angle, because these examinations can be performed effectively with the patient sitting at the slitlamp. Next, an Abraham or similar lens is applied.2,6’,87Although the Abraham lens is not an absolute requirement, it has advantages that enhance the safety and efficacy of the procedure. First, the suction of the lens and coupling agent (e.g., Goniosola) on the eye allows the surgeon to control fuation during the procedure. Second, the construction of the lens prevents inadvertent blinking during the laser treatment. Third, the converging button of the Abraham lens tends to focus the laser beam more sharply on the iris. 2 This results in a higher power density that achieves optical breakdown at lower total energy levels. Further, the increased cone angle is associated with a greater beam divergence distal to the treatment site.45,5g Although energy levels vary widely from machine to machine, and sometimes even within the same machine, the overwhelming majority of clinical iridotomies are made with settings between three and ten millijoules per shot. We find that the minimum settings for an iridotomy in a blue iris using an Abraham lens are approximately three to four millijoules per shot, one to three shots per burst.16 This minimum level corresponds roughly to the energy level required for visible spark formation in air when our machine is fired without using any external focusing device (such as the Abraham lens). Energy levels from 50% to 100% higher are necessary when performing iridotomy on thick, velvety smooth, brown irides.
DRAKE Energy delivery can be increased by using either more power per shot or more shots per burst. Higher energy levels and more shots per burst are associated with a greater degree of success in fewer treatment sessions, but also with a greater degree of intraocular damage. Human and experimental animals studies have shown that anterior lens capsule damage is a frequent complication when relatively central iridotomies are performed using energy settings of greater than seven milhjoules per shot and three or more shots per burst.23,2’,5’,86 These studies probably overestimate the actual incidence of lens damage at such energy settings in practice, because the iridotomies were purposely placed more centrally than usual. A more peripheral treatment site takes advantage of the fact that the iris diameter is greater than the lens diameter and that the lens begins to curve posteriorly toward its periphery. Thus, the anterior lens capsule is not directly adjacent to the posterior surface of the iris and any excess laser energy that penetrates the iris is less likely to damage the lens. In addition to choosing a peripheral treatment site, one can decrease the likelihood of intraocular damage by using fewer shots per burst and by not using the Nd:YAG laser to enlarge an iridotomy opening. 27 A series of five, six, or more shots per burst commits one to delivering the full pulse train with each treatment application. If the first or second shot produces a patent iridotomy, the latter shots in the sequence are delivered unimpeded into the iridotomy hole, potentially damaging intraocular structures. This same rationale applies to the prohibition against using the Nd:YAG laser to enlarge a smaller iridotomy opening. A small fixation shift or focusing error can result in the delivery of laser energy through the iridotomy hole and to deep intraocular structures. If an iridotomy opening is deemed too small, it is probably wisest to choose another means of enlarging the opening (such as an Argon laser) or to create an additional Nd:YAG iridotomy at a separate site. If the initial attempt at an iridotomy fails to produce a through and through hole, one can choose to retreat again at the same site or to move to a separate site, depending on the appearance of the partial thickness crater. The decision to retreat at the same site depends partially on the degree of pigment dispersion and hemorrhage caused by the previous partial treatment. Especially in thick, brown irides, an incomplete treatment may result in a thick cloud of dispersed iris pigment. This cloud makes it difficult to visualize or focus adequately on the base of the previous partial thickness treatment. Repeated applications of laser energy into this pigment cloud may result in increased pigment dispersion and
NEODYMIUM:YAG
hemorrhage rather than a patent iridotomy.** Currently, we either move to another site for our next iridotomy attempt or wait a few minutes until the pigment cloud has dispersed. If we choose to wait until the pigment cloud has dispersed and then attempt to complete the iridotomy at the initial site, we will generally use fewer shots per burst and/or less energy per shot. Conversely, if we move to a separate site for our second attempt, we may increase the energy settings appropriately. Following a successful iridotomy, as evidenced by a gush of pigment debris through the iridotomy site and direct visualization of the through and through opening, patients are examined at 30 minutes and at two to three hours after the procedure. Any immediate postoperative complications are treated. Patients are then discharged and seen at intervals of one day, one week, one month, and three months after the procedure. If.
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LASER IRIDOTOMY
Treatment Results
Using the parameters outlined above, a successful iridotomy is achieved in virtually all patients, usually in one treatment session.‘6,47~50~57~73 This is the case even when prior attempts at Argon laser iridotomy have failed .68The typical YAG laser iridotomy is a small (ZOOto 500 mu), irregularly oval opening oriented radially, with somewhat ragged edges (Fig. 1). The total energy required to produce an iridotomy ranges between seven or eight millijoules and 200 millijoules, depending on the various factors mentioned above. Except in eyes with uveitis or other inflammatory disease, YAG laser iridotomies show very little tendency to close. Overall patency rates as high as 99% have been reported. 73This contrasts to closure rates as high as 30% with Argon laser iridotomy.“~47~“~65~68 Our own results corroborate this. Of our first 51 YAG laser iridotomies, only four closed in the postoperative period. Ail four of these patients had active intraocular inflammation prior to the laser procedure, and a diagnosis of iris bombe. We have found that performing several iridotomies in such patients lessens the chance that the iris bombe will reoccur postoperatively.
III. Complications Minor complications occur with some frequency in YAG laser iridotomy. Most of these have no deleterious sequelae and are probably better termed “side effects.” There have been relatively few serious Complications.
A. CORNEA Cornea1 epithelial burns are seen with some frequency in Argon laser iridotomy, but are rare with
YAG laser iridotomy. I5This is due at least in part to the dramatic decrease in total energy required for a YAG laser iridotomy. In contrast to the 8-200 millijoules (mean: 25-30) required for YAG laser iridotomy, 5-50 joules (5000-50000 millijoules) may be required for Argon laser iridotomy. Furthermore, since the continuous wave Argon laser depends on a thermal effect to produce an iridutomy, energy absorbed by the cornea can result in local burns. The plasma formation associated with optical breakdown propagates back toward the laser delivery source, thereby directing a substantial amount of the energy used to perform a YAG laser iridotomy back toward the cornea1 endothelium. This is of particular concern when performing iridotomies in extremely shallow or flat anterior chambers. Experimental studies have shown a local denuding of cornea1 endothelial tissue when the YAG laser is focused 1 mm or less posterior to the endothelial surface.36+a4g Clinically, one may observe linear nonprogressive cracks at the level of Descemet’s membrane directly over the iridotomy site. Generally these cracks are approximately 500 mu in length and may be seen best by retroillumination. Spectromicroscopy has shown central endothelial cell loss to be minimal in patients who have undergone YAG laser iridotomy, compared to 8 or 10% with Argon laser iridotomy.‘j’j B. ANTERIOR
CHAMBER
Laser iridotomy results in a measurable breakdown in the blood-aqueous barrier. This is aimost assuredly a prostaglandin mediated response, as is seen following iris trauma from any number of sources.7o However, clinically significant uveitis is seen less often with YAG laser iridotomy than with In our patients treated Argon laser iridotomy. ‘3,73,76 with the YAG laser, antiinflammatory medications were required postoperatively only for patients with preoperative uveitis or other ocular inflammations. In contrast, Argon laser iridotomy produced significant uveitis in approximately 10% of our patients. C. INTRAOCULAR
PRESSURE
Postoperative intraocular pressure rise has been a serious concern with YAG laser iridotomy.72 This transient acute pressure rise has its peak incidence between one and three hours after the procedure. In some cases, severe pressure rises (up to 50 or 60 mm Hg) have been reported. 28~”There has not been a consistent relationship between the amount of energy required for the iridotomy and the increase in intraocular pressure following the procedure. Although it seems intuitively obvious that pigment
Surv Ophthalmol
Fig. I. Neodymium:YAG ragged-edged, irregularly
32(3) November-December
laser iridotomy oval appearance.
FROM
THE IRIDOTOMY
DRAKE
with typical
and iris stroma debris liberated by the procedure have the potential to clog the trabecular outflow system, other factors may also play an important role.26~44~45,67 The shock wave associated with YAG iridotomy may affect trabecular function or may lead to changes in the aqueous or vitreous that affect the intraocular pressure. A postoperative pressure rise is seen in 25120% of patients undergoing YAG laser iridotomy. This percentage is similar to that seen in patients undergoing Argon laser iridotomy or YAG laser capsulotFor this reason, all patients should be omy. 17,26,35,81,85 followed carefully for several hours after the procedure. Particular attention should be given to individuals who have severe glaucoma and in whom a transient severe pressure spike may have particularly disastrous results. 85We treat significant pressure spikes aggressively, using systemic carbonic anhydrase inhibitors and oral hyperosmotic agents as necessary. As with Argon laser iridotomy, the pressure spikes following YAG iridotomy are transient and resolve within the first several days postoperatively. D. BLEEDING
1987
SITE
A frequent and sometimes troubling side effect of YAG laser iridotomy is bleeding from the iridotomy site.‘6*64Some degree of hemorrhage may be found in over half of the patients treated. Most often this is a microhemorrhage visible either just around the edges of the iridotomy or visible as a thin hemorrhage cascade coursing a few millimeters over the surface of the iris (Fig. 2). Most of these hemorrhages are entirely self-limited, resolving spontaneously within a few seconds. Occasionally the hemorrhage is more active and the cascade continues for some time after the treatment has been given. In
Fig. 2. Self-limited hemorrhage cascade photographed fifteen minutes after Neodymium:YAG laser iridotomy. The hemorrhage is often visible for several hours after the procedure, but is usually gone by the next day.
such cases we use digital pressure on the Abraham lens for several seconds to a few minutes, until the hemorrhage stops. This procedure has successfully arrested the hemorrhage before hyphema formation occurred in all but one of our cases. In that one case, despite digital pressure for a period of several minutes, a pulsatile stream of hemorrhage issued forth from the iridotomy site and layered out, forming a 20% hyphema. This hemorrhage was associated with an immediate postoperative intraocular pressure rise from 2 1 to 37 mm Hg. The patient was not hospitalized and the hyphema resolved spontaneously overnight. Hyphema has been reported by others as a rare but potentially serious complication of YAG laser iridotomy.24 In an attempt to prevent hyphema formation, some have suggested pretreating iridotomy sites with the Argon laser before attempting a YAG laser iridotomy. 6g We do not advocate this for two reasons. First, in an unpublished series, we pretreated irides in anesthetized rabbits with Argon laser spots of various intensities before attempting YAG laser iridotomy. Unless the Argon laser iridotomy was made through and through, iris vessels deep to the Argon crater would bleed routinely when the YAG iridotomy was made. Others have noted similar findings. 42Further, the one patient in our experience who had a significant hyphema had been previously treated with an Argon laser. The YAG laser treatment in this case was delivered at the base of the
NEODYMIUM:YAG
175
LASER IRIDOTOMY
previous Argon crater, but significant hemorrhage. Although the reported resolved spontaneously, it some cases have occurred permanent damage results.
nevertheless
resulted
in a
cases of hyphema have is certainly possible that or will occur in which
E. LENS Inadvertent damage to the anterior lens capsule has been a major concern of ophthalmologists perConcern stems from forming YAG iridotomy. 23,27,78 the fact that YAG lasers have been used for years to perform posterior capsulotomy at energy levels that average approximately 5% to 20% of the levels used for iridotomy. Clinically, however, major lens complications have not been reported. There are several reasons why lens damage may not have been seen. First, iridotomies are routinely attempted in the far iris periphery. This is done both to insure free communication between the anterior and posterior chambers, and to avoid damaging the lens with any throughput of laser energy. The additional prismatic effect gained by using an Abraham lens often allows one to place the iridotomy site so far out under the peripheral arcus that it may be difficult to visualize directly. An iridotomy in this position is peripheral to the outer edge of the lens. Second, when the threshold for optical breakdown is reached, the resultant plasma shield prevents any further throughput of energy and the energy propagates back toward the delivery source rather than continuing on posteriorly. This phenomenon serves to protect the anterior lens capsule during iridotomy; however, it probably accounts for some of the intraocular lens damage seen when performing posterior capsulotomy, and for the linear cracks in Descemet’s membrane se& after performing iridotomy in eyes where there is close iridocorneal opposition. Third, the iris itself absorbs the bulk of the energy delivered during iridotomy and thus works as a protective barrier for the anterior lens capsule. Fourth, experimental animal and human studies in which iridotomy was performed in a way that would increase the chances for lens damage have shown that the YAG laser can produce small, nonprogressive pits on the anterior lens capsule. Therefore, it is possible that subclinical anterior lens capsule damage has occurred in some cases. However, the peripheral location of these lesions, their minute size, and their lack of progression have rendered them inconsequential. We reexamined 50 phakic patients 3-16 months after they had undergone YAG iridotomy. We found no focal or progressive lenticular opacities that we could attribute to the YAG laser. This
agrees with other reported series, and is in contrast to the 8-10% of patients who show small focal lens opacities, similar to lesions seen following Argon laser panretinal photocoagulation, after Argon laser iridotomy.41,47,48,50,57,75
Because the potential exists for creating an inadvertent and serious anterior capsular rent, the safe performance of iridotomies requires meticulous attention to detail. Patient positioning, fixation, and laser focus must be controlled precisely, and the lowest energy settings compatible with successful results should be used.
F. CILIARY
BODY AND RETINA
Ciliary body detachment has been reported after an attempt to reopen a sclerotic trabeculectomy site with the YAG laser.58 Retinal holes and subsequent detachment have been reported after YAG capsulotomy and vitreous band lysis.21~32 In all of these instances, deep intraocular damage occurred at a site distal to the intended treatment site. This is most likely due to a throughput of direct laser energy, the effects of the shockwave accompanying plasma formation, or a combination of the two. Bilateral nonrhegmatogenous retinal detachment has been reported following successful YAG iridotomy.33 By comparison direct retinal burns, choroidal and retinal detachment, hyphema, cystoid macular edema, and visual loss have been reported following Argon laser iridotomy.4,9.12,14.29,34
IV. Conclusions The initial experience with using the YAG laser for peripheral iridotomy has been generally positive. The YAG laser is more effective in producing iridotomies in one sitting than the Argon laser, while damage to the cornea1 epithelium, central corneal endothelium, and the anterior lens capsule are less frequent with the YAG laser than with the Argon laser. The incidence of post-laser intraocular pressure increase is approximately the same with YAG and Argon lasers. Although hemorrhage from the iridotomy site is seen more frequently with the YAG laser than the Argon laser, the hemorrhage is self-limited in the vast majority of cases and can usually be stopped with mild digital pressure in those rare cases where bleeding continues. Our patients and other patients4’s5’ who have had both YAG laser and an Argon laser iridotomy procedure generally prefer the YAG laser procedure. Most patients who are good candidates for YAG laser iridotomy are good candidates for Argon laser iridotomy as well; however, there are rare patients who are not suitable for the Argon laser but can be treated successfully with the YAG laser. We have
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32(3) November-December
DRAKE
1987
recently treated such a patient who was suffering from tardive dyskinesia after decades of phenothyrazine treatment. The patient’s constant dysrhythmic upper body movements and lip smacking made it impossible for him to hold his head still for treatment. Fortunately, the Abraham lens and YAG laser allowed treatment to be applied effectively in a split ‘second. Perhaps as a natural consequence of the ease and apparent safety of performing laser iridotomies, the indications for iridotomy have broadened in most centers. We have performed several times more iridotomies in the past five years than we performed in the prior decade, even though the longterm safety of YAG laser iridotomy has yet to be established. As was the case with surgical iridectomy, we may find that there are late visual acuity changes that are undetected during the first one to two years of followup.22~25~~~43~“~74J’* The ultimate position of YAG laser iridotomy in our .therapeutic armamentarium depends on further refinement in technique and on longterm follow-up studies of our patient populations.
References Argon laser iridectomy 1. Abraham RK, Miller CC: Outpatient for angle closure glaucoma: A two year study. Tram Am Acad OphthalmolOtolaryngol79:529-538, 1975 RK, Munnerlyn C: Laser iridotomy - Improved 2. Abraham methodology with a new iridotomy lens. Ophthalmology86: 126, 1979 M, Thyzel R: Use of the 3. Aron-Rosa D, Aron JJ, Griesemann Neodymium YAG laser to open the posterior capsule after lens implant surgery: A preliminary report. Am Intra-OculImplant SOC J 6:352-354, 1980 TJ, Hease RJ, Steigner B: Loss of 4. Balkan RJ, Zimmerman central visual acuity after lens peripheral iridectomy. Arm Ophthalmol I4:721-723, 1982 Beckman H, Barraco R, et al: Laser iridotomies. Am J Ophthalmol72:393-402, 1971 Beckman H, Sugar HS: Laser iridotomy therapy of glaucoma. Arch Ophthalmol!W:453-455, 1973 Belcher CD, Mainster MA, Buzney SM: Current status of neodymium YAG laser photodisruptors in ophthalmology: Part I. Ann OphthalmolL5:997-999, 1983 8. Belcher CD, Mainster MA, Buzney SM: Current status of Neodymium YAG laser photodisruptors in ophthalmology: Part II. Ann Ophthalmol15:1097-1099, 1983 from laser iridotomy. Oph9. Berger B: Fovea1 photocoagulation thalmolou 91:1029-1033, 1984 DE: Low energy Q-switched Ruby 10. Bonney CH, Gaasterland laser iridotomies in macaca mulatta. Invest Ophthalmol Vis Sci l&278-287, 1979 11. Brainard JO, Landers JH, Shark P: Recurrent angle closure following a patent 75 micron laser iridotomy: A case report. OphthalmicSurg 13:103C-1032, 1982 12. Chopin NT, Bene CH: Cystoid macular edema following laser iridotomy. Ann Ophthalmol15:172-l 73, 1983 13. Cohen JS, Bibler L, Tucker D: Hypopyon following laser iridotomy. OphthalmicSurg 15:604-606, 1984 14. Corrineau LA, Nasr Y, Fanous S: Choroidal and retinal detachment following Argon laser iridotomy. Can J Ophthalmol21: 107-108, 1986 YAG laser iridot15. Dragon DM, Robin AC, et al: Neodymium: omy in the cynmolgus monkey. Invest Ophthalmol Vis Sci 26: 789-796, 1985
16. Drake MV: Peripheral iridotomy using a Q switched Nd:YAG laser. Invest OphthalmolVis Sci (&ppl) .?7:253, 1986 17. Drake MV: Comolications ofAreon laser trabeculoolastv. Trans
Pat Coast Ota Opkalmol Sot 6Y:?l-74, 1983 A ’ 18. Fankhauser F, Lijrtscher H, van der Zypen E: Clinical studies
19.
20. 21.
22.
23.
24. 25.
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