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abstracts Edited by C. William Simcoe, M.D.

American Journal of Ophthalmology

Khwarg SG, Linstone FA, Daniels SA, Isenberg SJ, et al: Incidence, risk factors, and morphology in operat­ing microscope light retinopathy. Am J Ophthalmol 103:255-263, 1987

A review of 135 consecutive cataract operations identified ten cases (7.4%) of operating microscope light retinopathy. Ophthalmoscopically, these light retinopathy lesions appeared as a focal pigment epithelial change with varying degrees of pigment clumping the center. Fluorescein angiography ac­centuated the lesion by demonstrating a sharply demarcated transmission defect, occasionally with multiple satellite lesions. The shape of the lesion matched the shape of the illuminating source of the particular operating microscope used during the surgery. The most significant risk factor associated with the production of these light retinopathy lesions was prolonged operating time. Mean total operating time for the ten patients with light retinopathy was 51 minutes longer than for those without (P<. 0001). Other significant associated fac­tors were the presence of diabetes mellitus (P< .(3), young age (P<. 0.5), and the use of hydro­chlorothiazide (P<. 04).

Bradford RH Jr, Wilkinson CP: Vitreous opacification after cataract extraction. Am J Ophthalmol 103: 276-280, 1987

The authors performed pars plana vitrectomies on a consecutive series of 24 eyes in which nonhemor­rhagic vitreous opacification was responsible for loss of visual acuity after cataract extraction. Twelve eyes were aphakic and the remainder were pseudo­phakic. Preoperative fluorescein angiograms were performed in 20 cases, and the results of all studies were within normal limits. Postoperatively, a restor­ation of clear media and an improvement in visual acuity occurred in all cases. Visual acuity was 20/20 or better postoperatively in 15 of24 cases, and 22 of 24 achieved 20/30 or better. The remaining two cases improved to 20/40 and 20/50 from a preoperative level of 20/200 and 20/400, respectively. In carefully selected cases, vitrectomy techniques provide an effective means of managing this syndrome.

Archives of Ophthalmology

Apple DJ, Olson RJ: Closed-loop anterior chamber lenses. Arch Ophthalmol 105:19-20, 1987

The authors analyzed 1,122 surgically removed intraocular lenses (IOLs) from complicated cases and enucleated globes containing IOLs. Most of these were removed because of such ocular complications

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as uveitis, pseudophakic bullous keratopathy, cys­toid macular edema, secondary glaucoma, hemor­rhage, uveal chafing syndromes (e.g., uveitis-glau­coma-hyphema syndrome), opacification of the me­dia, and lens malpositions. Thirty-two were globes with IOLs in which the postimplantation complica­tions were severe enough to require enucleation. This series does not include 296 globes with IOLs that were obtained at autopsy and sent to the laboratory. These specimens are being analyzed separately with emphasis on IOL fixation sites and lens toleration. Anterior chamber IOLs represented 54.01 % of the implantations. Of these, 351 had closed, small-diameter, round loops, representing 31.30% of all IOLs received and 58.00% of all anterior chamber lenses accessioned in the labora­tory. In this letter, the authors report a relatively high incidence of complications leading to lens removal for closed-loop IOLs. The three most frequently accessioned anterior chamber lenses were the Surgidev style 10 Leiske lens, the IOLAB Azar 91Z lens, and the Optical Radiation Corpora­tion model 11 Stableflex lens. The latter lens has had the greatest recent percentage increase in rate of accession. In addition, the authors have received 30 removed Intermedics model 024 Hessburg IOLs, also a closed-loop design. Evidence of surgical difficulty in pseudophakos removal was verified in histopathologic and scanning electron microscopic analyses. This difficulty was caused in most cases by incarceration of the small-diameter round loops within synechias in the anterior chamber angle and on the iris root. When removal is necessary, this encapsulation often requires excessive cutting of the loops and/or surrounding tissues. In many instances, removal of the IOL is required for reasons other than problems with the implant itself; for example, ocular trauma. However, in the authors' opinion, even in these cases the excessive difficulties often encoun­tered during removal, as documented by the ex­planting surgeons' clinical records and scanning electron microscopic analyses, represent inherent design defects. As a basic prerequisite for IOL manufacture, the designer should anticipate the possibility that removal may be necessary. The lens should be designed to permit surgical removal with the least possible damage to delicate eye tissues. The authors conclude that closed-loop lens designs do not provide the safety and efficacy achieved by other anterior chamber lens designs, such as well­made all-polymethylmethacrylate (PMMA) open­loop styles. There is enough evidence to predict a higher-than-acceptable rate of complications and difficulties with lens removal with any closed-loop IOL design. A comparison of findings from this series of complicated cases with a separate study of

82 anterior chamber IOLs obtained from autopsy eyes also provides significant evidence that one­piece all-PMMA anterior chamber lens designs with fully integrated haptic or footplate fixation elements are better suited for anterior chamber angle implan­tation. Although these one-piece lenses now possess over 50% of the anterior chamber lens market share, only 85 one-piece all-PMMA flexible haptic anterior

'--chamber IOLs (compared with 351 closed-loop IOLs) have been received in this laboratory. The authors conclude that, in their opinion, the FDA should consider recalling all IOLs of this design, implantation of these lenses should be discontinued, and further distribution oflenses with a closed-loop design outside of the United States is not justified.

Lynn M], Waring GO III, Sperduto RD, PERK Study Group: Factors affecting outcome and predictability of radial keratotomy in the PERK study. Arch Ophthal­mol 105:42-51, 1987

The prospective evaluation of radial keratotomy (PERK) study used a standardized surgical tech­nique that included a central zone with a diameter of 4.0 mm, 3.5 mm, or 3.0 mm. Multiple regression analysis of the outcome in one eye from each of 411 patients disclosed that the diameter of the central clear zone, patient age, and depth of the incision scar were the major factors affecting the change in refraction one year after surgery. Preoperative fac­tors examined that did not significantly influence the outcome were sex, average central keratometric power, corneal thickness, corneal diameter, intra­ocular pressure, and ocular rigidity. The predict­ability of radial keratotomy, i.e., the precision with which the outcome can be estimated, was measured by the 90% confidence interval for the change in refraction based on the regression equation. The width of this interval within each clear zone group was as follows: 4.0 mm, 2.49 diopters (D); 3.5 mm, 3.38 D; 3.0 mm, 4.12 D. For all 411 eyes, the 90% confidence interval was approximately 3.50 D wide. Thus, the surgeon could be 90% certain that an in­dividual patient's refraction would be within 1.75 D of the predicted value one year after surgery.

Carter ], Barron BA, McDonald MB: Cystoid macular edema following corneal-relaxing incisions. Arch Ophthalmol 105:70-72, 1987

The authors believe that this is the first report of cystoid macular edema (CME) following corneal­relaxing incisions. Both cases occurred in pseu­dophakic eyes, one of which contained an ultraviolet light-absorbing intraocular lens. One case was com­plicated by a corneal perforation and postoperative inflammation. The other case had no apparent intraoperative or postoperative complications other

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than CME. In both cases, the CME resolved after the institution of medical treatment, and visual acuity returned to preoperative levels. Cystoid macular edema has been shown to occur following a variety of ocular manipulations, including cataract surgery with and without intraocular lens implanta­tion, aphakic keratoplasty, retinal detachment surg­ery, cryotherapy, and vitrectomy. Cystoid macular edema also occurs in several nonsurgical ocular conditions, such as uveitis , retinal vein occlusion and diabetes, and can be found in glaucomatous aphakic eyes treated with topical epinephrine . The histopathologic features of CME have been well described, but the actual mechanism of its develop­ment has never been elucidated with certainty. The role of the vitreous has received much attention. Inflammation, however, appears to be the common factor in conditions associated with CME. The role of prostaglandins in the pathogenesis of CME has been widely studied, and may have some implica­tion for treatment. The natural course ofCME after cataract surgery suggests that the majority of cases resolve without treatment , and that while treatment with corticosteroids or prostaglandin inhibitors may improve visual acuity in the early phase ofCME, the visual acuity in treated and untreated patients is not significantly different at 12 to 18 months after onset. It is not possible to document with certainty a cause­and-effect relationship between the corneal-relax­ing incisions and the occurrence of CME in these two cases. (Preoperative fluorescein angiograms were not obtained in either case.) However, the decreased visual acuities accompanied by angio­graphically confirmed CME occurring shortly after the corneal-relaxing incisions and the return of visual acuity to preoperative levels accompanied by the disappearance of fluorescein leakage indicate that the relaxing incisions were associated with the appearance of CME. The cause of CME in the first patient appears to be easily explained. The pro­cedure was complicated by a perforation and post­operative inflammation. Cystoid macular edema then became evident. It is likely that the preceding inflammation contributed to the development of CME. The early and dramatic response to indo­methacin supports a role for prostaglandins in the pathogenesis of CME in this case. However, the CME may have resolved with no treatment. The cause of CME in Case 2 is not as easily explained. There were no apparent intraoperative complica­tions and no clinically evident inflammation. The procedure was strictly extraocular. During a relax­ing incision, the eye is manipulated and distorted to some degree. This could possibly have altered the relationship of the vitreous to the macula and, hence, predisposed to macular edema. There may

have been subclinical postoperative inflammation that would have played a role in the development of CME in this case. Case 1 had previously had extracapsular cataract extraction and implantation of a posterior chamber, ultraviolet light-absorbing in­traocular lens. The second patient had a previous history of implantation of a nonultraviolet light­absorbing Leiske anterior chamber intraocular lens. In both these cases, but particularly in the second case, light toxic effects from the operating micro­scope must be considered. The pseudophakic eye is particularly susceptible to such damage because the microscope light is more likely to be focused by the intraocular lens on the retina. Decreased visual acuity after cataract surgery may be related to the intraoperative light exposure.

Sawelson H, Marks RG: Three-year results of radial keratotomy. Arch Ophthalmoll05:81-85, 1987

The authors compiled three year and longer follow­up data on 198 consecutive radial keratotomy sur­geries performed. Follow-up was obtained on 138 (70%) of these eyes. Results were compared with previously published two-year results. The mean spherical equivalence before surgery was - 4.3 diopters (D), the average keratometry value was 44.11 D, and 75% of the eyes had an uncorrected distance acuity of 20/400 or more. The average change in the spherical equivalence was 3.74 D for eyes examined at three years , compared with 3.71 D for eyes examined at 18 months. Average keratome­try value was 40 .96 D after three years, compared with 4l.16 D at 18 months . Uncorrected visual acuity was at least 20/40 in 73% of eyes examined after three years, as opposed to 72% at 18 months. In eyes examined at both 18 months and three years, the increase in spherical equivalence of 0.17 D was statistically significant, as was the decrease in aver­age keratometry value of 0 .20 D. Uncorrected visual acuity results were stable between 18 months and three years.

Santos VR, Waring GO III, Lynn MJ, Holladay JT, et al: Relationship between refractive error and visual acuity in the prospective evaluation of radial kerato­tomy (PERK) study. Arch Ophthalmoll05:86-92, 1987

As part of the prospective evaluation of radial keratotomy (PERK) study, the authors examined the relationship between postoperative refractive error and visual acuity without correction. They included 394 eyes (one eye per patient) with refractive errors ranging from - 3.00 diopters (D) to + 3.00 Done year after radial keratotomy. Within each I-D range of the spherical equivalence of the refractive error, the visual acuity spanned five to ten Snellen lines. For visual acuities of 20/16 to 20/50, the refractive

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error spanned 3.00 D to 5.00 D. Additionally, operated eyes had a better average uncorrected visual acuity than unoperated eyes with a similar refractive error. Within the narrow range of refrac­tion between - 2.00 D and - 2.50 D, the mean uncorrected visual acuity was 20/125 for 56 unope­rated eyes and 20/63 for 29 operated eyes, a differ­ence of three Snellen lines. Although the cycloplegic refraction is currently the most accurate and precise measure of the change induced by radial kerato­tomy, reporting the refractive error in the absence of visual acuity provides an incomplete picture of the radial keratotomy outcome. In the present study, patients within a 1-D range of refractive error had a difference in visual acuity of five to ten Snellen lines, so that the refractive error gave little information about the patient's visual acuity. Similarly, many patients with an acuity of 20/20 or better had a significant residual refractive error. For example, 12% (241198) of the PERK patients with a visual acuity of 20/12 to 20/20 had a postoperative refrac­tion between + 1.12 D and + 3.00 D . Presenting these patients' visual acuities without noting the refractive error would obscure the significant over­correction. Thus, both the cycloplegic refractive error and the visual acuity measured under stan­dardized conditions should be presented together.

McCarey BE, Waring GO III, Street DA: Refractive keratoplasty in monkeys using intracorneal lenses of various refractive indexes. Arch Ophthalmol 105: 123-126, 1987

The refractive power of the cornea can be altered with an intracorneallens when it is inserted within a freehand lamellar-pocket incision. The effectiveness of the implant in altering the refractive power of the cornea depends on the refractive index of the intracorneallens since little change in the anterior corneal curvature occurs. Thirteen nonhuman pri­mate eyes received intracorneal lenses made of synthetic polymers with refractive indexes ranging from 1.3686 to 1.6333. The lidofilcon-B hydrogel (refractive index, 1.3686) lenses created no signifi­cant alteration in the refractive power of the cornea. The polymethylmethacrylate (refractive index, 1.4900) and polysulfone (refractive index, 1.6333) lenses created a predictable and significant alter­ation of corneal power that increased with each implant with a successively higher refractive index. The polymethylmethacrylate lens created a refrac­tive alteration that was approximately 31% of the lens power in air. The poly sulfone lens created a corneal power alteration that was approximately 40% of the lens power in air.

Samples JR, Bellows AR, Rosenquist RC, Hutchinson BT, et al: Pupillary block with posterior chamber intraocular lenses. Arch Ophthalmoll05:335-337, 1987

The authors present 12 cases of pupillary block associated with extracapsular cataract extraction and posterior chamber intraocular lenses. In one case, pupillary block occurred despite the presence of a surgical iridectomy. The other 11 patients did not have a surgical iridectomy performed. The authors recommend that a surgical iridectomy or laser iridotomy be performed in all patients who have extracapsular cataract extraction with implantation of posterior chamber intraocular lenses. Ophthal­mologists need to be vigilant in watching for the development of pupillary block in these patients since it is not a benign event and serious visual loss or disability may occur.

Ophthalmology

Pepose JS, Pardo F, Kessler JA II, Kline R, et al: Screening cornea donors for antibodies against hu­man immunode6ciency virus; efficacy of ELISA test­ing of cadaveric sera and aqueous humor. Ophthal­mology 94:95-100, 1987

Coded cadaveric sera from 35 patients with acquired immunodeficiency syndrome (AIDS), from 45 ca­davers at high risk of human immunodeficiency virus (HIV) infection, and from 262 cadavers without known signs or risk of AIDS were assessed using three commercially available enzyme-linked immu­nosorbent assays (ELISA) kits and Western blot analysis. Greater than 94% sensitivity and 99% specificity was achieved with each of the ELISA test kits using cadaveric sera. The Western blot method gave 97.1 % sensitivity compared with the autopsy­proven diagnosis of AIDS. Positive results were obtained on sera from AIDS cadavers even if the time of blood draw was delayed 35 hours from death and the time of sera preparation was delayed up to 176 days. False-negative or false-positive ELISA results did not appear to correlate with hemolysis or any parameter of sera preparation. In contrast to the high sensitivity in testing sera, only 16% to 26% of aqueous humor samples from AIDS cadavers were ELISA-positive and 79% were positive by Western blot. These results indicate that three commercially available ELISA test kits are an effective means of screening cadaveric sera for antibodies to HIV, but that aqueous humor cannot be reliably substituted for cadaveric sera to screen potential corneal donors by an ELISA assay.

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