Excimer laser photorefractive keratectomy for hyperopia.

OBJECTIVE: To prospectively study excimer laser correction of hyperopia, with a 1-year followup. METHODS: Eleven consecutive hyperopic eyes (10 phakic and 1 aphakic) underwent correction of hyperopia using the Summit Technology SVS Apex Plus excimer laser. Data collection included cycloplegic refraction, spectacle-corrected visual acuity, contrast sensitivity, corneal haze, manual keratometry, and videokeratography. Prior to treatment the mean hyperopic spherical equivalent refraction (corneal plane) was +5.80 diopters (D) (SD2.10). The mean attempted correction was +3.09 D at the corneal plane. RESULTS: Refractive data for the group showed a mean overcorrection at 1 month of +3.18 D. This regressed slightly before stabilizing at 3 months, with a mean overcorrection of +1.88 D. Thereafter there was no statistically significant fluctuation in refraction (p = 0.67). The amount of overcorrection and regression was greater in eyes that received higher corrections. Changes in manual keratometry and videokeratography mirrored the attempted correction more closely than refraction, although stabilization did not occur until 6 months. CONCLUSIONS: Because the hyperopic correction achieved when measured by refraction was greater than expected, algorithms should be adjusted. The hyperopic erodible disc and Axicon lens system is capable of treating low to moderate amounts of hyperopia.

Intraocular lens power calculation for cataract surgery after photorefractive keratectomy for high myopia.

OBJECTIVE: To assess intraocular lens (IOL) power calculations in patients undergoing cataract surgery after excimer laser photorefractive keratectomy (PRK) for myopia. METHODS: Four eyes of two patients underwent phacoemulsification with IOL implantation after PRK for myopia. The estimated refractive error that would have been induced had the IOL predicted for emmetropia been implanted was calculated using SRK-II, SRK/T, Holladay, and Binkhorst formulas. Manual keratometry and videokeratography-simulated keratometry values measured before surgery were used. Keratometry values calculated by subtracting the refractive change induced by the excimer laser PRK from the manual keratometry or videokeratography-simulated keratometry values measured before PRK were also used. Both spectacle and corneal plane calculations were performed. RESULTS: Manual keratometry and videokeratography-simulated keratometry values underpredicted the IOL power. Corneal plane manual or videokeratography refraction-derived keratometry calculations were most accurate using the SRK/T formula, while spectacle plane calculations were most accurate using the SRK-II formula. In both methods the calculated refractive error was within 0.52 diopters (D) for the emmetropic lens power predicted. Statistical analysis was not performed. CONCLUSIONS: Refraction-derived keratometric values provided the most accuracy in calculating IOL powers. Our results suggest the SRK/T formula was the most accurate for corneal plane calculations, while the SRK-II formula was the most accurate for spectacle plane calculations.

Effect of scleral buckling on unsutured cataract wound strength.

BACKGROUND AND OBJECTIVE: Modern cataract surgery has evolved to include small, unsutured wounds with rapid visual rehabilitation and fewer complications. Properly constructed, these unsutured wounds can withstand increased intraocular pressures without leakage, rupture, or incarceration of intraocular contents. However, scleral buckling surgery may alter the architecture of these wounds and thus their strength. The authors wanted to study the effect of scleral buckling on the integrity of these unsutured cataract wounds. MATERIALS AND METHODS: Eighteen fresh human globes underwent creation of scleral and limbal corneal incisions so as to create self-sealing wounds. Scleral buckles were then placed. Intraocular pressures were elevated to 400 mm Hg before and after placement of the scleral buckles and evidence for wound leakage was sought. RESULTS: Two globes with clear corneal incisions and no scleral buckles leaked slightly at 300 mm Hg, but no globe with a scleral buckle, regardless of incision type or silicone element style, leaked at pressures to 400 mm Hg. CONCLUSION: Sutureless cataract incisions, if properly constructed, provide a strong, pressure-resistant wound. Scleral buckling does not appear to affect the strength of these wounds.

Multiple excimer laser retreatments for scarring and myopic regression following photorefractive keratectomy.

Excimer laser retreatment for scarring with myopic regression following photorefractive keratectomy (PRK) has been reported. We present the 38 month course of a patient who had PRK followed by two retreatments. The patient experienced scarring with myopic regression after an initial PRK with a 5.00 mm ablation zone. These complications recurred 13 months after retreatment with a 5.00 mm ablation zone. Refractive effect, computer-assisted videokeratography measurements, and corneal clarity remained stable 12 months after a second retreatment with a 6.00 mm ablation zone, indicating that retreatment with a larger ablation zone diameter appeared to be an appropriate method for handling this complication.

Age-related changes of glycosidases in human retinal pigment epithelium.

This study was undertaken to determine whether there are age-related changes in the specific activities of several glycosidases in fresh retinal pigment epithelial cells (RPE) isolated from the posterior pole of human donor eyes. One hundred and twenty-one pairs of eyes from human donors, between the ages of 43 and 95 years, were obtained from the National Disease Research Interchange (NDRI, Philadelphia, PA) and the Cleveland Ohio Eye Bank within 18 to 24 h of death. None had histories of diabetes, hepatitis, HIV infection, intraocular surgery, or documented age-related macular degeneration, although several older donors with evidence of drusen were included in the study. RPE cells were isolated from the posterior third of the retina using the conventional rush method and homogenized with a glass, Broeck tissue grinder. All post-nuclear supernatants were analyzed for glycosidase activity; a smaller number of nuclear pellets were assayed to verify that the majority of the enzyme activity was associated with the post-nuclear sypernatants. Glycosidase activity was quantitated fluorometrically by measuring the enzymatic release of umbelliferone from synthetic substrate preparations, specific for each enzyme. Total protein was determined by a micro BCA protein assay. Regression analysis revealed statistically significant age-related decreases for the specific activities of alpha-mannosidase (p = 0.0001), beta-galactosidase (p = 0.0001), N-acetyl-beta-glucosaminidase (p = 0.0001), and N-acetyl beta galactosaminidase (p = 0.0001) in fresh human donor RPE cells taken from the region of the posterior third of the retina that included the macula. Mannose and N-acetyl-glucosamine are major carbohydrate monomers of the oligosaccaride chains of human rhodopsin, and a relatively high percentage of the oligosaccharide chains are galactosylated. Defects in their degradation may lead to the accumulation of undigested residual material in the RPE.

Comparison of 5-mm and 6-mm ablation zones in photorefractive keratectomy for myopia.

BACKGROUND: Variation in ablation zone diameter may alter visual acuity and/or refractive effect in photorefractive keratectomy. Despite theoretical benefits of using a smaller diameter ablation zone, clinical studies suggest that a larger ablation zone may decrease problems associated with photorefractive keratectomy. METHODS: The results of our initial 34 consecutive eyes treated with a 5-mm diameter ablation zone using a Summit Technology ExciMed UV200LA excimer laser were compared retrospectively to our initial 34 consecutive eyes treated with a 6-mm diameter ablation zone using a Summit OmniMed excimer laser. Eyes had a spherical equivalent refraction between -1.00 and -6.00 diopters (D) and astigmatism less than 1.00 D. Patients were followed for a minimum of 6 months. RESULTS: Eyes treated with a 6-mm ablation zone had less hyperopia and a spherical equivalent refraction closer to emmetropia at 1, 2, and 3 months (P = 0.001). Eyes treated with a 6-mm ablation zone had better uncorrected visual acuity at 1 and 2 months (P = 0.001). Less subepithelial haze was noted at 2 months (P = 0.01) and 3 months (P = 0.002) in the 6-mm group. At 6 months postoperatively, 30 of 32 eyes (94%) treated with a 6-mm ablation zone had a spherical equivalent refraction within 0.50 D of emmetropia, and all 32 eyes (100%) were within 1.00 D of emmetropia; in the 5-mm ablation zone group, 28 of 34 eyes (80%) were within 0.50 D and 29 (85%) were within 1.00 D of emmetropia. Patients treated with a 6-mm ablation zone complained less of night halos and had fewer differences between night and day vision. CONCLUSIONS: In this study of myopia of -1.00 D to -6.00 D, eyes treated with a 6-mm ablation zone achieve a more rapid visual recovery with less variation in refractive outcome and less adverse effects than those treated with a 5-mm ablation zone.

Excimer retreatment for scarring and regression after photorefractive keratectomy for myopia.

AIMS/BACKGROUND: Scarring associated with regression of refractive effect can occur after photorefractive keratectomy (PRK) for myopia. The experience of treating these complications is reported. METHODS: Eighteen of 285 eyes (6.3%) were retreated with the excimer laser. Age, sex, preoperative primary treatment keratometry, pre-primary treatment, pre-retreatment and post-retreatment spherical equivalents, best corrected and uncorrected visual acuities were recorded and analysed. RESULTS: At 6 months post-retreatment, the mean spherical equivalent was -2.07 dioptres (D) (SD 4.60 D). This spherical equivalent persisted in eyes followed for 12 months (-2.85D, SD 4.09 D). Nine of 18 eyes (50%) had uncorrected visual acuity of 6/12 (20/40) or better. If retreatment was undertaken within 6.5 months of the initial PRK, then scarring was likely to recur (p = 0.035). Nine of 10 eyes (90%) which had a retreatment spherical equivalent less than two thirds of their primary treatment spherical equivalent were within plus or minus 1.25D from emmetropia after retreatment. Four of 11 eyes (36%) followed for 12 months after retreatment rescarred with further regression. CONCLUSION: The data showed that eyes with scarring and regression of myopia should not be treated with PRK within 6 months of the initial procedure. Eyes with the highest percentage of regression towards their initial myopia tend to have a poor response to retreatment.

Caruncular malignant melanoma in a black patient.

An 84-year-old black woman had a right caruncular lesion that had progressively enlarged over the past 3 months. Surgical excision and cryotherapy were performed. A biopsy confirmed the diagnosis of caruncular malignant melanoma, a rare lesion which, to our knowledge, has not been previously reported in a black patient.

Tunable dye laser photocoagulation for choroidal neovascularization complicating age-related macular degeneration.

We report our first 146 consecutive eyes treated with tunable dye laser for choroidal neovascular membrane (NVM) complicating age-related macular degeneration (AMD). They were treated with the orange (595 nm; N = 6), red (630 nm; N = 23), yellow (577 nm; N = 67), or sequential red-yellow (N = 50) wavelength of the tunable dye laser. All had a minimum 180 days follow-up. Eyes were analyzed as two groups categorized by pretreatment visual acuity (VA): 20/100 or better (N = 101), and 20/200 or worse (N = 45). Change in VA between baseline and most recent follow-up was studied by age, laser color, previous non-dye laser treatment, and number of treatments. Age was a statistically significant variable (chi 2 = 6.61, degree of freedom = 2, P less than 0.05). In eyes with initial VA of 20/100 or better, age also was significant for cumulative percent loss in VA of greater than or equal to 2 lines. We discontinued using orange after poor early clinical results. Our results suggest that the dye laser's variety and combination of wavelengths may provide advantages in treating NVM complicating AMD.