Daniel Epstein

EXCIMER LASER PHOTOREFRACTIVE KERATECTOMY FOR MYOPIA; CLINICAL RESULTS IN SIGHTED EYES

PURPOSE To evaluate the refractive results of excimer laser photorefractive keratectomy (PRK) performed on normal, sighted myopic eyes; to assess the role of postoperative topical steroid treatment in patients with PRK; and to study the regression of effect. METHODS An argon fluoride 193-nm excimer laser was used. Photorefractive keratectomy was performed on 420 eyes with preoperative refraction ranging from -1.25 to -7.50 diopters (D). Minimum follow-up time was 12 months, and 194 of the eyes were followed for 15 months. Postoperative treatment generally consisted of topical dexamethasone for 3 months, but in a sub-study, some eyes were treated for only 5 weeks. RESULTS Mean refraction (spherical equivalent +/- standard deviation) at 12 months was -0.04 +/- 0.84 D and at 15 months -0.22 +/- 0.78 D. At 12 months postoperatively, 86% of the eyes were within 1.00 D of emmetropia, at 15 months 87%. At 12 months, 91% of the eyes had an uncorrected visual acuity of at least 20/40, at 15 months 87%. Eyes treated with dexamethasone for 3 months regressed significantly less than those treated for only 5 weeks (P < 0.01). Dexamethasone also was effective in reversing regression later in the postoperative course. Eyes with preoperative myopia up to 4.90 D had significantly better refractive results at 12 months than eyes with myopia ranging from 5.00 to 7.50 D (P < 0.01). CONCLUSION These data show that excimer laser PRK can correct myopia with good predictability. Results at 12 and 15 months tend to suggest stability of postoperative refraction. Regression of effect was more common in higher myopes. Topical steroids postoperatively seem to play a crucial role for the refractive result.

Corneal Higher-Order Aberrations after Descemet's Membrane Endothelial Keratoplasty

PURPOSE We compared corneal higher-order aberrations (HOAs) in eyes after Descemets membrane endothelial keratoplasty (DMEK), Descemets stripping automated endothelial keratoplasty (DSAEK), and penetrating keratoplasty (PK), and in a control group that had not undergone surgery. DESIGN Retrospective analysis of clinical data. PARTICIPANTS Thirty eyes of 30 patients who had undergone standard DMEK, 20 eyes of 20 patients after DSAEK, 20 eyes of 20 patients after PK, and 20 eyes of 20 controls were analyzed. METHODS In addition to standard postoperative examinations, each participant was analyzed with the Pentacam high-resolution rotating Scheimpflug imaging system (Pentacam HR, Oculus, Wetzlar, Germany). Data were compared between groups. MAIN OUTCOME MEASURES Visual acuity and HOAs. RESULTS The mean follow-up was 6.5 ± 1.2 months after DMEK, 22.6 ± 11.8 months after DSAEK, and 103.1 ± 74.2 months after PK. There were no statistically significant differences for the anterior 4.0-mm zones between the DMEK group and the controls or between the DMEK and DSAEK groups. The DMEK procedure compared with PK showed statistically significant differences in all terms for the 4.0-mm zones. All combined Zernike terms for mean posterior aberrations of the central 4.0-mm zones showed statistically significant higher aberrations for DMEK compared with controls. The DMEK procedure compared with DSAEK showed statistically significant lower mean values for all combined Zernike terms, except for coma and coma-like terms in the central 4.0-mm zones of the posterior corneal surface. Compared with PK, DMEK showed statistically significant lower mean values for all combined Zernike terms for the central 4.0-mm zones of the posterior corneal surface, except for spherical aberration (SA) and SA-like terms. Best spectacle-corrected visual acuity (BSCVA) after DMEK was statistically significantly better than after DSAEK (P=0.001) and PK (P=0.005). There was no statistically significant difference when BSCVA was compared with controls (P=0.998). CONCLUSIONS Both DSAEK and PK exhibit increased posterior corneal HOAs even years after surgery. Patients receiving DMEK display only slight changes in posterior corneal HOAs.

Intraoperative and Postoperative Effects of Corneal Collagen Cross-linking on Progressive Keratoconus

OBJECTIVES To report intraoperative and 24-month refractive, topographic, tomographic, and aberrometric outcomes after corneal collagen cross-linking in progressive advanced keratoconus. METHODS Prospective, nonrandomized single-center clinical study involving 28 eyes. Main outcome measures included uncorrected and best spectacle-corrected visual acuities, sphere and cylinder refraction, topography, tomography, aberrometry, and endothelial cell count evaluated at baseline and follow-up at 1, 3, 6, 12, and 24 months after treatment. Topography was also recorded intraoperatively. RESULTS Two years after treatment, mean baseline uncorrected and best spectacle-corrected visual acuities improved significantly (P = .048 and <.001, respectively) and mean spherical equivalent refraction decreased significantly (P = .03). Mean baseline flattest and steepest meridians on simulated keratometry, simulated keratometry average, mean average pupillary power, and apical keratometry all decreased significantly (P < .03). Deterioration of the Klyce indices was observed in the untreated contralateral eyes but not in treated eyes. Total corneal wavefront aberrations Z(0) (piston), Z(2) (defocus), and Z(7) (III coma) decreased significantly (P < or = .046). Mean 12-month baseline pupil center pachymetry and total corneal volume decreased significantly (P = .045). Endothelial cell counts did not change significantly (P = .13). CONCLUSIONS Two years postoperatively, corneal collagen cross-linking appears to be effective in improving uncorrected and best spectacle-corrected visual acuities in eyes with progressive keratoconus by significantly reducing corneal average pupillary power, apical keratometry, and total corneal wavefront aberrations.

Two-Year Corneal Cross-Linking Results in Patients Younger Than 18 Years With Documented Progressive Keratoconus

PURPOSE To report refractive, topographic, aberrometric, and tomographic outcomes 24 months after corneal cross-linking (CXL) in patients up to 18 years of age with progressive keratoconus. DESIGN Prospective, interventional case series. METHODS Forty eyes underwent riboflavin-ultraviolet A-induced CXL. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), sphere and cylinder, topography, aberrometry, tomography, and endothelial cell counts were evaluated at baseline and at 1, 3, 6, 12, and 24 months. RESULTS Mean logarithm of the minimum angle of resolution baseline UCVA and BSCVA were 0.79 ± 0.21 and 0.39 ± 0.10, respectively. Mean UCVA and BSCVA at 2 years were 0.58 ± 0.18 and 0.20 ± 0.09, respectively. The improvement in UCVA and BSCVA was significant throughout the postoperative follow-up (P < .05). Mean spherical equivalent refraction showed a significant decrease of 1.57 diopters (D) at 24 months (P = .02). Mean baseline simulated keratometry was 46.32 D in the flattest meridian and 51.48 D in the steepest meridian; at 2 years, the values were 45.30 D (P = .04) and 50.21 D (P = .07), respectively. For a 3-mm pupil, there was a significant reduction (P < .05) in whole eye (total), corneal, higher-order, and astigmatic wavefront aberrations at 24 months. A significant difference (P < .05) in total coma and total spherical aberration 2 years after CXL also was observed. Mean baseline pupil center pachymetry decreased significantly (P = .04) at 6 months, but recovered by 12 months and remained stable thereafter through the 2-year follow-up. Endothelial cell counts did not change significantly (P = .32). CONCLUSIONS CXL improved UCVA and BSCVA in the study patients, most likely by significantly reducing corneal asymmetry and corneal as well as total wavefront aberrations.

Factors affecting epithelial hyperplasia after photorefractive keratectomy

Purpose: To determine the effect of patient age, postoperative time, ablation zone diameter and depth, attempted correction, and corneal topography on postoperative corneal epithelial thickness after photorefractive keratectomy (PRK). Setting: Private clinic and university hospital, Stockholm, Sweden. Methods: This retrospective, unmasked study comprised 136 myopic patients treated unilaterally with PRK. Seventy eyes had been treated with the Summit excimer laser 27 months ±7 (SD) earlier using ablation zone diameters of 4.1 to 5.0 mm. Sixty‐six eyes had been treated with the VISX excimer laser 6 ± 3 months earlier using a 6.0 mm zone diameter. The untreated fellow eyes served as controls. Epithelial thickness was measured at a standardized central corneal area with a modified optical pachymeter, and corneal topography was determined using computerized videokeratoscopy. Results: In the Summit group, the epithelial layer in the PRK eyes was 12.0 &mgr;m (21 %) thicker than in the control eyes (P < .001; 95% confidence interval [CI] 9.35 to 14.3 &mgr;m). This thickness differential correlated significantly with increased ablation depth and attempted correction. In the VISX group, the epithelium in the treated eyes was 7.0 &mgr;m (7%) thinner (P = .0009; 95% Cl −1.9 to −6.7 &mgr;m) and thickness did not correlate with ablation depth or attempted correction. There was no correlation between epithelial hyperplasia and patient age or postoperative followup. With the laser groups combined, epithelial hyperplasia was greater with smaller zone sizes and a greater rate of change in power at the edge of the ablation zone. Conclusion: The factors associated with an increase in epithelial thickness were small ablation zones, greater attempted corrections, and deeper ablations. Larger, smoother ablation profiles may result in less epithelial hyperplasia.

Excimer laser photorefractive keratectomy for presbyopia: 24-month follow-up in three eyes.

BACKGROUND For some patients, standard optical correction for presbyopia is not satisfactory. Using a specially designed mask, we developed a procedure for correcting presbyopia with excimer laser photorefractive keratectomy (PRK). METHODS A mask consisting of a mobile diaphragm formed by two blunt blades was used to ablate a 10 to 17 microm deep semilunar-shaped zone immediately below the pupillary center, steepening the corneal curvature in that area. Three eyes of three presbyopic patients were treated, aiming at a near addition of +3.00 D. Follow-up time was 24 months. RESULTS After an initial regression of 1.00 D during the first 6 months, the presbyopic correction remained stable for the duration of the follow-up period, enabling uncorrected near vision of J3 in all three eyes. Uncorrected distance visual acuity was not altered. Contrast sensitivity (Regan) was slightly decreased only at the 11% level. Videokeratography confirmed corneal steepening in the ablated area. CONCLUSION The visual and refractive outcome of excimer laser PRK for presbyopia with the Aesculap-Meditec MEL 60 is promising, especially in view of the 2-year follow-up.

Epithelial Alterations Following Photorefractive Keratectomy for Myopia

BACKGROUND A retrospective observational study was conducted to test the hypothesis that there is clinically measurable epithelial hyperplasia after photorefractive keratectomy (PRK), and to determine its effect on the epithelial oxygen uptake rate. METHODS One hundred myopic eyes who had been previously treated unilaterally with PRK were examined. Fifty eyes were treated with the Summit excimer laser (Summit Technology, Waltham, Mass) 27 +/- 7 months previously with ablation zone diameters of 4.1, 4.3, 4.5, or 5.0 mm. Fifty eyes were treated with the VISX excimer laser (VISX Inc, Sunnyvale, Calif) 5 +/- 4 months previously with one ablation zone diameter of 6.0 mm. The untreated eyes served as controls. Epithelial thickness was measured at a standardized central area within the ablation zone with a modified optical pachometer. Oxygen uptake rate was measured in a subgroup of 30 eyes (20 Summit and 10 VISX). RESULTS The epithelium after PRK was 24% thicker than in the control eye in the Summit group (mean difference 13 +/- 10 microns; p < .01) and 7% thinner in the VISX group (mean difference -4 +/- 10 microns; p < .01). A higher oxygen uptake rate correlated with a thicker epithelium (r = 0.42; p < .05). CONCLUSIONS The epithelium was significantly thicker after PRK between 13 and 37 months after treatment with the Summit excimer laser using ablation zone diameters of 4.1 to 5.0 mm. The epithelium was thinner between 1 and 15 months after treatment with the VISX laser using an ablation zone diameter of 6.0 mm. An increase in oxygen uptake rate reflected the metabolic rate of a greater number of cells in the hyperplastic layer.

Long-term Results of Photorefractive Keratectomy for Hyperopia and Hyperopic Astigmatism

PURPOSE This study was conducted to determine the safety and efficacy of using the Nidek EC-5000 excimer laser for photorefractive keratectomy to correct hyperopia and hyperopic astigmatism. METHODS We treated 67 eyes of 44 patients for hyperopia and hyperopic astigmatism with the Nidek EC-5000 excimer laser. The algorithm provided an ablation zone of 5.5 mm diameter with the addition of a tapered transition zone of 3.5 mm diameter, for a total ablation of 9 mm diameter. RESULTS Uncorrected visual acuity (geometrical mean) changed from 0.16 to 0.37 at 12 months; corrected visual acuity (geometrical mean) changed from 0.8 to 0.89; mean sphere decreased by 2.08 D from 3.76 to 1.40 D (range, 1.70 to 1.68 D) and cylinder by 1.40 D from 2.20 to 1.00 D. Refractive results for < or = 3.00 D were reasonably accurate and stable, but for > +3.00 D, undercorrection and regression over l year were the rule. CONCLUSION Hyperopic PRK proved to be a safe technique in regard to the risk of loss of visual acuity with no central corneal opacities and with a generally rapid recovery of baseline spectacle-corrected visual acuity, but the predictability of correction greater than +3.00 needs improvement.

Effect of postoperative steroids on the refractive outcome of photorefractive keratectomy for myopia with the Summit excimer laser

ABSTRACT To assess the role of topical steroids following excimer laser photorefractive keratectomy (PRK) for myopia, we compared the refractive outcome in 100 eyes that did not receive steroids in the immediate postoperative period (untreated eyes) with 100 eyes that were treated with topical dexamethasone for three months postoperatively. Photorefractive keratectomy was performed with the Summit laser, using 4.3 mm and 4.5 mm ablation zones. At three months after surgery, the untreated eyes had a mean refraction of ‐0.97 ± 1.15 diopters (D), significantly different (P < .01) from the mean refraction (+0.46 ± 0.74 D) of the steroid‐treated eyes. By six months postoperatively, 86% of the untreated eyes had regressed to a myopia of at least 0.50 D, whereas only 23% of the steroid‐treated eyes had regressed. In a second study, we compared the results in 25 patients whose first PRK eye was treated with steroids after surgery but whose second eye was not. At three months postoperatively, mean refraction in the steroid‐treated eyes was +1.23 ± 0.71 D, significantly different (P < .01) from the mean of ‐0.45 ± 1.29 D in the untreated eyes. The refractive results in PRK eyes treated with the Summit unit and with relatively small ablation zone diameters showed that eyes that received dexamethasone postoperatively were less likely to regress to myopia.

Refractive Surgery Trends and Practice Style Changes in Germany over a 3-Year Period

PURPOSE To study the current practice styles and preferences of refractive surgeons in Germany. METHODS In February 2008, a seven-item questionnaire regarding the practice of refractive surgery was mailed to 282 members of the German Society of Intra-ocular Lens Implantation, Interventional, and Refractive Surgery (DGII) and the Commission of Refractive Surgery (KRC). Most questions were identical to our 2005 German refractive surgery survey. All data were analyzed in a masked fashion. RESULTS The response rate was 42.2%. The majority (68%) of respondents reported that they perform refractive surgery in laser centers (exclusively or partially) followed by general hospitals (19.4%) and universities (12.6%). Although LASIK was the predominant type of refractive surgery performed (80.6%), other refractive procedures included refractive lens exchange (60.2%), photorefractive keratectomy (47.6%), phakic intraocular lens implants (45.6%), laser-assisted subepithelial keratectomy (36.9%), epithelial laser in situ keratomileusis (15.5%), intracorneal rings (5.8%), and limbal relaxing incisions (2.9%). The volume of refractive surgery procedures and the preferred type of excimer laser systems, microkeratomes, and diagnostic devices varied at different institutions. Most respondents performed either wavefront-guided custom ablation or wavefront-optimized ablation (63.1%) compared with conventional excimer laser correction (36.9%). CONCLUSIONS Refractive surgery practice styles and preferences in Germany are comparable to trends in other European countries. Although LASIK is the most commonly performed refractive procedure, the numbers of various surface ablation techniques and refractive intraocular lens procedures are increasing.