Hyperopic Photorefractive Keratectomy Research Articles

Laser-assisted subepithelial keratectomy and photorefractive keratectomy for the correction of hyperopia: Results of a 2-year follow-up

Purpose: To evaluate and compare the efficacy, safety, predictability, and stability of laser-assisted subepithelial keratectomy (LASEK) and photorefractive keratectomy (PRK) for low to moderate hyperopia with a 2-year follow-up. Setting: Department of Ophthalmology, Masaryk University Hospital, Brno, Czech Republic. Methods: This prospective comparative single-surgeon study included 216 eyes of 108 patients with hyperopia who received PRK in 1 eye and LASEK in the contralateral eye. The mean patient age was 38.3 years (range 25 to 58 years). The mean preoperative spherical equivalent (SE) cycloplegic refraction was +3.67 diopters (D) ± 1.15 (SD) (range +2.00 to +5.00 D), and astigmatism was less than 1.00 D. In each patient, PRK was performed in 1 eye (Group A) and LASEK was performed in the other eye (Group B) using the Nidek EC-5000 excimer laser. Postoperative uncorrected visual acuity (UCVA), best corrected visual acuity, contrast sensitivity, manifest and cycloplegic refractions, refractive stability and predictability, postoperative pain, and corneal haze were examined and statistically analyzed. A P value less than 0.05 was considered significant. Results: At 1 week, the UCVA was 20/40 or better in 58% of PRK eyes and 85% of LASEK eyes ( P = .037); at 2 years, it was 20/40 or better in 81% and 91%, respectively ( P = .076). At 2 years, the UCVA for near was N8 or better in 73% of PRK eyes and 89% of LASEK eyes ( P = .064). No patient lost 2 or more lines of Snellen visual acuity. The safety index was 1.03 in PRK eyes and 1.08 in LASEK eyes. Refractive stability was achieved at 6 months in LASEK eyes and at 12 months in PRK eyes. The mean SE cycloplegic refraction decreased from +3.58 D (PRK eyes) and +3.76 D (LASEK eyes) at baseline to +0.74 D and +0.32 D, respectively, at 2 years; in 57% and 78% of eyes, respectively, the refraction was within ±0.50 D of the targeted refraction. Peripheral corneal haze scores at 3 to 9 months and pain scores at 1 to 3 days were significantly lower in the LASEK group than in the PRK group. Conclusions: Laser-assisted subepithelial keratectomy for hyperopia up to +5.00 D provided good visual and refractive results. It significantly reduced postoperative pain, grade of peripheral ring-shaped corneal haze, and regression of hyperopia. Hyperopic LASEK provided quicker visual recovery and achieved better efficacy, predictability, and refractive stability than hyperopic PRK.

Photorefractive keratectomy to correct hyperopic shift after radial keratotomy

Purpose To evaluate the safety, efficacy, and predictability of photorefractive keratectomy (PRK) to correct post-radial-keratotomy (RK) hyperopic shift. Setting University of Sherbrooke, Sherbrooke, Québec, Canada. Methods This retrospective nonconsecutive case series comprised 53 eyes of 53 patients who had PRK to correct hyperopic shift after RK. Both RK and PRK were performed by the same surgeon at the same clinic from 1993 to 2001. Results The mean time after RK was 57 months (range 24 to 84 months). The mean follow-up after hyperopic PRK (HPRK) was 10 months (range 3 to 33 months). The mean hyperopic shift 1 month post-RK to HPRK was +1.6 diopters (D) ± 1.0 (SD) (range +0.25 to +4.125 D). The mean pre-HPRK spherical equivalent (SE) was +2.15 ± 0.80 D (range +1.00 to +4.125 D) and the mean post-HPRK SE, –0.10 ± 0.80 D (range –2.00 to +2.125 D). At the last examination, 47 eyes (88.7%) had a refractive error within ±1.0 D of emmetropia and 38 eyes (71.7%) had an uncorrected visual acuity of 20/25 or better. Two eyes lost 1 Snellen line of best corrected visual acuity. No significant haze or complications developed in any eye. Conclusions Hyperopic PRK with a conservative technique (large optical zone and small ablation thickness) can be used successfully to correct RK-induced hyperopia in patients with small to moderate refractive errors. It appeared to be effective, predictable, and safe.

First results with wavefront-guided photorefractive keratectomy for hyperopia.

To compare the results of traditional laser photoablation and wavefront-supported customized ablation (WASCA) in hyperopic photorefractive keratectomy (H-PRK). This was a prospective study, comparing two treatment groups, each comprising 40 eyes of 20 patients. Wavefront aberrations were examined using a Shack-Hartmann aberrometer. Preoperative refraction was similar in the two groups; in the traditional H-PRK group (Group 1) it was +3.10 +/- 0.85 D, and in the WASCA-guided group (Group 2) it was +2.90 +/- 0.80 D. H-PRK was performed with the Asclepion-Meditec MEL 70 flying-spot excimer laser. The follow-up time was 6 months. In Group 1, mean postoperative refraction was +0.14 +/- 0.24 D, and in Group 2, -0.10 +/- 0.25 D; mean uncorrected visual acuity was 0.92 +/- 0.16 in Group 1 and 0.95 +/- 0.18 in Group 2. Mean best spectacle-corrected visual acuity was 0.96 +/- 0.04 in Group 1 and 1.06 +/- 0.13 in Group 2. In Group 1, 67.5% (27 of 40 eyes), and in Group 2, 85% (34 of 40 eyes) were within +/-0.50 D of target refraction. Regarding change of spectacle-corrected visual acuity in Group 1, 5% (2 of 40 eyes), and in Group 2, 20% (8 of 40 eyes) gained one Snellen line compared to the preoperative; in Group 1, 10% (4 of 40 eyes), and in Group 2, 12.5% (5 of 40 eyes) lost two Snellen lines. In Group 2, the root mean square value for the higher order aberration increased from the initial 0.134 to 0.257 microm at 6 months after surgery. WASCA-guided hyperopic-PRK treatment was found to be safe and predictable. The results were better than those achieved with traditional PRK performed using the same flying-spot type excimer laser.

Results of photorefractive keratectomy for hyperopia using the VISX star excimer laser system.

To evaluate safety, efficacy, and predictability of photorefractive keratectomy (PRK) for hyperopic astigmatism of +1.75 to 00 D manifest refractive sphere and up to -2.50 D manifest refractive astigmatism using the VISX Star excimer laser system, version 2.5 software. Treatment was performed on 32 eyes of 21 patients. Eighteen of 21 patients were 45 years of age or older. Manifest and cycloplegic refraction together with Pelli-Robson contrast sensitivity assessment was performed prior to surgery and 1, 3, 6, 12, and 24 months after treatment. Twenty-seven of 32 surgical procedures were reviewed 1 year after treatment (84%). Corneal epithelial healing was complete between day 4 and 10. Twelve months after treatment, 25 of 27 eyes (93%) achieved 20/40 or better uncorrected visual acuity and 19 eyes (70%) achieved 20/20. No patient lost two or more lines of Snellen visual acuity assessed 6 months and later after treatment. The mean spherical equivalent refraction was reduced from +2.90 at baseline to +0.10 D at 1 year and +0.40 D at 2 years; 65% of eyes had a refraction within +/- 0.50 D. Four patients had further treatment by laser in situ keratomileusis for undercorrection in three eyes and overcorrection in one eye. Pelli-Robson contrast acuity was significantly reduced 12 months after treatment from a mean 1.72 before to 1.66 after PRK (P = .02, t-test). PRK for hyperopia using the VISX Star excimer laser system was effective in the treatment of hyperopic astigmatism. Although no patient lost two or more lines of high contrast best spectacle-corrected Snellen visual acuity 1 year after treatment, there was a significant decrease in Pelli-Robson contrast acuity.

Changes in measured intraocular pressure after hyperopic photorefractive keratectomy

Purpose: To investigate the effect of hyperopic photorefractive keratectomy (PRK) on intraocular pressure (IOP) measurements. Setting: University of Ottawa Eye Institute, Ottawa Hospital, Ottawa, Canada. Methods: In this retrospective cohort study, IOP and central corneal thickness (CCT) were measured preoperatively and at 1, 2, 3, 6, 12, 18, and 24 months in 191 eyes that had hyperopic PRK with the VISX Star excimer laser. All corrections applied were between +1.00 and +6.50 diopters (D) of sphere and less than 3.75 D of cylinder. Results: At all postoperative examinations, the mean IOP in the hyperopic PRK group was 1.0 to 1.8 mm Hg lower than the preoperative IOP ( P < .001). A large range of IOP changes was found across the population; eg, at 6 months, 49% of the eyes had a change in IOP from baseline of at least ±3 mm Hg. A mean reduction of 19 μm of CCT was found with pachymetry after surgery ( P < .001). The change in IOP readings postoperatively was not correlated with age, sex, keratometric readings, or applied correction. Changes in IOP were strongly correlated with preoperative IOP at all time points and with preoperative CCT at 18 and 24 months ( P < .001). After hyperopic PRK, the measured IOP was more likely to increase in patients with preoperative IOPs less than 14.5 mm Hg and more likely to decrease in patients with preoperative IOPs above 14.5 mm Hg. Conclusion: Changes in IOP after hyperopic PRK were similar to changes after myopic PRK, despite only minimal changes in the CCT. This suggests that hyperopic PRK results in biomechanical effects that modify the elastic properties of the cornea beyond the changes in rigidity expected from central corneal thinning. There was a strong negative correlation between the measured preoperative IOP and the change in IOP postoperatively that was likely the result of regression of the mean effect.

Anterior corneal optical aberrations induced by photorefractive keratectomy for hyperopia.

Photorefractive keratectomy (PRK) for hyperopia requires both a steepening of the central cornea and a flattening of the mid-periphery to achieve its effect and is likely to affect the optical aberrations of the eye. Nine patients underwent PRK to correct between +2.00 and +4.00 D of hyperopia (first eye treated for each patient) using the Summit Technology Apex Plus excimer laser. Anterior corneal aberrations for pupil diameters of 3, 5.5 and 7 mm were estimated from corneal topography data (TMS-1), assuming a uni-index, single surface cornea. Refractive error was assessed using retinoscopy and standard subjective tests. Apart from the intended change in refraction (mean spherical equivalent manifest refraction, +4.60 +/- 1.60 D before surgery and +0.70 +/- 1.60 D at 1 year after surgery), the most significant change was in spherical aberration. Anterior corneal spherical aberration was positive (+1.60 +/- 0.60 D for a 5.5-mm pupil) before surgery and became negative after surgery (-1.80 +/- 1.20 D at 1 year). The change in spherical aberration was related to the achieved change in refractive error. The large change (approximately 3.00 D) in spherical aberration (from positive to negative aberration) has implications for the optical performance of the whole eye, where the effects of lenticular aberration must also be considered.

Surgically induced astigmatism after hyperopic and myopic photorefractive keratectomy

Purpose To compare the axis and magnitude of surgically induced refractive astigmatism (SIA) after hyperopic and myopic photorefractive keratectomy (PRK). Setting Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA. Methods In this single-center retrospective study, the VISX Star S2 excimer laser was used to create a peripheral annular ablation profile to correct spherical hyperopia in 23 eyes of 16 consecutive patients. Attempted corrections ranged from +0.50 diopter (D) to +4.25 D with 0 to 1.00 D of astigmatism. The same laser was used to create a central ablation profile to correct spherical myopia in 25 eyes of 17 consecutive patients. Attempted corrections ranged from –2.25 to –6.50 D with 0 to 1.00 D of astigmatism. The absolute change in refractive astigmatism was calculated by taking the difference in magnitudes of astigmatism before and after laser treatment without regard to axis. Axis and magnitude of SIA were analyzed by vector differences. Magnitudes were compared using the Student t test, and axial shifts were compared using the chi-square test. All patients were followed for a minimum of 6 months. Results The mean changes in absolute astigmatism were 0.29 ± 0.28 D at 3 months and 0.34 ± 0.29 D at 6 months after hyperopic PRK and 0.40 ± 0.35 D at 3 months and 0.39 ± 0.36 D at 6 months after myopic PRK. The mean vectoral magnitudes were 0.49 ± 0.29 at 3 months and 0.52 ± 0.25 at 6 months after hyperopic PRK and 0.48 ± 0.39 at 3 months and 0.44 ± 0.38 at 6 months after myopic PRK. The mean values for SIA (the centroid) were 0.10 ± 0.57 D × 113 degrees at 3 months and 0.15 ± 0.57 D × 131 degrees at 6 months after hyperopic PRK and 0.04 ± 0.63 D × 160 degrees at 3 months and 0.08 ± 0.58 D × 171 degrees at 6 months after myopic PRK. There was no statistically significant difference between the 2 groups in vectoral axis or magnitude of SIA. Conclusion Surgically induced astigmatism after hyperopic PRK was comparable to astigmatism induced by myopic PRK. A peripheral annular ablation for hyperopic correction, similar to a central ablation in myopic PRK, did not appear to result in uneven corneal healing causing astigmatism.

Hyperopic photorefractive keratectomy with the erodible mask and Axicon system: two year follow-up

Purpose To evaluate efficacy and long-term stability of hyperopic photorefractive keratectomy (H-PRK) using the erodible mask and Axicon system. Setting Department of Ophthalmology, St. Thomas’ Hospital, London, England. Methods Forty-three patients (43 eyes), with a mean preoperative refraction (spherical equivalent) of +4.54 diopters (D) (range +1.75 to +7.50 D), were treated using an Apex Plus® excimer laser (Summit Technology). This uses an erodible mask to ablate a 6.50 mm diameter hyperopic correction and an Axicon to fashion a 1.50 mm blend zone around the correction. The overall ablation diameter was 9.50 mm. Follow-up was 2 years. Results At 2 years, the mean manifest refraction was +0.16 D (range +4.125 to −4.000 D), with the induced correction appearing stable after 9 months. Based on the Munnerlyn algorithm, predictability was acceptable for corrections up to +4.50 D, with 68% of eyes within ±1.00 D of the predicted correction. It was poorer for +6.00 D corrections, with 33% of eyes within ±1.00 D of that expected. Patient satisfaction was high. Forty eyes (93%) had an improvement in uncorrected near visual acuity and 37 (86%), an improvement in uncorrected distance acuity. A peripheral ring of haze, 6.5 mm in diameter, appeared in all eyes 1 month postoperatively. Its intensity was maximal at 3 to 9 months and then diminished over time. There were no significant differences in measurements of the central corneal transparency at 12 and 24 months and those preoperatively. Measurements of flicker contrast sensitivity, forward light scatter (glare), and scotopic halos showed no significant differences between preoperative values and those measured after 6 months. Conclusions Achieved H-PRK corrections with the erodible mask and Axicon system agreed closely with the Munnerlyn algorithm, with refractive stability after 9 months. Predictability was acceptable for corrections up to +4.50 D. Axial corneal transparency was not compromised and visual performance, in terms of best spectacle-corrected visual acuity, forward light scatter, and night halos, was not impaired.

Apical nodular subepithelial corneal scar after retreatment in hyperopic photorefractive keratectomy

PurposeTo report a complication, apical nodular subepithelial corneal scar, that can occur after hyperopic photorefractive keratectomy (PRK) retreatment. SettingIstanbul University Eye Research Center, Istanbul, Turkey. MethodsTwelve eyes of 6 patients with apical nodular subepithelial corneal scar were retrospectively studied. Mean age of the 5 men and 1 woman was 30.2 years ± 5.4 (SD). All eyes had hyperopic PRK retreatment for regression 9.5 ± 1.44 months after primary hyperopic PRK. Mean spherical equivalent refraction of the residual hyperopia before retreatment was +4.67 ± 0.81 diopters (D). All patients had a corneal haze grade of less than 1+. Hyperopic PRK retreatment was performed with a 193 nm excimer laser (Chiron Technolas Keracor 116). ResultsApical nodular subepithelial corneal scars developed within the first month of hyperopic PRK retreatment and progressed until the third month in 12 eyes of 6 patients. The lesion was round and symmetrical in both eyes, smaller than 2.0 mm, and centrally located. During the mean 40.66 ± 2.46 month follow-up, the lesion did not change in size or density. Mean spherical equivalent refraction after retreatment was 2.88 ± 0.88 D (range +1.50 to +4.00 D) at 1 month and +4.36 ± 1.83 D at last follow-up. Refraction was unmeasurable in 3 eyes. Five eyes lost 1 line of best spectacle-corrected visual acuity and 7 eyes, 2 or more lines. The surface regularity indexes were higher than 2.00 in all the eyes. ConclusionHyperopic PRK retreatment may cause the sight-threatening complication of apical nodular subepithelial corneal scar. This complication behaves unlike corneal haze and does not resolve spontaneously over time.

Central bump-like opacity as a complication of high hyperopic photorefractive keratectomy

PURPOSE: A new complication is reported in association with high hyperopic excimer laser photorefractive keratectomy. METHODS: One thousand consecutive eyes were treated with a Meditec MEL-60 excimer laser (Meditec Inc, Heroldsberg, Germany) for hyperopic refractive error between +1 diopters and +7 diopters. RESULTS: Three eyes with high hyperopic corrections between +5 and +6 diopters had a central, round bump-like subepithelial scar develop 1 month after hyperopic photorefractive keratectomy, which reduced the uncorrected and spectacle-corrected visual acuity. CONCLUSION: Central bump-like opacity is a new, visually significant complication of unknown origin associated with high hyperopic photorefractive keratectomy. Possible causes of this complication include drying and edema of the cornea as a result of prolonged exposure, interruption of the peripheral superficial nerve plexus affecting the central anterior stroma, and abnormal epithelial or tear film function resulting from excessive central steeping.

Photorefractive keratectomy for hyperopia: Long-term nonlinear and vector analysis of refractive outcome

Purpose To characterize the refractive changes after excimer laser photorefractive keratectomy for the correction of hyperopia over a follow-up up to 3 years and to assess refractive stability and changes in astigmatism. Design Noncomparative, nonrandomized, retrospective, interventional case series. Participants Thirty-eight hyperopic eyes of 28 patients (age range, 33–62 years) with refraction in the range +1.00 to +8.00 diopters (D). Mean attempted correction was +3.33 ± 0.98 D (range, +1.00 to +4.00 D). Data were compared to those from 216 eyes treated for myopia in the range −1.00 to −12.70 D. Intervention The hyperopic correction was made using an erodible mask inserted in the laser optical pathway to produce a circular ablation measuring 6.5 mm in diameter. An axicon was then used to create a blend transition zone from 6.5 mm up to 9.4 mm in diameter. Eyes were evaluated 3 to 11 times (5.5 ± 2.4) over a 3- to 34-month follow-up (16.8 ± 8.4 months). Main outcome measures Vector analysis of refractive error, applying a nonlinear statistical model fitting the spherical equivalent, and the sphere component data. The fit parameters were the long-term error at stabilization (ε ∞), the amount of regression (ε 0), being the difference of refractive errors immediately after surgery and at stabilization, and the time constant (T 1 2 ) giving the temporal scale length by which the overcorrection halves (regression half-life). Cylinder was analyzed by a linear regression. Results The initial overcorrection was much larger after hyperopic treatments than myopic ones (ε 0 = −3.26 ± 0.35 D vs. +1.43 ± 0.35 D), and it takes typically four times longer to regress (T 1 2 = 3.30 ± 0.91 months). Refractive stabilization is reached after more than 1 year, with a satisfactory refractive result. The hyperopic treatment induces a mean astigmatism of 1.00 D, which remains constant throughout the follow-up, and tends to be aligned along the with-the-rule meridian. Conclusions The advantages of a reasonably well-designed algorithm to correct hyperopia (ε ∞ = + 0.20 ± 0.23 D) are counterbalanced by the long time to refractive stabilization and by the induced astigmatism.

A Confocal Microscopic and Histological Study on Rabbit Corneas After Photorefractive Keratectomy for Hyperopia

To evaluate changes in corneas after PRK (photorefractive keratectomy) for hyperopia. Six rabbits were given PRK treatments for + 6.0 D of hyperopia. We observed these corneas by confocal microscopy at 3 days, 1 week, 2 weeks, 1 month, and 3 months after PRK, and examined them histologically. In the ablated area, proliferative changes in the subepithelial layer had already appeared three days after the operation. These changes progressed for one month, but had decreased at three months after operation. In confocal microscopy, the proliferative change in the subepithelial layer was observed as bright, highly refractive tissue interspersed with small spaces void of cells, and was especially evident at the wound edges of the peripheral side. The center of the cornea was slightly damaged by the excimer laser but proliferative changes were not observed there. The results of this study revealed that the damage to the center of the cornea caused by PRK for hyperopia was not very severe. But it is important to evaluate further the efficacy and safety of PRK for hyperopia.

Corneal iron ring after hyperopic photorefractive keratectomy

Purpose To report the incidence and course of corneal iron deposition after hyperopic photorefractive keratectomy (PRK). Setting Gazi University, Medical School, Department of Ophthalmology, Ankara, Turkey. Methods Between January 1995 and December 1997, 62 eyes had PRK to correct hyperopia. Results Nine eyes developed corneal iron ring 5 to 8 months (mean 6.25 months ± 1.3 [SD]) after PRK for hyperopia. The rings persisted during the mean follow-up of 19 ± 11.09 months. Conclusion The ring-shaped iron deposition after PRK for hyperopia must be differentiated from the Fleischer ring. Our results suggest that the slitlamp findings of peripheral corneal iron deposition in hyperopic PRK patients correlate with achieved correction.

Histology of rabbit corneas after 10-diopter photorefractive keratectomy for hyperopia.

To measure histological changes in the optical and transition zones of rabbit corneas treated with excimer laser photorefractive keratectomy (PRK) to correct hyperopia and to estimate the optical effect of these changes on the induced power profile. Corrections of +10.00 D were ablated by means of a Questek 2620 excimer laser and rotational masks on 8 rabbit eyes. On frozen sections of 4 stained corneas and historesine sections of 4 other corneas, stromal, new stromal, epithelial, and total corneal thickness were measured on four significant locations. The optical effect of each parameter on the axial power profile was estimated in a computer simulation. Mean stromal regrowth was 50% of the ablated tissue. Deposition was lenticular and could account for -5.00 D of regression. Stromal thickening without regrowth occurred in the optical zone and over the shoulder, causing augmentation instead of regression. The epithelium thickened 20% in the mid-transition zone and was thinner over the shoulder, accounting for 1.00 D of regression and an increase in asphericity in the optical zone. In these hyperopic rabbit PRK corneas, stromal regrowth and epithelial hyperplasia were lenticular and contributed to regression of the optical effect. Stromal swelling around interrupted collagen lamellae seemed to occur, augmenting the optical effect. The epithelium filters high spatial frequency stromal irregularities.

Laser vision correction for low hyperopia: An 18-month assessment of safety and efficacy

Objective This study aimed to assess the efficacy and safety of hyperopic photorefractive keratectomy (PRK) and to evaluate the effect of degree of hyperopia, two epithelial removal methods, and various postoperative patient management techniques on clinical outcomes. Design Prospective, nonrandomized, open-label clinical trial. Participants A total of 38 patients with mean follow-up of 13.9 months (n = 65 eyes with hyperopia from +1.00 diopter [D] to +4.00 D) participated. Intervention Hyperopic PRK with the VISX STAR Excimer Laser System was performed. Main outcome measures Spherical equivalent (SE) including vector analysis of SE; uncorrected visual acuity (UCVA); best-spectacle corrected visual acuity (BSCVA); low-, medium- and high-contrast visual acuities; topography; keratometry; pachymetry; and intraocular pressure, haze, and all other potential complications were measured. Results A total of 80% of eyes were within ±0.5 D and all but 1 eye (98%) were within ±1.0 D of intended manifest SE at 1 year. There was no induced astigmatism at 1 year. At 12 months, 72% of eyes had UCVA of 20/25 or better and 70% had achieved preoperative BSCVA, with no eye seeing worse than 20/25. These results remained constant at 18 months. There was a tendency toward regression between months 1 and 6 with stabilization of SEs between months 6 and 12. Thereafter, up to 18 months, there was some regression with a mean of +0.31 D, but the number of patients was small. There was one mild decentration and very slight decreases in mean intraocular pressure and central corneal thickness. One patient had grade 1.0 haze develop in both eyes at 12 and 18 months; all other patients experienced trace or no haze. There were no significant complications. Conclusions The results of this study support the hypothesis that laser vision correction is safe and effective for treating low hyperopia. The predictability of the hyperopic laser vision correction procedure used in this study was very good. Other than the slower recovery of BSCVA and UCVA seen with this procedure, as compared with myopic PRK, there were no significant complications. The trend toward some later regression needs to be further evaluated in a larger number of patients. Overall, patients were very pleased with the treatment, even in the first 6 months.

Evaluation of current techniques of corneal epithelial removal in hyperopic photorefractive keratectomy

Purpose: To determine the efficacy of 3 current methods used to remove corneal epithelium prior to photorefractive correction of hyperopia and to compare clinical data in patients who had rotary brush or blunt scrape epithelial removal in the treatment of hyperopic photorefractive keratectomy (PRK).Setting: University of Ottawa Eye Institute, Ottawa General Hospital, Ottawa, Ontario, Canada.Methods: The epithelium from human eye-bank eyes was removed using a Paton spatula, 15% alcohol, and the Amoils rotating plastic brush. The effects were examined by scanning and transmission electron microscopy. Twelve month postoperative data were obtained on 25 eyes with refractions of +1.00 to +4.00 diopters (D) that had been treated for hyperopia with the VISX Star excimer laser, using blunt scrape or the rotary brush to remove the corneal epithelium.Results: All 3 methods effectively removed corneal epithelium. The Paton spatula, however, left small nicks in Bowman's layer. Both the rotating brush and alcohol debridement left Bowman's layer intact. Alcohol treatment required follow-up epithelial debris removal, while brushing left minimal amounts of debris. There was a strong trend toward rapid epithelial healing in the brushed corneas compared with the scraped ones, but this was not statistically significant. Clinically, at 12 months postoperatively, brushed corneas showed a trend toward more superior outcomes than scraped corneas in actual refractive outcome, uncorrected visual acuity (UCVA), lines of UCVA gained, and predictability of the desired outcomes. However, only the outcome in UCVA of 20/40 or better and the decreased incidence of haze in the brushed corneas over scraped ones were statistically significant.Conclusions: Both alcohol and the rotating brush provide a quick, effective means of removing the corneal epithelium with minimal risk of damage to Bowman's layer. In our experience, the brush technique was as effective as and possibly superior to the blunt scrape for epithelial removal in hyperopic PRK.

Photorefractive keratectomy for hyperopia and aphakia with a scanning spot excimer laser.

To study the safety, efficacy, predictability, and stability of photorefractive keratectomy (PRK) for hyperopia and aphakia. Fifteen eyes of 15 patients (mean age, 33 +/- 5.95 yrs) were enrolled in the study and divided into three groups. The first group was comprised of six eyes that had hyperopia ranging from +1.75 to +4.75 D; the second group had seven hyperopic eyes ranging from +5.00 to +9.75 D; the third group included two eyes of two aphakic patients. All eyes had PRK with a 193 nm argon fluoride excimer laser (Chiron-Technolas, Keracor 116) with a 10 Hz repetition rate and a fluence of 120 mJ/cm2. The total follow-up time in all eyes was 12 months. In the lower hyperopia group, 0% eyes were within +/- 0.50 D and 66% (N = 4) of eyes were within +/- 1.00 D of emmetropia with the other two eyes between +1.00 and +2.00 D at 1 year after PRK. In the higher hyperopia group, all eyes had at least +3.00 D of hyperopia at 1 year. In the aphakic group, both eyes achieved less than 50% of the target correction of +10.00 D at 1 year. Final uncorrected visual acuity ranged from 20/20 to 20/30 in the lower hyperopia group, 20/30 to 20/50 in the higher hyperopia group, and count fingers in the aphakic group. PRK is a relatively safe, stable, and effective procedure with reasonably good predictability for eyes with less than +5.00 D of baseline hyperopia, and poor predictability for eyes with more than +5.00 D of baseline hyperopia. PRK is ineffective in the correction of aphakia.

Excimer Laser Photorefractive Keratectomy for the Correction of Hyperopia Using an Erodible Mask and Axicon System

Purpose: The purpose of the study is to evaluate photorefractive keratectomy for the correction of hyperopia using the erodible mask and Axicon system.Methods: Forty-three patients (43 eyes) with a mean refraction (spherical equivalent) of +4.54 diopter (D) (range, +1.75 to +7.50 D) were treated using a Summit Technology “Apex Plus” excimer laser. This system uses an erodible mask to create a 6.50-mm diameter hyperopic correction over the axial cornea. An Axicon then is used to fashion a 1.50-mm “blend zone” around the correction. On the basis of preoperative refractions, patients were assigned to 3 groups: 2 groups of 14 patients underwent either “+2.00 D” or “+3.00 D” corrections and 15 patients had “+4.00 D” corrections.Results: All patients had a reduction in their hyperopia with an overcorrection, especially in the first month after surgery and some stability in the refractive change at 3 to 6 months. The mean manifest refraction (n = 43) at 6 months was −0.17 D (range, +4.50 D to −3.125 D). Patient satisfaction was high. At 6 months, all eyes had an improvement in unaided near visual acuity. Unaided distance acuity was improved in 37 eyes (86%). A ring of haze 6.5 mm in diameter appeared in all eyes 1 month after surgery. Night halo measurements at 6 months showed no differences from preoperative levels. Flicker contrast sensitivity and forward light scatter (glare) measurements showed no differences after surgery.Conclusions: In this short-term study, photorefractive keratectomy for hyperopia using the erodible mask and Axicon system appeared to be a promising procedure. Visual performance, in terms of flicker contrast sensitivity, forward light scatter, and night halos, was not compromised. There was an overcorrection based on the manufacturer's algorithms. Manipulation of the treatment algorithms should improve future predictability.

Photorefractive keratectomy for hyperopia after radial keratotomy.

Progressive hyperopia is a common complication following radial keratotomy. Ten eyes of ten consecutive patients with hyperopia after radial keratotomy between +1.75 and +4.00 diopters (D) were treated with the hyperopia module of the Nidek Model EC-5000 excimer laser. The mean preoperative uncorrected visual acuity was 0.38 (20/60+). After excimer laser photorefractive keratectomy (PRK), mean uncorrected visual acuity improved to .72 (20/30+). No complications occurred with the exception of one eye with haze greater than 2+. PRK for hyperopia is a valuable method for correcting hyperopia after radial keratotomy.

Excimer laser photorefractive keratectomy for hyperopia

Purpose: To achieve less variation in the refractive outcome of hyperopic photorefractive keratectomy (PRK) by enlarging the treatment zone to 9.0 mm.Setting: Marienhospital, Amberg, Germany, and Klinika Ocni A Esteticke Chirurgie, Zlin, Czech Republic.Methods: This prospective clinical study was based on the results of PRK in 68 hyperopic eyes (62 patients) using an MEL 60 excimer laser. Mean attempted correction was +4.85 diopters (D) ±1.45 (SD) (range +2.00 to +8.25 D). Maximum follow-up was 12 months (68 eyes).Results: One year after PRK, 55 eyes (81 %) were within 1.00 D and 40 eyes (59%) were within 0.50 D of the intended correction (predictability). Best corrected visual acuity was unchanged or improved in 62 eyes (92%) (safety). Four eyes (6%) lost one line, 1 eye (1 %), two lines, and 1 eye (1 %), three lines. Sixty-six eyes (97%) had an uncorrected visual acuity of 20/40 or better (efficacy) and 27 (40%), 20/20 or better.Conclusion: Photorefractive keratectomy with a 9.0 mm treatment zone was an efficient and relatively safe procedure for correcting hyperopia of up to 8.25 D. The predictability was good. Great care must be taken to improve the centration of the optical zone.