Refractive results after photorefractive excimer laser treatment in mild myopic and in mild hyperopic eyes

Evaluation of 12-month results of photorefractive keratectomies (PRK) performed in low myopic (0 to -6.0 D) and low hyperopic (0 to +6.0 D) eyes. Myopic and hyperopic PRK treatments with the Aesculap Meditec MEL 60 ArF excimer laser. Prospective study, 30 eyes per group. The change in best corrected visual acuity (VA), refraction required, uncorrected VA and the postoperative haze were compared at the 12th postoperative month. The average preoperative correction in the low myopic eyes (Group I) was -4.65 +/- 1.24 D, which decreased to -0.17 +/- 0.56 D during the follow-up. In mild hyperopic eyes (Group II) the preoperative refraction was +3.9 +/- 0.93 D and decreased to +1.23 +/- 1.59 D post-PRK. Comparing the pre- and postoperative average best corrected VA values, there was no statistical change in either group. In the low myopic group all eyes had a 20/40 or better uncorrected VA, in hyperopic eyes 11 had a VA of 20/40 or better, four had a worse uncorrected VA. In Group I, 86.6% of the eyes were within +/-1.0 D of the intended refraction at 12 months postoperatively. In Group II, 46.7% of the eyes were within +/-1.0 D of final refraction. There were no intergroup differences in subjective complaints, reepithelization and average postoperative haze. Both methods are able to alter the refractive power of the cornea toward emmetropia. The predictability of the method was to be found higher in cases of mild myopia than in mild hyperopia. The upper limit of myopia is above -6.0 D, but in hyperopia, with the present technical facilities, good postoperative results can be obtained only as far as +4.25 D of preoperative refractive error.     

Pulmonary tuberculosis in the adult in a low prevalence area: is the radiological presentation changing?

BACKGROUND AND OBJECTIVE: To investigate the efficacy, predictability, stability, and safety of photorefractive keratectomy (PRK) with scanning spot ablation for the treatment of myopia of less than -6.0 D. PATIENTS AND METHODS: Twenty eyes of 20 patients (11 men, 9 women) were enrolled into the study. The mean age was 26.2 +/- 5.4 years. Mean spherical equivalent myopia was -3.53 +/- 1.13 D, ranging from -2.25 to -6.00 D. Patients underwent excimer laser PRK for the treatment of myopia. Follow-up time was at least 24 months in all patients. RESULTS: Mean spherical equivalent refraction was +0.84 +/- 0.99 D at 1 month, +0.19 +/- 0.54 at 3 months, -0.01 +/- 0.53 at 12 months, and -0.13 +/- 0.50 at 24 months. There was a mean regression of 0.65 D between 1 and 3 months. At 24 months, 16 (80%) of the eyes remained within +0.50 D of emmetropia and 18 (90%) of the eyes remained within +/- 1.0 D of emmetropia. Nineteen (95%) of the eyes had uncorrected visual acuity of 20/40 or better. The mean corneal haze score was maximum at 3 months (0.88 +/- 0.22). There was no clinically significant corneal haze (greater than 2+). One eye (5%) lost 2 or more lines of best-corrected visual acuity. CONCLUSION: Excimer laser PRK with the scanning spot ablation technique is effective, predictable, stable, and safe for the treatment of myopia of less than -6.0 D.     

Short-term effects of flurbiprofen and diclofenac on refractive outcome and corneal haze after photorefractive keratectomy

PURPOSE: To evaluate the short-term effects of topical nonsteroidal anti-inflammatory drugs (NSAIDs) on refractive outcome and corneal haze after excimer laser photorefractive keratectomy (PRK) according to the degree of myopia and to compare the results with those of topical steroids. SETTING: Seoul National University Hospital, Seoul, Korea. METHODS: Patients were divided into two groups: low to moderate myopia (-6.00 diopters [D] or less) and high myopia (greater than 6.00 D). Then, each patient was randomly assigned to one of three drug subgroups for initial management (4 months post-PRK): corticosteroids (fluorometholone 0.1%); flurbiprofen sodium 0.03% (Ocufen); diclofenac sodium 0.1% (Decrol). Follow-up was 6 months. RESULTS: In eyes with low to moderate myopia, the steroid and diclofenac subgroups had significantly different refractions 2 and 4 months postoperatively but no difference at 6 months; subjective haze grading was consistently lower in the steroid subgroup than in the NSAID subgroups (flurbiprofen, diclofenac) after 2 months. In eyes with high myopia, the steroid subgroup had significantly less myopic regression after 3 weeks and lower subjective haze after 2 months than the NSAID subgroups. The steroid subgroup had severe myopic regression or corneal haze less frequently than the NSAID subgroups. CONCLUSION: Topical NSAIDs were less effective than topical steroids in reducing myopic regression and haze after PRK, especially in highly myopic eyes.     

Analysis of prostate tissue DNA for the presence of human papillomavirus by polymerase chain reaction, cloning, and automated sequencing

BACKGROUND AND OBJECTIVE: As photorefractive keratectomy (PRK) becomes more widely used, the incidence of repeated PRK increases. The present study was conducted to evaluate results of repeated PRK in view of the meager data on this topic. PATIENTS AND METHODS: In this retrospective study, the authors reviewed the records of 1028 eyes that had undergone PRK, and analyzed the results of 66 eyes that required a second PRK for undercorrection according to baseline refraction. RESULTS: A second PRK was performed in 6.3%, 13.7%, and 10.1% of low, moderate, and high myopes, respectively. The mean refraction 1 year after repeated PRK was similar in both myopic groups: less than -1.00 D. Of the low myopes, 87.50% had residual refraction within 1 D after 1 year. Of the moderate myopes, 88.23% had residual refraction within 1 D after 1 year. All of the low myopes achieved uncorrected visual acuity (VA) of 20/25 or better 1 year after repeated PRK, compared with 58.82% of the moderate myopes. Loss of best-corrected VA never exceeded two lines. CONCLUSION: The overall results of PRK appear to be satisfactory.     

Multizone photorefractive keratectomy for high and very high myopia: long-term results

PURPOSE: To compare 2 year results of multizone excimer laser photorefractive keratectomy (PRK) in eyes with myopia (spherical equivalent [SE]) from 6.00 to 10.00 diopters (D) with those in eyes with myopia from 10.25 to 25.75 D. SETTING: Wellington Hospital and Laser Vision Harley Street, London, England. METHODS: Of the 281 PRK cases with an SE of at least -6.00 D, 59 eyes had a minimum follow-up of 2 years. Twenty-six of these had an SE from -6.00 to -10.00 D and 33, from -10.25 to -25.75 D. The single-pass, multizone technique was used to create ablation zones at 5.0, 5.5, and 6.0 mm. Postoperatively, patients received a minimum of 4 weeks of fluorometholone 0.1%; those exhibiting regression after corticosteroids were discontinued were restarted on a tapering regimen. RESULTS: The refraction stabilized 3 months postoperatively in the -6.00 to -10.00 D group, and the final mean SE refraction was a small undercorrection. Two years postoperatively, 88.5% of eyes had a visual acuity of 20/40 or better, and 77.0% were within +/- 1.00 D of the intended correction. In eyes with myopia greater than 10.00 D, regression continued during the 2 years and refraction did not stabilize. Forty-two percent had an uncorrected acuity of 20/40 or better, and 48.0% were within +/- 1.00 D of the intended correction. The incidence and severity of haze were higher in the group with myopia greater than 10.00 D. The overall incidence of complications was low. CONCLUSION: Two years after multizone PRK, refractive and visual acuity results in eyes with myopia from 6.00 to 10.00 D were good. Results in eyes with myopia of more than 10.00 D were not satisfactory, and refraction had not stabilized.     

A multicenter trial of photorefractive keratectomy for residual myopia after previous ocular surgery. Summit Therapeutic Refractive Study Group

PURPOSE: The Summit Therapeutic Refractive Clinical Trial is a nine-center prospective, nonrandomized, self-controlled trial to assess the efficacy, stability, and safety of using a standardized technique of excimer laser photorefractive keratectomy (PRK) to correct residual myopia in eyes with previous refractive surgery or cataract surgery. PATIENTS AND METHODS: Eligible eyes with a mean residual myopia of -3.7 +/- 1.8 diopters (D) (range, -0.63 to -11.00 D) underwent PRK with a 193-nm excimer laser for myopic corrections between -1.50 and -7.50 D. Standardized settings were used for the ablation zone, ablation rate, repetition rate, and fluence. One hundred seven of the first 114 treated eyes were examined 1 year after PRK, with 98% of eyes having had refractive keratotomy and 2% having had cataract surgery. RESULTS: One year postoperatively, the mean manifest spherical equivalent refraction was -0.6 +/- 1.4 D (range, -6.50 to 2.50 D); 63% of eyes were within +/-1.00 D of the attempted correction; and uncorrected visual acuity was 20/40 or better in 74% of eyes. Twenty-nine percent of eyes lost two or more Snellen lines of best-corrected visual acuity, and central corneal haze was moderate or severe in 8% of eyes. CONCLUSIONS: Excimer laser PRK is effective in reducing residual myopia after previous refractive and cataract surgery. However, it is less accurate than PRK in eyes that did not undergo surgery and is more likely to cause a loss of best-corrected visual acuity 1 year after treatment.     

Comparison of photorefractive keratectomy with excimer laser in situ keratomileusis in correcting low myopia (from -2.00 to -5.50 diopters). A randomized study

OBJECTIVE: To compare laser in situ keratomileusis (LASIK) with photorefractive keratectomy (PRK) in the correction of myopia from -2.00 to -5.50 diopters. DESIGN: Prospective, randomized, paired clinical trial. PARTICIPANTS: Fifty-two eyes of 26 myopic patients were enrolled in the study. INTERVENTION: Each patient received PRK on one eye (PRK eye) and LASIK on the other (LASIK eye); the procedure assigned to each eye, and the sequence of surgeries for each patient was randomized. MAIN OUTCOME MEASURES: Slit-lamp microscopy, manifest refraction, uncorrected and spectacle-corrected visual acuity, and videokeratography were done before operation, and 2 weeks, 6 weeks, 3 months, 6 months, and 12 months after operation. Patient satisfaction and preference were assessed by a subjective questionnaire. RESULTS: All LASIK eyes had fast, painless recovery. At 1 year, 24 patients (92.3%) were examined, the mean spherical equivalent refraction was -0.08 +/- 0.38 diopter in the PRK eyes and -0.14 +/- 0.31 diopter in the LASIK eyes, and the uncorrected visual acuity was 20/20 or better in 15 PRK eyes (62.5%) and 19 LASIK eyes (79.2%); no eye lost 2 or more Snellen lines of spectacle-corrected visual acuity. Both procedures were stable throughout the first year. One PRK eye developed dense subepithelial corneal haze. The strongest correlate to spectacle-corrected visual acuity after the two procedures was the coefficient of variation of corneal power over the pupil. Nineteen patients (79.2%) preferred the LASIK procedure because of the fast, painless recovery. CONCLUSIONS: In the current study, PRK and LASIK were found to be similarly effective, predictable, stable, and reasonably safe for the correction of myopia between -2.00 and -5.50 diopters. Laser in situ keratomileusis has the advantage of fast, painless recovery. Patients prefer LASIK.     

The effects of topical steroids on refractive outcome and corneal haze, thickness, and curvature after photorefractive keratectomy with a 6.0-mm ablation diameter

BACKGROUND AND OBJECTIVE: To study the effect of topical prednisolone acetate after photorefractive keratectomy (PRK) using a 6.0-mm ablation diameter on the refractive and visual outcomes, corneal haze, corneal thickness, and corneal curvature in a prospective, double-masked, randomized manner. PATIENTS AND METHODS: Seventy-two eyes of 36 patients who had excimer laser PRK for correction of myopia ranging from -3.00 to -6.00 D (-4.11 +/- 0.84 D in eyes treated with steroids and -4.38 +/- 0.79 D in eyes treated with placebo; mean +/- SD) were enrolled. PRK procedures were performed using a 193-nm argon-fluoride excimer laser with 180-ml/cm2 fluence, a 10-Hz repetition rate, and a 6.0-mm ablation diameter. One eye of each patient was treated with the steroid (prednisolone acetate) and the other eye with placebo. Patients were observed for at least 12 months after PRK. RESULTS: There was no statistically significant difference between the steroid and the placebo groups with regard to refraction measurements that were taken postoperatively at 3 months (P = .39) and 12 months (P = .51). The corneas showed an increase in thickness after PRK in both groups, but the difference was not statistically significant at 12 months postoperatively (P = .45). The corneal haze score was not statistically different at any stage between groups (P = .30 at 3 months, P = .84 at 12 months). Keratometric data derived from corneal topography did not show any statistically significant difference (P = .85 at 3 months, P = .96 at 12 months). The rate of uncorrected visual acuity of 20/40 or more was 79.4% (27 eyes) in the steroid group and 70.5% (24 eyes) in the placebo group (P = .40). The rate of loss of 2 or more lines in best spectacle-corrected visual acuity was 5.85% (2 eyes) in the steroid group and 8.8% (3 eyes) in the placebo group (P = 1.0). CONCLUSION: Topical prednisolone acetate use for 3 months after PRK with a 6.0-mm ablation diameter has no effect on refractive and visual outcome, corneal haze, corneal thickness, and corneal curvature.     

Amniotic fluid for screening of lysosomal storage diseases presenting in utero (mainly as non-immune hydrops fetalis)

PURPOSE: We studied the efficacy and safety of a recent technique of keratomileusis for myopia, excimer laser in situ keratomileusis. METHODS: We studied retrospectively 88 eyes of 63 patients who received excimer laser in situ keratomileusis with the Chiron Automated Corneal Shaper and the Summit OmniMed laser under a hinged corneal flap without sutures. RESULTS: Mean follow-up was 5.2 months. Mean spherical equivalent of the manifest refraction before surgery was -8.24 diopters (range, -2.00 to -20.00 diopters). Mean spherical equivalent refraction after surgery was +0.22 +/- 1.42 diopters. Of 40 eyes with a baseline refraction from -2.00 to -6.00 diopters, 25 eyes (63%) had refraction within +/- 0.50 diopter of emmetropia, and 37 eyes (93%) had refraction within +/- 1.00 diopter. In eyes with baseline refraction of -6.12 to -12.00 diopters, postoperative refraction was within +/- 1.00 diopter in 19 (65%) of 29 eyes. In eyes with baseline refraction of -12.10 to -20.00 diopters, postoperative refraction was +/- 1.00 diopter in eight (43%) of 19 eyes. Overall, 64 (72.8%) of 88 eyes had a refraction within +/- 1.00 diopter after surgery. Between three weeks and five months after surgery the change in the mean spherical equivalent refraction was -0.61 diopter in the myopic direction. Uncorrected visual acuity after surgery was 20/20 or better in 31 eyes (36%) and 20/40 or better in 61 eyes (71%). Three eyes (3.6%) lost two lines or more of spectacle-corrected visual acuity, two from progressive myopic maculopathy and one from irregular astigmatism. No eyes had vision-threatening complications. CONCLUSION: Excimer laser in situ keratomileusis under a corneal flap can be an effective method of reducing myopia between -2.00 and -20.00 diopters, with minimal complications. Current surgical algorithms need modification to improve predictability of outcome. Stability of refraction after surgery requires further study.     

Treatment of myopic astigmatism with the Summit Apex Plus excimer laser

PURPOSE: To assess the results of surface sequential toric photorefractive keratectomy (PRK) with the Summit Apex Plus excimer laser using an erodible mask. METHODS: A prospective study was performed on consecutive eyes having surface sequential toric PRK over a 4 month treatment period. Attempted astigmatism correction varied from 70 to 100%, depending on the power and axis of the cylinder. The myopic correction was adjusted so the combined treatment aim was emmetropia. Refraction, manual keratometry, corneal haze, and visual acuity data from preoperative and follow-up visits over 12 months were divided into various groups based on the preoperative refraction and analyzed. RESULTS: Fifty-nine eyes from 48 patients had sequential toric PRK. Preoperatively, the mean spherical equivalent at glasses plane (SEGP) was -4.88 diopters (D) +/- 3.20 (SD) and the mean refractive cylinder, 2.02 +/- 1.04 D. The mean attempted cylinder correction was 1.87 D. At 12 months the mean SEGP was -0.02 +/- 0.67 D, which was not statistically significant from plano. The mean refractive cylinder was 0.84 +/- 0.84 D, which was statistically significantly different from zero cylinder power. There was a statistically significant correlation between the preoperative and the 12 month postoperative refractive cylinder powers. At 12 months, 34 of 43 eyes (79.1%) had an uncorrected visual acuity of 6/12 or better. While 2 eyes in one patient (4.7%) lost two lines of best corrected visual acuity, with a final acuity of 6/12 in each, no patient lost more than two lines. CONCLUSION: The manifest refraction cylinder power is not fully corrected with the current treatment algorithms; however, surface sequential toric PRK using an erodible mask is capable of treating compound myopic astigmatism with moderate success.     

Laser thermal keratoplasty for the treatment of photorefractive keratectomy overcorrections: a 1-year follow-up

OBJECTIVE: To evaluate the results of holmium:YAG laser thermal keratoplasty (LTK) treatment for overcorrection of myopia after a photorefractive keratectomy (PRK) treatment. PARTICIPANTS: Thirty-six eyes (33 patients) were treated with a nontouch holmium:YAG laser (Sunrise Technologies, Model LTK, Freemont, CA) because of hyperopia (mean +/- standard deviation of +2.06 diopter [D] +/- 0.75, ranging from +1.0 to +3.5 D) following a PRK treatment. A control LTK group treated for primary hyperopia, who had preoperative refraction values not statistically different from the PRK + LTK group, was used for comparison. INTERVENTION: The number of spots applied varied from 8 to 24, and the energy used was 200 to 240 mJ. A maximum of three rings of four to eight spots were placed between 6 and 8 mm from the visual axis. RESULTS: Twelve months after the LTK retreatment for PRK patients, mean refraction was +1.14 D +/- 1.09. Regression from 1 to 12 months was 0.5 D +/- 1.1. At 12 months, 50% of eyes were within 1 D of emmetropia; 93% of eyes had uncorrected visual acuity (UCVA) of 20/40 or better; and 24% of eyes had UCVA of 20/20 or better. Refraction was not stable for 11 eyes (34%) that regained original sphere values or higher. Best-corrected visual acuity was not affected, and haze was not increased nor decreased by the procedure. CONCLUSIONS: Twelve months after an LTK retreatment for an initial PRK, two thirds of the retreated eyes did not need further retreatments. However, clinical data showed that LTK should be kept for +1 to +2 D of hyperopia for PRK overcorrection retreatments.     

Double zone PRK for high myopia

INTRODUCTION: Although excimer laser PRK is our operation of choice for treating myopia, the correction of myopia exceeding -8.00 dpt is still a challenge as this procedure requires a deeper keratectomy. Therefore a double zone treatment may be beneficial to reduce ablation depth. METHODS: Twenty-one eyes with myopia between -8.00 dpt and -14.00 dpt were included in this study. Twelve eyes were treated 60% of myopia by 5 mm zone and the remaining 40% in a 4 mm zone in the same session (Group 1). RESULTS: Nine eyes achieved 60% of the desired correction treated with a 4 mm zone whereas 40% correction was achieved in a 5 mm zone (Group 2). No significant difference in postoperative healing, pain, hyperopic shift, myopic regression and haze was observed at the end of the mean follow-up time (10.4 months) but photophobic complaints were less in Group 2. Best corrected visual acuity did not decrease significantly. CONCLUSIONS: Double zone treatment seems to be an interesting method for treating moderate to high myopia.     

Photorefractive keratectomy for -1.25 to -25.00 diopters of myopia

BACKGROUND: We evaluated prospectively the efficacy, predictability, stability, and safety of photorefractive keratectomy (PRK) for myopia. METHODS: Three hundred sixty-nine eyes of 257 patients were treated with an Aesculap-Meditec MEL 60 excimer laser. Treated eyes were divided into 3 groups: low myopes (-1.25 to -6.00 D), 226 eyes; medium myopes (-6.10 to -10.00 D), 104 eyes; high myopes (-10.10 to -25.00 D), 39 eyes. Follow-up at 12 months was available for 348 eyes (94%). RESULTS: One year after surgery the number of eyes within +/- 1.00 D of emmetropia was 182 (86.7%) for low myopes, 43 (40.5%) for medium myopes, and 12 (30.8%) for high myopes. Values for +/- 0.50 D were low: 142 (67.6%), medium: 29 (29.3%), and high: 9 (23.1%). Three eyes with low myopia (1.4%) and 5 eyes with medium myopia (5.1%) lost 2 or more lines of spectacle-corrected visual acuity. None of the high myopes lost 2 or more lines. Uncorrected visual acuity of 20/20 or better was achieved in 82 eyes (39%) with low myopia; 20/40 or better was achieved in 183 eyes (87.1%). Five eyes (5.1%) of medium myopes achieved 20/20 or better; 52 eyes (52.5%) with medium myopia achieved 20/40 or better. Zero eyes with high myopia achieved 20/20 or better; 11 eyes (28.8%) achieved 20/40 or better. CONCLUSION: Photorefractive keratectomy proved to be an effective method to correct myopia up to -6.00 D. For myopia greater than -6.00 D, good results were achieved in most eyes when myopia was less than -10.00 D, but efficacy and predictability decrease. To avoid systematic undercorrection, slight overcorrection must be attempted with the Aesculap-Meditec MEL 60 excimer laser for the treatment of myopia.     

Correlation of pituitary hormones in serum of male patients with fertility problems

The advent of the excimer laser has brought about the potential for improved vision in many individuals with myopia and astigmatism. However, photoastigmatic refractive keratectomy (PARK) remains a matter of controversy. The purpose of our study was to determine the predictability of VISX 20/20 excimer laser photorefractive keratectomy in the treatment of myopic astigmatism. PATIENTS AND METHODS: Our study comprised 31 eyes of 22 patients with myopic astigmatism. All patients underwent treatment with a VISX 20/20 excimer laser and were followed up for 6 months. Complete 12-month follow-up data were available from 18 eyes. Park was performed in eyes with myopia between -1.5 and -10.0 D and with astigmatism between -0.5 and -5.5 D. Thus, the corresponding spherical equivalent ranged from -1.75 to -10.5 D. RESULTS: Six months postoperatively, 21/31 (62%) eyes were within +/- 1.0 D of the target refraction and 13/31 (42%) within +/- 0.5 D of the target refraction. In 13 of 15 eyes (87%) with myopia less than -6.0 D, an uncorrected visual acuity of at least 0.8 was noted. In eyes with myopia greater than -6.0 D, 9/16 (56%) showed an uncorrected visual acuity of at least 0.5. Six months after PARK, an increase of one line on the Snellen Visual Acuity Chart was observed in 8/31 (26%) and an increase of two lines was noted in eyes 3/31 (10%). One of 31 eyes (3%) showed an increase of three lines. A decrease in visual acuity of 1 line on the Snellen Visual Acuity Chart was found in 4/31 (13%), and in 3/31 eyes (10%) a decrease of 2-4 lines was noted. Overall, we observed a statistically significant reduction of astigmatism from 1.93 +/- 1.43 D to 0.93 +/- 0.63 D. Reduction of corneal astigmatism less than -1.25 D was not statistically significant. In eyes with astigmatism ranging from -1.25 to -2.5 D or greater than -2.75 D, a significant reduction of the mean astigmatism was noted. The postoperative regression of astigmatic correction was low. However, an axis shift of more than 15 degrees was found in 42%/35% of eyes by subjective refraction (miosis/cycloplegia) and in 33% in corneal topography. No central islands were noted. CONCLUSION: Photoastigmatic refractive keratectomy (PARK) constitutes a potential means of correcting myopic astigmatism. In eyes with astigmatism greater than -1.0 D a significant reduction of 60% of the mean astigmatism was noted. However, the considerable proportion of eyes with a postoperative axis shift greater than 15 degrees and a decrease in visual acuity of two or more lines indicates that further research is needed on excimer laser surgery to improve the reliability and safety.     

Quantification of stromal thinning, epithelial thickness, and corneal haze after photorefractive keratectomy using in vivo confocal microscopy

PURPOSE: The authors establish, for the first time, observer-independent quantification of stromal thinning, epithelial thickness, and corneal haze after excimer laser photorefractive keratectomy (PRK) using a unique, new form of in vivo confocal microscopy. METHODS: Rapid, continuous z-scans of high-resolution confocal images, termed confocal microscopy through focusing (CMTF), were performed in the central corneal area of 17 patients before and 1 month after PRK for low- to moderate-grade myopia (-2.88-9.13 diopters [D]). Corneal, epithelial, and stromal thickness measurements and an objective haze estimate were obtained from each CMTF scan by digital image analysis. RESULTS: Epithelial thickness averaged 51 +/- 4 microns before and 45 +/- 10 microns 1 month post-PRK (P < 0.005), whereas stromal thinning ranged from 20 to 154 microns, representing a direct estimate of the actual photoablation depth. Corneal thickness averaged 560 +/- 36 microns before PRK and 462 +/- 52 microns at 1 month. The change in corneal thickness correlated closely with the change in spherical equivalent refraction (r = 0.94, P < 0.0001); linear regression analysis revealed a value of 14.3 microns corneal thinning per diopter of correction. A significant correlation was found between the objective CMTF haze estimate and a clinical haze grading obtained by slit-lamp examination (r = 0.73, P < 0.001). CONCLUSIONS: Confocal microscopy through focusing is a new, powerful in vivo tool that enables quantitative, unbiased evaluation of PRK procedures over time by providing epithelial and stromal thickness analysis, photoablation depth assessment, and unbiased haze measurement. The method is uniquely valuable in the pre- and postoperative assessment of PRK patients and for determining the optimal treatment strategy, especially in assessing refractive and visual outcomes in individual cases.     

Retinoscopy after excimer laser photorefractive treatments

Photorefractive keratectomy (PRK) is capable of changing the refractive power of the human cornea. Retinoscopy is an objective method of measuring the refractive power of the eye. The authors performed PRK in 28 myopic eyes with the Aesculap Meditec MEL 60 ArF excimer laser. During a prospective study, the subjective and objective refractive power of the eyes were assessed and compared 6 months after PRK. The average preoperative refractive error was: -5.11 +/- 2.51 D and -5.08 +/- 2.20 D on the right side (n = 16) and on the left side (n = 12), respectively. In order to obtain the best corrected visual acuity 6 months after PRK, the right and left eyes needed an average of -0.09 +/- 0.26 D and -0.33 +/- 0.64 D postoperative correction, respectively. The postoperative refractive change could be verified with the retinoscopy at +/-0.5 D accuracy. The authors describe a double refractive corneal ring after PRK, which may disturb retinoscopy. The post-PRK refractive change can be verified by retinoscopy. Postoperative funduscopy, fundus photography and possible future retinal procedures were not disturbed by the double corneal refractive rings in myopic eyes.     

Topical interferon alpha 2b for corneal haze after excimer laser photorefractive keratectomy. The Melbourne Excimer Laser Group

PURPOSE: To determine whether topical interferon alpha 2b (IFN-alpha) prevents corneal haze after excimer laser photorefractive keratectomy (PRK). SETTING: Tertiary referral ophthalmic hospital. METHOD: A prospective, double-blind, placebo-controlled, randomized study of 31 patients was undertaken. After surgery in a single institution, patients received a drop of either a placebo or IFN-alpha (5 x 10(6) IU/ml) four times daily for 4 weeks. The main outcome measures were corneal haze, refraction, and visual acuity. RESULTS: The major side effect of interferon alpha treatment was a significant delay in epithelial healing by a mean of 2 days. The means of the average post-treatment clinical scores for haze in all patients up to 12 months after surgery were 0.46 +/- 0.25 for the IFN-alpha group and 0.64 +/- 0.43 for the placebo group (P = .20). Of patients with a correction of greater than 5.00 diopters (D), the IFN-alpha group had significantly less haze over the course of the study (0.39 +/- 0.23 versus 0.98 +/- 0.50; P = .03). After 12 months, the mean absolute spherical equivalent in the two groups was not significantly different (1.02 +/- 1.13 D versus 1.44 +/- 2.64 D). There was a tendency toward better uncorrected visual acuity in the INF-alpha group (P < .10, Kolmogorov-Smirnov). CONCLUSION: Topical IFN-alpha may merit further investigation as a treatment to reduce corneal haze after excimer laser PRK for corrections greater than 5.00 D.     

Transcendence: the meaning of great-grandmothering

OBJECTIVE: To investigate the wound healing of the cornea following 193 mm excimer laser photorefractive keratectomy (PRK) and the effects of corticosteroid on it. METHODS: PRK was performed on both eyes of 6 monkeys. Corticosteroid was given to the right eyes, but not to the left ones. At 4 days, 1 week, 2 weeks, 1 month, 3 months and 6 months, corneal pachymetry was examined and the eyes of one monkey were enucleated and the corneas were stained immunohistochemically for collagen type III, type IV and type VII, fibronectin and laminin. RESULTS: The expression of collagen type Vii recovered to the normal linear patter at 1 month. With corticosteroid, the deposition of collagen type III and fibronectin was markedly reduced and the pachymetry of central cornea was closer to the expected value. CONCLUSION: This study suggests that corticosteroid help to minimize the postoperative myopic regression and corneal haze after PRK.     

Results of photorefractive keratectomy for myopia with the technolas keracor 116 excimer laser

BACKGROUND: The refractive results of first consecutive 157 myopic eyes undergoing photorefractive keratectomy with the Technolas Keracor 116 excimer laser are presented with a 6-month follow up. METHODS: Preoperative refractive errors (spherical equivalent) ranged between -1.75 diopters (D) and -20.00 D (mean: -7.19 +/- 3.73). A single ablation zone ranging from 4.5 mm to 6 mm was used. In all eyes except for those with myopia over -15 D, emmetropia was a goal. Postoperatively patients used fluoromethalone drops for 1 month. RESULTS: Treated eyes were divided into four groups based on preoperative myopia. Group 1 contained 15 eyes with myopia less than -3 D (93% were within +/- 1 D postoperatively). In Group 2 there were 53 eyes with preoperative myopia between -3.25 D and -6.00 D (64.1% were within +/- 1 D postoperatively). Group 3 consisted of 53 eyes with preoperative myopia between -6.25 D and -10.00 D (41.5% were within +/- D postoperatively). Group 4 contained 36 eyes with myopia over -10.00 D (13.8% were within +/- 1 D of attempted correction and 11.1% were within +/- 1 D postoperatively). CONCLUSIONS: Our study suggests that excimer laser photorefractive keratectomy using a 4.5 to 6.0 mm ablation zone effectively reduces myopia; however, predictability decreases as the attempted correction increases.     

A prospective clinical study of correction of myopic astigmatism by combined treatment with PRK and T-incision and photoastigmatic refractive keratectomy. The results after one year

BACKGROUND: In contrast to the correction of simple myopia there is no widely accepted technique for the correction of myopic astigmatism. Currently two techniques are available: the photoastigmatic refractive keratectomy (PARK) and the combination of arcuate keratotomies with standard PRK (PRK-T). METHODS: In two groups, 67 patients underwent a correction of myopic astigmatism in a total of 87 eyes (19 by PRK-T and 68 by PARK), and were followed for 1 year. The spherical equivalent was -6.7 D in both groups and the refractive astigmatism ranged from -1.0 to -6.5 D. The PARK procedure was performed by means of an elliptic ablation (Kertom I, Schwind) with a 5.8 x 8.1 mm zone. The PRK-T technique consisted of two arcuate keratotomies with a free optical zone of 7 mm and a standard myopic PRK at least 6 weeks later. RESULTS: The 1 year follow-up was completed in 57 out of 87 eyes included in the study. At 1 year post-operation, 83% of the PRK-T group and 80% of the PARK group had an uncorrected visual acuity of 20/40 or better. The refractive astigmatism was reduced by 76% in the PRK-T group and by 67% in the PARK group. The spherical equivalent was -0.59 +/- 1.1 D at 1 year after PRK-T and -0.28 +/- 1.04 D after PARK. In three eyes of the PARK group (6.7%) a visual loss of more than one Snellen line occurred. Two of these eyes had a preoperative myopia of more than -6 diopters. CONCLUSION: Both techniques have the potential to reduce myopic astigmatism, however, the success rate is not as high compared to spherical PRK. Also, the complication rate of 2.5% in corrections to -6 D is significantly higher than that with spherical myopic PRK.