Frequency of consanguinity and its effect on congenital malformation--a hospital based study

21 aphakic eyes of 21 patients corrected by glasses (A-G) were examined 1 and 6 months before and after secondary intraocular lens implantation (SILI). Visual acuity (VA) was tested using Snellen chart and computerized method with Landolt rings (CL). Contrast sensitivity (CS) was measured using computerized Contrast sensitivity system 8010 in spatial frequencies from 0.74 to 29.55 c/deg. Preoperative best corrected VA (BCVA) in A-G eyes was significantly lower in comparison with control group of the same age only using computerized method with Landolt rings. A reduction of BCVA by both methods at 1 month and its return to original values after 6 months were noted. Significantly lower values of CS were found in A-G patients before SILI compared to the control group of the same median age in spatial frequencies from 3.69 to 29.55 c/deg. After 1 and 6 months the values stayed on the preoperative level, except the frequency 29.55 c/deg, which increased significantly (p < 0.01) 6 months after SILI.     

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.     

Effect of beam variables on corneal sensitivity after excimer laser photorefractive keratectomy

AIM: To investigate changes in corneal touch sensitivity following excimer laser photorefractive keratectomy (PRK) using different beam configurations. METHODS: 20 subjects were given a unilateral -3.00 D correction with either a 5 mm (26 micrograms, n = 10) or 6 mm (42 micrograms, n = 10) beam diameter. Thirty subjects underwent a unilateral -6.00 D correction with 5 mm (62 micrograms, n = 10), 6 mm (78 micrograms, n = 10), or multizone (62 micrograms, n = 10) treatments. The multizone treatment was 6 mm in diameter with the depth of the 5 mm treatment. Corneal sensitivity was measured using a slit-lamp mounted Cochet-Bonnet aesthesiometer before and at 1, 3, 6, and 12 months after PRK. Stimulus locations included points lying within the ablated zone (central) and outside (peripheral). These were compared with the equivalent locations in control (untreated) eyes. RESULTS: There was a significant reduction in corneal sensitivity within the central (ablated) zone in all treatment groups after PRK. In most groups a return to full sensitivity was achieved by 6 months with the exception of the multizone treatment group which showed significant corneal hypoaesthesia at 12 months. Peripheral corneal sensitivity was also reduced in this group up to 3 months after the procedure. A comparison between the -3.00 D and -6.00 D treatment groups showed no significant difference. However, combining data from all treatment groups, a significant correlation was found between the interocular difference in central corneal sensitivity and postoperative haze at 3 and 6 months. CONCLUSIONS: For corrections up to -6.00 D ablation depth and treatment zone diameter do not appear to be clinically important determinants of corneal hypoaesthesia. In contrast, postoperative corneal haze appears to correlate with sensitivity loss.     

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.     

The effect of topical corticosteroids on refractive outcome and corneal haze after photorefractive keratectomy

BACKGROUND: The effect of topical corticosteroids after excimer laser photorefractive keratectomy (PRK) remains a matter of some controversy. Refractive effects may be different according to the amount of myopia and timing of instillation. METHODS: Two groups of patients were studied: Study A consisted of 215 eyes (128 patients) with PRK (mean baseline myopia, -6.53 +/- 2.22 D) that received no corticosteroids (No Corticosteroid Group) unless significant regression or corneal haze appeared (Delayed Corticosteroid Group), and in Study B, we randomly assigned eyes to the Initial Corticosteroid Group (mean baseline myopia, -6.39 +/- 1.84 D) or the No/delayed Corticosteroid Group (mean baseline myopia -5.78 +/- 2.02 D). Clinical results after PRK for low-to-moderate and high myopia were compared. RESULTS: In the first group, 70.9% (73 eyes) of moderately myopic eyes (mean, -4.56 +/- 1.10 D) belonged to the No Corticosteroid Group that had a mean refraction of -5.39 +/- 1.77 D. Delayed Corticosteroid Group eyes were more myopic (mean, -7.52 +/- 2.10 D), and showed more severe haze than those in the No Corticosteroid Group. In study B, only in high myopes with more than -6.00 D (mean, -7.76 +/- 1.15 D) did refraction and corneal haze outcomes show significant difference between the Initial Corticosteroid Group and the No/delayed Corticosteroid Group. CONCLUSIONS: The effects of topical corticosteroids after PRK were less in moderate myopes compared to high myopes. Delayed instillation of corticosteroids did not reverse the regression or haze whereas initial instillation showed a beneficial effect on high myopes but not on moderate myopes.     

Teledermatology and in-person examinations: a comparison of patient and physician perceptions and diagnostic agreement

PURPOSE: The aim of this study was to assess the outcome of reoperation following photorefractive keratectomy related to different techniques. MATERIAL AND METHODS: 265 retreated eyes were divided into 5 groups; low to moderate myopia, high myopia, enlargement, abrasion, and non-compliance. The low to moderate group was further subdivided into 5 categories based on the surgical approach of the reoperation. Outcomes were compared at 12 months after reoperation. RESULTS: There was no statistically significant difference in the median refraction prior to initial PRK, before reoperation, and after reoperation between the 5 categories 66%, of all reoperated patients achieved an uncorrected visual acuity of 0.5 or better after 12 months. 72% had a postoperative refraction between +/- 1 diopter. The other 4 groups were not statistically analyzed due to the wide variety of patients included and non-compliance. CONCLUSION: In low to moderate myopes, approximately 97% achieve uncorrected visual acuity of 0.5 or better following PRK, including one reoperation.     

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.     

Photorefractive keratectomy versus laser in situ keratomileusis for moderate to high myopia. A randomized prospective study

OBJECTIVE: This report presents the results of a randomized clinical trial of photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK). DESIGN: A randomized, prospective multicenter clinical trial. PARTICIPANTS: A total of 220 eyes of 220 patients entered the study cohort: 105 randomized to PRK and 115 to LASIK. The mean preoperative manifest refraction spherical equivalent was -9.23 diopters (D) in the PRK group and -9.30 D in the LASIK group. INTERVENTION: All patients received a one-pass, multizone excimer laser ablation as part of either a PRK or LASIK procedure using the Summit Apex excimer laser. Attempted corrections ranged from 6.00 to 15.00 D. MAIN OUTCOME MEASURES: Data on uncorrected and spectacle-corrected visual acuity, predictability,and stability of refraction, corneal haze, and flap complications were analyzed. Patients were observed for up to 6 months. RESULTS: One day after surgery, 0 (0.0%) and 3 (4.5%) eyes in the PRK group saw 20/20 and 20/40 or better uncorrected, respectively, while 7 (10%) and 48 (68.6%) eyes in the LASIK group saw 20/20 and 20/40 or better, respectively. At 6 months after PRK, 13 (19.1%) and 45 (66.2%) eyes saw 20/20 and 20/40 or better, respectively, while after LASIK, 16 (26.2%) and 34 (55.7%) eyes saw 20/20 and 20/40 or better, respectively (odds ratio = 0.56 for likelihood of uncorrected visual acuity < 20/40 for PRK vs. LASIK, 95% confidence interval [CI] = 0.31-1.19). After PRK, 39 eyes (57.4%) were within 1.0 D of attempted correction compared with 24 eyes (40.7%) in the LASIK group (odds ratio = 0.50 for likelihood fo undercorrection 1.0 D for PRK vs. LASIK, 95% CI = 0.24-1.04); however, the standard deviation of the predictability was similar between groups: 1.01 D for PRK and 1.22 D for LASIK. From months 1 to 6, there was an average regression of 0.89 D in the PRK group and 0.55 D in the LASIK group. After PRK, eight eyes (11.8%) had a decrease in spectacle-corrected visual acuity of two Snellen lines or more; after LASIK, two eyes (3.2%) had a decrease of two lines or more (odds ratio = 3.89 for risk of loss of spectacle-corrected visual acuity for PRK vs. LASIK, 95% CI = 0.71-21.30). Only two eyes had postoperative spectacle-corrected visual acuity less than 20/32, however. CONCLUSIONS: Although improvement in uncorrected visual acuity is more rapid in LASIK than in PRK, efficacy outcomes in the longer term generally are similar between the two procedures. There is a greater tendency toward undercorrection in LASIK eyes using the specific laser and nomogram in this study, but the scatter in achieved versus attempted correction is similar, suggesting little difference in the accuracy of the two procedures. A suggestion of decreased propensity for loss of spectacle-corrected visual acuity in LASIK eyes requires further investigation.     

Visual performance after photorefractive keratectomy. A prospective study

OBJECTIVE: To prospectively examine the effect of excimer laser photorefractive keratectomy (PRK) on best-corrected visual performance using psychophysical tests that were likely to be more sensitive to image degradation than high-contrast Snellen visual acuity. DESIGN: Prospective cases series. PATIENTS: A cohort of 18 subjects with an average of -5.08 diopters (D) of myopia (SD = +/- 1.63 D) was tested before PRK and at 3, 6, and 12 months after PRK. INTERVENTION: Photorefractive keratectomy was performed using a laser (Excimed UV200, Summit Technology, Waltham, Mass) and a polymethylmethacrylate mask; a 5-mm ablation zone was used. MAIN OUTCOME MEASURES: Best-corrected high-contrast visual acuity, best-corrected low-contrast visual acuity (18% Weber contrast), and best-corrected letter-contrast sensitivity. Measurements were repeated with dilated pupils and in the presence of a glare source. RESULTS: One year after PRK, the mean best-corrected high-contrast visual acuity was reduced by half a line (P = .01), and the mean best-corrected low-contrast visual acuity was reduced by 1 1/2 lines (P = .002). The losses were somewhat greater when the subject's pupils were dilated and a glare source was used. The reduction in dilated low-contrast visual acuity was positively correlated with the decentration of the ablation zone (r = 0.47), providing evidence of an association between corneal topography and the functional outcome of PRK. CONCLUSION: Low-contrast visual acuity losses after PRK are notably greater than high-contrast visual acuity losses for best-corrected vision. Low-contrast visual acuity is a sensitive measure for gauging the outcome success and safety of refractive surgery.     

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.     

Combined PRK and PTK in myopic patients with recurrent corneal erosion

AIM: To study the results of combined photorefractive keratectomy (PRK) and phototherapeutic keratectomy (PTK) in myopic patients with recalcitrant recurrent corneal erosion. METHODS: PRK was performed in 16 eyes with the Visx 20/20 excimer laser at a central 6.0 mm zone, following total epithelial scraping. Subsequently, confluent 3.0 mm zones of PTK were ablated at a depth of 6.0 microns, surrounding the zone of PRK. The follow up period ranged from 26 to 42 months. RESULTS: Complete alleviation of symptoms was demonstrated and there was no recurrence of corneal erosion. Visual acuity (VA) improved slowly following treatment, with a final uncorrected VA ranging between 6/9 and 6/12. A final myopic spherical equivalent < or = -1.0 D was found in 14 out of 16 eyes. CONCLUSIONS: A combination of PRK and PTK is effective in the alleviation of symptoms and prevention of recurrences of corneal erosion. It is suggested that recalcitrant recurrent corneal erosion is a diffuse disease, although it often manifests as a local problem, and therefore extensive excimer laser ablation is required to prevent recurrence and to alleviate symptoms completely.     

Periodontal repair in intrabony defects treated with a calcium sulfate implant and calcium sulfate barrier

THIS RANDOMIZED, CONTROLLED, CLINICAL STUDY was designed to evaluate outcome following surgical implantation of an allogeneic, freeze-dried, demineralized bone matrix-calcium sulfate (DBM+CS) composite with a CS barrier in intrabony periodontal defects. Twenty-six patients contributing 26 deep intrabony defects completed the study. Thirteen patients received the DBM+CS implant. Thirteen patients received gingival flap surgery alone (GFS; control). Clinical outcome was assessed at 6 and 12 months postsurgery. At 12 months postsurgery, probing depth (PD) reduction (mean +/-SD) for the DBM+CS and GFS group was to 4.3+/-0.5 and 3.0+/-1.3 mm; clinical attachment gain was to 2.9+/-0.8 and 1.7+/-1.5 mm; and probing bone level gain was to 2.9+/-1.4 and 1.2+/-1.2 mm, respectively. There were no apparent differences between evaluations at 6 and 12 months postsurgery. Clinical improvements were significantly different from presurgery for both groups at both observation intervals (P < 0.01). There were no significant differences between groups in PD reduction and clinical attachment gain. Probing bone level gain was significantly greater in the DBM+CS group compared to controls (P < 0.05). In summary, surgical implantation of DBM+CS with a CS barrier resulted in reduced PD and improved attachment levels comparable to that achieved by gingival flap surgery alone. However, gain in probing bone levels in deep intrabony periodontal pockets assessed by clinical parameters was greater than that observed by gingival flap surgery alone. These changes were noted at both 6 and 12 months after surgery. This regenerative technique needs further biologic evaluation before being generally accepted.     

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.     

Randomised double-masked placebo-controlled trial of a treatment for congenital nystagmus

Several therapies have been developed for congenital nystagmus (CN) but without placebo-controlled trials. We investigated a treatment which combined two therapies that had been advocated by several authors and were reported to improve visual acuity (VA). A placebo treatment was designed to mimic the time, attention, 'high tech' apparatus, and the explanation used in the experimental treatment. To each group, 38 subjects with CN were randomly allocated. Their VA and contrast sensitivity (CS) were assessed three times before undergoing treatment for 6 weeks and then once more. An improvement in VA occurred, however, this was not significantly different in the two groups. The improvement in CS was greater in the experimental than in the control group, but the difference failed to reach significance in most statistical tests. We conclude that putative therapies for CN should be assumed to be placebos until proven otherwise with randomized controlled trials.     

Complications of excimer laser photorefractive keratectomy for myopia

PURPOSE: To evaluate the safety and complication rates of excimer laser photorefractive keratectomy (PRK). SETTING: Assutah Laser Center, Tel-Aviv, Israel. METHODS: This retrospective study evaluated the complication rate after PRK in 825 consecutive patients who had PRK for myopia and had a follow-up of at least 12 months. RESULTS: At 12 months postoperatively, 4.0% of patients suffered from overcorrection and 8.6% from undercorrection. Induced astigmatism developed in 1.4% of all operated eyes. Three percent of the patients had haze, and 3.6% reported glare or halos. Twenty-three eyes (2.7%) lost one line or more of best corrected visual acuity (BCVA). Ptosis developed in 0.4% of the eyes, and 3.5% had a significant increase in intraocular pressure resulting from corticosteroid treatment. There were no complications in 678 eyes (82.5%). CONCLUSION: Eighty-two percent of eyes having PRK did not develop complications. In 18.0% one or more complication, mainly undercorrection, overcorrection, or loss of BCVA, occurred.     

Confocal microscopic characterization of wound repair after photorefractive keratectomy

PURPOSE: Development of postoperative corneal haze and regression of refractive effect are unfavorable clinical complications of excimer laser photorefractive keratectomy (PRK). Although exact mechanisms remain to be elucidated, these outcomes have been attributed to post-PRK corneal wound healing. The purpose of this study was to evaluate corneal wound repair quantitatively after PRK in a rabbit model using a newly developed in vivo technique, termed confocal microscopy through focusing (CMTF). METHODS: Twelve rabbit corneas received a monocular, 6-mm diameter, 9.0-diopter PRK myopic correction. Animals were evaluated sequentially up to 6 months after surgery by in vivo CMTF, which uses an image-intensity depth profile to measure epithelial and stromal thickness and uses corneal light reflectivity as an objective estimate of corneal haze. At differing temporal intervals, in vivo morphology was correlated with ex vivo histology using fluorescence microscopy. RESULTS: One week after PRK, an acellular layer of 86 +/- 24 microns was found anteriorly in the remaining stroma, which demonstrated surgically induced keratocyte death. Underlying keratocytes became activated and migrated toward the wound bed; repopulation was completed within 3 weeks. One week after PRK, there was a significant increase (P < 0.001) in light reflections detected from the photoablated stromal surface (1745 +/- 262 U) and from the underlying activated fibroblasts (713 +/- 607 U). Corneal reflectivity peaked at 3 weeks (4648 +/- 1263 U) and decreased linearly to 889 +/- 700 U by 6 months after the PRK; this corresponded to a reflectivity six times greater than the level seen in unoperated corneas. Two weeks after PRK, initial corneal edema had resolved, revealing an actual ablation depth (maximal stromal thinning) of 118 +/- 8 microns. Starting at 2 weeks after surgery, the stroma underwent gradual rethickening that reached 98% of the preoperative thickness at 6 months after PRK; at that time, only 6% of the initial photoablation depth persisted. By contrast, the central corneal epithelium showed no significant postoperative hyperplasia. CONCLUSIONS: Rabbit corneas treated by PRK showed a remarkable stromal wound-healing response that ultimately led to the restoration of the original stromal thickness by 6 months after surgery, demonstrating complete regression of the initial photoablative effect. Additionally, corneal wound healing was associated with increased light reflections from both the photoablated stromal surface and the activated wound-healing keratocytes underlying this area. Based on these findings, the authors hypothesize that the development of clinically observed corneal haze in PRK patients may be related, in part, to activation of corneal keratocytes and to putative changes in the extracellular matrix.     

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.     

Corneal reinnervation after photorefractive keratectomy and laser in situ keratomileusis: an in vivo study with a confocal videomicroscope

The purpose of this study was to compare the regeneration of corneal nerves after photorefractive keratectomy (PRK) versus laser in situ keratomileusis (LASIK) in vivo with a confocal videomicroscope. In all, 15 eyes that had undergone PRK and 15 eyes that had been subjected to LASIK were compared with a confocal in vivo slit-scanning video-microscope. The subepithelial nerves were observed preoperatively and at 3, 6, and 12 months postoperatively. In all eyes, good microscope images of the subepithelial nerve plexus could be obtained preoperatively. Because of postoperative light reflection and scattering in the treated area, subepithelial nerve-fiber regeneration could be followed satisfactorily only in seven eyes after PRK and in five eyes following LASIK. In the eyes treated with PRK, recovery of subepithelial reinnervation started from the margin of the ablation zone, being directed toward the center of the cornea. At 8 weeks postoperatively, rarefied subepithelial nerve fibers were visible at the edges, and after 3 months, single nonbranched nerve fibers could be visualized in the center of the ablation zone. At 6-8 months following PRK, subepithelial nerve regeneration seemed to be completed; however, abnormal branching and accessory thin nerve fibers were present without exception. After LASIK, corneal nerve-fiber regeneration followed the same course described for PRK except that regenerated subepithelial nerve fibers were barely visible in the center after 6 months. Further changes in nerve structure were visible for up to 12 months postoperatively. Recovery of corneal sensitivity in humans has been reported to start at 4-6 weeks after PRK and is said to be completed within 6-12 months of surgery. Slit-scanning videomicroscope findings were in accordance with these observations.     

Sweat gland carcinoma of the foot: a review and patient report

PURPOSE: To determine the accuracy of applanation tonometry in patients with corneas thinned by photorefractive keratectomy, and to correlate corneal changes with tonometric readings. METHODS: The intraocular pressure was measured with Goldmann applanation tonometry in 87 patients who underwent photorefractive keratectomy before and 1, 6 and 12 months after treatment. The treatments ranged from -1.5 to -14 diopters (mean=-7.6+/-4.1 diopters) and the fellow eyes were used as controls. RESULTS: In the treated eyes the intraocular pressure before surgery ranged from 11 to 26 mmHg (mean=17.7+/-2.8 mmHg). One month after surgery it ranged from 5 to 22 mmHg (mean=11.9+/-2.7 mmHg) with a significant underestimation (P=1x10(-33)). Six months after surgery it ranged from 6 to 22 mmHg (mean=12+/-3 mmHg) with a significant underestimation (P=5x10(-30)). Twelve months after surgery it ranged from 8 to 22 mmHg (mean=12.7+/-2.7 mmHg) with a significant underestimation (P=5x10(-31)). CONCLUSIONS: A correcting factor should be applied when using applanation tonometry to measure intraocular pressure in patients who have undergone PRK.     

Quantitative radiographic follow-up of apical surgery: a radiometric and histologic correlation

BACKGROUND: Morphological changes in the corneal surface after PRK may result not only in refraction fluctuations and reduction in visual acuity, but also in changes of contrast sensitivity. The aim of this study was to investigate whether PRK has an influence on contrast sensitivity with and without glare with a subsequent effect on the ability to drive cars. PATIENTS AND METHODS: Anonymous inquiries were made by means of a questionnaire sent to 114 patients after bilateral PRK in which the patients were asked to assess subjectly their driving ability. Additionally, in 66 eyes of 66 patients with a mean myopia of -5.3 D, an investigation on contrast sensitivity was performed according to the recommendations of the DOG (German Ophthalmological Society) using a Rodenstock nyctometer. RESULTS: Postoperatively, 55% of the patients felt more comfortable driving a car than preoperatively, 31% did not recognize any change, and 14% felt more uncomfortable driving car. Contrast sensitivity with or without glare 2 weeks postoperatively was so much reduced in 77% or 53%, respectively, of the patients that the criteria for driving a car in Germany were not fulfilled. Within the first 12 months after PRK the number of impaired patients diminished but even 1 year after PRK the number of patients with reduced contrast sensitivity with and without glare was higher than before PRK. Surprisingly, however, the criteria for driving a car with respect to contrast sensitivity with and without glare were not fulfilled even before PRK by as much as 44% and 24% of the patients, respectively. CONCLUSIONS: All patients must be in formed about the possible impairment for driving a car before PRK is performed.