Safety and e cacy of Photorefractive Keratectomy (PRK) for myopia using a new corneal epithelium debridement technique (original) (raw)
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journal of current ophthalmology, 2019
Purpose: To compare clinical outcomes between mechanical debridement photorefractive keratectomy (m-PRK) and trans-epithelial photorefractive keratectomy (t-PRK) in myopic patients. Methods: Eighty eyes of 40 myopic patients with age between 18 and 55 years were included in this study. In each patient, one eye was randomly assigned for t-PRK, using the Amaris laser's ORK-CAM software and the other eye for m-PRK, using a spatula. Stromal ablation was done by Schwind Amaris 750S. Uncorrected and best corrected visual acuity (BCVA), refractive outcomes, epithelial healing, pain, and discomfort were compared between the groups on day 1, 3, 7 and month 1, 3, and 6. Results: Preoperative spherical equivalent (SE) were À3.97 ± 2.08 diopter (D) and À3.98 ± 2.06 D in m-PRK and t-PRK eyes, respectively (P ¼ 0.981). Operation time was significantly shorter in the t-PRK group than m-PRK (P < 0.001). Postoperative pain was experienced significantly higher in the t-PRK group measured by 11-point numeric scale of pain questionnaire on the first postoperative day (P < 0.001). Photophobia, tearing, and vision fluctuation were also significantly higher in the t-PRK group postoperatively. However epithelial defect size and re-epithelialization time were lower in the t-PRK group (P ¼ 0.012 and P < 0.001, respectively). Postoperative parameters including SE, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and contrast acuity did not show any significant difference between the two groups during all intervals. Conclusions: Although epithelial defect size and epithelial healing time were lower in t-PRK, postoperative pain, photophobia, and vision fluctuation were significantly less in the m-PRK group in the first postoperative days. There was no statistically significant difference between the groups after one week, and both mechanical and trans-epithelial techniques were shown to be safe and effective.
Cornea, 2009
Purpose: To evaluate 8-year results of photorefractive keratectomy (PRK) for myopia in terms of safety, efficacy, stability, and late complications. Methods: From 371 myopic eyes of 203 patients who underwent PRK using NIDEK EC-5000 excimer laser with 5.5-to 6-mm ablation zones in Basir Eye Center, Tehran, Iran, during 1997-1998, data of 179 myopic eyes of 98 patients, who participated in annual examinations, were analyzed. Treated eyes were divided into 3 groups according to preoperative refraction: low myopia [#26.00 diopters (D)], moderate myopia (26.10 to 210.00 D), and high myopia (.210.00 D). The main outcome measures were safety, efficacy, stability, and postoperative complications. Results: Eight years after PRK, 69.64%, 44.44%, and 45.65% of the low, moderate, and high myopic groups were within 60.5 D of emmetropia. Sixteen eyes (4.31% of original cases) underwent retreatment mainly because of regression. Although a small myopic shift occurred up to 8 years after surgery, changes in myopic regression stabilized in all myopic groups within 24 months. Four eyes (2.06%) lost 2 lines of best spectacle-corrected visual acuity (1 eye for corneal haze and other 3 for problems not related to refractive surgery). Corneal haze occurred in 11.34% especially in medium and high myopic groups, but it cleared within 2 years in 68.2% of cases. Conclusions: Based on our study, PRK seems to be a safe, efficient, and stable surgical procedure, and if patients obtain a good result with the initial treatment, then their results are relatively stable over time.
Response of the cornea for up to four years after photorefractive keratectomy for myopia
Journal of Refractive …, 2006
PURPOSE: To analyze the long-term corneal topographic changes 4 years after myopic photorefractive keratectomy (PRK). METHODS: This study comprised 15 patients (30 eyes) who had PRK surgery with a scanning-spot excimer laser (Chiron Technolas 217C; Bausch & Lomb, Dornach, Germany) and were followed up to 4 years after surgery. The eyes were subdivided into three groups according to the preoperative spherical equivalent refraction. Corneal topographic maps were obtained for all eyes with a Placido disc topographer. Preoperative and follow-up topographical data were imported into a custom software program, which computed the average composite corneal maps and difference maps for each study group to quantify the anterior corneal changes following laser ablation. The software delineated three concentric zones of the corneal surface to characterize the regional corneal remodeling following the surgery. RESULTS: A signifi cant central corneal steepening (approximately 0.25 D, PϽ.001) was calculated between the 1-and 4-year postoperative maps in all study groups. A signifi cant steepening (PϽ.001) of the corneal periphery was also noted for the lower myopic ablations whereas a peripheral fl attening (PϽ.001) was observed for the deeper ablations between 1 and 4 years after surgery. CONCLUSIONS: The anterior corneal surface was observed to remodel for up to 4 years after surface ablation, steepening a mean of approximately 0.25 D.
International Journal of Ophthalmology
AIM: To evaluate the clinical results after implantation of a new intrastromal corneal ring segment (ICRS) associated with photorefractive keratectomy (PRK) to correct high myopia (HM) patients with thin corneas. METHODS: We evaluated 42 eyes of 23 HM patients that had ICRS implantation followed by PRK. The mean age of patients was 29.1±7.12y (range 18 to 40 years old). Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), keratometry, spherical equivalent, pachymetry, and aberrometry were compared using ANOVA with repeated measurements evaluated preoperatively and at last follow-up visit after the procedures. The refractive predictability and simulated/real corneal ablation were also assessed. RESULTS: The mean follow-up time after PRK was 6.8±1.6mo. The mean preoperative UCVA improved from 20/800 preoperative to 20/100 after ICRS and 20/35 after PRK. The mean preoperative BCVA was 20/25 (range from 20/30 to 20/20) and remained unchanged after ICRS implantation. Fo...
Investigative Ophthalmology & Visual Science, 2011
PURPOSE. To analyze the anterior corneal topography changes after 8 years after photorefractive keratectomy (PRK) for the correction of myopia and myopic astigmatism. METHODS. Sixty-six eyes (33 patients) underwent PRK using an excimer laser platform. Patients were subdivided into three groups: the low myopia (13 patients; range, Ϫ1.25 to Ϫ4.40 diopters [D]), the high myopia (13 patients; Ϫ4.50 to Ϫ9.00 D), and astigmatism (7 patients; cylinder component between Ϫ2.00 and Ϫ5.00 D) groups. The preoperative and 1-, 2-, 4-, 6-, and 8-year postoperative average corneal maps were computed for each study group. Changes inside and outside the optical zone, which was 6.00 mm in diameter for all eyes, during follow-up were further investigated. RESULTS. The topographic central region, 2.00-mm diameter, was almost stable in all study groups, with changes Ͻ 0.39 D between 1 and 8 years. The postoperative variations at the peripheral region, 6.00-to 8.00-mm diameter, were related to the type and amount of refractive correction: a higher flattening (P Ͻ 0.05) has been assessed in the high-myopia group (Ϫ0.85 D) in comparison with the low-myopia group (Ϫ0.42 D) between 1 and 8 years. On the contrary, corneal periphery steepened (ϩ2.22 D; P Ͻ 0.05) in the astigmatism group during follow-up, mainly at the superior and inferior emimeridians. CONCLUSIONS. The anterior corneal topography continues to change configuration even long term after PRK. Changes are confined outside the functional optical zone of the cornea. PRK for the correction of myopia was shown not to influence the mechanical stability of the corneal tissue at 8 years after surgery.
Purpose. To evaluate the safety, efficacy, and predictability of photorefractive keratectomy (PRK) on the corneal flap for correction of residual myopia following myopic laser in situ keratomileusis (LASIK). Patients and Methods. A retrospective study on eyes retreated by PRK on the corneal flap for residual myopia after LASIK. All eyes had no enough stroma after LASIK sufficient for LASIK enhancement. Data included spherical equivalent (SE), uncorrected and best corrected visual acuity (UCVA and BCVA), central pachymetry, corneal higher order aberrations (HOAs), corneal hysteresis (CH), corneal resistance factor (CRF), and corneal haze. Results. The study included 64 eyes. Before PRK, the mean central pachymetry was 400.21±7.8 í µí¼m, the mean SE was −1.74±0.51 D, and the mean UCVA and BCVA were 0.35 ± 0.18 and 0.91 ± 0.07, respectively. 12 months postoperatively, the mean central corneal thickness was 382.41 ± 2.61 í µí¼m, the mean SE was −0.18 ± 0.32 D (í µí± < 0.01), and the mean UCVA and BCVA were 0.78 ± 0.14 (í µí± = 0.01) and 0.92 ± 0.13 (í µí± > 0.5), respectively. The safety index was 1.01 and the efficacy index was 0.86. No significant change was observed in corneal HOAs. Conclusions. Residual myopia less than 3 D after LASIK could be safely and effectively treated by PRK and mitomycin C with a high predictability. This prevents postoperative ectasia and avoids the flap related complications but has no significant effect on HOAs.
Ophthalmology, 1995
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 (0) (range,-0.63 to-11.00 0) underwent PRK with a 193-nm excimer laser for myopic corrections between-1.50 and-7.50 O. 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 0 (range,-6.50 to 2.50 0); 63% of eyes were within ±1 .00 0 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. Conclusion: 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.
BMC Ophthalmology, 2022
Background To assess transepithelial photorefractive keratectomy (tPRK) in terms of corneal epithelial healing rate, postoperative pain, postoperative discomfort, and visual and refraction outcomes compared to mechanical epithelial debridement PRK (mPRK) and alcohol-assisted PRK (aaPRK). Methods In this double-masked, randomized clinical trial, thirty-nine patients underwent tPRK in one eye and mPRK in the fellow eye (arm A), and 33 patients underwent tPRK in one eye and aaPRK in the contralateral eye (arm B). All surgical procedures were done using the Schwind Amaris excimer laser. The area of corneal epithelial defect in all eyes was captured and analyzed using ImageJ software. Results Mean epithelial healing time was respectively 3.74 ± 0.82 and 3.59 ± 0.79 days in tPRK versus mPRK ( P = 0.21) in arm A, and 3.67 ± 0.92 and 3.67 ± 0.74 days in tPRK versus aaPRK ( P = 1.00) in arm B. Accounting for the initial corneal epithelial defect area, the epithelial healing rate was faster...