Keratectomy For Myopia Research Articles

Assessment of Refractive Outcome of Photo Refractive Keratectomy in Myopia and Myopic Astigmatism.

To determine the refractive outcomes of wavefront optimized photo refractive keratectomy (PRK) in patients having myopia and myopic astigmatism in terms of efficacy, safety, accuracy, stability and predictability of the procedure. Quasi-experimental study. Refractive Surgical Unit, Armed Forces Institute of Ophthalmology, National University of Medical Sciences, Rawalpindi, Pakistan, from October 2013 to August 2018. Patients having myopia and myopic astigmatism, consented to be a part of the study, underwent meticulous screening consisting of detailed medical history, ocular examination and investigations. Each case was compiled and evaluated. Those who satisfied the criteria for refractive surgery were subjected to PRK procedure. Postoperative follow-up was carried out and parameters were recorded at designated intervals of 1 week, 1, 3, 6 and 12 months. This study included 208 eyes of 106 patients with mean age of 25.33 + 5.196 years. At the end of one year, 97% (202 out of 208) eyes had uncorrected distance visual acuity (UDVA) better than 20/25 with efficacy index of 1.009 ± 0.132 and safety index of 1.019 ± 0.126. None of the eyes lost two or more lines. In this study, 207 out of 208 eyes remained within + 0.50 diopter (D) of intended spherical equivalent (SEQ). Results showed 100% accuracy of procedure since all the study patients achieved SEQ within + 1D. PRK is an effective, predictable, and safe treatment procedure for correcting myopia and myopic astigmatism. Key Words: Photorefractive keratectomy, Myopia, Refractive surgery, Myopic astigmatism, Uncorrected distance visual acuity.

Contralateral Eye Study of Topography Guided versus Q Value Adjusted Photorefractive Keratectomy in Myopia and Myopic Astigmatism.

Purpose of the StudyTo compare visual outcome, higher order aberrations (HOAs) of topography guided and Q value adjusted ablation in the fellow eye of patients undergoing photorefractive keratectomy (PRK) for the correction of myopia and myopic astigmatism.MethodsProspective randomized controlled interventional clinical study. The eyes of 52 patients undergoing PRK for myopia and astigmatism were included, that is, 104 eyes in total. In each patient, eyes were randomly allocated to group I: one eye received topography guided PRK using Contoura ablation software, or group II: the other eye received Q value adjusted PRK using Custom Q ablation software.Follow-UpSix months.ResultsAt the end of 6 months, LogMAR UDVA was −0.04 ± 0.12 and −0.05 ± 0.11 (p = 0.688), while LogMAR CDVA was −0.06 ± 0.09 and −0.06 ± 0.1 in group I and group II, respectively (p = 0.972). Both groups showed a progressive oblate shift with time. This oblate shift was insignificantly less in group I by Topolyzer at 6mm, 15° and 30° at 6 months (p = 0.102, p = 0.138, p = 0.245, respectively). Topolyzer identified a significant difference between the change in coma and trefoil in both groups at 6 months (p<0.001 and p = 0.001, respectively). This was caused by the significant worsening of coma in group II (p<0.001) and the significant improvement of trefoil in group I (p = 0.007). No significant difference was found between groups in the change of ISV or ABR (p = 0.955 and 0.982, respectively). Ablation depth is a significant predictor of ΔQ at 6mm, 15° and 30° (p = 0.009, 0.039 and 0, respectively). No significant difference was found in the Strehl ratio or contrast sensitivity, although they were insignificantly better in group I (p = 0.785 and p = 0.745, respectively).ConclusionTG PRK and CQ PRK yielded similar results regarding UDVA, CDVA, MRSE, safety, predictability and contrast sensitivity. Both groups showed a progressive oblate shift, which was less in the TG group but the difference was statistically insignificant. TG PRK showed significantly improved trefoil HOA as compared to CQ PRK.

Comparison of visual and refractive results after transepithelial and mechanical photorefractive keratectomy in myopia.

To compare postoperative visual outcomes and higher-order aberrations (HOAs) following transepithelial photorefractive keratectomy (t-PRK) and mechanical photorefractive keratectomy (m-PRK). The medical records of patients who underwent photorefractive keratectomy (PRK) were retrospectively evaluated. Forty-five patients were treated with m-PRK, and 45 were treated with t-PRK. Visual acuity, subjective manifest refraction, and corneal topography were analyzed before surgery and 12months after surgery for both groups. Total HOAs, spherical, coma, and trefoil aberrations were derived from topography data over the 6-mm corneal zone. In the m-PRK group, the mean preoperative spherical equivalence (SE) changed from -3.15±0.70 D preoperatively to -0.24±0.70 D 1year postoperatively. Likewise, SE decreased from -3.36±0.63 to -0.25±0.63 D in the t-PRK group 1year after the surgery. The number of eyes within±0.50 D of the target refraction was 89% for m-PRK and 87% for t-PRK groups (p=0.20). Eighty-four percentage of eyes in the t-PRK group and 80% of eyes in the m-PRK group showed an uncorrected distance visual acuity of 20/25 or better (p=0.24). Total HOAs, spherical aberration, coma, and trefoil aberrations increased in both groups after surgery, but no statistically significant differences were detected postoperatively among the corneal aberrations. t-PRK and m-PRK result in comparable refractive results for the correction of low and moderate myopia. Corneal aberrations induced by t-PRK and m-PRK were similar. Epithelial removal techniques do not affect visual, refractive results, or HOAs in PRK.

Single-step transepithelial photorefractive keratectomy in myopia and astigmatism: 18-month follow-up

To evaluate the long-term quantitative and qualitative optical outcomes of 1-step transepithelial photorefractive keratectomy (PRK) to correct myopia and astigmatism. Bina Eye Hospital, Tehran, Iran. Prospective interventional case series. Eyes with myopia with or without astigmatism were evaluated. One-step transepithelial PRK was performed with an aberration-free aspheric optimized profile and the Amaris 500 laser. Eighteen-month follow-up results for refraction, visual acuities, vector analysis, higher-order aberrations, contrast sensitivity, postoperative pain, and haze grade were assessed. The study enrolled 146 eyes (74 patients). At the end of follow-up, 93.84% of eyes had an uncorrected distance visual acuity of 20/20 or better and 97.94% of eyes were within ±0.5 diopter of the targeted spherical refraction. On vector analysis, the mean correction index value was close to 1 and the mean index of success and magnitude of error values were close to 0. The achieved correction vector was on an axis counterclockwise to the axis of the intended correction. Photopic and mesopic contrast sensitivities and ocular and corneal spherical, cylindrical, and corneal coma aberrations significantly improved (all P<.001). A slight amount of trefoil aberration was induced (P<.001, ocular aberration; P<.01, corneal aberration). No eye lost more than 1 line of corrected distance visual acuity. No eye had a haze grade of 2+degrees or higher throughout the follow-up. Eighteen-month results indicate the efficacy and safety of transepithelial PRK to correct myopia and astigmatism. It improved refraction and quality of vision. None of the authors has a financial or proprietary interest in any material or method mentioned.

Stereoacuity after photorefractive keratectomy in myopia

PurposeStereopsis, as a part of visual function, is the ability of differentiating between the two eyes' views (binocular disparity), due to the eyes' different positions. The aim of this study was to compare stereoscopic vision before and after photorefractive keratectomy (PRK) in myopia. MethodsIn a prospective interventional case series study clinical trial, forty-eight myopic individuals (age range: 18–34 years) who had undergone PRK surgery by a Bausch & Lomb Technolas 217z excimer laser were included. In all patients, stereoscopic vision was assessed using TNO test charts at 40 cm distance preoperatively and at 3 and 6 months postoperatively. ResultsA total of 48 cases (96 eyes, 69% female) with a mean age of 26.70 ± 4.89 years (range: 18–34 years) were treated. Uncorrected visual acuity (UCVA) was improved and refraction was corrected significantly after PRK surgery. The stereoscopic vision in patients was 246.56 ± 98.43 s of arc before PRK surgery. Postoperatively, the stereoacuities were recorded as 365.38 ± 112.65 s of arc and 343.51 ± 88.96 s of arc at 3 and 6 months, respectively. These differences were statistically significant (p < 0.001). ConclusionPRK was successful and safe in improving refractive error and UCVA, but it may deteriorate the stereoscopic vision. It may be due to an increase in higher order aberrations.

Evaluation of the Long-Term Effects of Photorefractive Keratectomy Correction for Myopia in China

To evaluate the long-term effects of photorefractive keratectomy (PRK) correction for myopia in China. A comprehensive literature research was conducted in 2 Chinese databases and PubMed. Statistical analysis was performed using the RevMan 4.2 software. Seven prospective studies involving 2,796 eyes were included. The follow-up period was 5 to 11 years. Meta-analysis showed efficacies in low to moderate myopia that surpassed those in high myopia, and pooled odds ratios were 9.14 (95% confidence interval [CI] 4.37-19.11) in the proportion of eyes with uncorrected visual acuity (UCVA)=20/20 and 5.61 (95% CI 3.97-7.93) in the proportion of eyes with UCVA=20/40. More than 10 years post operation, 82.0% had 20/20 or better UCVA and 96.1% had 20/40 or better in the =-6.00 D myopia group. Among patients with >-6.00 D myopia, 31.7% had 20/20 or better UCVA and 80.4% had 20/40 or better. Moreover, 82.1% and 46.4% of the treated eyes were within ±1.0 D of target refraction in the low to moderate myopia and high myopia group, respectively. About 1.4%-3.5% of eyes lost =2 lines of best spectacle-corrected visual acuity, and 0.6%-4.1% of eyes had grade 1 corneal haze. Photorefractive keratectomy for myopia is an effective and safe procedure for the long term in China. The efficacy and predictability of PRK in low to moderate myopia are better than in high myopia.

Meta-analysis: Clinical Outcomes of Laser-Assisted Subepithelial Keratectomy and Photorefractive Keratectomy in Myopia

Meta-analysis: Clinical Outcomes of Laser-Assisted Subepithelial Keratectomy and Photorefractive Keratectomy in Myopia

Meta-analysis: Clinical Outcomes of Laser-Assisted Subepithelial Keratectomy and Photorefractive Keratectomy in Myopia

To examine possible differences in clinical outcomes between laser-assisted subepithelial keratectomy (LASEK) and photorefractive keratectomy (PRK) for myopia. Systematic review and meta-analysis. Patients from previously reported randomized controlled trials (RCTs) and comparative studies of LASEK and PRK with clinical outcomes. A comprehensive literature search was performed using the Cochrane Collaboration methodology to identify RCTs and comparative studies comparing LASEK and PRK for myopia. Primary outcome parameters included uncorrected visual acuity (UCVA) of 20/20 or better, manifest refractive spherical equivalent (SE) within ± 0.50 diopters (D), final refractive SE, and final UCVA of 20/40 or worse. Secondary outcome parameters included healing time of corneal epithelium, postoperative pain, and corneal haze. Twelve studies were identified and used for comparing PRK (499 eyes) with LASEK (512 eyes) for myopia. There were no significant differences in odds ratio (OR), weighted mean difference (WMD), and standardized mean difference (SMD) in the primary and secondary outcome measures. The final mean refractive SE (WMD, 0.00; 95% confidence interval [CI], -0.08 to 0.07; P = 0.95), manifest refractive SE within ± 0.50 D of the target (OR, 0.90; 95% CI, 0.63-1.29; P = 0.56), patients achieving UCVA of 20/20 or better (OR, 0.86; 95% CI, 0.61-1.20; P = 0.37), final UCVA of 20/40 or worse (OR, 1.26; 95% CI, 0.63-2.51; P = 0.52), re-epithelialization time (WMD, 0.08; 95% CI, -0.44 to 0.59; P = 0.77), and postoperative pain (SMD, 0.26; 95% CI, -0.20 to 0.72; P = 0.27) were analyzed. However, LASEK-treated eyes showed less corneal haze at 1 month after surgery (WMD, 0.25; 95% CI, 0.10-0.39; P = 0.0007) and 3 months after surgery (WMD, 0.14; 95% CI, 0.01-0.26; P = 0.03) compared with PRK. No statistically significant difference was observed between the 2 groups at 6 months after surgery (WMD, 0.14; 95% CI, -0.02 to 0.30; P = 0.08). In this meta-analysis, LASEK-treated eyes had no significant benefits over PRK-treated ones with regard to clinical outcomes. Less corneal haze was observed in LASEK-treated eyes at 1 to 3 months after surgery.

Long-Term Evaluation of Complications and Results of Photorefractive Keratectomy in Myopia: An 8-Year Follow-Up

To evaluate 8-year results of photorefractive keratectomy (PRK) for myopia in terms of safety, efficacy, stability, and late complications. 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 [<or=-6.00 diopters (D)], moderate myopia (-6.10 to -10.00 D), and high myopia (>-10.00 D). The main outcome measures were safety, efficacy, stability, and postoperative complications. Eight years after PRK, 69.64%, 44.44%, and 45.65% of the low, moderate, and high myopic groups were within +/-0.5 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. 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.

Long-term results of photorefractive keratectomy for myopia and myopic astigmatism

To assess the long-term refractive outcomes of photorefractive keratectomy in myopia and myopic astigmatism. A retrospective study of 120 photorefractive keratectomy operated eyes with at least four-year follow-up (maximum of 96 months, mean follow-up 55 months). We divided patients into group 1 (G1) spherical equivalent (SE) up to -4.00 diopters (D) and group 2 (G2) SE >-4.00 D. The Summit Apex Plus excimer laser was used for ablation. All eyes were analyzed in terms of uncorrected and best spectacle corrected visual acuity (UCVA/BSCVA) and cycloplegic refraction. Data were analyzed using the Refractive Surgery Consultant Elite database software. G1 with 85 eyes (49 patients) presented mean SE -2.42 D and G2 with 35 eyes (22 patients) and mean SE of -4.45 D. Ninety-four percent of eyes in G1 and 82.9% of G2 were within +/-1.00 D of emmetropia at 4 years. The UCVA was 20/30 or better in 82.0% of G1 eyes and 77.0% of G2 in the last postoperative follow-up. No patient lost more than one line in G2 compared to 13.0% in G1. Eyes that gained one or more lines after 4-year follow-up were 11.9% G1 and 2.9% in G2, respectively. A statistically significant positive correlation was found between achieved versus attempted refractive correction in both groups (r=0.925, p<0.0005). Photorefractive keratectomy was a safe and stable surgical procedure to correct myopic refractive errors, with no significant change in mean postoperative spherical equivalent refraction in the long-term follow-up.

Evidence for Delayed Presbyopia after Photorefractive Keratectomy for Myopia

Evidence for Delayed Presbyopia after Photorefractive Keratectomy for Myopia

Phacoemulsification with intraocular lens implantation after excimer photorefractive keratectomy for myopia

目的 探讨准分子激光屈光性角膜手术后白内障吸出术中、植入人工晶状体的屈光度计算方法.方法 对4例(4眼)准分子激光屈光性角膜手术后的白内障行超声乳化吸出及人工晶状体植入术,术前采用OrbscanⅡ角膜地形图及角膜曲率计测量角膜的K值,分别应用第二代经验公式(SRKⅡ)计算所需人工晶状体的屈光度.术后验光记录术眼屈光状况,与术前结果对比,评价所选择的人工晶状体屈光度的准确性.结果 OrbscanⅡ角膜地形图和角膜曲率计分别测量的角膜K值,以及所计算的人工晶状体的屈光度,均有明显的差别.尽管按预留近视状态,选用角膜地形图测量的K值计算人工晶状体的屈光度,术后仍然欠矫,平均产生远视+1.57D,较术前预留度数仍相差约+3.44D.结论 采用OrbscanⅡ角膜地形图的K值来计算人工晶状体屈光度误差小,在预留的屈光度数基础上加3.50D来选择人工晶状体是较为精确和安全的。

Eight-year follow-up of photorefractive keratectomy for myopia

The authors evaluated the 8-year refractive stability of excimer laser photorefractive keratectomy (PRK) for myopia. Ninety-two eyes myopic eyes of 55 patients were treated with a single-step method using an Aesculap-Meditec MEL 60 excimer laser with a 5.0 mm ablation zone. Treated groups were divided into three groups according to preoperative refraction: low myopes (≤6.00D), medium myopes (−6.10 to −10.00D), and high myopes (>10.00D). Myopic regressions stabilized in all three groups within 12 months, although there was a small myopic shift of −0.42 ± 0.48D for low myopes, −0.37 ± 0.34D for moderate myopes, and −0.41 ± 0.50D for high myopes between 2 and 8 years after PRK. The percentage of eyes within ±1.00D of emmetropia 8 years after PRK was 78.3% in the low myopia group, 68.8% in the moderate myopia group, and 57.1% in the high myopia group. The percentage of eyes with uncorrected visual acuity of 20/40 or better was 78.3%, 62.5%, and 57.1%, respectively.—Michael D. Wagoner

Surgery for 4 refractive errors in 1 patient

We report a case of cataract extraction with implantation of a multifocal intraocular lens (IOL) after photorefractive keratectomy for myopia and astigmatism and subsequent laser thermal keratoplasty for surgically induced hyperopia. Good refractive results were obtained using standard biometry techniques for calculation of the IOL power.

On the structural origin of refractive instability and corneal haze after excimer laser keratectomy for myopia

On the structural origin of refractive instability and corneal haze after excimer laser keratectomy for myopia

Development of visual acuity in the early phase after photorefractive keratectomy in myopia

Photorefractive keratectomy (PRK) using the excimer laser is an accepted surgical technique for correction of myopic refraction errors in case of spectacle or contact lens incompatibility. The purpose of this study was to assess the development of uncorrected (UVA) and best-corrected visual acuity (CVA) in the early course following PRK. 48 eyes of 29 patients that underwent myopic photorefractive keratectomy using 193 nm excimer laser (MEL 60, Aesculap-Meditec) were included in this study. The mean preoperative spherical equivalent was -5.3 +/- 2.4 diopters (D) (range -1.75 to -9.5 D). Pre-, intra- and postoperative treatment was standardized. The median time interval to complete epithelial closure was 2 days. According to their spherical equivalent, patients were divided in two groups: group 1 with myopia < or = 6 D (n = 28), group 2 with myopia more than 6 D (n = 20). Examination of UVA and CVA were performed preoperatively and on days 3, 7 as well as 1 month, 3 and 6 months postoperatively. On day 3 after surgery UVA was 0.43 +/- 0.21 for group 1 with myopia < or = 6 D, and 0.36 +/- 0.14 for group 2 with myopia more than 6 D. The UVA was stable after 3 months (0.92 +/- 0.29 and 0.66 +/- 0.20, respectively), the CVA was stable after 1 month (1.04 +/- 0.18 and 0.86 +/- 0.19, respectively). After surgery, the UVA increased by +0.73 +/- 0.25, whereas the CVA increased by +0.05 +/- 0.10 for the whole group. The difference comparing pre- and postoperative UVA was significantly higher in group 1 (0.81 +/- 0.22) than in group 2 (0.60 +/- 0.26) (p = 0.002). However, postoperative CVA values were not significantly different from preoperative values in both groups after 6 months (p = 0.3). Useful uncorrected visual acuity is normally achieved at day 3 after PRK in eyes with mild to moderate myopia. With higher degrees of myopia the uncorrected visual acuity does increase slower towards a lower level. One of the reasons for this phenomenon might be a significant regression of the refractive effects during the first half year after surgery.

The Complications of Excimer Laser Photorefractive Keratectomy for Myopia in the First Year

Objective: To record the frequency and type of complications that occur following photorefractive keratectomy (PRK) for myopia. Design: Prospective, with follow-up for 1 year. Setting: Mater Private Hospital Laser Clinic, Dublin, Republic of Ireland. Patients: One hundred and sixty one myopic eyes in 120 patients. Main Outcome Measures: Any complications occurring in the follow-up period. Patient satisfaction rating, on a graded scale, was recorded in the first 50 eyes in 50 consecutive patients at 1 year. Results: Of 161 eyes 22.4% had early complications of their procedure. These were most commonly caused by the use of routine post-laser medications. Furthermore, only 6% of 50 patients surveyed, failed to achieve their original aim (wholely or in part) in undergoing the treatment. In no case was the visual outcome compromised by non-refractive complications. Conclusions: PRK is safer than extended wear soft contact lens use.

CORTICOSTEROID TREATMENT OF REGRESSION AFTER PHOTOREFRACTIVE KERATECTOMY FOR MYOPIA

CORTICOSTEROID TREATMENT OF REGRESSION AFTER PHOTOREFRACTIVE KERATECTOMY FOR MYOPIA

CENTRAL STEEP ISLANDS IMMEDIATELY FOLLOWING EXCIMER PHOTOREFRACTIVE KERATECTOMY FOR MYOPIA

CENTRAL STEEP ISLANDS IMMEDIATELY FOLLOWING EXCIMER PHOTOREFRACTIVE KERATECTOMY FOR MYOPIA

Photorefractive Keratectomy for Myopia: Six Month Results of 193 Eyes

Photorefractive Keratectomy for Myopia: Six Month Results of 193 Eyes