Excimer Laser Photorefractive Keratectomy Research Articles

Ten-year follow-up of photorefractive keratectomy for myopia

The aim of this study is to evaluate the long-term (10-year) outcome of excimer laser photorefractive keratectomy (PRK) on myopic eyes. This retrospective study included 42 eyes of 29 patients (13 male, 16 female; mean age 33.4 years, range 21 to 60) who were treated with myopic PRK at St. Luke's International Hospital, Tokyo, Japan, from May 1 1995 to December 31 1998, and followed up for more than 10 years. The main outcome measures were efficacy, predictability, stability, safety, and complications. We also evaluated the progress of intraocular pressure, corneal thickness, and endothelial cell density after the surgery. The cases of retreatments were excluded from this study. Ten years after the surgery, 17 eyes (40%) had 20/20 vision or better, and 35 eyes (81%) had 20/40 or better. With regard to the refractive predictability, 55 percent of the eyes were within ± 1.0D and 76% were within ± 2.0D, 10 years after the surgery. There was myopic regression with a mean change in refraction of-0.51 ± 1.78D. Best spectacle-corrected visual acuity (BCVA) was unchanged or improved in 95%, and only two eyes lost 1 line of BCVA. The mean corneal haze score was 0.19 ± 0.40, and the decreasing rate of endothelial cell was 8.30 ± 9.94% at 10 years, which was slightly higher than the spontaneous decreasing rate with age. PRK is safe and effective in refraction even 10 years after surgery; however, further long-term follow-up is needed to evaluate the decreasing of endothelial cells.

The shape of the corneal apical zone after excimer photorefractive keratectomy.

Applying an experimental photo-keratoscope, which assesses the shape of cornea within the pupillary region, to a group of subjects who have undergone excimer laser photorefractive keratectomy over a central 4 mm chord diameter of the cornea, we report the shape of the typical cornea within the ablated zone conforms to a steepening ellipse (average shape factor, 1.25). A statistically significant difference in the mean shape factor (asphericity) between the photoablated and the normal cornea (average shape factor 0.89) was not confirmed. However, there is more variability in the shape factors found in the photorefractive keratectomy group compared with normals, within the same distance from the corneal apex. Using the criterion of overlap within two standard deviations, averaging the vertical horizontal meridians, 75% of photorefractive keratectomy eyes fall within the shape factor limits of the normal eye group. In all cases the post-ablated corneal surface was found to be regular in terms of surface quality alone. The excimer photorefractive keratectomy technique is therefore a clinically acceptable method of refractive surgery.

Photorefractive Keratectomy With Mitomycin-C for Consecutive Hyperopia After Radial Keratotomy

To evaluate the safety, efficacy, and stability of excimer laser photorefractive keratectomy (PRK) and mitomycin-C (MMC) 0.02% for consecutive hyperopia after radial keratotomy (RK). A prospective, nonrandomized, noncomparative interventional case series of 35 eyes (22 patients) with consecutive hyperopia after RK. All eyes were treated with PRK, using a single intraoperative topical application of MMC 0.02% for 60 seconds. Uncorrected visual acuity, best spectacle-corrected visual acuity, refraction, slit-lamp evidence of corneal haze, and endothelial cell counts were evaluated for up to 18 months after surgery. Postoperative follow-up was 9.6 +/- 5.5 months (ranged from 3 to 18 months). The mean spherical equivalent was +3.36 +/- 1.94 diopters preoperatively and +0.27 +/- 1.38 diopters 12 months after surgery. The uncorrected visual acuity was > or =20/30 in 37.1% of the eyes at 1 month and 78.6% of the eyes at 12 months. At 12 months, 14% of the eyes lost up to 1 line of Snellen acuity in the best spectacle-corrected visual acuity. No corneal haze was observed and the endothelial cell counts remained unchanged postoperatively (P > 0.05). PRK with MMC 0.02% for consecutive hyperopia after RK seems to be a safe and effective procedure at least in the short-term period of 6 months.

The curative effect of Excimer laser photorefractive keratectomy in ten yers

目的 评价准分子激光角膜切削术(PRK)远期疗效.方法 收集存我院施行PRK手术随访10年近视156例(308眼).根据术前屈光度(等值球镜)分为A、B两组,A组屈光度-1.50D～-6.00D者224眼,B组-6.12D～-10.00D者84眼.术后随访视力、屈光度、眼前段及眼底表现,眼压、角膜地形图等.6个月后每年复查1次,以1、5、10年检查情况为准.结果 PRK术后随访10年,裸眼视力达预期矫正视力A组为91.96%、B组为76.19%,屈光度±0.75D正视范围内比率A组为90.18%,B组为75.00%.近视屈光回退-1.00D以上在5年和10年时A组为7.14%和6.70%,B组为22.62%和23.81%,屈光回退率相比,相同时间两组间P＜0.01,同一组5年和10年相比P＞0.05.随时间延长haze逐渐吸收,无角膜感染、角膜扩张及变性样角膜病变等发生.结论 PRK矫正近视远期效果稳定,预测性、安全性好,中低度近视优于高度近视.随时间延长haze逐渐吸收,回退的屈光度稳定。

Excimer laser–assisted lamellar keratoplasty for the surgical treatment of keratoconus

To evaluate the anatomical and functional results of excimer laser-assisted lamellar keratoplasty (ELLK) in keratoconus patients. Eye Clinic, University of L'Aquila, L'Aquila, Italy. This prospective case series comprised patients with keratoconus who had ELLK and were examined preoperatively and 3, 6, 12, and 24 months postoperatively. Outcome measures were uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, computerized videokeratography, pachymetry, and endothelial specular microscopy. Forty-one eyes (41 patients) were examined. The UCVA and BSCVA were significantly better at all follow-up examinations than preoperatively. After the 24-month follow-up (33 patients), the UCVA was better than 20/60 in 11 patients (33.3%) and the BSCVA was 20/40 or better in 29 patients (87.9%). The mean refractive astigmatism was 2.20 diopters (D) and the mean manifest refraction spherical equivalent refraction, -1.18 D. Corneal topographic patterns were regularly astigmatic in 28 (84.8%) of 33 eyes, and the mean corneal thickness (440.0 mum) was significantly greater than preoperatively (553.0 mum). No statistically significant changes in mean corneal endothelial cell density were observed postoperatively. Complications included corneal melting treated with penetrating keratoplasty (PKP) (1 case) and postoperative high refractive error requiring topographically guided excimer laser photorefractive keratectomy (7 cases). Two-year findings indicate that ELLK is as efficacious as PKP for the surgical treatment of moderate to advanced keratoconus. The procedure is relatively simple. Most steps can be standardized, and there are no time-consuming maneuvers.

Refractive surgery for children: laser, implants, current results and future directions

Two groups of visually impaired children now benefit from refractive surgery and stand to further benefit with future advances. These children have difficulties with spectacle-wear and are unsuitable for contact lens-wear. The majority are neurologically normal and have anisometropic amblyopia. They are treated by advanced surface ablation using the excimer laser (photorefractive keratectomy or laser-assisted subepithelial keratomilieusis). Surface ablation is safe in children; the drawback is the high rate of pediatric refractive regression (more pronounced for myopia > 10.0 D, and hyperopia > 4.5 D). Ametropia beyond this range may be treated using phakic intraocular lens implantation or clear lens extraction, with or without implantation of a posterior chamber intraocular lens (refractive lens exchange). The minority are neurobehaviorally impaired children (e.g., cerebral palsy, autism, Angelman syndrome, Down syndrome and mental retardation) with high bilateral ametropia. Spectacle noncompliance relegates them to a blurred level of legal blindness, exacerbating their handicaps. Refractive surgery, performed using the same techniques, can dramatically improve their quality of life.

Corneal endothelial cell injury induced by mitomycin-C in photorefractive keratectomy: Nonrandomized controlled trial

To evaluate the effect of intraoperative use of mitomycin-C (MMC) on the corneal endothelium during excimer laser photorefractive keratectomy (PRK). Vanak Eye Surgery Center, Tehran, Iran. This nonrandomized trial comprised 81 patients (162 eyes) with bilateral low to moderate myopia and adequate corneal thickness to allow PRK (estimated postoperative residual stromal thickness >350 microm without considering epithelial thickness). The indication for intraoperative application of MMC 0.02% (0.2 mg/mL) was an ablation depth of 75 microm or more. Patients were divided into 3 groups: bilateral (both eyes treated with MMC), unilateral (only 1 eye treated with MMC), and untreated (no eye treated with MMC). Visual acuity, refraction, endothelial cell density (ECD), and corneal thickness were measured preoperatively as well as 1 week and 1, 3, and 6 months postoperatively. Overall, 76 eyes were treated with MMC. Eyes treated with MMC and untreated eyes were comparable in postoperative visual acuity and refraction. Preoperative to postoperative changes in ECD were statistically significantly greater in the treated eyes (-14.8%) than in untreated eyes (-5.1%) 6 months after PRK (P<.001). Longer MMC contact time (P<.001) and male sex (P= .04) were the only factors independently associated with greater endothelial cell loss. The prophylactic use of diluted intraoperative MMC 0.02% solution caused corneal endothelial cell loss. The rate of cell loss was correlated with the duration of MMC exposure.

EXCIMER LASER

Objectives: To evaluate the efficacy and safety of excimer laserphotorefractive keratectomy for myopia in Pakistani people. Design: Prospective study. Setting: At Al-Shifa Trust EyeHospital Rawalpindi. Period: October, 1995 and Febrauray, 1996. Material &amp; Methods: The study group of thirteenpatients, comprises of 25 eyes, with refractive error ranging from -1.50 to -3.50 D.S (diopters sphere) and less than-1.50 D.C (diopters cylinder).Results: Thirteen eyes (52%) lost to follow up after three months. Only twelve eyes (48%)could be reviewed at six months after photorefractive keratectomy. At one month, eleven eyes (44%) and at threemonths, eight eyes (32%) were hypermetropic within +0.25 to +1.00 diopters of spherical equivalent .At six months onlythree eyes (25%) had hypermetropia within +0.25 to +1.00 diopters spherical equivalent. None of the eyes had anykind of astigmatism more than 1.00 diopter. No over correction of more than +1.00 diopter of spherical equivalent wasobserved in any case. At one month, three months and six months after photo-refractive keratectomy, 88%, 80% and100% eyes had 6/6 visual acuity respectively, without any optical aid. Hundred percent of the eyes showed completehealing of the epithelium on third post operative day. Moderate to severe postoperative pain was experienced by everyone for three days with gradual reduction in intensity. Only one eye (8.33%) had grade 1 haze at six months. Restsof the eyes were clear .No vision threatening complications occurred. Despite the short term follow up, photorefractivekeratectomy appears to be an effective and safe procedure with good predictability for the correction of low myopia.Conclusion: Despite relatively short term follow up of the study; photo refractive keratectomy (PRK) appears to be safeand quite predictable procedure for correction of low myopia.

Clinical measurement of anterior chamber depth and lens thickness in myopic eyes with ultrasound and pentacam scheinpflug system

Objective Anterior chamber depth （ACD） and lens thickness（LT） measurement gives important details in cataract or glaucoma stlrgery. And ACD is also strictly required in refractive surgery, such as excimer laser photorefractive keratectomy or phakic anterior ehamber lens implant. This investigation was to assess the accuracy of ultrasound and Pentaeam scheinpflug imaging system measuring ACD,LT in myopic eyes. Methods Thirty-eight eyes of 38 subjects aged 18 -28 years underwent non-contact tonometry, autorefraction and subjective refraction examination. After accommodative paralysis, ACD and LT from 38 right eyes were measured with scheimplug imaging system（Pentacam） and A sonography. Results The ACD value measured by Pentacam and A sonography was（ 3.33± 0. 24 ）mm and（ 3.81±0.24） ram, respectively, indicating a significant difference between the results of these two methods （ P 〈 0.01 ） and a positive linear correlation between them （ r = 0. 967, P 〈 0.01 ）. The LT value measured by Pentacam and A sonography was（3.34±0. 26） mm and（3.54±0. 17） mm respectively with the significant difference （ P 〈0.01 ） and a significant linear correlation between these two outcomes （ r =0. 815 ,P 〈0.01 ）. The difference in LT between the two methods was higher with the increase of diopter of refractive error, Conclusion Pentacam,as a new 3-dimensional mathematical model of the anterior segment, presents some different results from A sonography in the measurement of ACD and LT. Enough consideration should be payed to clinical evaluation of these results. Key words: Pentacam; anterior chamher depth; lens thickness; ultrasonography

Intraocular Pressure Measurements Using Dynamic Contour Tonometer After Photorefractive Keratectomy

Purpose: To assess the performance of the dynamic contour tonometer (DCT) in eyes undergoing excimer laser photorefractive keratectomy (PRK). Methods: Intraocular pressure (IOP) was measured in 30 eyes after first‐time excimer laser PRK pre‐ and three months post‐operatively using Goldmann applanation tonometer (GAT), noncontact air tonometer (NCT), and the DCT. Results: There was significant correlation between central corneal thickness (CCT) and IOP measurements by GAT and NCT (CCT vs GAT: r2=0.31, p

Changes in Contrast Sensitivity Function and Ocular Higher Order Aberration by Conventional Myopic Photorefractive Keratectomy

To evaluate the relation between induced changes in ocular higher order aberrations and changes in the contrast sensitivity function in patients undergoing excimer laser photorefractive keratectomy (PRK). Myopic PRK using excimer laser was performed in 31 patients (56 eyes). The preoperative refractive error was -6.2 +/- 2.9 diopters. Before and 1 month after surgery, we measured the ocular higher order aberrations for a 4-mm pupil, and three indices of contrast sensitivity function. From the data collected, the area under the log contrast sensitivity function (AULCSF) was calculated. PRK significantly reduced AULCSF (P = 0.004), low-contrast visual acuity (P = 0.004), and letter-contrast sensitivity (P = 0.013). Coma-like (P < 0.001) and spherical-like (P < 0.001) aberrations were significantly increased by surgery. The change in AULCSF by surgery significantly correlated with the change in coma-like (r = -0.468, P < 0.001) and spherical-like (r = -0.291, P = 0.033) aberrations. The change in low-contrast visual acuity by PRK significantly correlated with the change in coma-like aberration (r = 0.599, P < 0.007), but not with change in spherical-like aberrations (r = 0.136, P = 0.326). There were significant correlations between changes in letter-contrast sensitivity and changes in coma-like (r = -0.450, P < 0.001) and spherical-like (r = -0.255, P = 0.048) aberrations. PRK significantly increases ocular higher order aberrations, which compromise contrast sensitivity function after surgery.

Preventive nursing about cornea complications for patients with excimer laser photorefractive keratectomy

目的 探讨行准分子激光原位角膜磨镶术(LAsIK)患者预防角膜瓣并发症的护理措施.方法 收集1370例(2578只眼)行准分子激光原位角膜磨镶术的患者,所有患者均使用法国产Moria M2旋转式角膜板层刀,刀头分别为110号和90号来完成角膜瓣的制作.对所有手术患者进行角膜瓣并发症的预防护理.结果 本组角膜瓣并发症的发生率为2.3%.结论 LASIK手术中发生角膜瓣的并发症是不可避免的,正确的预防护理措施可有效地减少其发生。

Error in Author Name in: The Corneal Endothelium After Myopic Excimer Laser Photorefractive Keratectomy

Error in Author Name. In the article titled “The Corneal Endothelium After Myopic Excimer Laser Photorefractive Keratectomy,” published in the November 1995 issue of the ARCHIVES (1995;113:1356), the second author's name should have appeared as follows: M. C. Hernaez-Ortega, MD, PhD.

Prophylactic Mitomycin C to Inhibit Corneal Haze After Photorefractive Keratectomy for Residual Myopia Following Radial Keratotomy

To evaluate the efficacy and safety of mitomycin C (MMC) 0.02% in inhibiting haze formation after excimer laser photorefractive keratectomy (PRK) for residual myopia following radial keratotomy (RK). A prospective, nonrandomized, noncomparative interventional case series was conducted of 22 eyes (14 patients) with residual myopia after RK performed at a single institution. All eyes were treated with PRK and a single intraoperative topical application of MMC 0.02% solution for 2 minutes using a soaked cellulose sponge placed over the ablated area. Refraction, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and slit-lamp evidence of cotneal opacity (haze) were evaluated over 12 months. Twelve months postoperatively, 3 eyes showed grade 1 haze, and 2 eyes showed grade 0.5 haze. Twelve months postoperatively, 2 (9%) eyes had UCVA > or = 20/20. No eye before and 17 (77%) eyes after treatment had UCVA > or = 20/40, and no eye before and 9 eyes (40.9%) after treatment had UCVA > or = 20/25. Best spectacle-corrected visual acuity was > or = 20/40 in all (100%) eyes and 21 (95%) eyes before and after treatment, respectively, and > or = 20/25 in 12 (54.5%) eyes before and after treatment. One (4.5%) eye lost 1 line of BSCVA. Mean spherical equivalent refraction achieved was -0.18 diopters (D) (range: -0.75 to +0.50 D) compared to -2.72 D (range: -1.50 to -4.00 D) before treatment. Twelve months after treatment, 19 (85.5%) eyes had a refractive outcome within +/- 0.50 D. A single intraoperative application of MMC 0.02% for 2 minutes appears to be effective in preventing subepithelial haze after PRK for residual myopia in patients with undercorrection or regression following RK.

Photorefractive Keratectomy in a Patient with Epithelial Basement Membrane Dystrophy

Purpose: To report a case of excimer laser photorefractive keratectomy (PRK) in a patient with epithelial basement membrane dystrophy (EBMD). Methods: Interventional case report. Results: A 36-year-old male with clinical manifestations of EBMD underwent bilateral, simultaneous PRK for low myopia correction. A delay (up to 17 days) in the epithelial healing process with unstable epithelium was observed. During the first three postoperative months a visually significant subepithelial haze was developed in both eyes. One year postoperative, an improvement in haze formation and visual acuity in both eyes was found. Conclusions: PRK in patients with EBMD could result in favorable refractive and clinical outcome.

Corneal Ectasia After PRK

To describe the clinical and ultrastructural features of a prominent ectasia of the cornea that occurred 9 years after excimer laser photorefractive keratectomy (PRK). Analysis of corneal topography and ultrastructural examination by transmission electron microscopy (TEM) were used to assess the ectatic cornea. The intended laser ablation in the left eye was 74 microm, and the preoperative ultrasonic pachymetry was 536 microm. Orbscan II (V 3.00; Orbtek, Salt Lake City, UT) observations revealed inferior topographic steepening and protrusion of the anterior and posterior corneal surfaces 13 years after the patient underwent PRK. The least thickness of the cornea was 456 microm. TEM showed that the epithelial basement membrane had degenerated into subepithelial stroma, and apoptotic keratocytes with cell debris on the extracellular matrix were observed in the stroma. However, the endothelial cells were normal. Clinical examination of an eye that had developed corneal ectasia 9 years after PRK showed forward protrusion of both anterior and posterior corneal surfaces. Ultrastructural examination also revealed a degenerated stroma. However, there was no abnormality of the corneal endothelium.

Corneal infiltrates after excimer laser photorefractive keratectomy and LASIK

Corneal infiltrates after excimer laser photorefractive keratectomy and LASIK

Photorefractive Keratectomy in High Myopic Defects with or without Intraoperative Mitomycin C: 1-Year Results

To study the results of the prophylactic use of mitomycin C (MMC) to reduce haze formation and refractive regression after excimer laser photorefractive keratectomy (PRK) for high myopic defects (>5 diopters). Prospective, consecutive, observational study. A total of 124 eyes of 62 patients were divided into two groups of 31 patients, 62 eyes each (Groups A and B). Only Group A was treated with MMC 0.02%. The data of the two groups of eyes, related to the best-corrected visual acuity (BCVA), to the difference of refraction pre- and post-treatment, and to the corneal haze, were analyzed through combined permutation tests by using the NPC Test software . BCVA of Group A, 1 year after treatment, was better than that of the control Group B (one-sided p value = 0.013): Group A - 3 eyes (4.8%) had a loss of a decimal fraction and no eyes > 1; Group B - 13 eyes (20.9%) had a loss of a decimal fraction and 1 eye (1.6%) of 2. There was a smaller difference between attempted and achieved SE correction in Group A with respect to Group B (one-sided p value = 0.068): Group A - 43 eyes (69.3%) within +/- 0.50 D; Group B - 31 eyes (50%) within +/- 0.50 D. there was a smaller incidence of corneal haze in the group for which MMC was used (one-sided p value = 0.005). In this study, the application of MMC 0.02% solution immediately after PRK produced lower haze rates and had better predictability and improved efficacy 1 year after treatment.

Long-term Outcomes of Photorefractive Keratectomy for Anisometropic Amblyopia in Children

To evaluate the long-term visual acuity (VA) and refractive error responses to excimer laser photorefractive keratectomy (PRK) for treatment of anisometropic amblyopia in children. Prospective interventional case-control study. Eleven children, 2 to 11 years old, with anisometropic amblyopia who were noncompliant with conventional therapy with glasses or contact lenses and occlusion therapy were treated with PRK. A cohort derived retrospectively of 13 compliant and 10 noncompliant children with refractive errors similar to those of the PRK group who were treated with traditional anisometropic amblyopia therapy served as control groups. Photorefractive keratectomy for the eye with the higher refractive error. (1) Refractive error reduction and stability in the treated eye, (2) cycloplegic refraction, (3) VA, (4) stereoacuity, and (5) corneal haze up to 3 years after PRK. Compliant and noncompliant children with anisometropia amblyopia were analyzed as controls for refractive error and VA. Preoperative refractive errors were -13.70 diopters (D) (+/-3.77) for the myopic group and +4.75 D (+/-0.50) for the hyperopic group. Mean postoperative refractive errors at last follow-up (mean, 31 months) were -3.55 D (+/-2.2.5) and +1.41 D (+/-1.07) for the myopic and hyperopic groups, respectively. At last follow-up, cycloplegic refractions in 4 (50%) of 8 myopes and all hyperopes (100%) were within 3 D of that of the fellow eye. Five (63%) of 8 myopic children achieved a refraction within 2 D of the target refraction. Two (67%) of 3 hyperopic patients maintained their refractions within 2 D of the target. Refractive regressions (from 1 year after surgery to last follow-up) were 0.50+/-1.41 D (myopes) and 0.60+/-0.57 D (hyperopes). Seven children (77%) were able to perform psychophysical VA testing preoperatively and postoperatively. Five (71%) of the 7 children had uncorrected VA improvement of at least 2 lines, and 4 (57%) of 7 had best spectacle-corrected VA improvement of at least 2 lines, with 1 improving 7 lines. Five (55%) of 9 children had improvement of their stereoacuity at last follow-up. Subepithelial corneal haze remained negligible. The mean final VA of the PRK group was significantly better than that of the noncompliant control group (P = 0.003). The mean final refractive error for both myopic and hyperopic groups was also significantly better that that of the control groups (P = 0.007 and P<0.0001, respectively). Photorefractive keratectomy for severe anisometropic amblyopia in children resulted in long-term stable reduction in refractive error and improvement in VA and stereopsis, with negligible persistent corneal haze.

Effect of Homoharringtonine on corneal haze after excimer laser photorefractive keratectomy in rabbits.

To evaluate the inhibiting effect of Homoharringtonine (HHT) on the corneal haze after excimer laser photorefractive keratectomy (PRK) in rabbits. 18 healthy rabbits which underwent PRK were randomly divided into three groups (A, B and C). The refractive degree of ablation was - 10.0DS in each group. Group A was locally treated with a piece of filter paper soaked with 1 mg/mL HHT for 5 min, and then the entire cornea was repeatedly irrigated with balance solution; Group B was dropped with 0.1 mg/mL HHT after PRK for 3 months; Group C was the control group. Corneal haze, histopathology, response, ect. were investigated. The corneal haze was significantly less in group A, while the difference between group B and group C was insignificant. Keratocytes and fibrocytes in corneal stroma were more active up to 3 months in group B and group C. Intraoperative use of topical HHT can reduce corneal haze after PRK in rabbits.