Effectiveness of cultured human keratinocyte onlays on epithelial healing and clinical outcome after photorefractive keratectomy

PURPOSE: To evaluate epithelial healing time, postoperative pain, corneal haze, and visual and refractive outcomes following the application of cultured sheets of human allogeneic epidermal keratinocyte (CEAK) onlays on the photorefractive keratectomy (PRK) -ablated corneal surface as dressing material. METHODS: In total, 204 eyes from 103 patients with myopia or myopic astigmatism were prospectively evaluated for 6 months after PRK. The ablated cornea was dressed in three different ways. Specifically, CEAK onlays were placed in 80 eyes (CEAK group), CEAK with amniotic membrane (AM) strips in 63 eyes (CEAK with AM group), and therapeutic contact lenses only in 61 eyes (control group). All eyes were covered with bandage contact lens after the operation. Contact lens removal time, intensity of postoperative pain score on postoperative day 2, corneal haze, Snellen visual acuity, and remaining refractive errors were measured. RESULTS: The mean contact lens removal time was shorter in the CEAK with AM group (1.84 +/- 0.72 days) compared to the control (2.77 +/- 1.59 days) and CEAK only (2.24 +/- 0.79 days) groups (P < .001). However, no significant differences were evident among the groups in terms of immediate postoperative pain, Snellen visual acuity, remaining refractive errors, and corneal haze at 6 months postoperative. CONCLUSIONS: The CEAK onlay with AM facilitates epithelial healing, and is thus a good candidate dressing material to decrease the epithelial healing time after PRK. However, this onlay method did not affect the intensity of postoperative pain or final visual outcomes after surgery.     

Eight-year follow-up of photorefractive keratectomy for myopia

PURPOSE: We evaluated 8-year results of excimer laser photorefractive keratectomy (PRK) for myopia in terms of stability and late complications. METHODS: Ninety-two 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 eyes were divided into three groups according to preoperative refraction: low myopes (< or = -6.00 D), medium myopes (-6.10 to -10.00 D), and high myopes (>-10.00 D). RESULTS: Change in myopic regression stabilized in all myopia groups within 12 months, although a small myopic shift occurred up to 8 years after PRK. Mean change in refraction between 2 and 8 years was -0.42 +/- 0.48 D for low myopes, -0.37 +/- 0.34 D for medium myopes, and -0.41 +/- 0.50 D for high myopes. The percentage of eyes within +/- 1.00 D of emmetropia 8 years after PRK was 78.3% in the low myopia group, 68.8% in the medium myopia group, and 57.1% in the high myopia group. One eye lost 2 lines of best spectacle-corrected visual acuity due to irregular astigmatism. In 13.0% of eyes, a residual trace corneal haze was observed, which had no effect on visual acuity. Apart from the loss of 2 lines of BSCVA in one eye, there were no other late complications during the study period. CONCLUSIONS: The mean change in refraction between 2 and 8 years was less than -0.50 D, regardless of preoperative refraction, and may be attributed to natural age-related refractive change. The appearance of residual corneal haze after 8 years correlated with the amount of myopic correction. PRK was a safe and stable surgical procedure in this group of patients.     

Laser-assisted subepithelial keratectomy for myopia: two-year follow-up

PURPOSE: To assess and compare the clinical results (efficacy, safety, stability, and postoperative pain or discomfort) of laser-assisted subepithelial keratectomy (LASEK) and conventional photorefractive keratectomy (PRK) for the correction of low to moderate myopia. SETTING: Department of Ophthalmology, Masaryk University Hospital, Brno, Czech Republic. METHODS: A prospective comparative study was performed in 184 eyes of 92 patients who had surface excimer ablation for the correction of myopia. The preoperative mean spherical equivalent (MSE) was -4.65 diopters (D) +/- 3.14 (SD) (range -1.75 to -7.50 D). In each patient, LASEK was performed in 1 eye and PRK in the fellow eye by the same surgeon. The first eye treated and the surgical method used in the first eye were randomized. Both procedures were performed with the Nidek EC-5000 excimer laser using the same parameters and nomogram. The postoperative pain level, visual recovery, complications (haze), uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and refractive outcome were evaluated and compared. All eyes completed a 24-month follow-up. RESULTS: The postoperative MSE was -0.18 +/- 0.53 D in the PRK eyes and -0.33 +/- 0.46 D in the LASEK eyes. At 1 week, the mean UCVA was 0.64 +/- 0.21 and 0.87 +/- 0.23, respectively. No LASEK eye lost a line of BSCVA. There were no statistically significant differences between PRK and LASEK eyes in the safety and efficacy indices at 2 years. The mean pain level was significantly lower on days 1 to 3 in the LASEK eyes (P <.05). The mean corneal haze level was lower in the LASEK eyes (0.21) than in the PRK eyes (0.43) (P <.05). Seventy-nine patients preferred LASEK to PRK. CONCLUSIONS: Laser-assisted subepithelial keratectomy provided significantly quicker visual recovery, eliminated post-PRK pain, and reduced the haze level in eyes with low to moderate myopia compared with conventional PRK. It provided good visual and refractive outcomes. There were no serious complications.     

Laser in situ keratomileusis for residual myopia after photorefractive keratectomy

PURPOSE: To evaluate the efficacy and safety of laser in situ keratomileusis (LASIK) for myopic regression and undercorrection after photorefractive keratectomy (PRK). SETTING: The Eye Institute, Sydney, Australia. METHODS: Fifty eyes of 32 patients were treated by LASIK for residual myopia following primary PRK. The mean spherical equivalent refraction (SEQ) was -2.92 diopters (D) +/- 1.57 (SD) (range -0.75 to -7.88 D). The mean refractive cylinder was 0.96 +/- 0.74 D (range 0 to 3.50 D). For analysis, the eyes were divided into 2 groups: those with 0 or low corneal haze (Group 1) and those with severe corneal haze (Group 2). In Group 1, the SEQ was -1.99 +/- 0.79 D (range -0.75 to -3.75 D) and in Group 2, -3.77 +/- 1.62 D (range -0.75 to -7.90 D). The procedure was performed using the Chiron Automated Corneal Shaper and the Summit Apex Plus laser. The mean interval between PRK and LASIK was 25 months (range 9 to 59 months). The following parameters were studied before and after LASIK retreatment: SEQ, mean refractive cylinder, uncorrected visual acuity (UCVA), and best corrected visual acuity (BCVA). Complications after LASIK retreatment were evaluated. RESULTS: Six months after LASIK, the mean SEQ in all eyes was -0.65 +/- 0.86 D (range +1.50 to -3.35 D); 70.0% of eyes were within +/-1.00 D of emmetropia and the UCVA was 6/12 or better in 72.5%. The mean SEQ in Group 1 was -0.22 +/- 0.55 D (range -0.88 to -1.50 D) and in Group 2, -0.97+/- 0.92 D (range 0.12 to -3.25 D); the UCVA was 6/12 or better in 94.0% of eyes in Group 1 and in 56.0% in Group 2. No statistically significant between-group difference was found in lines of Snellen acuity lost or gained at 6 months. No eye lost more than 1 line of BCVA. CONCLUSIONS: Laser in situ keratomileusis appears to be a safe, effective, and predictable procedure for treating eyes with 0 or low haze with residual myopia after PRK. It is less predictable in eyes with severe haze.     

Five-year follow-up of photorefractive keratectomy for myopia

PURPOSE: To analyze long-term results of photorefractive keratectomy (PRK) for myopia and myopic astigmatism. METHODS: This retrospective study included 15 eyes of 8 patients who were examined annually for 5 years after PRK. The Nidek EC-5000 laser with an ablation zone of 5.0 mm was used. Evaluations included spherical equivalent manifest refraction, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), corneal haze, and corneal astigmatism calculated by Fourier analysis of videokeratography data. RESULTS: A tendency toward myopic regression was most evident within the first postoperative year, with manifest refraction changing from +0.80 +/- 1.62 D at 1 week to -0.45 +/- 0.70 D at 1 year postoperatively (P = .007). Regression continued after the second postoperative year. There was a statistically significant difference between manifest refraction at 2 years (-0.36 +/- 0.75 D) and 5 years (-1.11 +/- 1.12 D) (P = .002). Postoperative UCVA stabilized from 3 months up to 3 years, but slightly deteriorated at 4 years and thereafter due to the myopic refractive shift. BSCVA remained stable throughout the 5-year follow-up period. Several eyes developed mild corneal haze after surgery, but haze was minimal in the majority of patients by 1 year and continued to fade over time. The asymmetry component of the cornea significantly increased after surgery, with all postoperative values significantly higher than before PRK (P < .05). Higher order irregularity increased after surgery, with a statistically significant difference between preoperative and 1 year postoperative (P < .05), but values after 2 years were not different from preoperative baseline. CONCLUSION: Fifteen eyes with a baseline refraction of -3.00 to -9.00 D had PRK with the Nidek EC-5000 laser and a 5-mm-diameter ablation zone. Myopic regression occurred in the first year, with continued mild regression of approximately -0.75 D between 2 and 5 years. Nevertheless, the results show the procedure was relatively safe and effective in this group.     

Laser-assisted subepithelial keratectomy and photorefractive keratectomy for the correction of hyperopia. Results of a 2-year follow-up

PURPOSE: To evaluate and compare the efficacy, safety, predictability, and stability of laser-assisted subepithelial keratectomy (LASEK) and photorefractive keratectomy (PRK) for low to moderate hyperopia with a 2-year follow-up. SETTING: Department of Ophthalmology, Masaryk University Hospital, Brno, Czech Republic. METHODS: This prospective comparative single-surgeon study included 216 eyes of 108 patients with hyperopia who received PRK in 1 eye and LASEK in the contralateral eye. The mean patient age was 38.3 years (range 25 to 58 years). The mean preoperative spherical equivalent (SE) cycloplegic refraction was +3.67 diopters (D) +/- 1.15 (SD) (range +2.00 to +5.00 D), and astigmatism was less than 1.00 D. In each patient, PRK was performed in 1 eye (Group A) and LASEK was performed in the other eye (Group B) using the Nidek EC-5000 excimer laser. Postoperative uncorrected visual acuity (UCVA), best corrected visual acuity, contrast sensitivity, manifest and cycloplegic refractions, refractive stability and predictability, postoperative pain, and corneal haze were examined and statistically analyzed. A P value less than 0.05 was considered significant. RESULTS: At 1 week, the UCVA was 20/40 or better in 58% of PRK eyes and 85% of LASEK eyes (P =.037); at 2 years, it was 20/40 or better in 81% and 91%, respectively (P =.076). At 2 years, the UCVA for near was N8 or better in 73% of PRK eyes and 89% of LASEK eyes (P =.064). No patient lost 2 or more lines of Snellen visual acuity. The safety index was 1.03 in PRK eyes and 1.08 in LASEK eyes. Refractive stability was achieved at 6 months in LASEK eyes and at 12 months in PRK eyes. The mean SE cycloplegic refraction decreased from +3.58 D (PRK eyes) and +3.76 D (LASEK eyes) at baseline to +0.74 D and +0.32 D, respectively, at 2 years; in 57% and 78% of eyes, respectively, the refraction was within +/-0.50 D of the targeted refraction. Peripheral corneal haze scores at 3 to 9 months and pain scores at 1 to 3 days were significantly lower in the LASEK group than in the PRK group. CONCLUSIONS: Laser-assisted subepithelial keratectomy for hyperopia up to +5.00 D provided good visual and refractive results. It significantly reduced postoperative pain, grade of peripheral ring-shaped corneal haze, and regression of hyperopia. Hyperopic LASEK provided quicker visual recovery and achieved better efficacy, predictability, and refractive stability than hyperopic PRK.     

Effect of amniotic membrane after laser-assisted subepithelial keratectomy on epithelial healing: clinical and refractive outcomes

PURPOSE: To evaluate the effect of an amniotic membrane (AM) on reepithelialization time, corneal haze, and postoperative visual and refractive outcomes after laser-assisted subepithelial keratectomy (LASEK) for myopia and myopic astigmatism. SETTING: Department of Ophthalmology, Yonsei University College of Medicine, and Balgeunsesang Ophthalmology Clinic, Seoul, Korea. METHODS: One hundred fifty-two eyes of 84 patients with myopia or myopic astigmatism were prospectively evaluated for 6 months after LASEK. An AM was placed as a strip on the inferior limbus in 94 eyes of 54 patients after LASEK; 58 eyes of 30 patients served as the control group. Postoperative epithelial healing time, uncorrected visual acuity (UCVA), best corrected visual acuity, remaining refractive error, and corneal haze were examined. RESULTS: The reepithelialization time was shorter in the AM group (2.40 days +/- 0.94 [SD]) than in the control group (3.90 +/- 0.97 days) (P<.001). At 6 months, 86 eyes (91.5%) in the AM group had a UCVA of 20/25 or better and 90 eyes (95.7%) had a UCVA of 20/40 or better; 48 eyes (82.8%) and 53 eyes (91.4%) in the control group had a UCVA of 20/25 or better and 20/40 or better, respectively. The mean spherical equivalent in the AM group was -0.48 +/- 0.54 diopter (D) and in the control group, -0.94 +/- 0.60 D (P<.001). The corneal haze was significantly less in the AM group than in the control group (P<.001). CONCLUSION: Amniotic membrane use after LASEK induced rapid epithelial healing with more favorable visual and refractive outcomes and lower corneal haze scores than conventional LASEK.     

Ten-year follow-up of photorefractive keratectomy for myopia of less than -6 diopters

PURPOSE: To evaluate the long-term outcomes of excimer laser myopic photorefractive keratectomy (PRK) for myopia of less than -6 diopters (D). DESIGN: Long-term (10-year) follow-up retrospective, interventional case series. METHODS: The study included 225 eyes of 138 myopic patients with spherical equivalent (SE) between 0 and -6 D treated with myopic PRK at the Instituto Oftalmológico de Alicante, Alicante, Spain, using the VISX 20/20 excimer laser (Santa Clara, California, USA). The main outcome measures were refractive predictability and stability, mean corneal keratometry, topographical cylinder, safety, efficacy, stability of visual acuity, and postoperative complications. RESULTS: At 10 years, 169 (75%) of 225 eyes were within +/- 1.00 D and 207 (92%) were within +/- 2.00 D. Ninety-five (42%) eyes underwent retreatments because of overcorrection, regression, or both. The mean SE slightly decreased (myopic regression) with a mean magnitude of -0.10 +/- 1.08 D over 10 years (-0.01 +/- 0.11 D per year). Forty-one (58%) of 225 eyes demonstrated increase in best spectacle-corrected visual acuity after 10 years. Only one eye lost eight lines because of significant cataract, and two eyes lost vision (one lost seven lines and the other lost four lines) because of posterior segment-related complications. The mean corneal haze score gradually decreased from 0.22 +/- 0.39 at three months to 0.01 +/- 0.09 at 10 years. CONCLUSIONS: Photorefractive keratectomy for myopia of less than -6 D is a safe and effective procedure in the long-term.     

Prospective study of photorefractive keratectomy for myopia using the VISX StarS2 excimer laser system

PURPOSE: To evaluate the safety, efficacy, and predictability of excimer laser photorefractive keratectomy (PRK) for compound myopic astigmatism using the VISX StarS2 excimer laser system with international version 3.1 software. METHODS: We report a prospective consecutive study of myopic excimer laser PRK, performed in a multi-surgeon environment with 200 eyes of 117 patients, to correct naturally occurring compound myopic astigmatism of between -0.50 to -5.90 D manifest refractive sphere and up to -3.50 D manifest refractive astigmatism. Patients were assessed prior to surgery and at 1, 3, 6, and 12 months after treatment. RESULTS: One hundred and ninety-eight of 200 treatments (99%) were reviewed 1 year after surgery; 193 of 198 eyes (97%) achieved 20/40 or better uncorrected visual acuity and 163 of 198 eyes (82%) achieved 20/20 or better. One eye lost two lines of Snellen visual acuity assessed at 12 months but recovered acuity when assessed at 18 months. Mean spherical equivalent corneal plane power was reduced from -3.50 to +0.90 D 1 month after treatment and 0 D at 12 months (SD 0.67 D). Three eyes of three patients underwent further treatment, two with LASIK and one with PRK for residual refractive error. Refractive astigmatism of >1.00 D was reduced from a mean -1.70 to -0.70 D at 1 year after treatment. Vector magnitude was 79% of that intended and mean vector axis error (absolute) was 8.5 degrees. No eye had a severe haze response. Pelli-Robson contrast acuity was significantly reduced after treatment from a mean 1.72 D preoperatively to 1.63 D at 12 months (P<.01). CONCLUSIONS: PRK for myopia using the VISX StarS2 excimer laser system was effective in the treatment of low myopic astigmatism, although there was a significant reduction in Pelli-Robson contrast sensitivity.     

准分子激光角膜切削深度与术后角膜上皮下雾状混浊的关系

目的研究准分子激光角膜切削术（ｐｈｏｔｏｒｅｆｒａｃｔｉｖｅｋｅｒａｔｅｃｔｏｍｙ，ＰＲＫ）后角膜上皮下雾状混浊（ｈａｚｅ）与角膜切削深度之间的关系。方法选择治疗条件基本相同，对双眼同时接受ＰＲＫ治疗的３１例（６２只眼）近视性屈光参差（平均４．９７Ｄ）患者进行前瞻性自身对照研究，将高近视度数眼（－１４．１０±４．１７Ｄ）作为治疗组，低近视度数眼（－９．１３±３．５３Ｄ）作为对照组，术后随访６～１２个月，平均１０个月。结果术后两组的角膜上皮下雾状混浊程度经统计学分析差异有显著性（Ｐ＜０．０５）。结论准分子激光角膜切削术治疗近视，矫正度数越高，角膜切削越深，术后发生角膜上皮下雾状混浊的危险性则越大。     

Twelve-year follow-up of photorefractive keratectomy for low to moderate myopia

PURPOSE: To evaluate long-term safety and stability in a group of myopic patients who underwent photorefractive keratectomy (PRK) > or =12 years ago. METHODS: Myopic PRK was performed on 120 eyes of 80 patients using the Summit UV200 excimer laser with a 5-mm ablation zone. Of the original group, most of whom were followed for > or =2 years (mean 2.6 +/- 1.7 years), 34 patients (58 eyes) returned at 12 years (mean 12.7 +/- 0.79 years) and had refractive stability, refractive predictability, best spectacle-corrected visual acuity (BSCVA), corneal haze, and subjective patient symptoms, such as glare/halos, recorded. RESULTS: Preoperative mean refractive spherical equivalent (MRSE) ranged from -1.75 to -7.25 diopters (D) and astigmatism from 0.00 to 1.50 D. All eyes underwent a change in manifest refraction over 12 years. At 2 years, MRSE was -0.27 +/- 0.55 D and at 12 years was -0.58 +/- 0.72 D. In 87.9% of eyes, the level of preoperative BSCVA was maintained or improved, whereas 34.5% of eyes gained one line, and 12.1% lost one line of BSCVA. Uncorrected visual acuity > or = 20/20 was noted in 67% of eyes, whereas 62.1% were within +/- 0.50 D of emmetropia. Trace haze was noted in 17.2% of eyes at 12 years. One patient had a rhegmatogenous retinal detachment, but this was unlikely due to the PRK procedure. With respect to the small optical zone, 14 (41.1%) patients had night visual problems, particularly halos, which were severe in 2.7%. All patients questioned stated they would have the procedure done again. CONCLUSIONS: Photorefractive keratectomy with the Summit UV200 excimer laser effectively reduced myopia and showed good refractive stability from year 2 to 12 with good patient satisfaction.     

Corneal astigmatic change after photorefractive keratectomy and photoastigmatic refractive keratectomy

PURPOSE: To evaluate and compare the efficacy, safety, predictability, and surgically induced astigmatism (SIA) of photorefractive keratectomy (PRK) and photoastigmatic refractive keratectomy (PARK). SETTING: Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan. METHODS: In this retrospective study, 70 eyes were treated for myopia and 70 eyes were treated for myopic astigmatism. Refraction, corneal topography, slitlamp findings, and visual acuity in the 2 groups at 1, 3, and 6 months were evaluated and compared. Vector analysis was performed to determine the SIA in both groups. RESULTS: The mean preoperative spherical equivalent at the glasses plane in the PRK and PARK groups was -6.06 diopters (D) and -7.18 D, respectively. At 6 months, the mean reduction in astigmatism in the PARK group was 61.0%. Predictability was within +/-1.0 D in 85.2% of eyes in the PRK group and 62.5% in the PARK group. An uncorrected visual acuity of 20/40 or better was achieved in 91.8% and 83.9% of eyes, respectively. The mean SIA was 0.64 D in the PRK group, with a general with-the-rule axis shift. The results of vector analysis were more favorable when calculated from refractive values than from Sim-K corneal topography values. The mean astigmatism correction index and index of success calculated from refractive data were 0.75 and 0.38 in the PARK group. The mean magnitude and angle of error were 0.22 +/- 0.52 D and -2.13 +/- 24.41 degrees, respectively. CONCLUSIONS: Photorefractive keratectomy and PARK were effective and safe procedures for the correction of myopia and myopic astigmatism. However, SIA occurred with spherical myopic treatments. This small SIA may be a confounding factor in low astigmatic treatments.     

Long-term outcomes of photorefractive keratectomy in eyes with previous epikeratophakia for keratoconus

PURPOSE: To determine the long-term safety and effectiveness of photorefractive keratectomy (PRK) in the treatment of refractive errors after epikeratophakia (EP) for keratoconus. METHODS: Ten patients (14 eyes) who had refractive errors after EP for keratoconus received PRK surgery. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refractive error, corneal astigmatism, pachymetry, corneal topography, and complications were monitored. RESULTS: Mean follow-up after PRK was 63.4 +/- 19.8 months. Mean spherical equivalent was -5.5 +/- 3.9 D before PRK, -0.9 +/- 0.5 D at 1 month after PRK, and -1.5 +/- 1.0 D at 3 years. Mean astigmatism was 4.2 +/- 2.1 D before PRK, 1.2 +/- 0.5 D at 1 month after PRK, and 1.5 +/- 0.6 D at 3 years. Thirteen (93%) eyes had an UCVA <20/40, and 12 (86%) had a BSCVA of 20/40 or better before PRK. At 1 year, the UCVA was 20/40 or better in 8 (57%) eyes, and the BSCVA was 20/40 or better in all eyes. Mean central corneal thickness was 749 +/- 35 microm before PRK and 621 +/- 56 mum at 3 years. During the follow-up period, haze (grade no more than 1.0) was observed in 2 eyes. No immune rejection episode or recurrent keratoconus was found. CONCLUSIONS: PRK appears to be reliable and safe for the correction of residual ametropia after EP for keratoconus, and the visual acuity can remain stable after PRK for a long time.     

Evaluation of the prophylactic use of mitomycin-C to inhibit haze formation after photorefractive keratectomy

PURPOSE: To evaluate the results of the prophylactic use of mitomycin-C to inhibit haze formation after excimer laser photorefractive keratectomy (PRK) for medium and high myopia in eyes that were not good candidates for laser in situ keratomileusis (LASIK). SETTING: Carones Ophthalmology Center, Milan, Italy. METHODS: This prospective randomized masked study comprised 60 consecutive eyes (60 patients). The inclusion criteria were a spherical equivalent correction between -6.00 and -10.00 diopters (D) and inadequate corneal thickness to allow a LASIK procedure with a residual stromal thickness of more than 250 microm. The eyes were divided into 2 groups according to the randomization protocol. After PRK, the study group eyes were treated with a single intraoperative dose of mitomycin-C (0.2 mg/mL), applied topically with a soaked microsponge placed over the ablated area and maintained for 2 minutes. The control eyes did not receive this treatment. Refraction, uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), and slitlamp evidence of corneal opacity (haze) or other visible complications were evaluated. RESULTS: No toxic or side effects were encountered postoperatively. No study group eye had a haze rate higher than 1 during the 6-month follow-up; 19 eyes (63%) in the control group did (P =.01). At 6 months, the between-group difference in the refractive outcome was statistically significant (P =.05), with 26 study group eyes (87%) and 14 control eyes (47%) within +/-0.50 D of the attempted correction. No study group eye had a BCVA loss during the follow-up; 7 control eyes had lost 1 to 3 lines at 6 months (P =.0006). CONCLUSIONS: The prophylactic use of a diluted mitomycin-C 0.02% solution applied intraoperatively in a single dose after PRK produced lower haze rates, better UCVA and BCVA results, and more accurate refractive outcomes than those achieved in the control group.     

Photorefractive keratectomy with aspheric profile of ablation versus conventional photorefractive keratectomy for myopia correction: six-month controlled clinical trial

PURPOSE: To analyze ocular wavefront error and corneal asphericity (Q) in patients treated with aspheric profile photorefractive keratectomy (PRK) compared with patients having conventional PRK to correct myopia and myopic astigmatism and to evaluate the effect of postoperative corneal shape on visual performance. SETTING: Eye Clinic, University G. d'Annunzio, Chieti-Pescara, Italy. METHODS: Fifty eyes were treated with aspheric profile PRK using the MEL 80 flying-spot excimer laser, and 24 eyes were treated with standard PRK using the MEL 70 flying-spot excimer laser. RESULTS: Postoperative wavefront error increased in both groups. Six months after surgery, there was a smaller increase in root mean square (RMS) of total higher-order aberrations and spherical aberration (59% and 106%, respectively) in the aspheric profile PRK group than in the conventional PRK group (94% and 136%, respectively) (P<.01).The aspheric profile PRK group showed more prolate corneal asphericities (mean Q of 0.15 +/- 0.26) than the conventional group (mean Q of 0.45 +/- 0.26) (P<.001), with increasing oblateness for higher attempted corrections. A higher percentage of patients with better low-contrast uncorrected visual acuity and best corrected visual acuity was observed in the aspheric PRK group than in the conventional PRK group (P<.05). CONCLUSIONS: Aspheric profile and conventional PRK were safe and efficient for the correction of myopia and myopic astigmatism. Moreover, aspheric profile PRK induced a smaller increment of total wavefront error, was related to a smaller increase in spherical aberration, and better maintained the physiology of the corneal surface than conventional treatment.     

Ten-year follow-up of photorefractive keratectomy for myopia of more than -6 diopters

PURPOSE: To evaluate the long-term outcomes of excimer laser myopic photorefractive keratectomy (PRK) for myopia higher than -6 diopters (D). DESIGN: A long-term (10-year) follow-up retrospective, interventional case series. METHODS: The study included 267 eyes of 191 patients with myopia with spherical equivalent (SE) of more than -6 D treated with myopic PRK at the Instituto Oftalmológico de Alicante, Alicante, Spain, using the VISX 20/20 excimer laser (Santa Clara, California, USA). All patients were evaluated three months, one year, two years, five years, and 10 years after surgery. The main outcome measures were refractive predictability and stability, mean corneal keratometry, topographical cylinder, safety, efficacy, stability of visual acuity, and postoperative complications. RESULTS: At 10 years, 156 (58%) of 267 eyes were within +/- 1.00 D and 209 (78%) were within +/- 2.00 D. One hundred and twenty-four eyes (46.4%) underwent retreatments because of overcorrection, regression, or both. The mean SE decreased (myopic regression) in eyes that did not undergo retreatment, with a mean magnitude of -1.33 +/- 2.0 D over 10 years (-1.13 +/- 0.20 D per year). One hundred and twenty-one (48.3%) of 267 eyes demonstrated increase in best spectacle-corrected visual acuity, and only eight eyes lost lines of vision because of cataract and posterior segment-related complications. The mean corneal haze score decreased gradually from 0.48 +/- 0.69 at three months to 0.09 +/- 0.33 at 10 years. CONCLUSIONS: PRK for myopia of more than -6 D is a safe and effective procedure in the long-term.     

Prospective randomized comparison of wavefront-guided and conventional photorefractive keratectomy for myopia with the meditec MEL 70 laser

PURPOSE: To study refractive results and aberrometric changes in myopic patients treated with wavefront-guided photorefractive keratectomy (PRK) in comparison with standard PRK. METHODS: Sixty eyes of 60 patients with myopic astigmatism were randomly divided into two groups. Group 1 included 30 eyes (mean spherical equivalent refraction -4.39 +/- 1.31 D; range -2.50 to -6.50 D) treated with wavefront-guided PRK using the WASCA workstation and the Asclepion Meditec flying spot MEL 70 excimer laser. Group 2 had 30 eyes (mean spherical equivalent refraction -4.33 +/- 1.22 D; range -2.50 to -6.50 D) that underwent conventional PRK using the same laser, and served as the control group. Wavefront analysis of high order aberrations was performed before and 6 months after surgery. RESULTS: Postoperatively, wavefront error increased in both groups (5.0-mm wavefront aperture diameter). Six months after surgery, the eyes that received the WASCA ablation had a smaller increase in root-mean-square (RMS; 70% of increment) compared to the conventional PRK group (139% of increment) (P<.001). In the standard PRK group, all aberrations notably increased; in the wavefront-guided PRK group there was a smaller increase of trefoil and spherical aberrations (P<.001) and a decrease of coma aberrations (P<.001). The smaller increase of wavefront error in the wavefront-guided PRK group compared to the standard PRK group was more evident when preoperative RMS values were higher than 0.4 microm (P<.01). The visual parameters (spherical equivalent refraction, uncorrected and best spectacle-corrected visual acuity) did not show significant differences between the two groups. CONCLUSION: Wavefront-guided PRK induced a smaller increase of postoperative wavefront-error compared to conventional PRK, particularly in patients with higher preoperative higher order aberrations.     

Evaluation of photorefractive keratectomy retreatments after regressed myopic laser in situ keratomileusis

PURPOSE: To evaluate the results of photorefractive keratectomy (PRK) enhancements in eyes previously treated by myopic laser in situ keratomileusis (LASIK) showing an undercorrection due to either a refractive regression or a primary undercorrection, when an in-the-bed enhancement was not advisable because of residual stromal thickness limitations. DESIGN: Noncomparative, prospective, interventional case series. PARTICIPANTS: Seventeen eyes of 17 patients previously treated by LASIK for a spherical equivalent (SE) correction of -8.125 to -12.50 diopters (D; mean, -9.45 +/- 1.01 D), that after a follow-up of 6 to 14 months ended up with a refraction of -1.50 to -3.75 D (SE; mean, -2.48 +/- 0.74 D). Intended flap thickness was 160 microm for all eyes. In all cases, the residual stromal bed under the flap was considered too thin (255-305 microm) to allow an in-the-bed enhancement without exceeding an assumed safety thickness limit (250 microm). INTERVENTION: Eyes were treated by PRK at least 6 months after LASIK. The PRK ablation parameters (diameter, attempted correction) were selected to avoid theoretical flap perforation. The deepest ablation was 60 microm, for a -3.75-D correction. We used a Bausch & Lomb 217 C excimer laser (Bausch & Lomb, Rochester, New York). MAIN OUTCOME MEASURES: Refraction, uncorrected and best-corrected visual acuity (BCVA), slit-lamp evidence of corneal opacity or other visible complications, and corneal topography. RESULTS: Although the initial postoperative period was characterized by very satisfactory refractive results (mean SE error at 1 month, -0.04 +/- 0.37 D; range, +0.75 to -0.625 D), during follow-up, a dense haze (grade 3 and 4) developed in 14 eyes (82.3%) that induced a further myopic regression (SE, -1.725 to -5.50 D; mean, -3.11 D) and BCVA loss (two to six lines). These 14 eyes underwent a further surgical treatment to remove the severe haze at 3 to 10 months after PRK. CONCLUSIONS: Based on these results, we strongly advise against PRK as a possible option to correct eyes previously treated by myopic LASIK that resulted in an undercorrection.     

Clinical results and complications of refractive surgery

PURPOSE: To evaluate the efficacy of photorefractive keratectomy (PRK) with a scanning type excimer laser MEL-60 (AESCLUP-MEDITEC, Co). SUBJECTS AND METHOD: We performed PRK on 102 eyes of 62 myopic patients whose refraction ranged from-3.00 to -12.50 D (mean, -6.47 D) and examined the clinical results of postoperative refraction and complications. RESULTS: At 12, 18, and 24 months after the operation, the mean refraction was -1.57 +/- 1.25D, -1.63 +/- 1.51 D and -1.73 +/- 1.47 D. At 12 months after the operation, 36 eyes (46.2%) were within +/- 0.5 D of intended correction, 61 eyes (78.3%) within +/- 1.0 D, and 76 eyes (97.4%) within +/- 2.0 D. Twenty-four months after the operation, 12 eyes (37.5%) were within +/- 0.5 D, 18 eyes (56.3%) within +/- 1.0 D and 29 eyes (90.6%) within +/- 2.0 D. The complications were as follows: keratitis filamentosa was observed in 10 eyes (10.5%), decrease of contrast sensitivity in 7 eyes (7.4%), subepithelial corneal haze in 4 eyes (1.2%), steroid-induced glaucoma was 2 eyes (2.1%), increase of astigmatism in 2 eyes (2.1%), decrease of best corrected visual acuity in 2 eyes (2.1%), and corneal ulcer in 1 eyes (1.1%). CONCLUSION: PRK with a scanning type excimer laser MEL-60 was effective to reduce refractive error in low and mild myopia, but there were some complications, so that a long, careful follow-up seems necessary.     

Scraping and mitomycin C to treat haze and regression after photorefractive keratectomy for myopia

PURPOSE: To evaluate the efficacy, safety, and predictability of therapeutic scraping and application of a diluted 0.02% mitomycin C solution to treat haze and regression after photorefractive keratectomy (PRK) for myopia. METHODS: We performed a non-comparative, non-randomized retrospective study of 35 eyes of 30 patients who had previously undergone PRK for myopia and developed haze and regression after treatment. The range of refractive error after regression was -0.75 to -5.50 D (mean -2.92 D). Haze, ranging from grade 3 to 4 (scale: 0 to 4) caused a best spectacle-corrected visual acuity loss of 1 to 6 Snellen lines. All eyes were treated 6 to 12 months after PRK by scraping the stromal surface and application of a 0.02% mitomycin C solution for 2 minutes using a soaked merocel sponge. No laser ablation was performed. Corneal transparency, refractive error, and visual outcomes were evaluated over a 12-month follow-up period. RESULTS: All eyes had significant improvement in corneal transparency. Thirty-one eyes had haze grades lower than 1, which were maintained over time. Only four eyes showed haze grades 1 to 2 and two of them needed further treatment using the same technique. At 12 months after treatment, all eyes were within +/-1.50 of original intended correction (mean 0.04 +/- 0.63 D). BSCVA improved in all eyes. No toxic effects were observed during re-epithelialization or during follow-up. CONCLUSION: Single application of diluted mitomycin C 0.02% solution following scraping of the corneal surface was effective and safe in treating haze and regression after PRK.