Photorefractive keratectomy. A 6-year follow-up study (original) (raw)
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Characteristics Influencing Outcomes of Excimer Laser Photorefractive Keratectomy
Ophthalmology, 1996
To identify preoperative and intraoperative characteristics associated with outcomes of photo refractive keratectomy (PRK). Methods: In the phase III multicenter clinical trials of the Summit Technology excimer laser for corrections of 1.5 to 6.0 diopters (0) of myopia, three principal outcomes of PRK on 612 patients were examined: (1) uncorrected visual acuity of 20/40 or better, (2) predictability of refractive outcome within 1.0 0 of attempted correction, and (3) stability of refractive result between 12 and 24 months. Multiple logistic regression was used to test for independent associations of multiple preoperative and intraoperative characteristics with each of these outcomes. Results: Older age was independently associated with lesser likelihood of achieving 20/40 or better uncorrected visual acuity (odds ratio = 1.08 per incremental year of age, 95% confidence interval [CI] = 1.04-1.12) and with decreased predictability, specifically with overcorrection (odds ratio = 1.09, 95% CI = 1.06-1.12), but age was not associated with stability of refraction. Greater attempted correction was associated independently with a decreased likelihood of 20/40 or better uncorrected visual acuity (odds ratio = 2.78 for corrections of 3.5-5.5 0, 95% CI = 1.18-6.75; odds ratio = 4.19 for corrections of :2::5.5 0 , 95% CI = 1.66-10.58), with decreased predictability (odds ratio = 1.72 for corrections of 3.5-5.5 0, 95% CI = 1.05-2.85; odds ratio = 2.95 for corrections of :2::5.5 0, 95% CI = 1.65-5.26), and with a reduced likelihood of stability of refraction (odds ratio = 3.46 for corrections of :2::5.0 0, 95% CI = 1.32-9.11). No intraoperative characteristics were associated with any of the outcomes assessed. Conclusions: Using this specific excimer laser system with an optical zone of 4.5 or 5.0 mm, patient age and attempted correction are important preoperative characteristics associated with postoperative uncorrected visual acuity and predictability of PRK. Stability of refraction is strongly associated with attempted correction. Such information may help guide patient selection, determine timing of fellow eye treatment, and suggest changes in the laser treatment algorithm for individual patients. Although these findings may be representative of PRK in general, similar analyses should be performed before modifying patient treatments using either a 6.0-mm treatment zone or other laser systems.
Ophthalmology, 1998
This study aimed to assess the long-term stability and efficacy of excimer laser photorefractive keratectomy. Design: Patients who participated in the first United Kingdom photorefractive keratectomy clinical trial were asked to attend a 6-year follow-up assessment. Participants: Eighty-three patients (68%) of the original cohort of 120 participants were observed for 6 years. A Summit Technology UV200 excimer laser with a 4-mm ablation zone had been used with patients allocated to one of six groups according to their preoperative refraction. Each group received one of the following spherical corrections:-2,-3,-4,-5,-6, or-7 diopters (D). Within each group, all patients received an identical treatment, and thus emmetropia was not the goal in all patients. Intervention: The induced refractive change, objective corneal haze, glare, and halo measurements, together with possible late-phase complications, were analyzed. Main Outcome Measures: "All groups achieved a refractive undercorrection, and the magnitude of the undercorrection was related to the size of the attempted correction. The induced refraction stabilized by 6 to 12 months and has been maintained up to the 6-year follow-up stage. Results: Ninety-one percent of patients who underwent a-2.00-D correction and 76% of patients who received a-3.00-D correction were within _+1 D of the intended refraction at 6 years. Fifty-seven percent of the-4.00-D group and 50% of those in the-5.00-D group were within _+1 D, and this was reduced further to 43% in the-6.00-D group and 19% in the-7.00-D group. Six patients (7%) had evidence of residual corneal haze, which was visually significant in two patients (3%). Ten patients (12%) had significant night halos due to the small 4-mm ablation zone that was used in this early treatment trial. Conclusions: There was no further regression of the refraction after 1 year, and, more important, there was no sign of hyperopic shift or diurnal fluctuation in the patients' refraction. In addition, corneal haze appeared to reduce further with time, with no intraocular or retinal side effects being noted. Night halos remain a significant reported problem in a small number of patients who were treated with the 4-mm ablation zone.
Excimer laser Photorefractive Keratectomy (PRK): First report from the Italian study group
1991
To assess the visual and refractive results of excimer laser photorefractive keratectomy (PRK) in myopic astigmatism. Methods: Excimer laser PRK was performed using an Aesculap Meditec MEL 60 laser in 46 myopic astigmatic eyes. Preoperative corneal astigmatism was-1.50 D. (±0.50) in 7 eyes (15.2%);-2.50 D. (±0.50) in 14 eyes (30.5%);-3.50 D. (±0.50) in 13 eyes (28.3%);-4.50 D. (±0.50) in 8 eyes (17.4%); and-5.50 D. (±0.50) in 4 eyes (8.6%). Mean preoperative cylinder was-3.50 D. (±2.50). Mean preoperative sphere was-4.50 D. (±2.25). Pre and postoperative visual acuity, refraction, keratometer readings, corneal topography, intraocular pressure, and slit lamp findings were recorded. Results: By one year of follow-up, postoperative cylinder was between +0.50 and-0.50 D. in 31 eyes (67.4%); between-0.50 and-1.50 D. in 11 eyes (23.9%); between-1.50 and-2.50 D. in 4 eyes (8.7%). Mean post-operative cylinder was-1.21 D. (± 1. 70). Mean postoperative sphere was-1.09 D. (±1.25). Myopic and astigmatic improvement was achieved in each patient (100%). Topography analysis showed 69.4% were within 0.5 mm, 96.8% within 1 mm, 97.8% within 1.5 mm of centration; 55% of the patients achieved uncorrected visual acuity of 10/10 (Snellen). One patient (2.2%) lost one line of best corrected vision due to decentration and change of axis. Conclusion: These preliminary results of myopic astigmatic excimer laser PRK procedures compare favorably in efficiency and safety with reports of PRK for myopia.
Excimer laser photoastigmatic refractive keratectomy
Ophthalmology, 1998
To study the efficacy of photoastigmatic refractive keratectomy (PARK) by the MEL 60 (Aesculap-Meditec, Jana, Germany) scanning excimer laser for the treatment of myopic astigmatism, with follow-up of 18 months.
Visual performance after excimer laser photorefractive keratectomy for high myopia
Taiwan Journal of Ophthalmology, 2017
PURPOSE: To evaluate the efficacy, safety, predictability, and visual performance of excimer laser photorefractive keratectomy (PRK) for myopia greater than −8 diopters (D). METHODS: Fifty-four patients (104 eyes) with myopia from −8D to −13D and cylinder up to −4D received surface ablation technique with the Allegretto wave version 1009-1 excimer laser to correct their refractive error. The patients were examined on days 1, 3, 7, and 14 and 1, 3, 6, and 12 months postoperatively. Visual acuity, manifest refraction, corneal haze, topography, intraocular pressure, contrast sensitivity, and wavefront aberration were evaluated. RESULTS: Twelve months postoperatively, 95% of eyes were within 1D of the intended correction. In addition, 94% of eyes had attained uncorrected distance visual acuity of 20/25 or better, and 98% of eyes had improved or remained their corrected distance visual acuity. All eyes exhibited barely detectable corneal haze which peaked during the 1 st month with a gradual reduction in the 3 rd month. Ninety-five percent of patients had no or only mild degree of night glare. CONCLUSIONS: Excimer laser PRK is an effective and predictive treatment for high myopia greater than −8D with or without astigmatism up to −4D. The incidence of complication is low. All patients who are candidates for laser in situ keratomileusis can be candidates for surface ablation, especially those with preoperative thinner cornea or higher risk of corneal flap complications.
The Use of the 193-nm Excimer Laser for Myopic Photorefractive Keratectomy in Sighted Eyes
Archives of Ophthalmology, 1991
Photorefractive keratectomy was performed at three centers using the 193-nm excimer laser on 31 sighted myopic eyes. Preoperative refractive errors (spherical equivalent) ranged from -12.00 to -4.00 diopters (D) (mean, -6.49 +/- 1.75 D). Peribulbar anesthesia, a 5.2- to 6.0-mm beam diameter, and topical corticosteroids were used for up to 6 months after surgery. The epithelium healed within 3 to 4 days, and all patients returned to their best corrected visual acuity within 1 line of their preoperative acuity. There was minimal subepithelial reticular haze, peaking at 3 weeks and diminishing over the next 3 to 4 months, which was not felt to be visually significant. At 6 months, the average residual refractive error was -1.85 +/- 2.5 D. Sixty-eight percent of eyes were corrected within 2 D and 55% within 1 D of attempted correction. There was no significant change in astigmatism, contrast sensitivity, corneal sensation, or endothelial cell counts. This preliminary work shows that photorefractive keratectomy has promise in the reduction of moderate myopia.