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Predictability of spherical photorefractive keratectomy for myopia
S Shah1, A Chatterjee, R J Smith
1Optimax Laser Eye Clinic, Manchester, England, UK.
Objective:
This study aimed to examine the effects of purely spherical excimer laser photorefractive keratectomy (PRK) for myopia.
Design:
Consecutive case series.
Participants:
A total of 3218 eyes with a mean preoperative mean spherical equivalent (MSE) of -3.75 diopters (D) +/- 1.73 D standard deviation (SD) (range, -1.00 D to -11.88 D) underwent PRK with a Nidek EC-5000 excimer laser. Eyes were divided into groups based on the degree of preoperative myopia in 1 D steps.
Intervention:
All eyes underwent PRK with a Nidek EC-5000 excimer laser.
Main Outcome Measure:
Visual and refractive outcome of PRK treatment was measured.
Results:
After a mean follow-up period of 52.6 weeks (range, 26-150 weeks), the final MSE was -0.07 D (+/-0.68 D) (range, -5.50 D to +4.50 D). Of the 3218 eyes, 2919 (90.7%) were within 1.00 D of emmetropia, and 3038 (94.4%) of eyes had an uncorrected visual acuity of 20/40 or better, with 1886 (58.6%) achieving 20/20 or better visual acuity. Eyes in the lower preoperative myopia groups had a greater chance of attaining 20/40 unaided visual acuity than those in the higher groups (e.g., 98.3% of the -2D group and 53.6% of the -9D group achieved 20/40 unaided visual acuity). Overall, mean postoperative haze was 0.29+/-0.39 SD (scale, 0-3), and 29 eyes (0.9%) lost 0.3 or more logarithm of the minimum angle of resolution (LogMAR) unit of best-corrected visual acuity.
Conclusions:
Excimer laser PRK is an effective treatment for myopia of up to -9.00 D. The outcome parameters are less predictable for eyes with greater than -9.00 D of myopia.