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Efficacy, safety and predictability of photorefractive keratectomy compared to laser in situ keratomileusis for the treatment of high myopic astigmatism

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Session Details

Session Title: LASIK Outcomes II

Session Date/Time: Tuesday 16/09/2014 | 14:00-16:00

Paper Time: 14:46

Venue: Capital Hall B

First Author: : V.Suvajac SERBIA

Co Author(s): :    G. Suvajac   J. Suvajac   K. Savic   V. Novakovic   B. Djurovic  

Abstract Details

Purpose:

To compare efficacy, safety and predictability of Photorefractive Keratectomy compared to Laser in Sity Keratomileusis for the correction of high myopic astigmatism with cylinder component greater then 2.50 diopters (D).

Setting:

Profesional – dr Suvajac’’ Eye Clinic, Belgrade, Serbia

Methods:

Preoperative and postoperative data of 40 consecutive eyes that had undergone LASIK and 20 eyes that had undergone PRK for the correction of high myopic astigmatism with cylinder greater then 2.50 diopters (D) were analyzed in this randomized retrospective study. Average age was 32,80±8,1 years in the LASIK group and 32,45±8,1 in PRK group, with no significant difference between the two groups(p=0.875) Preoperative spherical equivalent(SE) and the manifest subjective cylinder were -3,58±1,33(range: -7.00 to -1.75) and -3,38±0,33(range: -4.50 to -3.50) in the LASIK group and -4,64±2,79(range: -11.25 to -1.38) and -3,33±0,46(range: -4,25 to -2,75) in PRK group. There was no statistically significant difference between the two groups neither in preoperative SE, nor the preoperative subjective cylinder (p=0.433 and P=0.425). LASIK flaps were created using mechanical Moria M2 microkeratome, while epithelial removal in PRK procedures was done using Amoils epithelial brush. Excimer ablations were performed with the Wavelight Allegretto Eye Q 400 Hz laser. In PRK procedures Mitomycin C (MMC) 0.02% was used intraoperatively in all cases . Postoperative follow up was six months in all eyes.

Results:

Postoperative SE and postoperative cylinder were -0,08 ±0,54(range: -1.25 to +0.88) and -0,70±0,73(range: -3.0 to +1.25) in the LASIK group, and -0,34±0,99(range: -2.0 to +1.0) and -0,40±0,60(range: -1,25 to +0,75) in PRK group. There was no statistically significant difference between the two groups neither in postoperative SE, nor the postoperative cylinder(p=0.525 and p= 0.116). Postoperative efficacy index and safety index were 1,08±0,14(range: 0,59 to 1,33) and 1,11±0,12(range: 1.0 to 1.42) in the LASIK group, and 1,00±0,22(range: 0.50 to 1.36) and 1,12±0,24(range: 1.0 to 2.0) in the PRK group. There was also no significant difference in efficacy index, nor in safety index(p=0.135; p=0.295) between the LASIK and PRK group. Regarding predictability, 70% of eyes in LASIK group were within ±0.50D of targeted emmetropia, while 90% of eyes were within ±1D. In PRK group 45% of eyes were within ±0.50D of emmetropia, while 70% were within ±1D. There was no statistically significant difference in percentage of eyes with SE within ±0.05D(p=0.09), but there was significant difference in percentages of eyes within ±1.0D between the groups(P=0.01). Six months postoperatively, corneal haze was present in five post PRK eyes(25%),but in all cases it was haze grade one without any visual impairment or clinical significance.

Conclusions:

When treating lower values of myopia and myopic astigmatism LASIK and PRK have showed comparable refractive results and safety profiles. However when discussing higher myopic and myopic astigmatism treatments, PRK has been associated with higher amounts of regression and increased risk for postoperative corneal haze formation. It was shown that the risk for postoperative corneal haze formation increases with the amount of astigmatism treated. Since the introduction of antimetabolite MMC use in PRK procedures for the treatment of higher myopic refractive errors, comparable results are obtained when compared to those of LASIK. On the other side, when talking about PRK for correction of high myopic astigmatism, there are conflicting results in the literature. In that context we wanted to compare efficacy, predictability and safety of LASIK versus PRK for the correction of high compound myopic astigmatism with cylinder component greater then 2.50D. In our patients, six months postoperatively, there were no significant differences between the two procedures regarding efficacy and safety, but overall predictability was better in LASIK group. In our opinion, based on the results obtained, PRK with adjunctive MMC use, although a bit less predictable compared to LASIK, is an efficient and safe option for the treatment of high myopic astigmatism.

Financial Interest:

NONE

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