Comparison Between Sub-Bowman Keratomileusis Versus Photorefractive Keratectomy To Correct Low To Moderate Myopia

Objectives: To determine the differences in the visual results, contrast sensitivity, wavefront aberrometry and K-structure in eyes undergoing either photorefractive keratectomy(PRK) or Sub-Bowman Keratomileusis(SBK). Method:Fifty patients (100eyes) were randomly enrolled at 2 sites respective- ly,twenty five patients(50eyes)underwent SBK and twenty five patients(50 eyes)underwent PRK .Preoperative and postoperative tests included best spectacle-corrected visualacuity, uncorrected visual acuity (UCVA), contrast sensitivity,wavefront aberrometry and K-structure.Results: One- and 3-month UCVA results showed a statistically significant difference: SBK, 88% 1.0 or better vs. 48% 1.0 or better for PRK. At 6 months, UCVA was 94% 1.0 or better for PRK and 92% for SBK;At 1 month,the PRK group had one eye lost more than 2 lines of BSCVA,at 3 and 6 months, the two groups had no eye lost more than 2 lines of BSCVA;At 1 month ,68.0% in SBK group,64% eyes in PRK group were wthin±0.50 D of emmetropia .and 100%were within±1.00 D in thin-flap LASIK group,88% eyes in PRK group were wthin±1.00 D,at 3 and 6 months ,all eyes in two groups were within±1.00 D;Among two groups ,at one month,every special frequency was depressed.Between two groups ,6,18c/deg of SBK group were significantly higher than PRK group(P<0.05).At 6 months,the contrast sensitivity of two groups restored the normal range, there is no significantly difference between two groups.at 1,3 months(P>0.05);total higher-order aberrations in PRK group higher than SBK group(P<0.05),there was no statistically significant difference in spherical aberration and coma between the 2 groups. at1,3,6 months(P>0.05);K-structure of SBK group can be observed in Bowman's membrane, the K-structure in PRK group was disappeard.Conclusions: 1,The SBK and PRK were both safe and predictable proced- ure for the treatment of low and Moderate myopia.The visual acuity of SBK group restored quickly than PRK group.2,The contrast sensitivity of the two groups were both depressed postoperative, Along with time passing, the contrast sensitivity of two groups restored the normal range.3,Postoperatively , higher-order aberrations were both increased among the two groups, at 1 and 3 months he total higher-order aberrations after PRK were higher than PRK group .4,The remaining of K-structure after SBK and disappearance- e of K-structure after PRK provide further evidence for the hypothesis that the K-structure was induced by the particular fiber alignment between Bowman's membrane and anterior substantia propria layer.