Clinical Investigation On Contrast Sensitivity And Higher Order Aberration After Q-factor Guided SBK And LASIK For Myopia

Objective:To investigate the contrast sensitivity(CS), higher order aberrations (HOA) and their affectionson visual qualityof myopic patients after Q-factor guided Sub-Bowman’s Keratomileusis (SBK) and Laser In Situ Keratomileusis (LASIK). The contrast sensitivity function and the higher order aberrations was measured with contrast sensitivity instrument and higher order aberration instrument.Methods:With non-randomly control clinical study, patients with myopic astigmatism who underwent Q-factor guided laser treatment between January2012and June2012were divided into two groups. Group A included36patients (72eyes,16males and20females) whounderwent SBK;Group B included28patients (56eyes,12males and16females) who underwent LASIK. All patients had stable refractive error over2years and patients withcontraindications were excluded from this study. HOA and contrast sensitivity in dark environment without glare were measuredand compared before and after surgery. All surgeries were performed by one experienced surgeon according to the regular surgery procedure, flap thickness was110μ f in SBK group and130μm in LASIK group respectively, optical zone of ablation was6.5mm in both groups.No complications were noted after all surgeries.Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), slit-lamp examination, non-contact tonometry, ultrasound pachymetry, corneal topography, contrast sensitivity and wave-front aberrations were measured1month,3months,6months and12monthspostoperatively. SPSS16.0was used for statistical analysis.Results:There was no significant difference of age, UCVA, BCVA, manifest refraction, HOA and contrast sensitivitybetween the two groups preoperatively (all P>0.05).After the surgery, contrast sensitivity of SBK group returned to the preoperative level at3-6months,and the LASIK group returned to the preoperative level at6-12months respectively. Furthermore, contrast sensitivities of each space frequency in SBK group were better than those in LASIK group at12months after surgery, the low and medium frequency were more significant. At6months after surgery, the mean HOA was0.31-1.05(0.613ths af)μm in SBK group and0.43-1.75(0.710BK gro)μm in LASIK group respectively, significant difference was found between2groups (P=0.001).Atl2months after surgery, the mean HOA was (0.476±0.137) μm in SBK group and (0.63±0.154) μm in LASIK group respectively, significant difference was found between2groups (P=0.001).HOA were increased in both groups compared to the preoperative values, the amount of increasement was lower in SBK group compared to LASIK group.HOAin both groups tended to decrease gradually at12months compared to6months after the surgery.Conclusions:Comparing with LAS IK, SBK under Q-factor guided treatment achieves a lower induced HOA, and faster recovery of contrast sensitivity at low, medium and high spatial frequencies. SBK combines the advantages of PRK and LASIK, provides better postoperative functional vision, significant improved visual quality, and better satisfaction after surgery.