Abstract
Purpose: :
The purpose of this study is to compare objectively the quality of vision assessed by double-pass imaging (OQAS, Visiométrics, Spain) in patients operated with PRK and FemtoLASIK for low to moderate myopia
Methods: :
Prospective comparative study of patients who underwent bilateral refractive surgery. Inclusion criteria were: <40 years old myopic, preoperative cylinder <1.5D. One hundred and 6 eyes of 53 patients were included. Thirty patients underwent PRK, and 23 FemtoLASIK. The optical quality of each eye was measured with the OQAS preoperatively and at 1 and 3 months postoperatively using double-pass aberrometry on a 4mm pupil. The Objective Scattering Index (OSI), the Modulation Transfer Function (MTF) cut-off frequency (c/deg) and the Strehl ratio (SR) were compared at each visit
Results: :
Preoperatively there was a significant difference in the treated spherical equivalent (p<0.05). Mean OSI was 0.53+/-0.08 in the PRK group and 0.66+/-0.10 in the FemtoLASIK group (p=0.04). The MTF cut-off frequency (c/deg) was 41.07+/-2.6 in the PRK group and 36.32+/-3.2 in the FemtoLASIK group (p=0.02). One month postoperatively mean OSI was 0.74+/-0.12 in the PRK group and 0.85 +/-0.11 in the FemtoLASIK group (p=0.25). Mean MTF cut-off frequency (c/deg) was 34.71+/-2.12 in the PRK group and 34.64+/-2.68 in the FemtoLASIK (p=0.96). Three months postoperatively mean OSI was 0.59+/-0.08 in the PKR group and 0.82+/-0.18 in the FemtoLASIK group (p=0.02). Mean MTF cut-off frequency (c/deg) was 36.77+/-2.3 in the PRK group and 36.5+/-3.6 in the FemtoLASIK group (p=0.89). There were significant differences in the intragroup comparison in all the data for the PRK group preoperatively and at 1 month and preoperatively and at 3 months for the OSI (p<0.05). In the FemtoLASIK group there was a significant difference for the OSI preoperatively and at 1 month (p<0.03)
Conclusions: :
in the early postoperatory period the OSI increases less and there is a better contrast sensitivity in the FemtoLASIK group. At 3 months postoperatively the OSI increases less in the PRK group. The MTF cut-off frequency (c/deg) in the FemtoLASIK group remains stable and decreases in the PRK group. FemtoLASIK provides unchanged contrast sensitivity and more scattering than PRK.
Keywords: refractive surgery: optical quality • refractive surgery: LASIK • refractive surgery: PRK