Effect of Lasik on Objective and Subjective Visual Functions in Patients with Myopia

Overview

Purpose:
to determine the effect of laser in situ keratomileusis (LASIK) on visual functions: visual acuity (VA) and contrast sensitivity (CS) and to evaluate functional complaints.

Patients and methods:
prospective study includes results of VA and CS preoperatively and 1, 3, 6 and 12 months after the surgery in patients with middle and high myopia. 105 eyes of 53 patients (37 females, 16 males) were divided according to spherical equivalent into 2 groups: group A (more than –5D, 51 eyes) and group B (less than -5D, 54 eyes). Mean patients’ age was 28,2 years. Visual acuity was measured on log MAR charts. Contrast sensitivity at spatial frequency of 3, 6, 12 and 18 c/deg was tested using CSV 1000 Contrast sensitivity Unit. Influence of glare on CS was determined by BAT (Brightness Acuity Tester). Functional complaints were evaluated using a wide-ranging questionnaire focusing on 4 main topics.

Results:
Visual acuity preoperatively in both groups was significantly decreased in comparison to controls. A considerable decrease can be detected at 1 month postoperatively but later (1 year after the surgery) it reaches the values of 1.02. Postoperatively, a significant decrease of CS can also be detected, above all at intermediate spatial frequencies. During postoperative period, values of CS slowly increase in both groups. However, only in group B (with less than –5D), the preoperative values have been reached. Further, glare has decreased CS at spatial frequency of 6 c/deg, i.e. the most sensitive spatial frequency for human eye. The satisfaction with final outcome has reached 91%. However, some patients (14%) reported reduced vision under dim illumination and at night and also difficulty with night time driving.

Conclusions:
our study suggests that both used methods (VA and CS) are very sensitive to evaluation of visual functions after refractive surgery. Changes of contrast sensitivity can reveal even slightly changed optic factors of cornea that can cause subjective complaints of patients.

Key words:
LASIK, contrast sensitivity, logMAR, subjective complaints