Night vision of the post-LASIK myope

Abstract

Purpose: Poor night vision has been reported as one of the side-effects of LASIK,  however, this area has not been widely studied.  This study therefore set out to assess and quantify the visual status of the post-LASIK patient in dim illumination as an indication of visual performance at night.  This was achieved by assessing the night vision threshold, glare vision threshold and glare recovery time. Setting: The study was carried out in Durban, Kwazulu-Natal in South Africa. Method: This study used the Night Sight Meter for assessment of the night vision thresholds, glare vision thresholds and glare  recovery times of individuals who had had LASIK at least one year before commencement of the study.  The inclusion criteria were post-surgical interval following LASIK of at least one year and willingness to participate in the study.  The exclusion criteria included previous ocular surgery other than LASIK, current ocular disease and any systemic illnesses.   One hundred subjects were selected from participating ophthalmologists’ records, using convenience sampling, at different post-operative periods that ranged from 12 to 57 months.  Other refractive findings taken included post-LASIK visual acuity measured using the Snellen Visual Acuity chart and post-LASIK refractive error, measured with the standard subjective refraction tests which included duochrome, Jackson crossed-cylinder and Humphrey’s Immediate Contrast test, which are used for comparison in this study. Results: Post-operatively, the majority of the eyes (89.2%) were classified as having ‘poor’ night vision thresholds.  A similar trend was observed in the case of the glare vision thresholds as 84.7% of the eyes fell into the classification of below average.  The degree of pre-operative myopia appears to have an effect on the post-LASIK night vision and glare  thresholds.  Only glare recovery  time was not affected as 51.2% of the subjects displayed good recovery times. Conclusion: This study suggests that the post-LASIK myope has difficulty with night vision due to poor night vision and glare vision thresholds which are linked to the higher aberrations and intraocular scatter resulting from LASIK.   As macular integrity is not affected in the LASIK patient, the glare recovery time appears to be within normal limits