Abstract
Abstract: :
Purpose:To investigate the differences between wavefront–derived spectacle prescription and subjective manifest refraction. Methods: Forty eyes (25 myopic and 15 emmetropic) were measured. The average age was 41.60 (± 9.22). Emmetropia was defined as manifest refraction within a spherical equivalent of ± 0.50 D. The VISX WaveScan Wavefront® system was used to collect wavefront–derived spectacle corrections, which were calculated from 3mm, 4mm, 5mm, and 6mm pupils. Subjective manifest refractions were performed using a phoropter and a high contrast visual acuity chart with 85cd/m2 at 4m. Reported manifest refractions were adjusted for distance. The plus–lens–fogging technique was used to obtain maximum plus refractions. Subjects were measured in the morning and in the afternoon. Results:Any differences between the subjective refractions and the WaveScan refractions were analyzed. The average difference between manifest refraction results and WaveScan results was –0.15D. Data were stratified based on the time of measurement. Paired t–tests disclosed no statistically significant difference between data collected in the mornings and afternoons for either the WaveScan Rxs (all pupil sizes) or the Manifest Rx. Data were also stratified based on refractive error measured with manifest refraction. No significant difference was found between myopes and emmetropes in WaveScan and Manifest Rxs. The trend continued when the data were stratified by time of measurement. Paired t–tests showed strong similarity between morning and afternoon refraction discrepancy for both myopic and emmetropic eyes. Conclusions:In this study, both manifest refraction and WaveScan Rxs were found to remain stable during the day. Time of measurement has no influence on the discrepancy between WaveScan Rx and manifest refraction. The discrepancy between manifest refraction and WaveScan is not clinically significant.
Keywords: cornea: clinical science • refraction