EFFECT OF AMBIENT LIGHT INTENSITY ON AUTO- REFRACTOMETER RESULTS

BACKGROUND : Refractive errors are considered a public health problem in many countries as well as by the WHO. This study compares refractive errors readings on auto-refractometer in the different intensity of illuminations such as bright light and dim light conditions. OBJECTIVE:  To determine the difference in auto-refractometer results in dim and bright light. STUDY DESIGN AND METHODS:  It was a descriptive cross-sectional study conducted on 100 patients having a different degree of myopia and hyperopia. This study includes the effect of ambient light intensity on auto-refractometer results in myopic and hyperopic patients with no associated ocular pathology. Distance (6m) visual acuity was measured by using Snellen distance visual acuity chart. Retinoscopy was also performed. RESULTS : Light intensity affected both hyperopic and myopic. 0.25 diopter difference between dim and bright light auto-refractometer results was 26%, 0.50 diopter difference is in 22%, 1.0 diopter difference is in 14% and no difference is in 38% patients. Accommodation is also affected. Pupil size was large in darkroom procedure. In most patients, type of refractive error was myopia and prevalence of refractive error is more in females as compared to males. CONCLUSION:  It is concluded that a significant number of patients with myopia and hypermetropia show a minor difference in auto-refractometer readings in dark and lightroom. In high refractive errors, the difference in results between dim and bright light was large as compared to small refractive error.