Correlation of Visual Acuity, Optical Aberrations, and Light Scatter During Periods of Non-blinking in Soft Contact Lens Wearers

Abstract

Abstract: : Purpose: To investigate the relation between optical quality and visual acuity in soft contact lens wearers during periods of non-blinking.Methods: High contrast visual acuity was measured continuously in five soft contact lens wearers and 2 control spectacle lens wearers during periods of normal blinking (30 seconds) and short periods of non-blinking (up to 30 seconds) while tear film disruption was monitored simultaneously using infrared retroillumination and Shack-Hartmann aberrometry. Retroillumination was used to determine the spatial location of tear film break-up. Shack-Hartman aberrometry measurements obtained every 0.8 seconds were used to determine the time course of development of optical aberrations and light scatter.Results: During periods of normal blinking, tear film break-up was minimal for all subjects. In the absence of tear break-up, optical aberrations and scatter remained constant with no change in visual acuity. During periods of non-blinking, tear break-up occurred in six of the seven subjects. Visual acuity at the end of blink suppression ranged from MAR equal to 0.73 minutes of arc for the subject with no tear break-up to greater than 4.5 minutes of arc for contact lens wearers with extensive tear break-up. Aberrations and scatter developed in areas corresponding to tear film break-up. Light scatter began to increase immediately after the blink, especially in contact lens subjects. Aberrations increased at a slower rate initially, but increased rapidly with the development of larger areas of tear break-up.Conclusions: The loss of visual acuity following cessation of blinking is correlated with increased optical aberrations and light scatter secondary to break-up of the tear film. These results provide an explanation for the symptoms of fluctuating, blurry, or disturbed vision reported by soft contact lens wearers.

Keywords: contact lens • cornea: tears/tear film/dry eye • visual acuity