The Use of Bifocal Soft Contact Lenses in the Fort Rucker Aviation Environment.

Abstract

Abstract : There are problems with the compatibility of spectacles and certain helmet mounted electro-optical visual display systems. The incompatibility has been partially resolved with single vision contact lenses. However, these contact lenses have not helped senior aviators, who must wear bifocal glasses due to their presbyopia. The purpose of this study was to compare the performance of bifocal soft contact lenses with that of bifocal spectacle lenses to determine if contact lenses are an option for helping older aviators meet the visual requirements needed to fly military aircraft. Seventeen volunteer presbyopic aviators from Fort Rucker were fitted with five bifocal soft contact lens combinations and bifocal glasses. A four-phase investigation was conducted: a clinical phase involving the fitting of the bifocal contact lenses; a laboratory phase involving measurements of visual functions; a simulator phase involving measures of visual performance in simulated flight conditions; and an operational phase consisting of subjective responses regarding in-flight use of bifocal contact lenses. In general, vision in the best performing bifocal contact lenses typically was slightly reduced from vision in bifocal spectacles. The amount of the reduction, and whether it was clinically significant, depended on the refractive error of the subject (myopes generally performed better), the add group of the subject (low add group subjects performed better), and the type of bifocal contact lens. Aviators performed flight simulation maneuvers better in bifocal contact lenses than in bifocal glasses, and they evaluated their own ease of vision while performing aviation duties to be much easier in bifocal contact lenses than in bifocal glasses. In actual flight operations, each aviator preferred bifocal contact lenses over bifocal spectacles. Bifocal soft contact lenses are an acceptable