High and Low Contrast Visual Acuity and Optical Aberration Correlations With Naval Aviation Flight Performance

Abstract

Abstract: : Purpose: To explore correlations between high and low contrast visual acuity, pupil size and aberrations with flight performance measured by aircraft carrier landing grades. Methods: 446 deployed Naval aviators from four carrier air wings were examined using 100%, 5% and 25% visual acuity charts. Pupil size was also measured using a Colvard pupillometer under the same lighting conditions as the respective eye charts (lights "on" for the 100% chart and lights "off" for the 5% and 25% charts). The 25% chart was fitted with a neutral density filter to decrease light emanating from the eye chart to 1 cd/m² and open the pupil to its maximal scotopic size. Low and high order aberrations were measured using the Visx WaveScan. Landing grades from the previous at–sea period were obtained to search for correlations between clinical and aberration results and flight performance (day, night and overall landing grades). Results: There were positive correlations between age and landing grades (p<.001) and between landing grades and 100% contrast visual acuity (p<.01). There were random correlations with higher order optical aberrations. There were no significant correlations between the low contrast charts and day, night or overall landing grades, except for 5% contrast acuity and propeller overall (p<.01) and day (p<.01) landing grades. No correlations exist between performance on the eye exams and pupil size or between landing grades (day or night) and pupil size. This lack of correlation persisted throughout the air wing, regardless of type aircraft flown. Conclusions: The strongest correlation found related flight experience and landing grade performance as well as high contrast visual acuity and landing performance. Low contrast visual acuity did not correlate with flight performance. Further analysis is required to search for associations between the optical properties (higher order aberrations) of the eye and flight performance. No evidence exists to support the addition of a low contrast vision test or higher order optical aberration measurement as additional aviation medical standards.

Keywords: contrast sensitivity • refractive surgery: optical quality • vision and action