Using the Freiburg Acuity and Contrast Test to measure visual performance in USAF personnel after PRK.

PURPOSE: Photorefractive keratectomy (PRK) may be an alternative to spectacle and contact lens wear for United States Air Force (USAF) aircrew and may offer some distinct advantages in operational situations. However, any residual corneal haze or scar formation from PRK could exacerbate the disabling effects of a bright glare source on a complex visual task. The USAF recently completed a longitudinal clinical evaluation of the long-term effects of PRK on visual performance, including the experiment described herein. METHODS: After baseline data were collected, 20 nonflying active duty USAF personnel underwent PRK. Visual performance was then measured at 6, 12, and 24 months after PRK. Visual acuity (VA) and contrast sensitivity (CS) data were collected by using the Freiburg Acuity and Contrast Test (FrACT), with the subject viewing half of the runs through a polycarbonate windscreen. Experimental runs were completed under 3 glare conditions: no glare source and with either a broadband or a green laser (532-nm) glare annulus (luminance approximately 6090 cd/m) surrounding the Landolt C stimulus. RESULTS: Systematic effects of PRK on VA relative to baseline were not identified. However, VA was almost 2 full Snellen lines worse with the laser glare source in place versus the broadband glare source. A significant drop-off was observed in CS performance after PRK under conditions of no glare and broadband glare; this was the case both with and without the windscreen. As with VA, laser glare disrupted CS performance significantly and more than broadband glare did. CONCLUSIONS: PRK does not appear to have affected VA, but the changes in CS might represent a true decline in visual performance. The greater disruptive effects from laser versus broadband glare may be a result of increased masking from coherent spatial noise (speckle) surrounding the laser stimulus.

Intraocular lens and corneal status following aircraft ejection by a USAF aviator.

Prior to 1967, military aviators who developed visually significant cataracts that affected visual performance were grounded. Those that ultimately required surgical removal were permanently grounded because of significant optical effects post-operatively. With the advent of contact lenses, a limited number of aircrew were returned to the cockpit because of improved optical factors provided by contacts post-cataract surgery. However, development of the intraocular lens (IOL) in the 1970s marked a major technological breakthrough that provided the potential to restore post-cataract surgical vision to near normal conditions. This case report is the first known occurrence of ejection from a high performance militaryaircraft by an aviator with an IOL. The success and stability of the IOL through this event provided additional clinical and operational information relative to the overall USAF experience with certain types of IOL approved for use in USAF aircrew. The aviator also sustained unexpected corneal foreign bodies due to the canopy fragmentation system.