Dennis R J, Tredici T J, Ivan D J, Jackson W G
Armstrong Laboratory, Ophthalmology Branch, Brooks AFB, TX 78235-5117, USA.
Aviat Space Environ Med. 1996 Apr;67(4):303-7.
Although soft contact lens (SCL) wear for aircrew with refractive errors was approved in June 1989, aircrew with certain ocular disorders, such as keratoconus, have been waivered to fly with contact lenses (CL) since the 1960's. These aircrew are members of the United States Air Force (USAF) Medical Contact Lens Study Group and are fitted [with SCL's or hard contact lenses (HCL)] and followed by the Ophthalmology Branch at Armstrong Laboratory; Brooks Air Force Base, TX. Because HCL's are perceived to be more susceptible to a disabling foreign body (FB) under a lens and are more difficult to remove in flight, Study Group aircrew are the only USAF HCL wearers allowed to fly.
The medical records of the 142 aircrew members followed for CL wear between 1970 and 1993 were retrospectively examined to determine the type of CL worn, crew position, and the medical reason for CL wear. The Study Group was then surveyed to ascertain whether there were any significant operational problems for aircrew wearing medically indicated CL's. Aircrew were divided into HCL (51 surveys returned) and SCL (44 surveys returned) wearers to compare each modality's efficacy in the flight environment.
HCL wearers were more likely than SCL wearers to have endured at least one FB incursion under a lens during flight (p = 0.053). HCL wearers were also more likely to have had a lens come off-center at least once in their careers during flight (p = 0.035). Both groups reported problems with CL dryness in the 5-15% relative humidity of the cockpit. Only four aircrew reported any CL-related Duties Not Involving Flying (DNIF) days during their careers.
Because HCL's are necessary to correct vision adequately to return aircrew with keratoconus and other corneal anomalies to the cockpit, the USAF needs to continue to investigate the use of rigid gas-permeable HCL's with aircrew.
