Use of Soft Contact Lenses by Tactical Aircrews

Richard Dennis

The soft contact lens test with Tactical Air Command (TAC) is a joint operational test. Jeff Hill of the Tactical Air Warfare Center (TAWC), Eglin Air Force Base, Florida, is the project manager and is responsible for collecting and evaluating the operational data. Richard Dennis of the U.S.Air Force School of Aerospace Medicine (USAFSAM), Brooks Air Force Base, Texas, is the project coordinator of the supporting laboratory and is responsible for gathering and evaluating the medical data. Hill coordinates the day-to-day operations with participating TAC units. All contact lenses and lens solutions are ordered through USAFSAM.

Aircrews from five TAC bases are participating in the soft contact lens test. Two bases, Seymour-Johnson Air Force Base, North Carolina, and Eglin Air Force Base, Florida, are F-4 test bases. Both of these bases have hot, humid climates. Cannon Air Force Base, New Mexico, is the test base for F-lll aircraft and is considered to have a drier, more arid climate. Aircrews in F-15s are being tested at Tyndall Air Force Base, Florida, again a hot and humid climate, and at Luke Air Force Base, Arizona, a dry arid climate. F-16 aircrew are also being tested at Luke Air Force Base.

Approximately 85 subjects have volunteered for the soft lens test. Of these, 50 are pilots and 35 are weapon system officers (WSOs). WSOs are utilized in the F-4 and F-lll aircraft. A greater percentage of WSOs are spectacle wearers, as their entry visual standards are lower. The field optometrists are tasked with subject selection (from prescribed criteria), contact lens fitting and dispensing, and all follow-up exams. At multioptometrist bases one optometrist is designated to support the project.

The test was designed to incorporate the idea of flexible wear. Being conservative, we did not want to subject our crew members to extended wear. However, there may be times when they may be in a situation when



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Considerations in Contact Lens Use Under Adverse Conditions: Proceedings of a Symposium Use of Soft Contact Lenses by Tactical Aircrews Richard Dennis The soft contact lens test with Tactical Air Command (TAC) is a joint operational test. Jeff Hill of the Tactical Air Warfare Center (TAWC), Eglin Air Force Base, Florida, is the project manager and is responsible for collecting and evaluating the operational data. Richard Dennis of the U.S.Air Force School of Aerospace Medicine (USAFSAM), Brooks Air Force Base, Texas, is the project coordinator of the supporting laboratory and is responsible for gathering and evaluating the medical data. Hill coordinates the day-to-day operations with participating TAC units. All contact lenses and lens solutions are ordered through USAFSAM. Aircrews from five TAC bases are participating in the soft contact lens test. Two bases, Seymour-Johnson Air Force Base, North Carolina, and Eglin Air Force Base, Florida, are F-4 test bases. Both of these bases have hot, humid climates. Cannon Air Force Base, New Mexico, is the test base for F-lll aircraft and is considered to have a drier, more arid climate. Aircrews in F-15s are being tested at Tyndall Air Force Base, Florida, again a hot and humid climate, and at Luke Air Force Base, Arizona, a dry arid climate. F-16 aircrew are also being tested at Luke Air Force Base. Approximately 85 subjects have volunteered for the soft lens test. Of these, 50 are pilots and 35 are weapon system officers (WSOs). WSOs are utilized in the F-4 and F-lll aircraft. A greater percentage of WSOs are spectacle wearers, as their entry visual standards are lower. The field optometrists are tasked with subject selection (from prescribed criteria), contact lens fitting and dispensing, and all follow-up exams. At multioptometrist bases one optometrist is designated to support the project. The test was designed to incorporate the idea of flexible wear. Being conservative, we did not want to subject our crew members to extended wear. However, there may be times when they may be in a situation when

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Considerations in Contact Lens Use Under Adverse Conditions: Proceedings of a Symposium overnight wear is inevitable. Consequently, we are using extended-wear lenses for daily use only. Two pairs of lenses are being dispensed to each crew member, with a third set in reserve at the optometry clinics. For those crew members who can be deployed worldwide to supplement other units, one pair of lenses and accompanying care solutions are stored in the individual's “mobility” bag. There will be a continued reliance on spectacles as a backup system. During missions the crew members are required to carry their spectacles in their flight suits. Each subject was instructed in emergency removal of their lenses and must be able to remove both lenses within an adequate time period before being allowed to fly with them. Every subject must meet the Air Force's visual standard of 20/20 acuity in both eyes with their soft lenses. METHOD For statistical purposes only two types of extended-wear soft contact lenses were used for the test. We wanted to compare a medium-water-content lens with a low-water-content lens. Hydrocurve II 55 percent spherical and toric lenses were chosen as the medium-water-content lenses, and CSI-T (38 percent) lenses were chosen to represent the low-water-content lenses. The disinfecting/cleaning system was designed to be as simple and maintenance-free as possible. Heat disinfection was not an option due to the possibility of the lack of electricity at forward basing. The AOSept peroxide system is being used along with Ultrazyme enzymatic tablets. We did have a couple of clear cylindrical cases crack under the pressure of the combination disinfection/enzyming system. These have been replaced with the sturdier opaque cases. Bausch & Lomb Sensitive Eyes preserved saline, daily cleaner, and rewetting drops are also being used. THE TEST PLAN The test plan is divided into three phases. Before beginning the test, a safety-of-flight board was held at USAFSAM to review the research data and to determine if it was safe to fly with soft contact lenses. The first phase included five missions flown for each subject, one of which was a night mission, and a 1-month optometric evaluation. Following phase I, a series of safety-of-flight boards were held to evaluate the data for day and night missions in each aircraft. Phase II will end after each crew member has a total of 25 missions flown while wearing contact lenses, one mission in chemical warfare gear, and a 3-month optometric evaluation. An interim report will be forwarded to TAC after phase II is completed. Phase III will be dedicated to collection of medical data.

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Considerations in Contact Lens Use Under Adverse Conditions: Proceedings of a Symposium Phase I is already completed, while the target date for phase II completion is November 15, 1988. The final completion date of the test is scheduled to be July 5, 1989. A complete initial evaluation was done on each entering crew member by the base optometrist. The ocular indicators also were graded during this exam and will be used as baseline measures. Visual acuities and grading of the ocular indicators with the slit lamp were measured again at the dispensing exam. The follow-up exam times are determined from the date of the dispensing exam. Each follow-up exam consists of the following tests: visual acuity with soft lenses, visual acuity with spectacles after removing the lenses, keratometry, and slit lamp grading of the ocular indicators. We are using the following as ocular indicators: corneal edema, corneal vascularization, corneal staining with fluorescein, contact lens deposits, conjunctival injection, and any papillae formation in the upper papillary conjunctiva. The categories of the grading scale were made broad enough to ensure a high probability of the graders reaching similar conclusions. Each optometrist was given a slit lamp quantification chart to help define each category for all ocular indicators. TEST PROTOCOL The aircrew postmission questionnaires are filled out by each crew member after all 25 missions. They are asked to compare soft contact lenses to spectacles (i.e., better, same, worse) for the items found in Table 1 Other data to be collected during the soft lens test with TAC include the overall cost of lenses and solutions for the entire program and the mean individual costs for lenses and solutions. Visual acuity with spectacles upon immediate removal of the lenses is another item of concern to the Air Force that will be monitored closely. We are also monitoring DNIF (duties TABLE 1 Questionnaire Items Analyzed Following Aircrew Use of Contact Lenses Comfort Ability to see outside objects Displacement/dislodgement Ability to see at night Fogging Tactical air mission tasks Reflections Interference with helmet Effects of vibrations Interference with chemical defense gear Peripheral vision Interference with other flight gear Ability to see cockpit displays Ground activity visual tasks

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Considerations in Contact Lens Use Under Adverse Conditions: Proceedings of a Symposium not including flying time) due to contact lens wear through the base flight surgeons and the number of lost or torn contact lenses. PRELIMINARY RESULTS The overall subjective response to soft contact lens wear by aircrew members has been very positive. In interviews with crew members the major advantage of soft contact lens wear during operations reportedly is increased peripheral vision when “checking six” (i.e., when a pilot throws his head and eyes back to check for a target). Crew members also commented that they no longer had to worry about their spectacles fogging, slipping, causing reflections, or being blurred due to sweat beads. They reported the biggest disadvantage to be dehydration of the lenses due to the aircraft's air conditioners. Although most fliers reported better vision at night with their contact lenses, two pilots complained of inferior night vision. No subject has been lost to the test for medical indications. Only one day of DNIF time has been reported. This was due to a corneal scratch from a fractured lens early in the test. A number of lenses have been torn during the test. This was not unexpected with our test philosophy of extended-wear lenses for daily wear and the preponderance of hard to handle low-powered lenses. Three lenses have been dislodged during flight. Two were involved with +Gz loading, but they may have dislodged because of other factors. One lens was determined to be an extremely loose fitting lens, while the other was a low-powered lens (−0.25 sph CSI-T) that may have been inside out.