Contact Lens Use Under Adverse Conditions Applications in Military Aviation (1990) / Chapter Skim
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4. Evaluating Risks in the Military Aviation Environment
4. Evaluating Risks in the Military Aviation Environment
Pages 30-35
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From page 30... ...
The working group divided the principal risk factors into three groups: high risk factors those most likely to render contact lens use unacceptable or dangerous; moderate risk factors those of definite concern but unlikely to cause irremediable problems; and minimal risk factors—those with little possibility for causing lens failure or long-term complications. Military aviators generally represent a relatively young and healthy group, with greater than average immunological resiliency and high motivation.
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From page 31... ...
Low Humidity and High Air Flow Low cockpit humidity and the related problem of air flow directed in the vicinity of the eyes can be regarded as the single greatest threat to the aviator's ability to wear lenses comfortably and avoid complications. Good data do not exist describing the humidity level below which dry-eye symptoms become a problem or at what level they become unbearable, but clinical experience clearly demonstrates that the 5 to 15 percent humidity levels present in aircraft are sufficiently low to cause difficulties.
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From page 32... ...
The subject of unhygienic conditions is of particular importance to assault helicopter missions conducted by the Army and the Marines. In them, field conditions may prevail for one to many weeks, with no obvious means of ensuring sterile lens insertion or removal or even adequate lens cleaning, especially in combat situations.
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From page 33... ...
Fortunately, hydrogel lenses minimize the problems caused by particulate contamination and may even act as a protective barrier against particle irritation of the cornea. Rigid lenses are much more sensitive to foreign body involvement.
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From page 34... ...
Of greater concern is the possibility of repeatedly experiencing hypoxic conditions while using contact lenses in an extended-wear mode when inadequate recovery time is allowed. In any case, no consequences to visual acuity are expected but, as mentioned before, frequent assault by hypoxic conditions may compromise corneal health and ultimately lead to more serious complications.
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From page 35... ...
In fact, it is possible that contact lenses may act to insulate the eye from temperature extremes. In any case, clinical experience shows that contact lens wearers can participate in both cold winter and hot summer outdoor activities with no hindrance from their lenses.
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