Medical Problems Associated With Contact Lens Use

Robert P. Green, Jr.

Military medicine supports commanders by providing for the individual warrior's medical needs. As part of that support, it provides commanders with the medical knowledge and data to make managerial decisions. It is in that context that we must assess the risks versus the benefits of contact lenses. Ultimately, a military commander will decide whether to commit money and people to provide soft contact lenses to aviators.

Military medicine must help commanders define the benefits and risks of soft contact lenses. Some of the visual benefits are obvious and have been covered by previous speakers (e.g., increased visual field, elimination of lens fogging). Medical personnel will find it hard to easily define other benefits. Aircrew members may simply report that they are “better.” Before we let what may be vague benefits override known possible risks, we should ask commanders to ensure that reported benefits and risks be as clearly defined as possible. This is important so that commanders can clearly understand what they are choosing in the form of visual benefits and accepting in the form of ocular risks. Commanders must support and encourage medical personnel to gather as objective data as possible. We must know whether contact lenses improve bomb and range scores, as well as whether test subjects (aviators) develop complications over the long term.

RATES OF COMPLICATIONS

At the present time over 23 million people wear contact lenses in the United States (Kirn, 1987). Only 28 percent of them are males (Stehr-Green et al., 1987). Yet in terms of complications men are more represented than females (Stehr-Green et al., 1987). Therefore, in the military, where



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Considerations in Contact Lens Use Under Adverse Conditions: Proceedings of a Symposium Medical Problems Associated With Contact Lens Use Robert P. Green, Jr. Military medicine supports commanders by providing for the individual warrior's medical needs. As part of that support, it provides commanders with the medical knowledge and data to make managerial decisions. It is in that context that we must assess the risks versus the benefits of contact lenses. Ultimately, a military commander will decide whether to commit money and people to provide soft contact lenses to aviators. Military medicine must help commanders define the benefits and risks of soft contact lenses. Some of the visual benefits are obvious and have been covered by previous speakers (e.g., increased visual field, elimination of lens fogging). Medical personnel will find it hard to easily define other benefits. Aircrew members may simply report that they are “better.” Before we let what may be vague benefits override known possible risks, we should ask commanders to ensure that reported benefits and risks be as clearly defined as possible. This is important so that commanders can clearly understand what they are choosing in the form of visual benefits and accepting in the form of ocular risks. Commanders must support and encourage medical personnel to gather as objective data as possible. We must know whether contact lenses improve bomb and range scores, as well as whether test subjects (aviators) develop complications over the long term. RATES OF COMPLICATIONS At the present time over 23 million people wear contact lenses in the United States (Kirn, 1987). Only 28 percent of them are males (Stehr-Green et al., 1987). Yet in terms of complications men are more represented than females (Stehr-Green et al., 1987). Therefore, in the military, where

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Considerations in Contact Lens Use Under Adverse Conditions: Proceedings of a Symposium there are more males than females, a higher complication rate might occur than in the civilian community. It is unclear what the incidence is of ocular complications from contact lenses. In one large study from Japan (Hamano et al., 1985), the investigators looked at 124,821 eyes of 66,218 patients and asked, “How many people had eye problems, defined by pain, that precipitated a visit to a medical institution?” The rate for polymethylmethacrylate (PMMA) hard contact lens wearers was 1.6 percent; for soft contact lens wearers, it was 1.2 percent; and for rigid gas-permeable lenses (RGP), it was 0.6 percent. The results of that study yielded rather low numbers. In fact, only 14 eyes developed corneal ulcers—a rate of 0.011 percent. In another study, 70 aphakic patients wore soft contact lenses for 3 to 7 years (Salz and Schlanger, 1983). Eleven percent developed corneal vascularization, 17 percent developed bacterial conjunctivitis, and 7 percent developed corneal ulcers. These are rather alarming percentages. The Food and Drug Administration estimates that the risk ratio for extended-wear versus daily-wear soft lenses is about 10 to 1 (Kirn, 1987). Good prospective studies of soft contact lenses to define risk factors and complication rates have not been done and are needed. CONTRAINDICATIONS Most of the medical contraindications are relative. They include chronic hyperemia, chronic conjunctivitis, vernal conjunctivitis, chronic allergic conjunctivitis, symblepharon of the conjunctiva, pterygium, chronic staphylococcal blepharitis, stye, chalazion, trichiasis, entropion, ectropion, corneal degenerations, corneal dystrophies, corneal vascularization, recurrent keratitis, corneal ulcers, and dry eyes. NONMEDICAL CONSIDERATIONS The nonmedical problems associated with contact lenses have for the most part been discussed—edge glare, fluctuating vision with blinking and dehydration, bubbles beneath lenses, and displacement under positive G's. The aircraft environment is not totally hospitable. Humidity ranges from 5 to 10 percent. Current fighter aircraft have been “set” so that they cannot be stressed above 9 G's. Studies at the U.S. Air Force School of Aerospace Medicine have observed subjects wearing contact lenses up to 8 G's. In November 1988 the USAF/SAM Human Use Committee approved the testing of humans to 12 G's in light of the development of new aircraft and tactics.

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Considerations in Contact Lens Use Under Adverse Conditions: Proceedings of a Symposium MEDICAL COMPLICATIONS Medical complications from soft contact lenses can range from temporary and relatively insignificant ones that can ground an aviator for hours to days to more serious corneal problems that may affect an aviator's entire flying career. Examples of less worrisome problems include thimerosol toxicity, corneal edema, giant papillary conjunctivitis, corneal deposits, pseudodendritic keratitis, and corneal abrasions. Examples of the more serious corneal complications include vascularization, molding, and infections. The issue of corneal infections in association with contact lenses is evolving into a major problem. There has been an alarming increase in the number of reports of serious contact-lens-related infectious ulcerative keratitis (Stevson, 1986). From 20 percent (Alfonso et al., 1986) to 70 percent (Ormerod and Smith, 1986) of corneal infections occur in contact lens wearers. In addition, individuals who get corneal infections in association with contact lens wear have worse bacteria cultured from their corneas. Aviators who suffer a corneal infection may be grounded for a long time or even permanently. In one study involving 573 eyes with corneal infections (Alfonso et al., 1986), those persons who had been wearing contact lenses had gram-negative bacteria cultured in 78 percent of culture positive cases versus only 45 percent for those not wearing contact lenses. Most of these gram-negative organisms, 75 percent in one study (Cohen et al., 1987), are pseudomonas, a particularly destructive organism in the cornea. Furthermore, a new and more difficult to treat organism is making its appearance on the scene— acanthamoeba. It is not killed by hydrogen peroxide sterilization, but only by heat. Of corneas infected with this new organism, 83 percent wore contact lenses (Stehr-Green et al., 1987). The effectiveness of soft contact lens sterilization is even in question. In one study by Mondino et al. (1986), 9 of 11 people (82%) using daily-wear soft contact lenses who developed an ulcer were not caring for their lenses properly. This is reassuring because it suggests that education might help. On the other hand, among individuals using extended-wear soft contact lenses in the same study, 12 out of 29 (41%) who developed corneal ulcers were caring for their lenses religiously. That is frightening. Further, in at least one large study, 82 percent of 210 randomly selected contact lens patients were not using the directed procedures for sterilization and cleaning (Roth, 1978). In another study up to 52 percent of patients wearing contact lenses had contaminated contact lens care systems, with 13 percent of commercial contact lens solutions being contaminated (Donzis et al., 1987). While heat sterilization may kill bacteria and acanthamoeba, it markedly shortens the life of daily-wear lenses and cannot be used with the higher-water-content extended-wear lenses. Hydrogen peroxide sterilization is effective against bacteria, but it does not easily kill acanthamoeba. Further, it

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Considerations in Contact Lens Use Under Adverse Conditions: Proceedings of a Symposium is not known what concentration of residual H2O is safe for the eye. Although most companies aim for a residual hydrogen peroxide level of no more than 50–60 ppm after neutralization, in actuality the residual concentration varies from 1 to 300 ppm. Rabbit studies have shown that a hydrogen peroxide concentration of <3 ppm caused a significant increase in corneal hydration and alteration in corneal metabolism (Hartstein, 1985, 1988). The long-term effect on the human cornea of chronic exposure to higher levels of hydrogen peroxide is unknown. It is known that soft contact lenses cause polymegethism and pleomorphism, although less than the older PMMA hard contact lenses. At least with hard contact lenses, this has not been shown to be totally reversible (Mac Rae et al., 1986). CONCLUSION There are other significant issues that must be addressed also. How much is soft contact lens use by military aviators going to cost? How many eye care professionals will be needed to care for these patients? How many aircraft sorties and how much space in aircraft going to the front will be used for contact lens support instead of for the transportation of guns, ammunition, and troops? Will the use of contact lenses help a military organization to achieve its goals? Operational commanders need to talk with the medical people. The operational commander will, ultimately, make the decision to implement a soft contact lens program for aviators. However, the commander must judge whether a clear operational advantage exists to justify military sponsorship of what some might consider the excessive expenditure of money, men, and equipment for a program that will not be suitable for everyone and will cause harm to some. REFERENCES Alfonso, E., S. Mandelbaum, M. Fox, and R. Forster 1986 Ulcerative keratitis associated with contact lens wear. American Journal of Ophthalmology 101:429–433. Cohen, E.J., P.R. Laibson, J.J. Arentsen, and C.S. Clemons 1987 Corneal ulcers associated with cosmetic extended-wear soft contact lenses. Ophthalmology 94:109–114. Donzis, P.B., B.J. Mondino, B.A. Weissman, and D.A. Bruckner 1987 Microbial contamination of contact lens care systems. American Journal of Ophthalmology 104:325–333. Hamano, H., J. Kitano, S. Mitsunaga, S. Kojima, and G. Kissling 1985 Adverse effects of contact lens wear in a large Japanese population. Contact Lens Association of Ophthalmologists Journal 11:141–147.

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Considerations in Contact Lens Use Under Adverse Conditions: Proceedings of a Symposium Hartstein, J. 1985 Soft contact lens DB infection with hydrogren peroxide. Ocular Surgery News July:15, 17. 1988 Hydrogen peroxide solutions: are they harmless? Ocular Surgery News August:22, 23. Kirn, T.F. 1987 As number of contact lens users increases, research seeks to determine risk factors, how best to prevent potential eye infections. Journal of the American Medical Association 258:17–18. Mac Rae, S.M., M. Matsuda, S. Shellans, and L.F. Rich 1986 The effects of hard and soft contact lenses on the corneal endothelium American Journal of Ophthalmology 102:50–57. Mondino, B.J., B.A. Weissman, M.D. Farb, and T.H. Pettit 1986 Corneal ulcers associated with daily-wear and extended-wear contact lenses. American Journal of Ophthalmology 102:58–65. Ormerod, L.D., and R.E. Smith 1986 Contact lens-associated microbial keratitis. Archivies of Ophthalmology 104:. Roth, H.W. 1978 The etiology of ocular irritation in soft lens wearers: distribution in a large clinical sample. Contact Lens Association of Ophthalmologists Journal 4:38–43. Salz, J.J., and J.L. Schlanger 1983 Complications of aphakic extended-wear lenses encountered during a seven-year period in 100 eyes. Contact Lens Association of Ophthalmologists Journal 9:241–244. Stehr-Green, J.K., T.M. Bailey, F.H. Brandt, J.H. Carr, W.W. Bond, and G.S. Visvesvara 1987 Acanthamoeba keratitis in soft contact lens wearers. Journal of American Medical Association 258:57–60. Stevson, S. 1986 Soft contact lenses and corneal infection. Archives of Ophthalmology 104:1287–1289.