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ACUTE EFFECTS AND BIOLOGICAL MECHANISMS

Dose-Related Considerations

Because of the constant presence of a tear film over its surface and mucous membranes, the eye is more sensitive to sulfur mustard than any other organ of the body. The fact that fluid is present in the eye at all times probably accounts for the fact that varying conditions of humidity do not influence the degree of injury as compared, for example, to skin. Table 8-1 summarizes dose-related effects of sulfur mustard on eyes at 16°C-7°C. The degree of visual loss depends on the concentration and exposure time to sulfur mustard. Concentrations of less than 50 to 100 mg·min/m3 cause simple conjunctivitis (inflammation of the conjunctiva) that, at most, can disable an individual for one to two weeks (Papirmeister et al., 1991). When doses exceed 200 mg·min/m3, however, corneal edema or swelling occurs. At even higher doses, severe corneal damage takes place, with significant loss of vision (Papirmeister et al., 1991).

Ocular injury with sulfur mustard liquid increases the risk of perforation of the cornea and thus is far more damaging to the cornea than vapor-induced injury. Some permanent loss of vision is also more likely as the severity of such exposure is increased.

The time between injury and the appearance of clinical symptoms varies, depending on the severity and duration of exposure. The less severe the injury, the longer is this latency period. With conjunctival injury alone, the latent period is 4 to 12 hours. After more severe exposures in which the cornea is damaged, this latent period may be decreased to as little as 1 to 3 hours. The latency period after liquid sulfur mustard injury is less than 1 hour (Papirmeister et al., 1991).

The exquisite sensitivity of the eye, compared to respiratory tract and skin, to sulfur mustard is evident in the data previously presented in Table 3-4. Symptoms appear in the eye before most other tissues. As the concentration of sulfur mustard increases, however, the injury to the eye parallels that of the respiratory tract. Unlike sulfur mustard, Lewisite exposure causes immediate pain and blepharospasm (spasm of eyelid muscle), especially when the agent is aerosolized (Adler and Leopold, 1945). Eye morbidity from liquid and vapor Lewisite is summarized in detail in Table 8-2.

Clinical Observations

The acute clinical course of severe sulfur mustard injuries of the eye has been well described in the rabbit (Figure 8-2). Hughes (1942) described five stages following severe damage to the cornea in rabbit and man:



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