epithelium was mildly injured, but would return to normal in one or two days.
Class III: about 10 percent had severely affected eyes, both the cornea and the conjunctiva being involved. Class III was subdivided into IIIa (mild corneal changes with a prognosis of return to active duty in six weeks to three months) and IIIb (severe corneal changes resulted in disability of more than three months). It is from members of the latter 10 percent of Class III that ''delayed keratitis" developed 8 to 25 years later (see below).
Experience with Lewisite eye injuries is much less extensive. However, Lewisite can produce some changes similar to those of sulfur mustard (Goldman and Dacre, 1989; Mann et al., 1946; also see Table 8-3). Although severe visual loss occurs with Lewisite exposure, no long-term ocular effects were reported by Mann and colleagues (1946). However, animals in the Mann study were only followed for 30 days following exposure.
The corneal epithelium continues to appear viable and respond in a normal manner for hours after exposure to sulfur mustard, even if the epithelium is separated from the underlying layers of the cornea. However, even very low doses of sulfur and nitrogen mustard cause cessation of mitotic activity in the corneal epithelium. Exposed cells in mitosis complete their cell division normally. If exposed to the poison before the onset of mitosis, however, the mitosis is either greatly prolonged or completely suppressed (Friedenwald, 1945). This is consistent with the effects of these agents on all rapidly proliferating cells.
Mann and Pirie (as cited in Friedenwald, 1945) found that corneal collagen reacts with sulfur mustard and, in the presence of an excess of sulfur mustard, more molecules of sulfur mustard are bound by the protein than the number of sulfhydryl groups present in the material before exposure. Further they reported that collagen was abnormally resistant to attack by pepsin after reacting with the agent. This suggests that a specific physical or chemical reaction occurred between the collagen and the sulfur mustard, namely, a denaturation of collagen, potentially making it more vulnerable to degradative enzymes.
The histological changes taking place after sulfur mustard injury of the eye have been summarized by Scholz (1945). Thirty to 60 minutes after exposure, the first change noted was edema of the basal epithelial cells of the cornea. At one to two hours, the basal nuclei relocated toward the central portion of the cell. Between two and 12 hours, the goblet cells had lost their mucus and were sloughed off, followed shortly