Incidence of refractive errors in victims of chemical weapons as delayed effects
Introduction: Many victims of chemical warfare (VCW) manifest some degree of refractive errors which were not present before exposure. These refractive errors are presumably long-term (delayed) effects of sulfur mustard exposure. However, no related research studies have been done to confirm this. Myopia, hyperopia, and astigmatism are the refractive errors of the eye and prevalence of these errors depends on several factors such as hereditary factors, age, profession, and also several geographical factors. The effect of sulfur mustard on the eye may be very complex and relates basically to the intensity of the injury. Sulfur mustard targets the cornea resulting in early effects of exposure. The delayed effects of exposure are less documented and are discussed in this study. Materials and Method: In this study, cross-sectional study refractive errors were studied as one of the delayed effects of sulfur mustard in VCW. 2252 eyes of VCW and 2248 normal eyes were chosen as controls. The mean age of both groups were 34.3 (SD=9.1) and 32.1 (SD=10.1) respectively. Both groups went through an optometric and ophthalmic examination. The refractive errors were measured by autorefractometer (Topcon RM 2300). The Student t-test and chi-square test were used and P < 0.05 was considered significant. Results: The prevalence of refractive errors in the VCW group was 89.8% which was higher than the control group of 72.6% p < 0.001. Astigmatism was the main refractive error in the VCW group and their prevalence (76.2%) was higher than the control group (47%) p < 0.001. The types of astigmatism found were "against" and 11 oblique." Prevalence of myopic astigmatism in the VCW group was also higher than in the other types of astigmatisms. Discussion: There are three main causes for refractive errors. Change in anterior-posterior length of the eye or change in curvature of refractive surfaces and change in the index or combinations of them. All VCW have photophobia, dry eyes, and excessive blinking. They have narrow eye opening (narrow palpebral fissure). Eyelid pressure and excessive blinking, and dry eyes add gradual pressure on the cornea and in the long term lead to induce refractive errors such as astigmatism. Further studies will be needed however to confirm this.