Presumed Ocular Histoplasmosis III

Histoplasmin skin tests and dilated funduscopic examination for presumed ocular histoplasmosis were carried out on 842 individuals, aged 13 years and older, from Walkersville, Md. Seventy percent of the male and 51% of the female population were sensitive to the histoplasmin skin test; among reactors, males had a mean diameter of induration of 11.6 mm, and females had a mean induration of 9.7 mm. Histoplasmin sensitivity was most frequent in the third to the sixth decade, and mean induration size was largest in the third to the fifth decade. Twenty-one individuals were identified as having only peripheral atrophic scars of presumed ocular histoplasmosis. The frequency of these scars was 2.5% and was similar in both sexes and at all age groups. One case of a disciform lesion was identified by the survey, giving a prevalence of about 0.1% in the community and a prevalence of about 4.5% among those with peripheral atrophic scars. All cases of presumed ocular histoplasmosis were histoplasmin-positive; male cases had a mean induration of 15.0 mm, and female cases had an induration of 10.7 mm. Woods and Wahlen,1 in 1959, de¬ scribed a specific ocular disease characterized by an acute macular or paramacular elevated disciform-appearing lesion in the presence of more peripheral atrophie punched-out scars. Because persons with this fun¬ dus picture tended to be sensitive to the histoplasmin skin test, they felt that this disease resulted from sys¬ temic infection with Histoplasma capsulatum. In describing epidemiologie charac¬ teristics of individuals with presumed ocular histoplasmosis, most attention has been given to the disciform le¬ sions.2" Two studies have commented on characteristics of persons with pe¬ ripheral scars,7·8 but only one has con¬ centrated on them." Evidence is accumulating that the proliferative macular disease proba¬ bly arises in individuals who have such peripheral atrophie scars al¬ ready present in their fundi.1"" Therefore, it becomes important to try to predict which persons with pe¬ ripheral scars are likely to develop the more serious vision-impairing disciform lesion. The ideal method of accomplishing this would be to observe a large group of persons with peripheral scars for a long period of time and to compare the characteristics of those who de¬ veloped the disciform process with those who did not. A quicker, though less precise method, is to compare persons with peripheral scars, most of whom will never develop the rela¬ tively rare disciform lesion, with per¬ sons with the disciform lesion. If, as in this study, the two groups of cases come from different populations, they will reflect, in part, differences inher¬ ent in the source populations. How¬