Risk of visual impairment attributable to ocular histoplasmosis. Washington County Follow-up Eye Study Group.

Purpose: To compare 15-year incidence rates of visual impairment and vision-threatening conditions between cases with ocular histoplasmosis and controls residing in the same endemic community.
Methods: Controls and cases with and without disciform lesions who were between 30 and 69 years of age when selected, interviewed, and examined in 1970 were reinterviewed and reexamined in 1985.
Results: Of the 252 cases and controls examined in 1970, 216 were still alive in 1985. Of these, 202 (94%) were interviewed; 197 (91%) underwent visual acuity measurement; and 173 (80%) were examined by a study ophthalmologist. Both in 1970 and in 1985, cases with disciform macular lesions of ocular histoplasmosis had a higher prevalence of both unilateral and bilateral visual impairment and blindness. Although prevalence of visual impairment and blindness in 1985 was similar among controls and cases of ocular histoplasmosis without disciform lesions, this group of cases had about twice the incidence of visual impairment as that of controls. However, the 95% confidence intervals on estimates of relative risks were broad and included unity. No new disciform lesions attributable to ocular histoplasmosis were found in 28 eyes of 18 cases free of them in 1970 or among 148 controls.
Conclusions: The 15-year risk of visual impairment and blindness appears to be somewhat higher among adults aged 30 years and older who have only peripheral atrophic scars characteristic of ocular histoplasmosis than among individuals without such scars who live in the same endemic community. Adults who already have a disciform lesion attributed to ocular histoplasmosis in one eye are at low risk of development of a disciform lesion in the fellow eye later in life.