IMPACT OF AGE, VARIOUS FORMS OF CATARACT, AND VISUAL-ACUITY ON WHOLE-FIELD SCOTOPIC SENSITIVITY SCREENING FOR GLAUCOMA IN RURAL TAIWAN

Objective: To evaluate the impact of age, various forms of cataract, and visual acuity on whole-field scotopic sensitivity screening for glaucoma in a rural population. Design: Clinic-based study with population-based recruitment. Setting: Jin Shan Township near Taipei, Taiwan. Subjects: Three hundred forty-six residents (ages, greater than or equal to 40 years) of Jin Shan Township. Interventions: Whole-field scotopic testing, ophthalmoscopy with dilation of the pupils, cataract grading against photographic standards, and screening visual field testing in a random one-third subsample. Main Outcome Measures: Whole-field scotopic sensitivity (in decibels) and diagnostic status as a case of glaucoma, glaucoma suspect, or normal. Results: Participants in Jin Shan Township did not differ significantly in the rate of blindness, low visual acuity, or family history of glaucoma from a random sample of nonrespondents. Scotopic sensitivity testing detected 100% (6/6) of subjects with open-angle glaucoma at a specificity of 80.2%. The mean +/- SE scotopic sensitivity for six subjects with open-angle glaucoma (32.78 +/- 1.51 dB) differed significantly from that of 315 normal individuals (38.51 +/- 0.22 dB), when adjusted for age and visual acuity (P = .05, t test). With linear regression modeling, factors that correlated significantly with scotopic sensitivity were intraocular pressure, screening visual field, best corrected visual acuity, presence of cortical cataract, and increasing age, Conclusion: Although cataract affects the whole-field scotopic threshold, it appears that scotopic testing may be of value in field-based screening for glaucoma.