Impact of age, various forms of cataract, and visual acuity on whole-field scotopic sensitivity screening for glaucoma in rural Taiwan
N. G. Congdon, H. A. Quigley, P. T. Hung, T. H. Wang, T. C. Ho and Y. Glovinsky
Dana Center For Preventive Ophthalmology, Johns Hopkins University, Baltimore, Md, USA.
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, > or = 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. CONCLUSIONS: Although cataract
affects the whole-field scotopic threshold, it appears that scotopic
testing may be of value in field-based screening for glaucoma.
