A comparison of the dicon screening field with the humphrey threshold field in detecting glaucoma

Purpose. To assess the sensitivity and specificity of the suprathreshold 40-30 screening program of the Dicon LD400 perimeter in screening for glaucoma by comparison with the Humphrey 24-2 threshold test. Methods. Humphrey 24-2 threshold visual fields and Dicon LD400 Suprathreshold 40-30 screening fields were obtained from the same eye of 100 subjects at a hospital-based tertiary referral center. Fifty subjects were followed in a glaucoma clinic and had previous experience with automated perimetry. The remaining 50 subjects were referred from a community ophthalmic screening clinic and were naive to automated perimetry. Results. The sensitivity of the Dicon perimeter in detecting glaucoma is 80% with an 80% specificity. This compares to a 91% sensitivity and a 44% specificity obtained with the Humphrey perimeter. The average time for a Dicon screening exam is 2.9 minutes compared with 12.0 minutes for the Humphrey 24-2 field (p< 0.01). With the naive subjects, the Dicon perimeter is 69% sensitive and 73% specific in detecting glaucoma. This contrasts with the 92% sensitivity and 32% specificity obtained with the Humphrey perimeter. In experienced subjects, the sensitivity and specificity of the Dicon increases to 94% and 92% respectively compared to 89% and 63% for the Humphrey. The poor specificity of the Humphrey 24-2 fields correlates directly with unreliable fields, increased examination time, and other artifacts that contribute to a "phony" field. Conclusions. The Dicon LD400 Suprathreshold 40-30 screening test is faster, more specific, and less sensitive in glaucoma detection than the Humphrey 24-2 field examination.