INTEROBSERVER AND INTRAOBSERVER VARIABILITY IN THE DETECTION OF GLAUCOMATOUS PROGRESSION OF THE OPTIC DISC

Purpose: To evaluate the potential value of obtaining follow-up stereo scopic photographs on glaucoma suspects in identifying progressive opt ic nerve damage.Methods: Nineteen sets of stereoscopic optic disc phot ographs, reflecting one eye from each of 19 patients at two time point s, were selected from the records of subjects enrolled in the Glaucoma Screening Study. By consensus, three experts judged 13 of these eyes to have progressive glaucomatous optic nerve damage. Four other ophtha lmologists who were masked to the expert panel evaluation then assesse d glaucomatous progression in the same eyes. They were asked to evalua te glaucomatous progression in three ways: first, by drawing the optic nerve head appearance from initial stereoscopic photographs and later comparing their own drawings to follow-up stereoscopic photographs; s econd, by comparing serial stereoscopic photographs directly; and thir d, by comparing drawings of the optic nerve head made by another exami ner to the follow-up photographs. Results: Neither sensitivity nor spe cificity was consistently better for serial stereoscopic photographs t han for drawings. Individual ophthalmologist agreement rates with the expert panel's determinations of progression were 23-62% when examiner s compared their own drawings to follow-up photographs, 54-71% when ex aminers compared serial stereoscopic photographs, and 38-85% when comp aring another ophthalmologist's drawings to follow-up photographs. Con clusion: Baseline stereoscopic photographs of the optic nerve head did not substantially improve recognition of progressive glaucomatous opt ic nerve damage when compared with the use of baseline drawings of the optic nerve head made from photographs in subjects who developed visu al loss in the interim.