Specificity of the Heidelberg Retina Tomograph’s Diagnostic Algorithms in a Normal Elderly Population: The Bridlington Eye Assessment Project

Purpose To determine the specificity of the Moorfields regression analysis (MRA) and R. Burk (RB) and F. S. Mikelberg (FSM) linear discriminant functions (LDFs) in classifying the optic discs of normal elderly patients imaged with the Heidelberg Retina Tomograph. Design Cross-sectional study. Participants Optic nerve head analysis of 459 eyes of 459 normal elderly patients was performed by 2 operators. All patients were consecutive in a cohort screened for eye disease. Normals were defined as having a normal visual field (VF) on automated suprathreshold screening, normal intraocular pressure, and normal visual acuity. Main Outcome Measures Specificity of the optic nerve head classification by MRA and the RB and FSM LDFs. Results Subjects' mean age (262 female, 197 male) was 72.6 years. Males were found to have significantly larger cups than females. Eighty-three percent, 11.3%, and 5.7% of discs were classed as within normal limits, borderline, and outside normal limits by MRA. Percentages of optic discs classified as outside normal limits in the smallest and largest quartiles for disc size were 0.9% and 14.9%. The association of disc size with the classification of outside normal limits was significant in males only. Agreement in MRA classification between 2 investigators separately placing the optic disc contour was moderate (Cohen's κ = 0.54, P Conclusions Using the MRA and RB/FSM LDFs, specificity fell dramatically with increasing disc size, particularly in males. This may reflect the finding of significantly larger cups in males than in females in the normal elderly population. This divergence was not predicted by these diagnostic functions, which were developed on samples of younger subjects.