EFFECT OF REPETITIVE IMAGING ON TOPOGRAPHIC MEASUREMENTS OF THE OPTIC-NERVE HEAD

Objective.-A confocal scanning diode laser ophthalmoscope was used to determine the number of examinations needed to obtain highly reproducible topographic measurements of the optic nerve head and peripapillary retina. Design.-Topographic images of the optic nerve head and peripapillary retina were obtained in one randomly selected eye on five separate visits. On each occasion the selected eye had five examinations. For each examination, one image was acquired (a total of 25 images per eye). Reproducibility was calculated as the average SD of all image elements (65 536 pixels). Setting.-Glaucoma referral center. Subjects.-Five normal subjects and five patients with glaucoma. Intervention.-Topographic imaging of the optic nerve head and peripapillary retina. Main Outcome Measure.-Number of examinations needed to obtain highly reproducible topographic measurements. Results.-In healthy subjects, reproducibility with one examination per visit was 35.5 mum; this improved to 25.7 mum with three examinations and 22.5 mum with five examinations. In older patients with glaucoma, the reproducibility improved from 40.2 mum with one examination per visit to 28.5 and 24.1 mum with three and five examinations, respectively. Conclusion.-We recommend a series of three examinations to provide high reproducibility with optimal efficiency in terms of time and materials used.