REPEATABILITY AND REPRODUCIBILITY OF OPTIC DISC MEASUREMENT WITH THE ZEISS 4-MIRROR CONTACT-LENS

Background: A simple clinical quantitative method of optic disc diamet er measurement using a 4-mirror gonioscope contact lens has been descr ibed recently. Methods: Intraobserver and interobserver variations are assessed on 77 eyes of 41 patients. Of these eyes, 63 had refractive errors within 3 diopters of emmetropia. The disc was measured by proje cting a slit beam of known height onto the disc. Results: Intraobserve r variation: the coefficient of variation was 3.04% for observer 1 (ex perienced) and 4.76% for observer 2 (novice) The mean of the three mea surements by the two observers was not significantly different (P = 0. 2318). For observer 1, the mean variance of the eyes with higher refra ctive errors did not differ significantly from the eyes with lower ref ractive errors. Interobserver variation: the coefficient of variation was 4.52%. The measurements for the novice were slightly larger for th e smallest discs and slightly smaller for the largest discs (regressio n analysis P = 0.0209). Conclusion: Repeatability and reproducibility for this method are comparable with other methods of measurement. Unti l experienced with the technique, the authors recommend that the mean of three readings is used.