Optic disc measurements with the 78 diopter lens, Zeiss 4-mirror contact lens and computerized image analysing system

We evaluated the 78 diopter (D) lens and Zeiss 4-mirror lens for the measur ement of vertical and horizontal optic disc diameters during slit-lamp biom icroscopy and compared the results with the measurements made with the comp uterized image analysing system (IMAGEnet 640, Topcon, Japan) in 30 eyes of 30 patients. The 78D lens and Zeiss 4-mirror lens measurements both correl ated well with the computerized image analysis measurements (r=0.881 for ve rtical and r=0.895 for horizontal disc diameter measurements with the 78D l ens and r=0.883 for vertical and r=0.891 for horizontal disc diameter measu rements with the Zeiss 4-mirror lens). The 780 lens measurements overestima ted vertical disc diameter by 5.3% and horizontal disc diameter by 4.4%. Th e Zeiss 4-mirror lens underestimated the vertical disc diameter by 2.4% and horizontal disc diameter by 2.2%. Thus either lens can be used for a quick estimation of the optic disc size, since the results correlate well with t he computerized image analysis measurements.