OPTIC DISC HEIGHT MEASUREMENT WITH THE ZEISS 4-MIRROR CONTACT-LENS AND 78 DIOPTER LENS COMPARED

Measurements of optic disc diameter with the Zeiss 4-mirror contact le ns and 78 dioptre (D) lens, made by projecting a slit-beam of known he ight onto the image of the disc, were compared with planimetric measur ements in 30 eyes. The 78 D lens measurements were significantly large r than both the Zeiss lens and planimetric measurements (p<0.0001 and p = 0.0047 respectively). The measurements using the Zeiss lens and pl animetry did not differ significantly. Compared with planimetry, for t he 24 eyes within 3 D of emmetropia, the correlation was greater for t he Zeiss (r = 0.8591) than for the 78 D lens (r = 0.7148), The Zeiss l ens also showed better agreement and less scatter of results compared with the 78 D lens (standard error of the mean +/- 0.0373 mm for the Z eiss and +/- 0.0418 mm for the 78 D lens). The Zeiss contact lens meas urements of optic disc diameter show stronger correlation and better a greement,vith planimetry than measurements using a 78 D lens.