[Optic disc measurements with computerized image analysis in experimental chronic glaucoma].

ABSTRACT

We quantitatively analyzed morphological changes of the optic disc of ten Japanese monkey eyes exposed to sustained intraocular pressure (IOP) elevation by repeated argon laser application to the trabecular meshwork. Using a computerized image analyzer (Topcon IMAGEnet), we measure the cup-disc ratio (CDR), disc area (DA), cup volume/disc area (CV/DA), and rim area/disc area (RA/DA). The duration of IOP elevation was 48.4 +/- 0.8 (mean +/- SD) weeks, and the mean IOP during the experiment was 26.3 +/- 2.6 mmHg [the mean IOP during the experiment/pre-treatment IOP was 2.05 +/- 0.55 (IOP ratio)]. In advanced glaucomatous eyes (the duration of IOP elevation of approximately one year), comparing pretreatment, the CV/DA increased 4.96 times, the vertical CDR increased 1.78 times, the horizontal CDR increased 1.69 times, the DA increased 1.42 times, and the RA/DA decreased 0.54 times. A significant positive correlation was found between the IOP ratio and, both the vertical CDR (gamma = 0.65) and the CV/DA (gamma = 0.68). These results suggested that the development of glaucomatous optic disc cupping correlated with the degree of IOP elevation in monkey eyes. Using this computer image analyser, the longitudinal quantitative follow-up of disc changes of experimental glaucoma may be useful for understanding the mode of human glaucomatous optic nerve damage.