THE RELATIONSHIP BETWEEN DETERIORATION AND REVERSAL OF OPTIC DISC CUPPING IN MONKEYS WITH CHRONIC EXPERIMENTAL HIGH-PRESSURE GLAUCOMA

Purpose: To investigate the correlation between the deterioration in o ptic disc cupping during the chronic elevation of intraocular pressure (IOP) and the reversal of cupping during a subsequent reduction in IO P in experimental glaucoma. Methods: We examined changes in the vertic al and horizontal cup to disc ratios, the rim area to disc area ratio, and the cup volume to disc area ratio in 11 monkey eyes with laser-in duced glaucoma using computerized stereo-image analysis. Correlations between changes in disc parameters during a spontaneous IOP reduction and changes in disc parameters during a period of chronic IOP elevatio n from baseline before laser exposure (baseline) to before the IOP red uction (pre-IOP reduction) and during the period from baseline to afte r the reduction in IOP (post-IOP reduction) were determined by linear regression analysis. Results: All disc parameters improved significant ly during IOP reduction and deteriorated significantly during the peri ods from baseline to the pre-IOP reduction and from baseline to the po st-IOP reduction. The degree of reversal in disc parameters was correl ated with the deterioration from baseline to the pre-IOP reduction and from baseline to the post-IOP reduction in the vertical cup to disc r atio (r=0.68, P=0.0218 and r=0.97, P<0.0001, respectively), the horizo ntal cup to disc ratio (r=0.57, P=0.0649 and r=0.98, P<0.0001, respect ively), the rim area to disc area ratio (r=0.68, P=0.0227 and r=0.98, P<0.0001, respectively), and the cup volume to disc area ratio (r=0.67 , P=0.0256 and r=0.88, P=0.0004, respectively). Conclusion. The degree of deterioration in cupping from baseline before the induction of gla ucoma may be an important determinant of the degree of cupping reversa l during subsequent reductions in IOP in primate glaucoma.