Relationship Between Iop and Nerve Fiber Layer Loss in Primary Open-Angle Glaucoma

Abstract

Purpose: : To define the relationship of IOP and the retinal nerve fiber layer loss and to determine the effect of IOP on structural damage in primary open-angle glaucoma.

Methods: : 167 normal subjects, including 26 patients with IOP>21 mmHg and 205 glaucoma patients were classified in low-teens (IOP<16 mmHg), high-teens (16 mmHg ≤IOP ≤21 mmHg) and high-tension (IOP>21 mmHg) groups. Diurnal peak IOP readings, CCT measurements, VF testing with Humphrey SAP and RNFL thickness assessment by means of Stratus OCT was performed in normals and glaucoma subjects. Means comparison was evaluated by one-way ANOVA, Pearson correlation coefficient was defined between IOP, CCT adjusted IOP and average (AVG) RNFL thickness and regression analyses was computed to determine the effect of IOP on RNFL loss in each group.

Results: : Significant correlation was found between IOP and RNFL thickness in high-tension glaucoma group (r=-0.47), while the effect of IOP on structural damage (R²=0.2213) was rather low. The CCT adjusted IOP did not influence our results. In all other groups no correlation could be detected.

Conclusions: : The role of IOP remains still unclear in low-tension glaucoma development. We could highlight a good correlation, but a rather low effect size of the IOP on the RNFL loss in high-tension glaucoma.Our goal remains to seek for pathogenic factors other than IOP and incorporate them into daily glaucoma management.

Keywords: intraocular pressure • nerve fiber layer • visual fields