Evaluation of lamina cribrosa tolerance to the increase of intraocular pressure in healthy people and primary open angle glaucoma patients.

Abstract

The assessment of optic nerve head (ONH) stability in measured short-term increase of intraocular pressure (IOP) in healthy group and initial primary open angle glaucoma (POAG) patients. METHODS: 147 healthy people were divided in two groups according to the age. The first one (59 people) was comprised of those who were from 16 to 35 years old. The second group included 88 healthy adults from 35 to 78. 64 patients (39 - 80 years old) with initial POAG were included in the third group. The mean cup depth (MCD) of the optic disc was determined with the Heidelberg retina tomographer (HRT II). After baseline examination a suction cup was used to increase IOP for 10 mm Hg above baseline and MCD was determined again. IOP level was controlled by Perkins’ tonometer before and during suction. RESULTS: IOP increase always resulted in MCD increase. In group 1 mean increase was 18,3±1,96 μm. In the second group the value was 22,4±2,63 μm. There was no statistically significant difference in MCD mean increase values in groups 1 and 2 (t=1,46, p>0,05). In POAG group mean MCD increase was 49,2±8,41 μm. The difference of this value was statistically significant when compared with that in group 2 (t=5,38, p<0,05). CONCLUSIONS: 1. There was no correlation between age and MCD mean increase in healthy people. 2. Results of the investigation permit us to establish criteria of normal and decreased stability of ONH to the induced elevation of IOP: we consider the MCD increase less than 25 μm as normal, 25 - 40 μm as borderline and more than 40 μm as lack of lamina cribrosa stability.