High Tension Versus Normal Tension Glaucoma. A Comparison of Structural and Functional Examinations

Purpose: The aim of the study was to compare the results of structural and functional examinations in a group of high tension glaucomas of different aetiologies and normal tension glaucoma. Methods and patients: The authors examined 80 eyes in 40 patients; out of this number 30 patients had high tension glaucoma of three types: ten of the patients had primary open angle glaucoma (POAG), ten of them had pigmentary glaucoma (PG) while ten of the monitored patients had pseudoexfoliative glaucoma (PEXG). Ten patients had normal tension glaucoma (NTG). Results of the examinations of the visual field, GDx, macular volume, PERG and PVEP were compared with the results of the same examinations in the control group consisting of 40 eyes in 20 healthy subjects of comparable age and refraction. Results: The results were processed using the Kruskal-Wallis test, Changes in the visual field were statistically significant in all the clinical groups compared to the control group (p ). Similarly, statistically significant changes were found in the nerve fibre layer (p ) and in the macular volume (p ). While PERG P50-N95 amplitude in the high tension glaucoma was significantly lower ( ), no statistically significant difference was observed in the normal tension glaucoma (p=0.463). PERG N95 latencies were statistically significantly prolonged in POAG and PG (p=0.000025 and 0.000128, respectively); no difference was observed in PEXG (p=1.0), while NTG had the statistically highest difference (p=0.000). The amplitudes N70-P100 and P100-N140 were pathological in all of the glaucoma types; when comparing individual groups, the greatest difference was observed for PG (p=0.000) and NTG (p=0.000). Conclusion: Using the examination technique of PERG and PVEP, the authors found that in high tension glaucomas of varied etiology (POAG, PG, PEXG), the damage occurs in the whole optic pathway (from the retinal ganglion cells up to the centers of vision in the brain). Patients with PG had the highest degree of damage of the optic pathway. In the normal tension glaucoma, however, the ganglion cell layer was relatively normal but significant pathological changes were found in the optic pathway.

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