Abstract
Purpose: :
Controversy about the functional and morphological differences between normal (NTG) and open angle high tension glaucoma (HTG) remains despite modern technologies for examination of the optic nerve and visual field. Aim of the study was to determine differences of central corneal thickness (CCT) of patients with NTG and with HTG who were dedicated in pairs by the same structural glaucomatous damage of the optic nerve.
Methods: :
126 eyes with NTG (52 male, 74 female) were paired case-by-case to 126 eyes with HTG (63 male, 63 female) by the same optic disc area and cup/disc-ratio. The glaucomatous damage of the optic pit was verified by analysis of neuroretinal rim volume and rim area. The nerve fiber layer was measured by HRT (RNFL) and GDxVCC. A retrospective comparison of the differences of CCT was made for the pairs, respectively. CCT was measured by ultrasonic pachymetry. IOD classification enfolded NTG <21 mmHg in untreated pressure and HTG >21 mmHg. Patient of age >65 and of visual acuity <0,5 and refraction abberance >+/-5 dpt were excluded. Comparison was analyzed by Wilcoxon Test and correlation was made by Spearman Test.
Results: :
Mean CCT of NTG was 545,87 µm ± 35,42 µm and of HTG 544,13 µm ± 35,38 µm, without statistical significance p=0,716. When dividing HTG patients by IOD level, patients with IOD <25 mmHg (549,32 ± 38,93 mmHg in NTG vs. 537,59 ± 38,26 mmHg in HTG; p=0,089), IOD between 26-30 mmHg (541,96 ± 37,69 mmHg vs. 547,72 ± 32,68 mmHg; p=0,348), IOD between 30-40mmHg (542,15 ± 28,61 mmHg vs. 548,85 ± 35,06 mmHg; p=0,455) and IOD about 40 mmHg (554,55 ± 15,35 mmHg vs. 540,82 ± 39,59 mmHg; p=0,213) showed no statistical significant difference of CCT to the matched NTG eye. Furthermore HTG patients showed a positive significant correlation of CCT to rim area volume of the optic nerve head in HRT (r=0,216, p=0,015), but not in NTG patients (r=0,108, p=0,229) as well as a correlation to nerve fiber thickness in GDxVCC (HTG - r=0,365, p=0,001; NTG - r=0,025, p=0,778).
Conclusions: :
No significant difference of corneal thickness was found between NTG and HTG patients, especially at each IOD level while having the same structural glaucomatous damage in both. High tension glaucoma patients seem to have thinner corneas when having more morphological defects of the optic nerve in HRT and GDxVCC.