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Yi Fang Lee, Charles Ong, Zhu Li Yap, Clarissa Cheng, Aditi Mohla, Monisha Esther Nongpiur, Shamira Perera; Comparison of retinal oxygenation and vasculature, retinal nerve fiber layer and visual field defects in different subtypes of glaucoma. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2926.
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© ARVO (1962-2015); The Authors (2016-present)
To explore how retinal oxygen saturation and vessel caliber vary in different subtypes of glaucoma, and their correlation with varying severities of visual field defects and retinal nerve fiber layer(RNFL) loss.
Patients with primary open angle(POAG), primary closed angle(PACG), normal tension glaucoma(NTG) and normal controls were recruited at the Singapore National Eye Centre for this prospective cross sectional study. Retinal oxygen saturations and vessel calibers of all patients were measured using a spectrophotometric retinal oximeter(Oxymap ehf, Reykjavik, Iceland). Cirrus optical coherence tomography(Carl Zeiss Meditec, Dublin, CA) and Humphrey visual field testing(Carl Zeiss Meditec, Dublin, CA) were also performed. An AGIS score was derived from the visual fields. An analysis of variance(ANOVA) with Bonferroni method was used for comparisons among different subtypes of glaucoma and a paired t-test was used to compare the inter-eye differences.
Forty normal controls and one hundred and twenty six patients with glaucoma (PACG N=40; POAG N=44; NTG N=42) were included. All three subtypes of glaucoma showed a significant difference in the RNFL thickness and the corresponding visual field defects between the better and worse eyes (p<0.001). The RNFL was also thinner in the worse eyes compared to better eyes in all three groups: POAG Better eye 75.1±13.0μm, Worse eye 60.9±8.5μm(p<0.001); PACG Better eye 85.0±5.8μm, Worse eye 62.5±10.2μm(p<0.001); NTG Better eye 85.4±13.8μm, Worse eye 73.3±9.3μm(p<0.001). Venular diameter of glaucomatous eyes was thinner than non-glaucomatous eyes (Normals 170.8±15.3μm, PACG 152.6±19.2μm, POAG 153.6±22.5μm, NTG 156.5±15.3μm;p<0.001). The arteriolar diameter and arterio-venous difference in oxygen saturations were narrower in the worse eyes of the PACG group: Better eye 120.1±18.4μm, Worse eye 108.7±18.4μm;(p=0.002) and Better eye 44.1±12.2 % and 51.9±19.2,(p=0.028). However, the retinal vessel diameters and oxygen saturations between better and worse eyes of the POAG and NTG groups were similar.
Retinal venules in glaucomatous eyes were constricted compared to normals. PACG eyes exhibited narrowing of their arteriolar diameters and in arterio-venous oxygenation difference. However, there was no difference in the inter eye retinal oxygenation and vessel caliber in the other glaucoma subtypes.
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