Capillary density and retinal diameter measurements and their impact on altered retinal circulation in glaucoma: a digital fluorescein angiographic study

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Abstract
Aim: Normal pressure glaucoma (NPG) patients exhibit prolonged retinal arteriovenous passage times in fluorescein angiography and colour Doppler imaging suggests increased resistance downstream from the central retinal and posterior ciliary arteries. The aim of the study was to elucidate the morphological source of decreased perfusion and increased resistance of the ocular circulation in NPG. Methods: Retinal arteriovenous passage time (AVP) and peripapillary arterial and venous diameters were measured in digital scanning laser fluorescein angiograms. For estimation of retinal capillary density the area of the foveal avascular zone (FAZ) and the perifoveal intercapillary area (PIA) was quantified. 36 patients with NPG (mean age 57 (SD 13) years) and 21 healthy subjects (mean age 51 (13) years) were enrolled in the comparative study. Results: In NPG patients the AVP (2.55 (1.1) seconds) was significantly prolonged (pr=0.35 (pr=−0.28), visual field indices (MD: r=−0.3; PSD: r=0.3; CPSD: r=0.3), and contrast sensitivity (r=−0.34}. Conclusion: AVP times are significantly prolonged in NPG. The slowing of the retinal transit does not result from capillary dropout, or changes of peripapillary arterial or venous diameters with increased vascular resistance.