Retinal mean transit time in patients with primary open-angle glaucoma and normal-tension glaucoma

Purpose: To compare the mean transit time (MTT) of retinal circulation in eyes with primary open-angle glaucoma (POAG) and eyes with normal-tension glaucoma (NTG) and examine the possible relationship between MTT and visual field damage, expressed as mean deviation (MD). Methods: Video fluorescein angiography was performed in 40 patients with POAG or NTG. Dye curves for fluorescein passing through the retinal arteries and veins were used to calculate MTT in each patient with a computer-assisted technique based on an impulse-response analysis (MTTir). Results: We were able to analyse MTTir in all 40 angiograms. Mean (SD) MTTir was 5.0 (1.5) seconds in eyes with POAG and 4.7 (1.4) seconds in eyes with NTG. The difference was not statistically significant. There was a weak but significant correlation between the MD and MTTir (MTTir = 4.12-0.08*MD; r = -0.49, p = 0.0013). Conclusions: The results demonstrate that loss of neuronal tissue in glaucoma is combined with an effect on the retinal circulation and that the effect is similar in eyes with NTG and eyes with POAG.