Purpose: Current evidence indicates that alteration in ocular blood flow may be relevant in open-angle glaucoma (OAG) patients independent of intraocular pressure (IOP). Presently, the lack of an adequate methodology capable of assessing all vascular beds limits the clinical role of blood flow parameters in glaucoma management. We aimed to compare differences in retinal nerve fibre layer (RNFL) thickness and retrobulbar haemodynamics between OAG patients and healthy age-matched control subjects.
Methods: Sixty eyes of 30 OAG patients and 30 healthy age-matched controls were enrolled into the prospective, randomized study. Retinal nerve fibre layer thickness was analysed by scanning laser polarimetry (SLP). Standard SLP parameters were determined, including: average temporal, superior, nasal, inferior thickness (TSNIT); superior and inferior averages; TSNIT standard deviation (TSNIT-SD), and nerve fibre indicator (NFI). Retrobulbar haemodynamics were assessed using colour Doppler imaging (CDI). Peak systolic velocity (PSV), end-diastolic velocity (EDV), pulsatility index (PI) and resistivity index (RI) in the ophthalmic artery (OA), central retinal artery (CRA) and short posterior ciliary artery (SPCA) were evaluated.
Results: The RNFL in OAG patients was statistically significantly thinner compared with that in age-matched controls: the NFI was 24.9 +/- 10.24 in OAG patients and 16.13 +/- 7.95 in healthy controls (p < 0.05). Statistically significant differences were observed: CRA PSV was 20.54 +/- 7.84 cm/second in OAG subjects and 16.5 +/- 6.19 cm/second in healthy controls (p = 0.0038); OA EDV was 8.99 +/- 4.71 cm/second in OAG subjects and 5.93 +/- 3.23 cm/second in healthy controls (p = 0.0048). Correlation analysis of NFI was in positive association with CRA EDV (r = 0.395; p < 0.05) and CRA PI (r = 0.403; p < 0.05) in OAG subjects, but no statistically significant association was seen in healthy controls.
Conclusions: Statistically significant thinning of the RNFL in association with reduced retrobulbar blood flow velocities was observed in OAG patients. Combining ocular structural alterations with ocular circulation assessment may increase our ability to elucidate potential IOP-independent glaucomatous risk factors.