Structural and haemodynamic differences between emmetropic and highly myopic eyes:An exploratory study aiming to identify possible haemodynamic risk factors for glaucoma susceptibility in high myopes

Abstract

It is well recognized that myopic eyes are more prone to develop glaucoma later on in life. The exact processes leading to the onset and progression of glaucoma however, is still not fully understood. Characteristic in glaucoma is the loss of neuroretinal tissue (ganglion cells and their axons). It is hypothesised that glaucoma develops due to an imbalance between intraocular pressure and impaired blood flow in the eye (vascular theory). This cross-sectional, explorative study carried out a wide range of retinal blood circulation measurements (vessel calibres, vessel network complexity as well as vessel function and oxygen content in retinal vessels) and related these with neuroretinal tissue thickness measurements in emmetropic and highly myopic eyes. A glaucoma sample was qualitatively compared with the healthy groups. The main objective was to determine haemodynamic parameters which may explain glaucoma susceptibility in myopic eyes. Emmetropic eyes were not significantly different from highly myopic eyes regarding visual field indices, retinal nerve fibre layer thicknesses, retinal vessel complexity, vessel function and the retinal vessel oxygen content. Vessel calibres were significantly narrower in highly myopic eyes as well as the relationship between systolic and diastolic perfusion pressure. As expected, the glaucoma sample exhibited thinner neuroretinal tissue, narrower vessel calibres, a sparser retinal vessel network and a increased oxygen content in veins. Multiple correlation analysis between structural and haemodynamic parameters could not identify haemodynamic predictors for neuroretinal tissue loss in high myopes and glaucoma subjects. The results of this study suggest that the impact of retinal haemodynamic parameters (CRAE and deficiency in perfusion) may partly contribute to the increased glaucoma risk in myopia.