Reduced metabolic function and structural alterations in inherited retinal dystrophies: investigating the effect of peripapillary vessel oxygen saturation and vascular diameter on the retinal nerve fibre layer thickness

Abstract

Purpose: To evaluate the relationship between the peripapillary metabolic alterations [retinal vessel Oximetry (RO)] and the structural findings [retinal vessel diameter and retinal nerve fibre layer thickness (RNFL)] in patients with inherited retinal dystrophies (IRD).

Methods: Patients with IRD [24 patients with rod-cone dystrophy (RCD), 15 patients with cone-rod dystrophy, 13 patients with inherited maculopathy] and 18 age-matched controls, who underwent RO imaging and spectral domain optical coherence tomography, were included. The average and quadrant oxygen saturation in all four major peripapillary retinal arterioles (A-SO₂ ) and venules (V-SO₂ ) were measured, and their difference (A-V SO₂ ) was calculated. The corresponding retinal vessel diameter of these arterioles (D-A) and venules (D-V) was measured. The data were compared to the peripapillary RNFL thickness within the IRD subgroups and to the data obtained in the controls.

Results: In general, patients with IRD had higher average V-SO₂ values when compared to controls (p ≤ 0.029). Rod-cone dystrophy (RCD) patients differed from controls, but also from patients with other IRDs, when the average and quadrant oxygen saturation values (A-SO₂ and V-SO₂ ) were evaluated (p ≤ 0.026). Within the RCD group, the correlations of RNFL thickness to V-SO₂ , A-V SO₂ , D-A and D-V were significant (p ≤ 0.030), thus indicating a different relationship between the RNFL thickness and the examined parameters, when compared to the other groups.

Conclusion: It becomes evident from our combined metabolic-structural approach that a prediction model, to identify which individual is at risk of developing a photoreceptor degeneration of RCD type, can be proposed. It will take into account the peripapillary retinal oxygen saturation, the retinal vessel diameter and the RNFL thickness values.

Keywords: cone-rod dystrophy; inherited maculopathy; inherited retinal dystrophy; peripapillary retinal vessel diameter; retinal nerve fibre layer thickness; retinal vessel oxygen saturation; rod-cone dystrophy.