Primary objective-to investigate the effect of retinal vessel oxygen saturation (SO ₂ ) on macular oedema (ME) in retinitis pigmentosa (RP) patients. Secondary objective-to link the presence of ME to metabolic (oxygen saturation of retinal vessels, SO ₂ ), functional (multifocal electroretinography, mfERG) and structural (Spectral Domain Optical Coherent Tomography, SD-OCT) alterations in RP.
Prospective, cross-sectional, non-interventional study.
Patients with typical RP (N = 37) and controls (N = 19), who underwent retinal vessel Oximetry (RO), SD-OCT and mfERG, were included.
A computer-based program of the retinal vessel analyser unit (IMEDOS Systems UG, Jena, Germany) was used to measure SO ₂ . We evaluated the mean SO ₂ , in all major retinal arterioles (oxygen saturation in retinal arterioles, A-SO ₂ , %) and venules (oxygen saturation in retinal venules, V-SO ₂ , %). MfERG responses were averaged in zones (zone 1 (0-3°), zone 2 (3-8°) and zone 3 (8-15°)) and compared to corresponding areas of the OCT. The effect of ME on SO ₂ was evaluated dividing the RP in two subgroups: with clinical appearance of ME (ME-RP) and without it (no-ME-RP).
Parallel recording and juxtaposition of metabolic (SO ₂ ) to structural (OCT) and functional-(mfERG) measures. Mean ( ± SD) A-SO ₂ and V-SO ₂ were higher in no-ME-RP (96.77% (±6.31) and 59.93% (±7.76)) and even higher in the ME-RP (99.82% (±6.21) and 65.63% (±7.63)), compared to controls (93.15% (±3.76) and 53.77% (±3.70), p ≤ 0.006).
The subgroup ME-RP differed significantly from the subgroup no-ME-RP by increased A-SO ₂ and V-SO ₂ , p ≤ 0.026. The presence of ME confirmed a different relationship between the altered SO ₂ and the vessel diameters, against the functional and structural parameters.
Based on our results, the presence of macular oedema indicates a tendency toward greater alteration of the metabolic function in RP patients.