The impact of macular oedema on microvascular and metabolic alterations in retinitis pigmentosa

Purpose The primary aim of our study was to evaluate retinal microvascular anomalies recorded with optical coherence tomography angiography (OCTA) and the retinal metabolic function measured with retinal oximetry (RO) in patients with retinitis pigmentosa (RP). The secondary aim of the study was to link the presence of macular oedema to evaluated microvascular and metabolic parameters in RP. Methods OCTA and RO were performed on 94 eyes: 64 eyes diagnosed with RP with (ME‐RP) and without (no‐ME‐RP) macular oedema were compared to 30 control eyes. Study endpoints were: mean superficial (FAZ‐S) and deep foveal avascular zone (FAZ‐D) determined by OCTA. In addition, we evaluated the mean arterial (A‐SO 2 ; %), venular (V‐SO 2 ; %) oxygen saturation, their difference (A‐V SO 2 ; %), as well as the corresponding mean diameter of the retinal arterioles (D‐A; μm) and venules (D‐V; μm). Results RP patients differed from controls by enlarged FAZ‐S and FAZ‐D (p ≥ 0.001), attenuated retinal vessels (p < 0.001) and increased retinal vessel oxygen saturation (p ≥ 0.010). Subgroup analyses within RP patients revealed more pronounced alterations of microvascular parameters and metabolic function in the presence of macular oedema. In the no‐ME‐RP subgroup, significant interactions were present between FAZ‐S, A‐SO 2 and V‐SO 2 , whereas in the ME‐RP subgroup, we found significant correlations between FAZ‐D and D‐A. Conclusion A combined microvascular structure‐metabolic function approach enhances our understanding of inherited retinal diseases. The presence of macular oedema in retinitis pigmentosa seems to be a result of more altered microvascular‐metabolic function. However, its presence should be taken into consideration, as it may also influence the interpretation of the results.