Purpose: To objectively quantify cone density (CD) and microvascular density (MVD) in normal subjects and patients with moderate or severe retinitis pigmentosa (RP) by adaptive optics (AO) and optical coherence tomography angiography (OCTA) and to evaluate the changes in the parafoveal regions.
Method: Thirty-seven eyes from 20 RP patients and 54 eyes from 29 age-matched healthy participants underwent AO fundus and OCTA imaging. AO images covering a 3-mm-diameter area centered on the fovea were subdivided into 5 equidistant concentric rings (C1-C5). An automated algorithm was used to quantify the mean cone density (mCD; cells/mm2). Macular MVDs (%) in the superficial capillary plexus (SCP) and deep capillary plexus (DCP) were assessed by OCTA.
Results: In the moderate RP group, CDs in C2 and C3 were each significantly lower than in the normal group (both P < 0.05). In the severe RP group, CDs were significantly lower than in normal eyes in each concentric ring (all P < 0.001; C1-C5). In both RP groups, MVDs were significantly lower than in normal eyes for both the SCP and DCP (both P < 0.05). The mean CD was significantly correlated with the MVD in the DCP (r = 0.43; P = 0.028) but not in the SCP (r = -0.19, P = 0.323).
Conclusions: Decreased CD was present in the moderate and severe RP groups. This was accompanied by a decreased MVD in the DCP. Direct assessment of photoreceptors in RP patients by high-resolution imaging technologies is crucial for the future development of RP therapeutics.