Relations among foveal blood flow, retinal-choroidal structure, and visual function in retinitis pigmentosa

PURPOSE. To investigate the relationships between foveal blood flow as measured by laser speckle flowgraphy (LSFG), the retinal-choroidal structure in enhanced depth imaging– optical coherence tomography (EDI-OCT), and central visual function in patients with retinitis pigmentosa (RP). METHODS. We studied 52 consecutive typical RP patients ≤50 years old and 21 age- and sex-matched controls. The mean blur rate (MBR), which represents the blood flow volume, was calculated in a 2.4-mm² area centered on the fovea by LSFG. Subfoveal horizontal EDI-OCT images were recorded, and the choroidal area, choroidal hyporeflective area, and choroidal hyperreflective area were analyzed in the central 2.4-mm-wide region. The central foveal thickness (CFT), subfoveal choroidal thickness (SCT), and ellipsoid zone (EZ) width were also measured. Visual acuity (VA) and retinal sensitivity (Humphrey 10-2 program) were measured in the RP patients. RESULTS. The MBR, choroidal area, hyporeflective area, hyperreflective area, and SCT were significantly decreased in the RP patients (all P < 0.001, versus controls). Spearman’s rank testing demonstrated no significant correlation between the MBR and the choroidal structural parameters in the RP patients. Decreased MBR was significantly associated with reductions in VA, retinal sensitivity, CFT, and EZ width (all P < 0.05). The choroidal structural parameters did not correlate with central visual function, and the choroidal area, hyperreflective area, and SCT were inversely associated with CFT (all P < 0.05). CONCLUSIONS. These results demonstrated the divergence between the choroidal structure and blood function, and suggest that decreased choroidal flow, rather than the structural alteration, is closely associated with foveal degeneration in RP.