Reduced Central Retinal Artery Blood Flow Is Related to Impaired Central Visual Function in Retinitis Pigmentosa Patients

Purpose: We evaluated the test-retest repeatability of blood flow velocities in the retrobulbar central retinal artery (CRA) and explored whether reduced blood flow is related to the degree of visual function loss in retinitis pigmentosa (RP) patients with wide range of disease severity.Materials and Methods: We measured CRA peak systolic velocity (PSV) and end diastolic velocity (EDV) to calculate mean flow velocity (MFV) in 18 RP patients using color Doppler imaging with spectral flow Doppler (GE Logiq7 ultrasound) twice in each eye at each of two visits within a month. At each of these two visits, we measured ETDRS visual acuity (VA), quick Contrast Sensitivity Function (qCSF), Goldmann visual fields (GVF), 10-2 Humphrey visual fields (HVF), and dark-adaptation at 5 degrees from fixation with the AdaptDx; multifocal electroretinography (mfERG) was obtained at a single visit.Results: Mean coefficients of variation for PSV, EDV and MFV were 16.1-19.2% for within-visit measurements and 20.1-22.4% for between-visit measures. Across patients, greater visual function loss assessed with VA (p = 0.04), extinguished versus measurable amplitude in ring 1 for mfERG (p = 0.001), and cone-only versus rod function with the AdaptDx (p = 0.002) were statistically significantly correlated with reduced MFV in the CRA when included a multilevel multivariate regression model along with the qCSF and HVF results, which all together accounted for 47% of the total variance in MFV. GVF log retinal areas (V4e and III4e; p = 0.30 and p = 0.95, respectively) and measurable far peripheral vision during GVF testing (p = 0.66) were not significantly related to MFV.Conclusions: MFV in the CRA decreased with impaired central vision due to loss of both rod and cone function, had good test-retest repeatability, and may serve as a biomarker outcome to determine the potential physiological basis for improvements in RP clinical trials of therapies with indirect effects on blood flow to the retina.