Abstract
Purpose: :
To explore the potential of quantitative OCT (qOCT) analysis as a tool to correlate structural changes and visual field defects in patients with retinitis pigmentosa (RP).
Methods: :
Prospective study in 18 patients with RP and 18 healthy controls. Diagnosis of RP was established by clinical examination, ERG (ISCEV protocol), Goldmann visual field (VF) and dark–adaptometry. Twelve OCT images of 3mm length emanating from the foveola in a centrifugal fashion were acquired using Zeiss Stratus OCT 3. Images were analyzed by calculating longitudinal reflectivity profiles (LRP) every 43.5 µm resulting in 60 LRP per image. Control subjects were used to establish standard LRP. Standard LRP contain 6 (four in foveola) peaks (P1–P6). Outermost peaks presumably represent retinal pigment epithelium (P1) and a highly reflective layer delimiting inner and outer rod segments (P2). LRP were analyzed quantitatively for distances between P1 and P2 and their respective reflection intensities. RP patients were subdivided based on remaining VF size (target I4e): group A (<10°) and group B (>10°). LRP of both groups (A & B) were compared against control LRP. We defined statistical significance as p<0.01.
Results: :
Significant concentric constriction of VF size in the RP patients vs. controls was found. Difference between A&B and controls remained significant when comparing their respective P2 detectability: In controls, P2 was detectable in all LRP along the full length of scans. Group A (mean VF 6.97±3.55°) showed no P2 after 0.30±0.2mm centrifugal of the foveola, whereas in B (mean VF 25.20±6.68°) P2 could be detected up to 1.57±0.4mm distal of foveola. Analysis of complete dataset showed highly significant correlation between detectability of P2 and VF size (Pearson's correlation coefficient, r=0.69).
Conclusions: :
QOCT analysis in RP patients showed significant correlation between extent of VF and detectability of P2 in OCT scans. We hypothesize that the retinal structure originating P2 is of critical importance for retinal function. Lack of P2 appears to be a helpful marker to estimate VF defects in diseases affecting photoreceptors.
Keywords: retinal degenerations: hereditary • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina: distal (photoreceptors, horizontal cells, bipolar cells)