Purpose:
The boundary of visual field (VF) loss was compared to the locus of outer segment (OS) loss seen with frequency domain optical coherence tomography (fdOCT) in patients with retinitis pigmentosa (RP).
Methods:
10-2 VFs (Zeiss, Inc.) and 3D macular cube scans were obtained for 6 RP patients (47.8±11.1 yr) and 20 controls (51.4±9.4 yr) using fdOCT (Topcon, Inc.). 5 patients were tested again, on average 20.6 mos later. Repeat scans were obtained at each session. Scans were manually segmented [1] from the fovea (0°) to ±3mm (±10.4°) to determine OS thickness [region between the inner segment/OS boundary (IS/OS) and the retinal pigment epithelium (RPE)]. OS thickness versus retinal location plots provided an objective measure of IS/OS border loss, i.e. where OS thickness asymptotes at zero.[2] OS thickness was measured for the scan centered on the fovea and for 10 other scans (±1°,±3°,±5°,±7°, and ±9°) corresponding to the locations of the 10-2 VF test points. All patients had reliable 10-2 VFs with center sensitivities of 31 to -39dB.
Results:
The fig. shows VF loss (db) for one patient along with IS/OS loss contours for the 2, same-day scans. The contour of IS/OS agreed well with the VF points corresponding to a VF loss of about -9dB, consistent with [3]. Assuming VF test variability is ±4dB, the IS/OS contour lines predicted a -9dB contour of sensitivity loss in 404 of 408 test points. Median sensitivity for points adjacent to the inside of the IS/OS contour was -4dB compared to -12dB just outside. The average mean difference between IS/OS contour on scans repeated on the same day was 0.01±0.09mm (figure). For the 5 patients returning for follow-up, the IS/OS contour moved closer to the fovea on average by 0.13±0.11mm and the VF mean deviation decreased on average by -1.51±2.26dB.
Conclusions:
The IS/OS contour shows promise as a measure of progression. It exhibited good agreement with the contour associated with a sharp drop in VF sensitivity, as well as good within day repeatability. 1. Hood et al IOVS, 2009; 2. Hood et al, IOVS, 2010; 3. Rangaswamy et al, IOVS, 2010.
Keywords: photoreceptors: visual performance • retina: distal (photoreceptors, horizontal cells, bipolar cells) • visual fields