Functional Spectral OCT/SLO Mapping: A Pilot Study

Abstract

Purpose:: To evaluate the ability of a prototype spectral OCT/SLO system (OTI, Toronto, Canada) equipped with real-time tracking to integrate OCT topographic mapping with SLO microperimetry.

Methods:: Retrospective analysis was performed on imaging studies using the OCT topographic mapping and SLO microperimetry functions of the OTI spectral OCT/SLO from forty patients with a variety of macular diseases. Spectral OCT/SLO studies consisted of combined cross-section OCT and confocal SLO anatomic imaging of a 29 degree field of the posterior pole. Retinal Topographic mapping was performed at high speed (32 frames per second) to minimize movement artifacts. 3-dimensional volumetric analysis produced high resolution thickness maps linked to SLO fundus features with one-to-one correlation. SLO microperimetry was performed with a variety of stimulus patterns presented through a high-resolution fixation display integrated with high-speed tracking to a live SLO image. Threshold sensitivities were determined over focal macular lesions and areas of normal retina. Semi-automated alignment software overlayed the studies to allow point-to-point comparisons. Serial studies performed in 10 patients were evaluated to compare changes in anatomic features versus corresponding threshold sensitivities over time.

Results:: Comparison of OCT retinal thickness maps and overlayed corresponding SLO microperimetric fields demonstrated variable correlation between anatomic changes and functional visual responses. In several instances, retinal elevation without thickening produced significant changes in threshold sensitivity. In other cases, sensitivity was maintained despite elevation. Retinal elevation due to macular edema appeared to decrease sensitivity most consistently. Visual acuities were frequently inconsistent with surrounding threshold sensitivities.

Conclusions:: Functional Spectral OCT/SLO Mapping using corresponding OCT topography and SLO microperimetry provides a more comprehensive analysis of macular status than is achievable by either modality separately. While thickness changes and threshold sensitivities demonstrated correlation in many cases, the variability observed suggests that more complex physiologic factors are at play. Further study will be required to determine if the unique facility of this system will be helpful in evaluating therapeutic endpoints in chronic treatment regimens.

Keywords: retina • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • perimetry