Purpose:
To describe a novel method of en face visualization of the photoreceptor inner segment/ outer segment junction (IS/OS) using spectral domain Cirrus optical coherence tomography (SD OCT), quantification of the central macular IS/OS area and its association with visual acuity.
Methods:
Case control study of fifty eyes of 44 patients using Cirrus SD OCT en face visualization and IS/OS-RPE slice mode. The central 1 mm and 400 um IS/OS foveal zones were analyzed with Metamorph computer software, set to the same threshold value for all images.
Results:
Twenty-five eyes (23 patients) had retinal disease (group 1) with mean logMAR visual acuity (VA) = 0.235, whereas twenty-five eyes (21 patients) served as healthy, age-matched controls with mean VA= 0.081. In group 1, mean central 1 mm and 400 um zone IS/OS areas were 59.2% (+/- 12.7%) and 56.7% (+/-14.7%), which correlated significantly greater with VA (absolute Pearson coefficient= 0.56 and 0.62) than did mean central subfoveal thickness, macular volume or average macular thickness (= 0.16, 0.22, 0.05.) In the control group, mean central 1 mm and 400 um zone IS/OS areas were 76.1% (+/- 13.9%) and 69.8% (+/-13.1%), which correlated significantly greater with VA (= 0.63 and 0.64) than did other macular thickness measurements (= 0.12, 0.06, 0.05.) There was no significant difference between the two IS/OS zone measurements in each group (p>0.05). 68% of group 1 and 52% of controls had cataracts. Figure 1 demonstrates an example of group 1 and control images, central zone measurements and corresponding VA.
Conclusions:
Central IS/OS area measurement correlates with VA in both healthy eyes and those with retinal disease. It may be a better predictor of VA than other routine SD OCT values, including central subfoveal thickness. The presence of cataract may affect this correlation, and it should be used with caution in patients with significant media opacity. Advancements in SD OCT software may allow for routine en face IS/OS visualization and analysis.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • photoreceptors: visual performance • image processing