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Ou Tan, Liang Liu, John C Morrison, David Huang; Glaucoma increases retinal surface contour variability as measured by optical coherence tomography. Invest. Ophthalmol. Vis. Sci. 2016;57(12):382.
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© ARVO (1962-2015); The Authors (2016-present)
Focal nerve fiber bundle loss and accentuated vessel relief may increase the irregularity of the surface contour of the inner retina (Figure 1). This study was designed to investigate the feasibility of glaucoma detection by measuring retinal surface contour variability (RSCV) using optical coherence tomography (OCT).
The peripapillary region in one eye of each participant was scanned over an 8x8mm area with a swept source OCT prototype. The retinal surface contour was sampled at 1.5~3.5mm radius circles centered on the optic nerve head (ONH). An automated algorithm was developed to measure RSCV by spatial frequency analysis. Nerve fiber layer (NFL) thickness was sampled around a 1.7mm radius circle. Glaucoma severity was assessed by automated static perimetry.
There were 17 participants in the glaucoma group and 17 age-matched healthy controls. A majority of the glaucoma group had early stage damage (visual field MD average - 2.48 ± 3.73 dB). Significant differences were found for RSCV between glaucoma eyes and control eyes (p<0.001) at all radii. The area-under-the-receiver-operating-characteristic-curve (AROC=0.90) of RSCV was best at 3.5mm radius. The RSCV averaged over circles with radii from 2.5-3.5mm gave the best diagnostic accuracy (AROC=0.91). This was not significantly better than NFL thickness (AROC=0.84). At a cutoff of 99 percentile point of normal distribution (2.33 standard deviation above the normal reference mean), the glaucoma detection sensitivity was 53% for RSCV and 29% for NFL thickness. The difference was not significant (p=0.13). The RSCV was significantly correlated with NFL (r=-0.61, p=0.02) but not MD (R=-0.32, p=0.21) in glaucomatous eyes.
Retinal surface contour variability was significantly increased in glaucoma patients. The diagnostic accuracy of RSCV was at least equal to NFL thickness in early glaucoma. Since the RSCV detects small-scale focal damage and the average NFL thickness measures global damage, they provide different diagnostic information that may be synergistic. A larger study is needed to validate the utility of RSCV in glaucoma detection.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Figure 1. Superior quadrants of cylindrical OCT cross section of peripapillary retina at 3mm radius. In glaucoma eye (B), the inner retinal boundary had larger variability than normal eye (A) due to vessel relief and nerve fiber bundle dropout.
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