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Bright Senyo Ashimatey, William H Swanson, Brett King; Customized imaging and analysis protocols for detecting glaucomatous retinal nerve fiber bundle (RNFB) reflectance abnormality in the temporal raphe.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):365.
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© ARVO (1962-2015); The Authors (2016-present)
The conformation of the retinal nerve fiber bundles (RNFBs) in the region of the temporal raphe makes it possible to predict the spatial location of the ganglion cells whose axons contribute to an individual RNFB. This feature may prove helpful in understanding the structural-functional relationship in glaucoma. With the recent improvements in imaging techniques it is now possible to visualize the RNFBs in the raphe. We investigate a novel imaging protocol and analysis technique to quantify RNFB abnormalities in patients with glaucoma using the relative reflectance in the raphe region.
High density optical coherence tomography (OCT) images sized 15° by 23° and customized for each individual based on the angle of raphe were acquired across 25 controls and 5 patients with glaucoma using the Spectralis OCT. An 8-micron slab centered at 18 microns depth from the inner limiting membrane (ILM) and referenced to Bruch’s membrane was generated for each subject. A thresholding technique was used to transform the mean pixel reflectance to zero (0) in regions where RNFBs were non-visible. A grid of 26 pixel by 26 pixel boxes (1° by 1°) was superimposed on the image and the pixels within each box averaged to generate a reflectance index for that box. Normative reference values were computed for each box within the grid across controls at a p value of 0.05 assuming a Gaussian distribution. Areas of potential RNFB damage in the patients were predicted based on the normative data. The agreement between the areas identified as showing abnormality using our novel technique and frequency-doubling perimetry (24-2) was assessed using Cohen’s kappa (k).
Eighty percent (80%) of the time the finding of our technique was in agreement with the perimetric finding at the given perimetric location. Cohen's kappa showed a moderate agreement in RNFB abnormality detected by our technique and perimetric data, k = .669, p<0.05.
Customizing imaging protocols and analysis techniques for the temporal region have the potential to detect RNFB abnormalities in the temporal raphe.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Damage predicted by our technique compared to pattern of visual field damage (in subject 1022).
Damage predicted by our technique compared to pattern of visual field damage (in subject 1017).
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