DIRECTIONAL OPTICAL COHERENCE TOMOGRAPHY PROVIDES ACCURATE OUTER NUCLEAR LAYER AND HENLE FIBER LAYER MEASUREMENTS. Issue 8 (August 2015)

• Record Type: Journal Article
• Authors: Lujan, Brandon J.; Roorda, Austin; Croskrey, Jason A.; Dubis, Adam M.; Cooper, Robert F.; Bayabo, Jan-Kristine; Duncan, Jacque L.; Antony, Bhavna J.; Carroll, Joseph
• Is Part Of: Retina. Volume 35:Issue 8(2015:Aug.)
• Publication Date: 2015-08
• Subjects: spectral domain -- Fourier domain -- directional reflectivity -- outer plexiform layer -- Henle's fiber layer -- photoreceptors -- cones -- rods -- biomarker; Retina -- Diseases -- Periodicals; Retinal Diseases; Vitreous Body; 617.735
• DOI: 10.1097/IAE.0000000000000527
• Languages: English
• ISSNs: 0275-004X

Abstract

Abstract : Purpose: The outer nuclear layer (ONL) contains photoreceptor nuclei, and its thickness is an important biomarker for retinal degenerations. Accurate ONL thickness measurements are obscured in standard optical coherence tomography (OCT) images because of Henle fiber layer (HFL). Improved differentiation of the ONL and HFL boundary is made possible by using directional OCT, a method that purposefully varies the pupil entrance position of the OCT beam. Methods: Fifty-seven normal eyes were imaged using multiple pupil entry positions with a commercial spectral domain OCT system. Cross-sectional image sets were registered to each other and segmented at the top of HFL, the border of HFL and the ONL and at the external limiting membrane. Thicknesses of the ONL and HFL were measured and analyzed. Results: The true ONL and HFL thicknesses varied substantially by eccentricity and between individuals. The true macular ONL thickness comprised an average of 54.6% of measurements that also included HFL. The ONL and HFL thicknesses at specific retinal eccentricities were poorly correlated. Conclusion: Accurate ONL and HFL thickness measurements are made possible by the optical contrast of directional OCT. Distinguishing these individual layers can improve clinical trial endpoints and assessment of disease progression. Abstract : Standard Fourier-domain optical coherence tomography images do not reliably distinguish between the photoreceptor-containing outer nuclear layer and the axon-containing Henle fiber layer, resulting in a significant overestimation of outer nuclear layer thickness, a key biomarker. Directional optical coherence tomography (D-OCT) adds optical contrast to overcome this limitation.