Revealing Henle's Fiber Layer Using Spectral Domain Optical Coherence Tomography
ABSTRACT Spectral domain optical coherence tomography (SD-OCT) uses infrared light to visualize the reflectivity of structures of differing optical properties within the retina. Despite their presence on histologic studies, traditionally acquired SD-OCT images are unable to delineate the axons of photoreceptor nuclei, Henle's fiber layer (HFL). The authors present a new method to reliably identify HFL by varying the entry position of the SD-OCT beam through the pupil.
Fifteen eyes from 11 subjects with normal vision were prospectively imaged using 1 of 2 commercial SD-OCT systems. For each eye, the entry position of the SD-OCT beam through the pupil was varied horizontally and vertically. The reflectivity of outer retinal layers was measured as a function of beam position, and thicknesses were recorded.
The reflectivity of HFL was directionally dependent and increased with eccentricity on the side of the fovea opposite the entry position. When HFL was included in the measurement, the thickness of the outer nuclear layer (ONL) of central horizontal B-scans increased by an average of 52% in three subjects quantified. Four cases of pathology, in which alterations to the normal macular geometry affected HFL intensity, were identified.
The authors demonstrated a novel method to distinguish HFL from true ONL. An accurate measurement of the ONL is critical to clinical studies measuring photoreceptor layer thickness using any SD-OCT system. Recognition of the optical properties of HFL can explain reflectivity changes imaged in this layer in association with macular pathology.
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ABSTRACT: To characterize perifoveal intraretinal cavities observed around full-thickness macular holes (MH) using en face optical coherence tomography and to establish correlations with histology of human and primate maculae. Retrospective non-consecutive observational case series. Macular en face scans of eight patients with MH were analyzed to quantify the areas of hyporeflective spaces, and compared with macular flat-mounts and sections from one normal human donor eye and two normal primate eyes (Macaca fascicularis). Immunohistochemistry was used to study the distribution of glutamine synthetase, expressed by Müller cells, and zonula occludens-1, a tight-junction protein. The mean area of hyporeflective spaces was lower in the inner nuclear layer (INL) than in the complex formed by the outer plexiform (OPL) and the Henle's fiber layers (HFL): 5.0×10(-3) versus 15.9×10(-3) mm(2), respectively (P < 0.0001, Kruskal Wallis test). In the OPL and HFL, cavities were elongated with a stellate pattern, whereas in the INL they were rounded and formed vertical cylinders. Immunohistochemistry confirmed that Müller cells followed a radial distribution around the fovea in the frontal plane, and a "Z-shaped" course in the axial plane, running obliquely in the OPL and HFL, and vertically in the inner layers. In addition, zonula occludens-1 co-localized with Müller cells within the complex of OPL and HFL, indicating junctions in between Müller cells and cone axons. The dual profile of cavities around MHs correlates with Müller cell morphology and is consistent with the hypothesis of intra- or extracellular fluid accumulation along these cells. Copyright © 2015 Elsevier Inc. All rights reserved.American Journal of Ophthalmology 02/2015; 159(6). DOI:10.1016/j.ajo.2015.02.013 · 4.02 Impact Factor
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ABSTRACT: Purpose:To quantify and compare phase retardation amplitude and regularity associated with the Henle fiber layer between non-exudative age-related macular degeneration (AMD) patients and age-matched controls using scanning laser polarimetry (SLP) imaging. Methods:A scanning laser polarimeter was used to collect 15 x 15 deg macular centered images in 25 patients with non-exudative AMD and 25 age-matched controls. Raw image data were used to compute macular phase retardation maps associated with the Henle fiber layer. Consecutive, annular regions of interest from 0.5 to 3.0 deg eccentricity, centered on the fovea, were used to generate intensity profiles from phase retardation data and analyzed with two complementary techniques: a normalized 2f FFT component analysis and a curve fitting analysis using a 2f sine function. Paired t-tests were used to compare the normalized 2f FFT magnitude at each eccentricity between the two groups, the eccentricity that yielded the maximum normalized 2f FFT between paired individuals across the two groups, and curve fitting RMS error at each eccentricity between the two groups. Results:Normalized 2f FFT components were lower in the AMD group at each eccentricity, with no difference between the two groups in the maximum normalized 2f FFT component eccentricity. The RMS error from curve fitting was significantly higher in the AMD group. Conclusions:Phase retardation changes in the central macula indicate loss and/or structural alterations to central cone photoreceptors in non-exudative AMD patients. SLP imaging is a non-invasive method for quantifying cone photoreceptor changes associated with central macular disease. Copyright © 2014 by Association for Research in Vision and Ophthalmology.Investigative Ophthalmology & Visual Science 12/2014; 56(1). DOI:10.1167/iovs.14-14459 · 3.66 Impact Factor
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ABSTRACT: To determine whether annual decline in visual field sensitivity is greater in the transition zone at the edge of the frequency-domain optical coherence tomography (fdOCT) inner segment ellipsoid zone (EZ) than at other locations in the visual field. Prospective, longitudinal, observational study. Forty-four patients with X-linked retinitis pigmentosa (XLRP) resulting from a mutation in the RPGR gene. Static perimetric fields (Humphrey 30-2; Carl Zeiss Meditec, Dublin, CA) were obtained annually for 4 years. Beginning with year 2, fdOCT scans were obtained annually with a Heidelberg Spectralis HRA + OCT (Heidelberg Engineering, Heidelberg, Germany). The rate of visual field decline at locations near the edge of the EZ compared with the rates for the macula and in the mid periphery. Sensitivity just inside and outside the edge of the EZ declined at rates of 0.84 and 0.92 dB/year, respectively. By comparison, average sensitivity in the macula and mid periphery declined by 0.38 and 0.61 dB/year, respectively. The edge of the EZ in each patient with XLRP indicates a transition zone between relatively healthy and relatively degenerate retina. The annual loss of sensitivity in the transition zone is more rapid than it is elsewhere in the retina. Copyright © 2015 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.Ophthalmology 12/2014; 122(4). DOI:10.1016/j.ophtha.2014.11.005 · 6.17 Impact Factor