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Ari Dylan Schuman, Rithambara Ramachandran, Vivienne C Greenstein, Stephen H Tsang, David G Birch, Donald Hood; The Thickness of the Outer Nuclear and Henle Fiber Layers in Patients with Photoreceptor Abnormalities Measured Using Optical Coherence Tomography.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5973.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the feasibility of obtaining separate measures of outer nuclear layer (ONL) and Henle fiber layer (HFL) thickness from spectral domain optical coherence tomography (SD-OCT) of healthy controls and patients with photoreceptor abnormalities.
Using horizontal midline SD-OCT scans and computer-aided manual segmentation, the thicknesses of the ONL (external limiting membrane to distal border of the fibers of Henle) and the HFL (distal border of the inner nuclear layer to the distal border of the fibers of Henle) were measured. The B-scans were modified for best visualization of the ONL/HFL boundary by altering their brightness and contrast. ONL and HFL thicknesses in 30 healthy eyes (age: 35.6±16.6 yrs.) were compared to histological data from Curcio et al. (18 eyes, age: 67.6±16.0 yrs.). The histological data were displayed without (purple line, Fig. 1) and with adjustment for shrinkage (green line, Fig. 1, dashed lines are max. and min. estimates). ONL and HFL measurements were also made for patients with cone dystrophy (CD: 15 eyes, 31.8±18.6 yrs), achromatopsia (A: 14 eyes; 33.2±16.8 yrs), and retinitis pigmentosa (RP: 8 eyes; 35.3±19.5 yrs). The RP patients had foveal sensitivities within normal limits, and the A and CD patients had reduced or non-recordable cone function on full-field electroretinography.
The ONL and HFL thicknesses for controls decreased with eccentricity in a similar way to the histological data (Fig. 1). In general, the ONL and HFL thicknesses (solid black lines, Fig. 1) fell within the maximum and minimum adjusted histological thicknesses (green dashed lines, Fig. 1). However, the average ONL (45.4±10.3um) and HFL (47.5±13.5um) thicknesses were greater than those for histology (46.7 and 42.6um respectively), perhaps due to differences in age, criteria for boundary locations, and/or differential shrinkage of tissue. As expected for eyes with CD and A, the ONL thickness was thinner than normal, while for RP eyes it was only abnormal outside the central 1mm (Fig. 2).
It appears possible to obtain measures of ONL and HFL thickness in patients with photoreceptor abnormalities.<br /> 1. Lujan et al. IOVS 2011. 2. Curcio et al. IOVS 2011.
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