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Case Reports
. 2011 Nov;152(5):807-14.e1.
doi: 10.1016/j.ajo.2011.04.027. Epub 2011 Jul 20.

Feasibility of a method for en face imaging of photoreceptor cell integrity

Justin Wanek  1 , Ruth Zelkha, Jennifer I Lim, Mahnaz Shahidi
Affiliations
Case Reports

Feasibility of a method for en face imaging of photoreceptor cell integrity

Justin Wanek et al. Am J Ophthalmol. 2011 Nov.

Abstract

Purpose: To report a method for en face imaging of the photoreceptor inner and outer segment junction by spectral-domain optical coherence tomography (SD OCT) and to describe findings in normal subjects and patients with various retinal diseases.

Design: Observational case series.

Methods: SD OCT images were acquired from 6 normal subjects (mean age, 44 ± 11 years) and from 5 subjects with retinal diseases (mean age, 66 ± 22 years). A customized high-density SD OCT volume scan was acquired on the retina. SD OCT B-scan images were segmented automatically to extract intensity data along the inner and outer segment junction. Data obtained from the raster B-scans were combined to generate an inner and outer segment en face image in a 4.4 × 4.4-mm retinal area centered on the fovea. The foveal-to-parafoveal mean intensity ratio was measured, and repeatability was determined. An infrared scanning laser ophthalmoscope image was acquired and was cropped to provide a field of view similar to the inner and outer segment en face image.

Results: Inner and outer segment en face images generated in normal subjects provided clear visualization of the retinal vasculature, matching the vascular network observed in the infrared scanning laser ophthalmoscope image. In normal subjects, the foveal-to-parafoveal mean intensity ratio was 0.88 ± 0.06, and repeatability of measurements was, on average, 7%. In macular hole, a dark circular region was observed in the inner and outer segment en face image, indicative of photoreceptor cell loss. In age-related macular degeneration, the en face image displayed nonuniform texture corresponding to topographic variations in the inner and outer segment junction. In central serous retinopathy, areas of lower intensity were visible on the en face image corresponding to regions of prior neurosensory elevation. In cystoid macular edema, reduced intensity was present in the inner and outer segment en face image in areas with increased retinal thickness. In diabetic retinopathy, the inner and outer segment en face image displayed regions of reduced intensity resulting from edema, laser scars, or both.

Conclusions: Detection of intensity abnormalities in the inner and outer segment en face image is useful for monitoring the integrity of photoreceptor cells in the course of disease progression and therapeutic intervention.

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Figures

Figure 1
Figure 1
(Top) An example of a SDOCT B-scan acquired in a normal subject. (Bottom) The mean intensity profile (gray) was derived by horizontal averaging of pixel values within the region of interest shown in (Top). The locations of two maximums and the minimum (indicated with arrows) were determined from the smoothed intensity profile (black). The location of the largest local maximum (indicated with an arrow) of the mean intensity profile (gray) that occurred between the local minimum and the posterior maximum of the smoothed intensity profile coincided with the inner and outer segment junction.
Figure 2
Figure 2
Normal Subject: (Left) Examples of SDOCT B-scans with the automatically detected inner and outer segment junction shown with white lines. (Center) A reconstructed inner and outer segment enface image of a 4.4 mm × 4.4 mm retinal area centered on the fovea. Location of B-scans shown in (Left) are marked by horizontal arrows. (Right) A cropped infrared SLO image acquired with the SLO/OCT instrument. The high intensity spot present in the center of the IR image is an artifact associated with the instrument and is unrelated to the retina.
Figure 3
Figure 3
Normal Subject: (Top) An inner and outer segment enface image from a normal subject, revealing a focal dark region located superonasal to the fovea (black arrow). (Bottom) A SDOCT B-scan traversing the dark region in (Top). A small discontinuity in the inner and outer segment junction is marked with a white arrow.
Figure 4
Figure 4
Age-related Macular Degeneration and Macular Hole: (Left) Examples of SDOCT B-scans with the detected inner and outer segment junction shown with white lines. (Center) The inner and outer segment enface image. Horizontal arrows indicate the location of the B-scans. (Right) A cropped infrared SLO image acquired with the SLO/OCT instrument.
Figure 5
Figure 5
Age-related Macular Degeneration: (Left) Examples of SDOCT B-scans. (Center) The inner and outer segment enface image. Horizontal arrows indicate the location of the B-scans. (Right) A cropped infrared SLO image acquired with the SLO/OCT instrument.
Figure 6
Figure 6
Central Serous Retinopathy: (Left) Examples of SDOCT B-scans. (Center) The inner and outer segment enface image. Horizontal arrows indicate the location of the B-scans. (Right) A cropped infrared SLO image acquired with the SLO/OCT instrument.
Figure 7
Figure 7
Cystoid Macular Edema: (Left) Examples of SDOCT B-scans. (Center) The inner and outer segment enface image. Horizontal arrows indicate the location of the B-scans. (Right) A cropped infrared SLO image acquired with the SLO/OCT instrument.
Figure 8
Figure 8
Diabetic Retinopathy: (Left) Examples of SDOCT B-scans. (Center) The inner and outer segment enface image. Horizontal arrows indicate the location of the B-scans. (Right) A cropped infrared SLO image acquired with the SLO/OCT instrument.
See this image and copyright information in PMC

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