Spectral domain optical coherence tomography for quantitative evaluation of drusen and associated structural changes in non-neovascular age-related macular degeneration

K Yi, M Mujat, B H Park, W Sun, J W Miller, J M Seddon, L H Young, J F de Boer, T C Chen, K Yi, M Mujat, B H Park, W Sun, J W Miller, J M Seddon, L H Young, J F de Boer, T C Chen

Abstract

Background/aims: To demonstrate how spectral domain optical coherence tomography (SDOCT) can better evaluate drusen and associated anatomical changes in eyes with non-neovascular age-related macular degeneration (AMD) compared with time domain optical coherence tomography (TDOCT).

Methods: Images were obtained from three eyes of three patients with AMD using an experimental SDOCT system. Both a titanium-sapphire (Ti:sapphire) laser and a superluminescent diode (SLD) were used as a broadband light source to achieve cross-sectional images of the retina. A qualitative and quantitative analysis was performed for structural changes associated with non-neovascular AMD. An automated algorithm was developed to analyse drusen area and volume from SDOCT images. TDOCT was performed using the fast macular scan (StratusOCT, Carl Zeiss Meditec, Dublin, California).

Results: SDOCT images can demonstrate structural changes associated with non-neovascular AMD. A new SDOCT algorithm can determine drusen area, drusen volume and proportion of drusen.

Conclusions: With new algorithms to determine drusen area and volume and its unprecedented simultaneous ultra-high speed ultra-high resolution imaging, SDOCT can improve the evaluation of structural abnormalities in non-neovascular AMD.

Conflict of interest statement

Competing interests: None.

Figures

Figure 1. Colour fundus photograph and StratusOCT…
Figure 1. Colour fundus photograph and StratusOCT fast macular scan of the right eye of a patient with dry age-related macular degeneration (patient A). (A) Multiple large soft drusen temporal to the macula. (B) Six standard OCT radial scans showing only two frames show small drusen (arrowhead). (C) Radial lines indicating the positions and directions of the six radial scans.
Figure 2. Spectral domain optical coherence tomography…
Figure 2. Spectral domain optical coherence tomography (SDOCT) images of the right eye of a patient with dry age-related macular degeneration (patient A). (A) Integrated reflectance image. Letters a, b and c indicate the position of the selected frames. (B) Upper frame: centre of the fovea (a, asterisk, top right); middle frame: from inferior to the fovea (b, middle right). Last frame (c, bottom right): several drusen temporal to macula (hollow arrows). Note the reduced reflectance of the boundary between the inner and outer segments of the photoreceptors (IS/OS) around drusen (short arrows). (C) Baseline (blue line) and drusen boundary (lower red line) as determined by our algorithm. The single frames are expanded vertically by 2.67 for better visualisation of the retinal layers. The light source was a Ti:sapphire laser with axial resolution of 3 μm. G/IPL, ganglion cell/inner plexiform layer; INL, inner nuclear layer; IS/OS, boundary between the inner and outer segments of the photoreceptors; ONL, outer nuclear layer; OPL, outer plexiform layer; RNFL, retinal nerve fibre layer; RPE, retinal pigment epithelium.
Figure 3. Results of the automated drusen…
Figure 3. Results of the automated drusen analysis from fig 2. (A) Retinal area of drusen analysis. (B) Corresponding retina with a false-colour scale after analysis. (C) Retina area with drusen, elevated above the baseline more than 8 µm (5 pixels of 1.6 µm), shown as white. The proportion of retina with drusen was calculated as 5.85% of the total scan surface. (D) Analysed retina displayed three-dimensionally. The height was elongated in this figure by five times. The colour bars are scaled as actual size in microns. (E) One of the drusen (circled, from top figures) shown without height elongation. The calculated area of this druse is 1.46×105 μm2 or 0.146 mm2, and the volume is 9.31×106 μm3 or 9.31×10−3 mm3. The total area of scan was 4.97 mm×5.18 mm×1.24 mm.
Figure 4. Colour fundus photograph and optical…
Figure 4. Colour fundus photograph and optical coherence tomography (OCT) imaging of the right eye of a patient with dry age-related macular degeneration (patient B). (A) Small degree of geographic atrophy noted nasal to the fovea (short arrow). (B) Integrated reflectance image. Letters a and b indicate the position of the selected frames. (C) Horizontal scan from the StratusOCT showing multiple drusen (arrowheads). (D) Spectral domain OCT images. Increased transmission due to pigment loss (short arrows) is noted along with the drusen (arrowheads). The light source was a Ti:sapphire laser with an axial resolution of 3 μm. G/IPL, ganglion cell/inner plexiform layer; INL, inner nuclear layer; IS/OS, boundary between the inner and outer segments of the photoreceptors; ONL, outer nuclear layer; OPL, outer plexiform layer; RNFL, retinal nerve fibre layer; RPE, retinal pigment epithelium.
Figure 5. Colour fundus photograph and spectral…
Figure 5. Colour fundus photograph and spectral domain optical coherence (SDOCT) images of the right eye of a patient with dry age-related macular degeneration (patient C). (A) Several pigment clumpings with surrounding atrophy (arrows) in the superior macula in fundus photography. (B) Small hyper-reflective elevations (hollow arrows) just above the level of the retinal pigment epithelium (RPE) corresponding to the pigment clumping noted on the colour fundus photo. Frames a and b were expanded vertically by 2.7, and frames c and d by 1.5 for better visualisation of the retinal layers. The light source was a superluminescent diode laser with an axial resolution of 6 μm. A retinal tracker was applied. G/IPL, ganglion cell/inner plexiform layer, between the inner and outer segments of the photoreceptors; RNFL, retinal nerve fibre layer; RPE, retinal pigment epithelium. (C) Integrated reflectance image. The letters a, b, c and d indicate the position and width of the selected frames.

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