Three-dimensional ultrahigh resolution optical coherence tomography imaging of age-related macular degeneration

Abstract

Ultrahigh resolution optical coherence tomography (OCT) enhances the ability to visualize different intra retinal layers. In age-related macular degeneration (AMD), pathological changes in individual retinal layers, including photoreceptor inner and outer segments and retinal pigment epithelium, can be detected. OCT using spectral / Fourier domain detection enables high speed, volumetric imaging of the macula, which provides comprehensive three-dimensional tomographic and morphologic information. We present a case series of AMD patients, from mild drusen to more advanced geographic atrophy and exudative AMD. Patients were imaged with a research prototype, ultrahigh resolution spectral / Fourier domain OCT instrument with 3.5 microm axial image resolution operating at 25,000 axial scans per second. These cases provide representative volumetric datasets of well-documented AMD pathologies which could be used for the development of visualization and imaging processing methods and algorithms.

Figures

Fig. 1

Ultrahigh resolution, spectral / Fourier domain OCT volumetric dataset and fundus photograph of the right eye of a 54 year old male subject with mild dry AMD (View 1). The en face OCT fundus image (top-left) is generated by axial summation of the 3D-OCT dataset. Color fundus photo (bottom-left) showing the location of the 3D-OCT volumetric data. Three OCT cross-sectional images are selected from superior to inferior near fovea to show representative pathology. The positions of the OCT images are marked with black arrows on the en face OCT fundus image. Discrete drusen can be seen in the fundus images and in corresponding positions in the OCT cross-sectional images. Ultrahigh resolution enables most of the individual retinal layers to be resolved. RNFL: retinal nerve fiber layer, GCL: ganglion cell layer, OPL: outer plexiform layer, ONL: outer nuclear layer, IPL: inner plexiform layer, INL: inner nuclear layer, ELM: external limiting membrane, IS/OS: photoreceptor inner and outer segment junction, RPE: retinal pigmented epithelium, and CH: choroid.

Fig. 2

Image data from the right eye of a 58 year old female subject diagnosed with dry AMD in both eyes (View 2). Her right eye had a visual acuity of 20/25. The OCT cross-sectional images show elevation of the RPE due to drusen and changes in the photoreceptor inner and outer segment (IS/OS) boundary (thin arrows). Bruch's membrane appears under the area with large drusen deposits (solid arrows), but is not visible in the normal areas of the retina.

Fig. 3

Image data from the left eye of a 60 year old female subject with dry AMD diagnosed in both eyes (View 3). Both en face OCT fundus image (left) and cross-sectional OCT (right) images show that the soft drusen have started to coalesce and form larger, confluent drusen. Three selected OCT cross-sectional images (right) clearly show the confluent drusen. Bruch's membrane cannot be identified as distinct from the drusen. The en face OCT fundus image also shows the smooth border between confluent drusen.

Fig. 4

Image data from the left eye of a 91 year old female subject with AMD (View 4). A large retinal pigment epithelial detachment (PED) can be seen in the macula. The subject had a visual acuity of counting fingers at 5 feet (CF5’). The cross-sectional OCT images show many irregular scattering features and loss of photoreceptor integrity as evidenced by disruption of the photoreceptor inner and outer segment (IS/OS) boundary. Bruch's membrane is visible under the PED (solid arrow), but would not be visible in a normal retina. The inner retina is distorted by the elevation of the RPE and photoreceptors. Atrophy of the outer nuclear layer is also evident.

Fig. 5

Image data from the right eye of a 67 year old male with dry AMD (View 5). Drusen deposit creates identifiable RPE and photoreceptor irregularities. The hyperscattering signal from the choroid beneath the lesion implies RPE atrophy. The IS/OS junction and RPE were no longer separable for UHR-OCT frames from the lesion area. Instead, the Bruch's membrane appeared under the RPE with a smooth contour.

Fig. 6

Image data from the left eye of an 84 year old female subject diagnosed with geographic atrophy and a visual acuity of 20/160 (View 6). Hyper-scattering appears on OCT images beneath the disrupted photoreceptor /RPE layers where Bruch's membrane can be easily identified. Both color photo and en face image of OCT demonstrate similar highly scattering area of RPE atrophy.

Fig. 7

Image data from the right eye of a 77 year old female subject with wet AMD (View 7). Visual acuity was counting fingers at four feet. Fluorescein angiograms at 67 seconds (B) and 5 minutes and 8 seconds (C) indicate the development of choroidal neovascularization. A large volume of intraretinal fluid (small arrows) was identified from the OCT frames. The fluid developed over a large PED where the bottom arrow points the detached Bruch's membrane.

Fig. 8

Image data from the same 77 year old female subject as in Fig. 7, after treatment with intravitreal ranibizumab (View 8). Visual acuity was counting fingers at five feet. OCT images show clearly reduced fluid volumes. Fluorescein angiography was not performed at this examination. The en face OCT fundus view exhibits a more uniform scattering intensity compared to that before treatment (Fig. 7).