CASE STUDY

Incorporating OCT Angiography Into Clinical Practice

A series of three cases

MICHAEL JAVAHERI, MD

Optical coherence tomography angiography (OCTA) is a new, noninvasive imaging technique that generates volumetric angiographic images in a matter of seconds, without the use of dyes. OCTA has the clinical capability to specifically localize and identify pathology along with the ability to show both structural and blood flow information.

Published studies have hinted at the potential use of OCTA in the evaluation of common diseases, such age-related macular degeneration, diabetic retinopathy, and venous and arterial occlusive diseases. Here we review the use of OCTA in a few common clinical scenarios and compare the images to conventional imaging modalities.

CASE 1

A 71-year-old man presented with a history of one month of decreased vision in the right eye and visual acuity of 20/200. He was diagnosed with a superior branch retinal vein occlusion with macular edema.

Color fundus photography (Figure 1A) showed dot hemorrhages superior to the horizontal raphae. Figure 1B shows a late-phase fluorescein angiogram demonstrating late leakage in the macula. Figure 1C shows an OCT angiogram overlay demonstrating the location of the OCT angiogram relative to the macula.

Figure 1D shows an OCT of the macula showing significant intraretinal and subretinal fluid. Figure 1E shows an OCT angiogram of the superficial plexus indicating areas of ischemia, as seen by the lack of flow in the occluded area. The initial formation of anastomoses can be identified temporally.

Figure 1F demonstrates an AngioPlex map, combining superficial (red), deep (green), and avascular retina (blue), thus highlighting regions of abnormal vasculature within the retina. The superficial ischemia from the BRVO is noted respecting the horizontal raphae.

Figure 1. A case of BRVO in a 71-year-old man. A) Color fundus photograph; B) Late-phase fluorescein angiogram; C) OCTA demonstrating the location relative to the macula; D) OCT showing significant intra- and subretinal fluid; E) OCTA of the superficial plexus; E) AngioPlex map.

In eyes affected by BRVO, OCTA highlights the vascular network with evident areas of nonperfusion that correspond to areas of nonperfusion on FA. However, these areas look much sharper because there is no masking effect from dye leakage in the mid and late stages. The entire vascular network is visualized better, including visualization and identification of arteriovenous anastomoses and vascular loops.

CASE 2

An 80-year-old man presented for follow-up for dry AMD in both eyes. The VA was 20/30 in each eye. A color photograph of the right eye (Figure 2A, next page) shows significant medium to large drusen with mild pigmentary changes. Figure 2B shows fundus autofluorescence of the right eye showing areas of hypofluorescence surrounded by areas of hyperfluoresence.

Figure 2C demonstrates an AngioPlex map, indicating areas of deep retinal ischemia surrounding the drusen, corresponding to the previous areas of fundus hyperfluoresence. Figure 2D is an OCTA of the choriocapillaris, showing clear areas of alteration below Bruch’s membrane, representing atrophy or impaired blood flow. Figure 2E is a b-scan OCT, corresponding to the OCTA image in Figure 2D, indicating decreased green color (blood flow) around the large drusenoid deposits.

Figure 2. A case of dry AMD in an 80-year-old man. A) Color photograph; B) Fundus autofluorescence showing areas of hypofluorescence surrounded by areas of hyperfluorescence; C) AngioPlex map; D) OCTA of the choriocapillaris; E) B-scan OCT corresponding to the OCTA image.

In eyes affected by dry AMD, OCTA highlights alterations in the choriocapillaris, which are present in each stage of this disease. By helping to emphasize subtle changes in blood flow, we may be able to detect subtle advances in early stages of AMD, potentially using that information to facilitate the identification of future treatments.

CASE 3

A 65-year-old woman returned for follow-up after multiple injections of aflibercept (Eylea, Regeneron, Tarrytown, NY) for treatment of diabetic macular edema in her left eye. Her vision improved from 20/200 to 20/50.

Figure 3A shows a color fundus photograph of the left eye showing a few scattered microaneurysms and mild macular lipid. Figure 3B shows a late-phase FA demonstrating late leakage corresponding to mild DME.

Figure 3C shows an OCT angiogram overlay, demonstrating the location of the OCTA relative to the macula. Figures 3D and 3E demonstrate deep and superficial plexus OCTA images, respectively, depicting early areas of remodeling of the foveal avascular zone, capillary tortuosity, and dilation of capillary terminals adjacent to the FAZ. In eyes with nonproliferative diabetic retinopathy with or without macular edema, OCTA helps to identify early vascular remodeling of the FAZ, to visualize microaneurysms and intraretinal microvascular abnormalities, and to diagnose DME by identifying vascular loops in the presence of cysts in both deep and superficial vessels.

Figure 3. A case of diabetic macular edema in a 65-year-old woman. A) Color fundus photo; B) Late-phase fluorescein angiogram demonstrating late leakage; C) OCTA overlay with location relative to the macula; D) Deep OCTA image; E) Superficial OCT image.

However, OCTA does have the small disadvantage of difficulty in imaging the deep capillary plexus because it cannot visualize changes in pericyte vascular permeability, which is normally indicated by dye leakage during a FA.

CONCLUSION

While just starting to break into clinical practice, the uses of OCTA seem to be growing rapidly. We see here how OCTA generates extremely high-quality images of areas of the retina never fully visualized until now that are not blurred by dye leakage.

The ability to image different layers of the retina and to identify so many structural changes will only serve to help us battle a great number of diseases in the present and future. RP