Multicolor Imaging of Optic Disc Drusen

A 39-year-old Caucasian woman was referred to neuro-ophthalmology clinic for the evaluation of incidentally noted bilateral optic disc swelling. She had visual acuity of 20/20 in the right eye and 20/30 in the left eye, normal intraocular pressure, and dilated fundus examination showed prominent elevation of bilateral optic nerve head and yellowish refractile deposits consistent with bilateral optic disc drusen (ODD). Color fundus imaging using broad-spectrum white light revealed a lumpy-bumpy appearance of the optic disc, blurred disc margins, visible ODD, and slightly narrowed and irregular arterioles (Fig. 1). Using confocal scanning laser ophthalmoscope (cSLO) (Spectralis HRA + OCT MultiColor Module; Heidelberg Engineering, Heidelberg, Germany), blue-light fundus autofluorescence (FAF) imaging (excitation 488 nm, emission >500 nm) showed clusters of hyperautofluorescent deposits throughout the optic disc, and spectral-domain optical coherence tomography (OCT) (815 nm) revealed deposits with signal pore core and hyperreflective margins—all typical of ODD (Fig. 1).

F1FIG. 1.:

Multimodal ophthalmic imaging of ODD (right eye) with MultiColor (MC) reflectance imaging, color fundus imaging (color), blue-light fundus autofluorescence (FAF) imaging, and optical coherence tomography (OCT). In the MC image (pseudocolored composite of the blue, green, near-infrared images in the middle row), there is green hyperreflectance of the entire optic disc. There is prominent green reflectance of the papillary and peripapillary arteriolar sheaths, which corresponds to the subtle white sheathing around the narrowed vessels seen on color fundus imaging. A cluster of small ODD at 9-o'clock position of the optic disc is most distinct on near-infrared reflectance image (red arrows) but also visible on blue and green reflectance images. There is also a ring of peripapillary hyperreflectance due to the loss of retinal pigment epithelium on OCT (yellow arrows). This ring appears dark on blue-light FAF. OCT, optical coherence tomography; ODD, optic disc drusen.

We performed MultiColor (MC) imaging, which simultaneously uses blue (488 nm), green (514 nm), and near-infrared (815 nm) laser lights with cSLO. On MC imaging, the normal optic disc appears dark with slight greenish hue on pseudocolor representation, and there is distinct demarcation of the cup, optic disc, and retinal vessels (1,2). MC imaging in our patient with ODD showed that the entire optic disc appeared brightly green on pseudocolor representation due to hyperreflectance of blue and green lights as a result of prominent optic nerve head elevation (Fig. 1). The sheaths of the papillary arterioles appeared brightly green on MC imaging, which strikingly extended into the peripapillary region. The sheath around the papillary venules also appeared brightly green, with limited sheathing of the peripapillary venules compared with the arterioles.

On near-infrared reflectance imaging, there was a cluster of hyperreflective, pearl-like superficial ODD at 9-o'clock position, which corresponded with clusters of small ODD with bright margins on spectral-domain OCT (Fig. 1). This cluster of superficial ODD was more distinct on near-infrared reflectance than on blue or green reflectance. Near-infrared reflectance imaging also revealed a slightly hyperreflective ring (pseudocolored orange) immediately adjacent to the optic disc, which resulted from the deeper penetrance of near-infrared light from atrophy of the peripapillary retinal pigment epithelium (RPE). This corresponded to the hypoautofluorescent black ring around the optic disc on FAF imaging (loss of lipofuscin-containing RPE cells) and loss of the RPE layer on OCT B-scan (Fig. 1).

Our case illustrates important en-face imaging features using MC imaging of ODD in combination with FAF and OCT imaging (3). Features of ODD on MC imaging include (1) prominent green hyperreflectance of the optic disc, (2) green sheathing of the papillary and peripapillary vasculature, and (3) presence of orange superficial ODD. Perivascular green hyperreflectance along papillary and peripapillary vasculature on MC imaging has not previously been described in ODD but is visible in a previous publication on ODD (2) and has been seen in nonarteritic anterior ischemic optic neuropathy (2) and central retinal artery occlusion (4). Although perivascular sheathing may be due to different causes, such as retinal vasculitis (5) and retinal arteriolar hypertension (6), this vascular sheathing in ODD likely corresponds with prominent perivascular space surrounding both papillary arterioles and venules described by Tso in 1981 and may reflect the accumulation of axoplasmic debris containing calcified mitochondria remnants and vascular compromise in ODD (7).

MultiColor imaging is an innovative technology that performs rapid high-contrast imaging using reflectance of 3 different wavelengths of laser lights through a pinhole and cSLO. It is superior to traditional color fundus imaging, which uses broad spectrum white light with scattered light reflectance. The 3 reflectance images can be viewed separately or in a composite pseudocolored MC image to reveal structural information of different layers of the optic disc because the lights of different wavelengths penetrate tissue at different depths (1,8). A limitation of en-face reflectance imaging in general is difficulty visualizing ODD below Bruch membrane opening, even with near-infrared wavelength (9).

MultiColor imaging has been used in imaging different causes of optic nerve head elevation, including papilledema (10), ODD (2,10), anterior ischemic optic neuropathy (2), optic disc melanocytoma (11), and myelinated nerve fibers (12). In a study of 20 children with suspected papilledema using MC imaging, optic discs with papilledema looked like a green ring (hyperreflective disc with a dark center), blurred disc margins, and obscuration of blood vessels, whereas eyes with pseudopapilledema, such as ODD, had green hyperreflectance of the entire optic disc without a dark center, distinct disc margin, and well-delineated disc vasculature (10). This green hue of the optic disc on MC occurs with different causes of optic nerve head elevation, and the more elevated the surface of the optic disc, the greater the intensity of green hue (2). Also, MC has been useful in imaging inner retinal ischemia and edema, vasculopathy, calcification in central retinal artery or venous occlusions, diabetic retinopathy, macular degeneration, and retinal astrocytoma associated with calcifications, respectively (4,13). Thus, MC imaging with cSLO is a useful en-face imaging modality that provides rapid, high-resolution, nonmydriatic imaging of the optic disc, which helps nonophthalmic-trained clinicians diagnose ODD without ophthalmoscopy. It could be more commonly used in point-of-care locations and studied further in large studies of ODD and other causes of optic nerve head elevation, such as papilledema and anterior ischemic optic neuropathy.

STATEMENT OF AUTHORSHIP

Category 1: a. Conception and design: Y. Yan and Y.J. Liao; b. Acquisition of data: Y. Yan, S. Pugazhendhi, and S. Beres; c. Analysis and interpretation of data: Y. Yan, S. Pugazhendhi, S. Beres, and Y.J. Liao. 2. Category 2: a. Drafting the manuscript: Y. Yan and Y.J. Liao; b. Revising it for intellectual content: Y. Yan, S. Pugazhendhi, S. Beres, and Y.J. Liao. 3. Category 3: a. Final approval of the completed manuscript: Y.J. Liao.

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