Assessment of Optic Nerve Head Drusen Using Enhanced Depth Imaging and Swept Source Optical Coherence Tomography

Abstract

Background Optic nerve head drusen (ONHD) are calcific deposits buried or at the surface of the optic disc. Although ONHD may be associated with progressive visual field defects, the mechanism of drusen-related field loss is poorly understood. Methods for detecting and imaging disc drusen include B-scan ultrasonography, fundus autofluorescence, and optical coherence tomography (OCT). These modalities are useful for drusen detection but are limited by low resolution or poor penetration of deep structures. This review was designed to assess the potential role of new OCT technologies in imaging ONHD. Evidence Acquisition Critical appraisal of published literature and comparison of new imaging devices to established technology. Results The new imaging modalities of enhanced depth imaging optical coherence tomography (EDI-OCT) and swept source optical coherence tomography (SS-OCT) are able to provide unprecedented in vivo detail of ONHD. Using these devices it is now possible to quantify optic disc drusen dimensions and assess integrity of neighboring retinal structures, including the retinal nerve fiber layer. Conclusions EDI-OCT and SS-OCT have the potential to allow better detection of longitudinal changes in drusen and neural retina and improve our understanding of drusen-related visual field loss.

Imaging Methods in the Diagnosis of Optic Disc Drusen

“…Furthermore, because the posterior margins of ODD can be better determined by EDI-OCT, their area and volume can also be calculated. 21 It has been reported that drusen have a central hyperreflective focus and an outer hyperreflective edge, with a hyporeflective area in between (Figure 8). A negative correlation between drusen diameter and RNFL thickness as well as greater RNFL loss in drusen located in the optic canal have been demonstrated.…”

“…The major advantage of USG is the ability to show even the posterior borders of buried drusen, but its drawbacks are low resolution and inability to provide data on the neural retina. 20,21 Although fundus autofluorescence (FAF) is a convenient method of visualizing more superficial drusen, it is insufficient for detecting buried drusen. Superficial drusen appear on FAF as round or oval hyperautofluorescent structures with irregular edges (Figure 4).…”

Optic disk drusen in children

“…125; 183; 194 Merchant et al examined 32 eyes with clinically definite optic disc drusen and 25 eyes with suspected optic disc drusen in children and adults. 125 They found that B-scan ultrasonography, SD-OCT, and EDI-OCT all detected every case of clinically definite optic disc drusen; however, in 25 eyes with suspected buried optic disc drusen, EDI-OCT detected 17 cases, while SD-OCT and B-scan ultrasonography were positive in 14 and 7 eyes, respectively.…”

Volumetric Measurement of Optic Nerve Head Drusen Using Swept-Source Optical Coherence Tomography

“…16,17 Enhanced depth imaging (EDI) OCT and swept source (SS) OCT have also enabled qualitative descriptions of ONHD. 18-20 Although EDI-OCT, like SS-OCT, may allow for better visualization of deep ocular structures compared to SD-OCT, EDI-OCT, and SD-OCT in general, exhibits worse signal roll-off and reduced signal uniformity than SS-OCT. 21 SS-OCT provides both high penetration of tissue and high axial uniformity of images, at the expense of slightly reduced image contrast. To our knowledge, the only study which has attempted to quantify the size, shape, and location of ONHD used an experimental SD-OCT instrument.…”