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Fundus imaging methods used to identify three pseudodrusen subtypes
Diseases caused by mutations associated with retinoid cycling may provide clues to the pathology underlying pseudodrusen.
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Multimodal fundus imaging enabled classification of pseudodrusen into three subtypes, according to a study.
Investigators used color fundus photography, infrared scanning laser ophthalmoscopy (IR-SLO) and spectral-domain optical coherence tomography to classify lesions as dot, ribbon or peripheral pseudodrusen.
Each subtype has different features and may pose a variable risk of progression to advanced age-related macular degeneration, the study authors said.
“For being small and hard to see, pseudodrusen are controversial,” Richard F. Spaide, MD, the corresponding author, said in an email interview with Ocular Surgery News. “They have been attributed to being abnormalities of the large choroidal vessels, the stroma near choroidal vessels, in between large choroidal vessels, abnormalities of the choriocapillaris and, more recently, accumulations of material in the subretinal space. We found that pseudodrusen have one of several different appearances. Each one of these appearances has material visualized in the subretinal space using optical coherence tomography.”
Richard F. Spaide
The study was published in the American Journal of Ophthalmology.
Study design and results
The retrospective study included 132 eyes of 93 patients who underwent color fundus photography, IR-SLO and SD-OCT performed by masked readers.
Patients with a history of laser photocoagulation of the macula, rhegmatogenous or tractional retinal detachment, high myopia, acquired vitelliform detachment, or any retinal dystrophy or tapetoretinal degeneration were excluded.
The first subtype, dot pseudodrusen, was an orderly array of discrete white accumulations located mainly in the perifovea.
The second subtype, ribbon pseudodrusen, comprised interconnected bands of yellow-white material forming a reticular pattern in the perifovea.
“The dot pseudodrusen obviously can’t make a net. The word ‘reticular’ is derived from the Latin word rete, or net. So it is hard to call these reticular pseudodrusen. The ribbon form does suggest a net. The ribbon form is not easy to see in infrared scanning laser ophthalmoscopic images, while the dot form are particularly easy to visualize with this modality. They are modestly hypoautofluorescent. In OCT, these accumulations are more rounded on top than are the dot form,” Spaide said.
The third subtype, peripheral pseudodrusen, featured yellow-white globules mainly located peripheral to the perifoveal region. The third type appeared hyper-reflective in IR-SLO images.
“This configuration is unusual in our practice, although there was a paper from Korea describing hyperautofluorescent pseudodrusen. These drusen have a rounded appearance in OCT imaging,” Spaide said.
Dot pseudodrusen were identified in 127 eyes (96.1%). They were identified more frequently with IR-SLO imaging than with color fundus photography (P = .014).
Ribbon pseudodrusen were identified in 53 eyes (40.2%). They were identified more commonly in color fundus images than in IR-SLO images (P < .001).
Dot and ribbon pseudodrusen were seen together in 48 eyes.
Peripheral pseudodrusen were seen in eight eyes.
All three types of pseudodrusen appeared as subretinal drusenoid deposits on SD-OCT.
Clinical observations
Pseudodrusen have been associated with choroidal neovascularization, geographic atrophy and outer retinal atrophy, Spaide said.
“Between the dot and ribbon forms, we don’t know the relative variation in risk. It is possible that the more peripheral hyperautofluorescent version of pseudodrusen does not show the same risk profile since the location of the lesions is located largely outside of the macula,” he said.
Material resulting from various retinal diseases may be linked to pseudodrusen, Spaide said.
“Patients with vitamin A deficiency can have subretinal deposition of material,” he said. “Also of interest is that patients with either retinitis punctata albescens or fundus albipunctatus, diseases caused by mutations involving retinoid cycling, have subretinal deposition of material that in OCT imaging is virtually indistinguishable from what is seen in eyes with pseudodrusen. It is possible these diseases are clues to the underlying pathology in pseudodrusen.” – by Matt Hasson
Reference:
Suzuki M, et al. Am J Ophthalmol. 2014;doi:10.1016/j.ajo.2014.01.025.For more information:
Richard F. Spaide, MD, can be reached at Vitreous-Retina-Macula Consultants of New York, 460 Park Ave., 5th Floor, New York, NY 10022; 212-861-9730; email: rick.spaide@gmail.com.Disclosure: Spaide has no relevant financial disclosures.
Perspective
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Andrew P. Schachat, MD
The presence of “pseudodrusen” has been associated with various manifestations of AMD. Using different imaging modalities, the authors explain that there are three categories or appearances of pseudodrusen. We are taught that there are “dot,” “ribbon” and “peripheral” patterns, some imaged better with one modality or another.
My problem, which I hope you do not have, is not being sure just what is meant by “pseudodrusen.” The authors cite a classic paper by Mimoun from 1990, Arnold from 1995 and some other seminal papers. But there is no crisp definition of what pseudodrusen are. For me, the key value of the current manuscript is the finding that there appear to be three distinct patterns, and the authors, in the “image grading” section of the manuscript, offer definitions that they relied on to grade the presence of these lesions. The work offers a basis for future studies that may elucidate the cause of these lesions, their composition and, importantly, whether their presence has predictive value for the course of AMD or its response to treatment.
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