Studies find OCTA helpful in glaucoma diagnosis, management
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OCT angiography can detect vessel density loss associated with glaucoma, according to a review of relevant published studies.
“OCT angiography provides remarkable detail of the microvasculature of the peripapillary and macular regions of the retina and choroid,” Darrell WuDunn, MD, PhD, from the University of Florida College of Medicine, and colleagues wrote. “Current technologies are able to segment the different vascular layers and allow users to visualize the superficial layers serving the RNFL and macular ganglion cell layer, both of keen interest in glaucoma disease diagnosis and management.”
To review and synthesize recent literature regarding the use of OCTA for detecting changes with a diagnosis of primary open-angle glaucoma, the study authors examined PubMed and Cochrane Library databases for peer-reviewed articles published over a 2-year period. After applying relevant inclusion and exclusion criteria, they narrowed down 459 abstracts to 75 concerning OCT and glaucoma. These 75 articles were then reviewed by a panel methodologist who applied a three-tiered rating system based on each study’s strength of evidence.
The methodologist rated three articles as level 1 and 57 articles as level 2. The 15 articles rated as level 3 were excluded from further review. The accepted level 1 and 2 articles revealed the efficacy of OCTA in detecting decreased capillary vessel density in the peripapillary nerve fiber layer, which is strongly correlated with glaucoma. OCTA-measured choroidal or deep-layer microvasculature dropout was associated with glaucoma-related damage in most studies.
In addition, lower peripapillary and macular vessel density and choroidal microvasculature dropout was associated with faster rates of disease progression, according to the study. Study results differed on whether OCTA of peripapillary and macular vessel density was diagnostically comparable to structural OCT retinal nerve fiber and ganglion cell thickness measurements in differentiating glaucomatous from healthy eyes.
The authors wrote that additional research is needed to shed more light on key considerations of OCTA diagnostic discrimination.
“OCT angiography provides complementary information to the traditional structural and functional parameters,” WuDunn and colleagues wrote. “It may be particularly helpful in the evaluation of patients who are glaucoma suspects and in the monitoring of advanced disease when structural OCT parameters have reached the floor of their dynamic range.”
Perspective
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In managing patients through the glaucoma continuum, perhaps the greatest challenge lies in the extremes: establishing a diagnosis as early as possible and detecting progression in advanced disease.
Over the last 15 years, conventional OCT has evolved to inform both ends of the spectrum. Now, OCTA appears poised to push these boundaries even further and shed more light on the enigmatic relationship between structural damage and functional loss.
OCTA has demonstrated decreased radial peripapillary and superficial macular capillary vessel density that is spatially concordant with, but occurs in advance of, both retinal nerve fiber layer/ganglion cell-inner plexiform layer (RNFL/GCIPL) thinning and manifest visual field loss. That is, decreased vessel density appears to be a cause, not a consequence, of glaucomatous optic neuropathy and may be a marker of retinal ganglion cell dysfunction preceding death, affording an opportunity for earlier diagnosis and intervention.
On the other end of the continuum, while both RNFL and GCIPL thickness eventually reach a measurement floor, perifoveal vessel density continues to decrease, providing value in monitoring advanced disease.
OCTA is proving to be a valuable complement to, albeit not a replacement for, conventional OCT and automated visual field assessment, and its utility in myopic and normal-tension glaucoma is also being explored. Stay tuned.
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