• Vessel density loss on OCT-A was the earliest detected glaucomatous change, but overall specificity was lower than OCT.
• OCT-A may complement standard OCT and visual field testing.

OCT angiography may help detect glaucoma progression earlier than standard OCT or visual field exams, although its specificity was lower than that of structural OCT, according to data published in JAMA Ophthalmology.

“Glaucoma progression is commonly monitored with structural OCT and visual field testing, but these tests do not always show progression at the same time,” Takashi Nishida, MD, PhD, associate project scientist at the Shiley Eye Institute, told Healio. “We conducted this study to compare when progression is detected by OCT-A, structural OCT and visual field testing using event-based criteria and to determine whether OCT-A could provide an earlier signal of disease worsening.”

Nishida and colleagues retrospectively analyzed data on 180 eyes from 116 patients with glaucoma included in the Diagnostic Innovations in Glaucoma Study. They reviewed patient records to determine when they had crossed cutoff points of glaucoma progression on OCT, OCT-A and visual field tests with the Humphrey Field Analyzer II (Zeiss).

The cutoff point on OCT was 4.02 m of circumpapillary retinal nerve fiber layer thickness, and on OCT-A it was 4.1% circumpapillary capillary density. The cutoff for visual field progression was worsening pattern deviation in at least three identical test locations on three examinations vs. the average of two baseline tests.

“OCT and OCTA changes had to exceed established test-retest variability and be confirmed on two consecutive visits,” Nishida said. “We also evaluated specificity in clinically stable eyes, because earlier detection is useful only if it does not come with an excessive number of false-positive events.”

At least one modality detected progression in 107 eyes. The following showed glaucoma progression earliest:

• OCT-A circumpapillary capillary density (40 eyes; 37.4%);
• OCT circumpapillary retinal nerve fiber layer thickness (32 eyes; 29.9%); and
• Visual field testing (26 eyes; 24.3%).

“Among eyes that progressed by both modalities, OCT-A vessel density changes preceded visual field progression by an average of 2.3 years,” Nishida said, “while OCT [retinal nerve fiber layer] thinning preceded visual field progression by about 1.5 years.”

Different stages of glaucoma had different events that appeared first.

“[Retinal nerve fiber layer] thinning was more often the first signal in preperimetric glaucoma, while OCT-A vessel density loss was more often first in more established disease,” Nishida said.

The rates of false-positive events in the 45 stable eyes were 31.1% for OCT-A and 24.4% for OCT, from which the researchers calculated specificities of 68.9% and 75.6%, respectively.

The results “support a multimodal approach to glaucoma monitoring,” Nishida said.

“Different tests often identified progression in different eyes or at different times,” Nishida said. “This suggests that no single test captures all aspects of glaucomatous change.”

Nishida said OCT-A “may provide complementary information rather than replace OCT or visual field testing.”

“The main clinical message is that OCT-A may be particularly useful as an additional source of information when structural and functional tests are discordant,” Nishida said. “Further work is needed to standardize OCT-A progression criteria, address image artifacts and reproducibility and determine whether adding OCT-A to routine monitoring improves long-term patient outcomes enough to justify the additional testing.”

Takashi Nishida, MD, PhD, can be reached at tnishida@health.ucsd.edu.