AS-OCTA Derived Conjunctival Vessel Density Can Assess Ocular Redness

Conjunctival vessel density, obtained via anterior segment-optical coherence tomography angiography (AS-OCTA) is the best parameter for assessing ocular redness severity, according to a study published in Cornea. This is due to its strong correlation with validated bulbar redness scales, according to the report. 

“Currently, ocular redness is most widely assessed through grading scales based on photographic or illustrated images of increased redness within 5 categories of severity,” the study authors note. “They are easy to perform at low cost but are inherently subjective and prone to variability from environmental illumination, photographic device and color resolution, judgment influence bias, and low discrimination to detect small incremental changes, particularly given the limited scale.”

Researchers from the Cornea Service of New England Eye Center included 40 patients (eyes, 60) in the retrospective, cross-sectional investigation and stratified them according to ocular redness stages as determined by the 5-category validated bulbar redness scale. The team performed AS-OCTA imaging of the nasal and bulbar conjunctiva and obtained vessel density and vessel diameter index measurements. A subset of participants with slit lamp photographs (n=23; eyes, 35) underwent a 10-category validated bulbar redness scale assessment, and AS-OCTA parameters were compared in both cohorts. 

No statistically significant differences were noted between groups for age (P = .118), sex (P = .501), eye laterality (P =.111), or location (nasal vs temporal; P = .932), according to the report. Vessel density increased according to ocular redness score (31.5%, 33.4%, 36.0%, 40.2%, and 46.5% for scores 1, 2, 3, 4, and 5, respectively). AS-OCTA derived vessel density values strongly correlated with the 5- and 10-category validated bulbar redness scales (r, 0.805 and r, 0.893, respectively; P <.001 for both). 

Vessel diameter index increased significantly from bulbar redness scores of 1 to 2 (2.90 vs 3.00; P = .004) and 4 to 5 (2.92 vs 3.33; P = .001) with  correlations of 0.550 (P < .001) and 0.625 (P < .001) for the 5- and 10- category validated bulbar redness scales, respectively. 

“[W]e show that the average [vessel density] of the nasal and temporal conjunctiva, as measured by AS-OCTA, was the best parameter to assess ocular redness with the strongest correlation to [validated bulbar redness] scales,” according to the researchers. “Therefore, AS-OCTA is a promising tool to measure ocular inflammation as it provides quantitative assessment of the bulbar conjunctival vasculature in vivo and noninvasively.”

Study limitations include a retrospective and cross-sectional nature, the use of software not designed for anterior segment imaging, and limits to the ranges and capabilities of the OCT.