Compared with vessel diameter index and fractal dimension, vessel density demonstrated the strongest correlation to validated bulbar redness scales in this study.

Compared with vessel diameter index and fractal dimension, vessel density demonstrated the strongest correlation to validated bulbar redness scales in this study. Photo: Julie Tyler, OD, and Melissa Tawa, OD. Click image to enlarge. 

A common sign that often prompts patients to seek care, ocular redness is typically associated with ocular surface disease such as dry eye, ocular allergy and other inflammatory conditions affecting the conjunctiva. The issue lies in that, due to the inherent subjectivity of most grading scales, ocular redness can be difficult to assess. In search of a more objective method, researchers recently performed a study to determine which anterior segment OCT angiography (AS-OCT-A) parameters can be used to quantitatively measure ocular redness severity. They concluded in their paper in Cornea that “changes in the density, diameter and branching complexity of the ocular surface vasculature correlate to ocular redness grading.”

The retrospective, cross-sectional single-center study analyzed 60 eyes of 40 patients whose medical charts included clinical ocular redness grading and AS-OCT-A imaging of the nasal and temporal bulbar conjunctiva. The patients were divided into groups based on the five-category validated bulbar redness scale (groups one to five). For comparison purposes, the researchers also assessed 35 eyes of 23 patients with slit lamp photographs using the 10-category validated bulbar redness scale.

In the five-category scale, the researchers observed that vessel density significantly increased from groups one to two (31.5% and 33.4%), two to three (36%) and four to five (40% and 46.5%). The correlations were 0.81 for the five- and 0.89 for the 10-category scales.

Vessel diameter index also showed a significant increase from groups one to two (2.9 and 3.0) and four to five (2.9 and 3.3). The correlations for the five- and 10-category scales were 0.55 and 0.63, respectively. The fractal dimension showed no significant differences between subsequent groups.

These findings show that “the number of vessels within the conjunctiva (vessel density) on AS-OCT-A was better than vessel density index and fractal dimension to represent the severity of ocular redness,” the researchers wrote in their paper. “When compared with a higher discriminatory classification, such as the 10-category validated bulbar redness scale, all AS-OCT-A parameters showed stronger correlations when compared with the five-category scale. This suggests that AS-OCT-A has a high precision in detecting conjunctival vascular changes.”

When assessing ocular redness in patients, measuring average vessel density of the nasal and temporal conjunctiva with AS-OCT-A may be a noninvasive and objective way to determine severity, data from this study concludes.

Binotti WW, Nosé RM, Pondelis NJ, et al. Novel application of conjunctival anterior segment optical coherence tomography angiography to assess ocular redness. Cornea. 2023;00:1-8.