Detecting Change in Conjunctival Hyperemia Using a Pixel Densitometry Index.

To investigate a pixel densitometry index (PDI) for measuring ocular surface inflammation (OSI). Efron's grading was performed by two independent observers. Color photographs and indocyanine green angiography were undertaken before and after instillation of phenylephrine (PE) hydrochloride 2.5%. A total of 15 patients with and 10 without OSI were included. PDI before and after PE was 73.29 ± 30.71 and 50.87 ± 17.46 (p = 0.036) in patients with inflammation and 52.86 ± 16.90 and 39.63 ± 12.04 (p = 0.0024) in those without OSI. The reduction in Efron grades following PE was 25% (mean 0.46 ± 0.50, median 0.50; p < 0.01). The coefficient of variation pre- and post-PE was lower using the PDI (42% and 50%) than with the Efron grades (59% and 72%). The PDI allows the objective detection of change in conjunctival hyperemia with potential direct applicability to noninvasive angiography such as optical coherence tomography-based angiography.