AUTOMATIC QUANTITATIVE MEASUREMENT OF OCULAR HYPEREMIA

Evaluation of ocular hyperemia has been an important assessment in res earch studies of effects of contact lenses, medications, and pollutant s on the eye. Hyperemia has been difficult to quantitate objectively. The purpose of this study was to validate a computer based image analy sis system to quantitate hyperemia automatically and objectively in pi xelated images of the external eye using two measures, the percent of the red color, RR, and the fraction of pixels which are blood vessels, VA. Validation was against an established photographic reference scal e of ocular hyperemia and against the clinical pharmacologic effects o f 0.5% dapiprazole hydrochloride, known to increase hyperemia, and 2.5 % phenylephrine hydrochloride, known to decrease hyperemia. Color tran sparencies from the reference scale were converted to digital images. Temporal and nasal regions of the external eye were imaged directly to magnetic disk before and after pharmacologic intervention. Custom sof tware automatically excluded unwanted regions, and quantitative image analysis produced RR and VA. RR and VA were each correlated with the r eference scale. For each region and for each pharmacologic interventio n, the mean RR and the mean VA, respectively, were compared at time ze ro and at a mean elapsed time of 713 +/- 47 a. RR and VA consistently increased as the hyperemia in the reference scale increased. Pearson c orrelation coefficients were 0.98 and 0.99, respectively, (p < 0.01). At 713 +/- 47 s after each pharmacologic intervention, RR and VA incre ased and decreased as expected (p < 0.001). Thus, this study successfu lly validated the methodology against expert clinical judgment and was able to measure automatically and objectively clinical changes in ocu lar hyperemia.