Use of laser flaremetry to measure aqueous humor protein concentration in dogs

The blood-aqueous barrier in dogs is compromised by uveitis, surgery, and limbal paracentesis. Breakdown of the blood-aqueous barrier allows protein into the aqueous humor and results in mild to severe inflammation. Diagnosis of protein in the aqueous humor is traditionally a subjective measurement. Laser flaremetry was used for noninvasive quantitation of aqueous humor protein concentration in dogs. Flaremetry data were compared with aqueous humor protein concentrations obtained from aqueous humor paracentesis and slit-lamp flare evaluations. Results from clinically normal eyes and those with uveitis and cataracts were compared. Subjective evaluations of flare were correlated with a range of flaremetry readings and aqueous humor protein concentrations. Clinically normal eyes had a range of flaremetry readings of 1.4 to 7.0 photon counts (PC)/ms, with a mean of 3.8 PC/ms. Corresponding aqueous humor protein concentrations ranged from 5 to 28 mg/dl, with a mean of 15.1 mg/dl. Eyes with uveitis or cataracts had a range of aqueous protein concentrations of 13 to 729 mg/dl. Flaremetry readings accurately and sensitively measured total protein concentrations in the aqueous humor of dogs.