Purpose: To determine if measurement of lens protein in serum is a feasible means to gain information on the physiologic status of the lens in human subjects.

Methods: The gamma-crystallin concentration was measured by a sandwich radioimmunoassay in the sera of 280 subjects aged 25-94 years. Medical records were reviewed for diagnoses of cataract and aphakia.

Results: There was no effect of age or sex on the serum gamma-crystallin concentration. There were 57 subjects with cataract and 27 with aphakia. gamma-Crystallin was higher in all cataract groups and lower in aphakia. The mean gamma-crystallin concentrations for selected subject groups were as follows: clear lens 301 pg/ml; pure nuclear cataract 344 pg/ml; pure cortical cataract 439 pg/ml and aphakia 255 pg/ml.

Conclusions: This is the first published report to show that lens protein is measurable in serum and to demonstrate the feasibility of using serum assays of lens proteins to gain information on the physiological status of the lens. Our results confirm the hypothesis that molecular and cellular events leading to cataract cause increased leakiness of lens cell membranes with release of lens proteins appearing in the blood. It is conceivable that measurement of lens proteins in serum might find future use in the evaluation of cataract risk, potentially cataractogenic and anticataractogenic agents, retained lens fragments after phacoemulsification, secondary cataract, phacolytic glaucoma, anaphylactic endophthalmitis, eye injuries, and other eye diseases.