Differentiation between local production of antibody and passive leakage from the blood involves calculation of the Goldmann-Witmer (GW) coefficient, which is generated by comparison of the ratio of intraocular fluid/serum antibody concentration for the specific antibody in question to the intraocular fluid/serum ratio of total immunoglobulin levels.
http://creativecommons.org/licenses/by-sa/3.0/