The authors have tested two formulas by means of which the filtrated and the intraocularly (intrathecally) synthesized fraction of particular protein can be distinguished. The laser nephelometric method was applied to determine the serum (IgG, IgA, IgM, C3, albumin), aqueous humor (IgA, IgM, albumin) and CSF (IgG, IgM, C3, albumin) protein values in 42 subjects to test two models in physiological conditions. It was confirmed that the best results were achieved using the formula after Stambuk. Computer simulation performed to compare the formulas after Stambuk and Reiber & Felgenhauer showed a strong correlation (r greater than 0.98) between the calculated filtrated fractions of both models in a wide range of different barrier permeabilities. Laser nephelometry proved to be a useful method to determine low IgA and IgM values in aqueous humor.