The polarization state of light double passing through the eye is mainly modified by the birefringent structures of the cornea and the retina. The effects of depolarization are often light in normal young eyes but these could change with age, ocular pathologies and refractive surgery. The influence of depolarization on the calculation of the ocular retardation has been studied. Results show that the larger the depolarization, the larger the error in the computed ocular retardation. Moreover, the influence of the corneal compensation on measurements of ocular polarimetry has also been explored. We found that an incomplete compensation of the retardation and/or corneal axis leads to both wrong estimation of the ocular retardation and an erroneous computation of the corneal axis.