The clinical classification of various types of albinism depends in part on the amount of ocular involvement as judged by the translucency of the iris. While the globe is transilluminated, the quantification of iris translucency (QUIT) can be obtained by matching the brightness of light transmitted through the iris and through the pupil when graded neutral density filters are interposed between the pupil and the observer. In patients with ocular albinism the QUIT was 0.4 neutral density (ND). The technique, sources of error, and applications of the method are discussed.
Wirtschafter JD, Denslow GT, Shine IB. Quantification of Iris Translucency in Albinism. Arch Ophthalmol. 1973;90(4):274-277. doi:10.1001/archopht.1973.01000050276004