Subjective and objective systems are used to quantify cataract at The Center for Clinical Cataract Research. We have described each system and its use, presented data on reproducibility and validity, and for objective systems, demonstrated the correlation to the subjective grade of the cataract as defined by the Lens Opacities Classification Systems, Versions II and III (LOCS II and III). The subjective systems are used to classify nuclear color, nuclear opalescence, cortical cataract, and posterior subcapsular cataract. Reported kappa scores for LOCS II range from 0.85 to 1.0. Intra-class correlation coefficients for LOCS III (n) range from 0.67 to 0.94. The computerized objective systems are: (1) fast spectral scanning colorimetry (FSSC) for assessment of nuclear color (n = 0.96 to 0.98); (2) nuclear mean density (NMD) for assessment of nuclear opalescence (r, = 0.97); and (3) percent area opacity (anterior = a; posterior = p) (OPAC-a and OPAC-p) for assessment of cortical and posterior subcapsular cataract (r, = 0.92 to 0.96).