Relationship between spectral transmittance and slit lamp color of human lenses.

PURPOSE To study the relationship between subjective lens color as observed with slit lamp biomicroscopy and spectral transmittance of the lens. To propose a model for this relationship to derive quantitative information on lens pigmentation from slit lamp observation. METHODS Twenty-nine normal lenses, from donors aged 14 to 86 years, were used. The fraction of light transmitted from a narrow beam was measured as function of wavelength. The spectra were fitted with the one-parameter TL model of Pokorny et al. The relationship between this parameter and the color grading from Chylack et al. (lens opacity classification system III nuclear color score) was established. RESULTS After slight adaptation of the TL model, the shapes of the transmittance spectra corresponded closely to the TL model (average residual error 0.05 log units). Log transmittance and lens opacity classification system nuclear color score were closely related (r = 0.90, 0.77, and 0.55 for 400, 500, and 602 nm, respectively). CONCLUSIONS A mathematical relationship between TL parameter and lens opacity classification system nuclear color score could be established to predict lens transmittance from lens opacity classification system nuclear color score. This relationship was successful in predicting the correction for lens absorption needed in blue-on-yellow perimetry.