Age‐related lens yellowing per se contributes little to the increase in Farnsworth‐Munsell 100 hue error scores with age

Abstract

Purpose: To investigate the effects of real and simulated age‐related changes in crystalline lens yellowing on Farnsworth–Munsell (FM) 100 hue total and partial error scores.Methods: FM 100 hue total and partial error scores were measured in a group of younger (n = 10, mean age 22.2 ± 2.65 years) and a group of older (n = 10, mean age = 54.5 ± 2.64 years) normal observers along with psychophysical estimates of crystalline lens optical density and pupil size measurements. Three younger observers underwent repeated FM 100 hue testing using a variety of simulated age‐related lens yellowing conditions, using filters with well‐defined absorption properties which mimicked the real age‐related lens yellowing changes of the older group. FM 100 hue scores were also measured under different levels of background illumination and pupil size in the 3 younger observers.Results: FM 100 hue total and partial error scores were significantly higher in the older age group compared to the younger group (p <0.01). Lens density measures were significantly higher in the older age group compared to the young group (p<0.01), but showed less scatter with age than FM 100 hue error scores. Pupil size was significantly larger in the younger group compared to the older group (p<0.01). Simulated lens yellowing in the three younger observers, equivalent to the level of that of the older observers, did not affect any of their FM 100 hue total or partial error scores. Reductions in pupil size and illumination significantly affected the younger observers’ performance, with increases in error score equivalent to the observed age‐related decline between the younger and older group.Conclusions: Lens yellowing per se makes little contribution to the increase in Farnsworth–Munsell 100 hue error score with increasing age. Retinal illumination levels and pupil size can significantly affect the error score and should be considered when interpreting FM 100 hue error scores in older subjects. Clinicians should also consider iris colour and macular pigment density when interpreting FM 100 hue error scores.