Examining the Association of Cadmium With Contrast Sensitivity

Abstract

Contrast sensitivity (CS) is an important dimension of visual function that to our knowledge is not as well examined as visual acuity in ophthalmic research. Data from the populationbased Salisbury Eye Evaluation study suggest that a doubling of the contrast threshold (reducing sensitivity by 0.3 log CS units or 6 letters on the Pelli-Robson chart) has a comparable association with task performance and quality of life as that of a doubling of MAR (increase of 0.3 logMAR or 15 Early Treatment Diabetic Retinopathy Study letters). 1,2 The study by Paulsen et al 3 contributes to the understanding of the potential risk factors for CS impairment. Furthermore, to our knowledge it is the first study to find an association between the incidence of CS impairment and cadmium. Cadmium is an environmental toxic trace metal that is known to accumulate in the body, and contrast sensitivity impairment is found to be more prevalent in the older population. 4,5 Notably, the association between cadmium and CS impairment should be interpreted with caution.Associations such as those found in this study must be considered as hypothesis development, not hypothesis testing. These associations may be true or may be related to chance findings or confounding. Chance findings from large observational studies such as this are inevitable because of the dozens of associations that are tested. In addition, the categorization of cadmium levels by quintiles and the presentation of