Early detection of changes in visual function in diabetes mellitus.

Psychophysical measurements were performed with a view to providing an assessment of early neural functional integrity in the presence of no or minimal diabetic retinopathy (DR). The investigations were carried out on a normal group and a number of age- and sex-matched non-insulin dependent diabetic groups with different levels of DR. Results were considered in terms of the presence of functional changes relative to the severity of DR and the duration of diabetes. Significant deficits were found for visual acuity (VA), contrast sensitivity (CS) and colour vision. Both CS and colour vision measurements differentiated between non-diabetics and those with diabetes but without DR. However, none of the tests reliably distinguished diabetics without DR from those with early retinal changes although VA and colour vision (especially along a blue-yellow colour axis) were sensitive to more substantial retinal changes. This finding suggests such tests may be useful as screening tests for more advanced levels of background DR.