SUMMARY A simple technique is described for assessing the sensitivity of the human visual system to gratings at-threshold contrast. The technique has advantages for clinical use in that it is (1) inexpensive, (2) quick to administer, (3) portable, and (4) relatively free from bias. Forty-two diabetic patients and 84 normal controls have been tested. Fifteen diabetic patients (6/20 with retinopathy and 9/22 without) had test scores more than two standard deviations below the norm for age-matched controls.The threshold contrast at which a pattern of stripes is just visible is a measure of visual function that has recently received great attention. It differs from conventional acuity in several respects'-3 and can pick up deficits not detected by more conventional measures in lens4-5 and retinal6-"' pathology, glaucoma, 1-'5 retrobulbar neuritis,""' and other disorders.3 [19][20][21] The contrast threshold is best measured by electronically varying the contrast Halliday26 devised a printed contrast sensitivity test with four-alternative forced choice format, in which subjects were required to report the orientation of the stripes.Correspondcncc to Dr A J Wilkins.

SUMMARY A consecutive series of patients with normal activity and a diagnosis of multiple sclerosis (10 male and 31 female) underwent extensive ophthalmological examination including visual evoked potentials (VEPs) and a new test of contrast sensitivity, which is described in detail. Seventy three per cent of patients had abnormal contrast sensitivity and 83% had abnormal VEPs. There was no association between abnormalities of the two types, but patients who had impaired contrast sensitivity and normal VEPs were younger than those whose contrast sensitivity was normal but whose VEPs were not.

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