Existing methods for early detection of ocular injury from diabetes have serious limitations. We describe a new method, measuring visual flicker discrimination of the blue-sensitive mechanism of vision. This method is noninvasive, quantitative, and capable of distinguishing two types of impairment. Blueflicker discrimination was measured in 10 adults with type I (insulin-dependent) diabetes for <5 yr. Although no evidence of diabetic changes was detected by careful ophthalmic examination by an experienced ophthalmologist, 12 of 19 eyes (63%) had flicker discrimination scores considered abnormal in comparison with those of a control group, and 8 of 10 subjects (80%) had at least 1 eye with abnormal performance. In all but 2 abnormal eyes the deficit of blue-flicker discrimination was of the “absorptive” type, suggesting increased absorbance or scattering of blue light in the optical media. These data show that a functional impairment of vision can be measured very early in the course of type I diabetes, before visible retinopathy is present, and suggest this test procedure may have both investigative and clinical applications.

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