The Bedford Survey: observations on retina and lens of subjects with impaired glucose tolerance and in controls with normal glucose tolerance.

After the Bedford Survey observations were made upon retina and lens in borderline diabetics (persons with impaired glucose tolerance) and in age and sex matched controls with normal glucose tolerance. Seven years after the Survey, the prevalence of retinal abnormalities ("microaneurysms" and "exudates") was similar in each group. Of 145 initially borderline diabetics examined 10 years after the Survey, 25 had worsened to diabetes. Only two of the total group had "micro-aneurysms" present and the maximum recorded in any eye was three. Lens opacities were of similar frequency in both groups shortly after the Survey and at the seven year follow-up examination. By contrast, 24% of 79 diabetics newly diagnosed during the Survey had "microaneurysms" recorded five years later. These results further justify the diagnostic category of impaired glucose tolerance, which, at least when discovered by population screening, carries no risk of clinically apparent eye disease for at least ten years after ascertainment.