Corneal hypesthesia and retinopathy in diabetes mellitus.

Testing with the Cochet-Bonnet esthesiometer revealed a strong correlation between corneal sensitivity and retinal status in a group of diabetic patients. Eyes with normal fundi had normal corneal sensitivity. Those with background retinopathy had somewhat poliferative retinopathyl showed a greater loss of sensitivity. Eyes that had received panretinal photocoagulation treatment demonstrated the most severe reduction in corneal sensation. Two independent processes appear to be responsible for the observed data: in untreated patients, corneal hypesthesia is a form of diabetic sensory neuropathy, while the hypesthesia associated with laser treatment is attributed to laser damage to sensory nerves lying beneath the choroid. The data show that corneal sensitivity testing can be used as a simple, sensitive, and accurate screening test for proliferative diabetic retinopathy.