Ocular surface diabetic disease: A neurogenic condition?

PURPOSE

To investigate clinical and inflammatory changes in the ocular surface of insulin-dependent type I diabetic patients.

METHODS

Two hundred and nine eyes of 106 patients with diagnosis of type I diabetes were recruited in a prospective observational study. Ocular surface clinical assessment, corneal sensitivity and tear film stability tests were performed to evaluate ocular surface system function. Ocular Surface Disease Index (OSDI) questionnaire was administered to all enrolled subjects. Conjunctival impression cytology specimens were also collected to detect neuromediators and inflammatory molecules. Duration of disease, HbA1c levels and diabetic retinopathy stage were recorded.

RESULTS

Corneal sensitivity assessed by Cochet-Bonnet esthesiometer was reduced in patients with more chronic disease, higher HbA1c levels and proliferative diabetic retinopathy. Tear break-up time (TBUT) was reduced in subjects with long-standing diabetes or with more severe retinopathy. OSDI questionnaire scores showed direct correlation with increased HbA1c values. Significant increase of NPY, STAT-5 and ICAM-1 was found in diabetic patients compared to healthy controls. A direct correlation between NPY concentration and ICAM-1 values in patients with type I diabetes was demonstrated.

CONCLUSIONS

Patients with long-standing type I diabetes showed chronic inflammation of the ocular surface, due to neurogenic dysregulation of para-inflammatory homeostatic mechanisms. These patients with ocular surface system failure complained of ocular discomfort but had modest reduction of corneal sensitivity and no signs of neurotrophic keratopathy. Disease duration, increased HbA1c levels and severe diabetic retinopathy appear the most critical factors.