Neurotrophic effects of topical insulin in persistent epithelial defects

To evaluate the effect of topical insulin eye drops in promoting epithelial healing in patients with neurotrophic keratopathy (NK) and persistent epithelial defects (PED), and to assess their impact on corneal sensitivity as an indicator of neurotrophic function.

This retrospective study included 24 patients with PED unresponsive to standard medical and surgical treatment. Patients received topical insulin eye drops (1 IU/mL) every six hours for one month. Corneal sensitivity, measured with Cochet-Bonnet esthesiometer, and PED size were recorded at baseline, and at 1st, 2nd week and 1st month after treatment initiation.

The most common underlying etiology was epithelial debridement during vitrectomy and NK due to herpes simplex virus (n=6, 25.0% each), followed by chemical injury (n=4, 16.6%). While the initial epithelial defect area was 16.23±11.23 mm², the defect area at 1 month after initiating insulin eye drops was 0.63±1.27 (p=0.0019). Corneal sensitivity values showed improvement in all quadrants one month post-treatment (central, p=0.002; superior, p<0.001; inferior, p<0.001; nasal, p=0.002; temporal, p=0.001). Following treatment, recurrence was noted in 2 cases, while 6 patients showed a partial response. In 3 of these partial responders, isolated hyperkeratinized epithelial islands were identified. The mean duration of insulin drop use was 45.6±15.3 days, and the mean time to complete epithelial defect closure was 22.7±12.8 days. A mean total follow-up duration was 172.0 ± 71.7 days.

Topical insulin promotes epithelial healing in PED and may improve functional corneal sensitivity, potentially reflecting enhanced corneal neurotrophic function. Its accessibility and favorable safety profile make it a promising therapeutic option.