EVALUATION OF OCULAR SURFACE CHANGES AND THE RELATIONSHIP BETWEEN CORNEAL NEUROPATHY AND RETINOPATHY IN TYPE 2 DIABETES MELLITUS PATIENTS USING IN VIVO CORNEAL CONFOCAL MICROSCOPY

To investigate the relationship between the presence and degree of diabetic retinopathy (DR) and ocular surface changes, corneal sensitivity loss and corneal subbasal nerve plexus alterations using in vivo corneal confocal microscopy in Type 2 Diabetes Mellitus (DM) patients 

Department of Ophthalmology, Erciyes University Hospital, Turkey.

This retrospective study included patients examined at Erciyes University Hospital Ophthalmology clinic between January 2021 and May 2022. 83 patients with Type 2 DM and 28 healthy controls were included in the study. DM patients were classified into 3 groups regarding the presence and degree of diabetic retinopathy. 24 of the patients with Type 2 DM did not have DR (NDR), 28 patients had non-proliferative DR (NPDR) and 31 patients had proliferative DR (PDR). Ocular surface disease index score (OSDI) and average tear break up time (aBUT) was assessed. Corneal sensitivity was measured using the Cochet-Bonnet Esthesiometer (CBE). Cornea nerve fiber length (CNFL), cornea nerve fiber density (CNFD) and cornea nerve branch density (CNBD) of the corneal subbasal nerve plexus was evaluated using in vivo corneal confocal microscopy (IVCCM).

The OSDI score and aBUT showed significant decrease in all DM groups compared to non-diabetic controls. No significant difference was found between DM patient groups regarding these two parameters. Corneal sensitivity was significantly decreased in NPDR and PDR patients compared to healthy controls. Corneal sensitivity was significantly decreased when DR was present, compared to non retinopathic (NDR) diabetic patients, but no significant difference was found between NPDR and PDR groups. Regarding IVCCM parameters, CNFD decreased in all groups compared to healthy controls but significant decrease was only detected between the control group and NPDR-PDR patients. CNFD also showed a significant decrease when comparing both NDR and NPDR groups with PDR patients. When compared to healthy controls, CNBD was only found to be significantly different from the PDR group. CNBD was also found to significantly decrease with the presence of DR and its progression. CNFL was found to significantly decrease when comparing NPDR and PDR groups to healthy controls. Also in DM patients, as DR developed and progressed, CNFL showed a significant decrease.

In vivo corneal confocal microscopy is a non-invasive technique which can detect early structural corneal nerve changes in diabetic patients. DM patients with moderate to severe retinopathy should be evaluated for all ocular surface elements including tear film and functions and corneal neuropathic changes.