Abstract
Purpose: :
To evaluate the effect of type 2 diabetes on autonomic and peripheral nervous system using pupillometry and corneal confocal microscopy (CCM) respectively.
Methods: :
Fifty-six eyes of 30 patients affected by type 2 diabetes and 32 eyes of 32 age-matched healthy subjects underwent pupillometry and CCM evaluations. Pupil diameter was dynamically measured at 0.04, 0.4 and 4.0 lux in scotopic, low and high mesopic light conditions respectively (Procyon P 3000, Procyon Instruments, London, UK). Images of the central cornea were obtained with a 40x non contact lens and the Z-ring device (ConfoScan 4.0, Nidek, Gamagori, Japan). Number of fibers, branchings and beadings, density and tortuosity of the sub-basal nerve plexus (SNP) were analyzed. Glycosylated haemoglobin values and diabetic neuropathy levels (Michigan Neuropathy Screening Instrument, MNSI) were quantified and relate with the results of pupillometry and CCM.
Results: :
Mean pupil diameter was statistically lower in diabetic than in control subjects at scotopic (4.77±0.81 vs. 5.90±0.51), low (3.99±0.64 vs. 4.93±0.70) and high mesopic (3.28±0.56 vs. 3.71±0.49) light conditions (p<0.001). CCM showed that the number of fibers, branchings, beadings and density of fibers of SNP was statistically lower in diabetics toward controls (p=0.001). A statistically higher percentage of fiber fragments was seen in diabetic patients (p=0.044). Pupil diameter was correlated to glycosylated haemoglobin in all light conditions (p<0.01). Mean pupil diameter was lower in patients affected by diabetic neuropathy (p<0.005).
Conclusions: :
Type 2 diabetic patients showed alterated pupil diameter, pupil dynamics and corneal small nerve fibers. Diabetic neuropathy was associated with alterations of both pupillometry and CCM in all patients. Pupillometry and CCM may be useful as noninvasive diagnostic tests to study and monitor peripheral and autonomic nervous system involvement secondary to diabetes.
Keywords: diabetes • pupil • cornea: clinical science