Quantitative automated pupillometry in diabetic patients and correlation with retinal nerve fibre layer thickness

To evaluate pupillary function in diabetic patients by automated pupillometry, and to study the correlation between retinal nerve fibre layer (RNFL) thickness and pupillary parameters.

Diabetic patients underwent detailed systemic and ophthalmic examination including automated pupillometry. The pupillometer used a white stimulus and was equipped with a high-resolution infrared (880 nm) camera. Static pupillary diameters were captured at different levels of background intensity-photopic high (100 cd/m2), photopic low (10 cd/m2), mesopic high (1 cd/m2), and mesopic low (0.1 cd/m2). Dynamic pupillary responses were elicited with white-light flashes (total luminance 100 cd/m2, stimulus on time 200 ms, off time 3300 ms). RNFL thickness was measured using spectral domain optical coherence tomography (OCT) RESULTS: The study had 38 diabetic patients with retinopathy (DWR), 27 diabetic patients without retinopathy (DWOR), and 25 healthy controls. Static pupillometry showed significant differences between the three groups. Diabetic patients, both with and without retinopathy had significantly smaller pupillary diameters compared to controls, (p < 0.001). The amplitude of contraction and velocity of contraction was significantly lower in diabetic patients compared to controls (p < 0.001), and between DWR compared to DWOR (p < 0.001). Percent pupillary contraction differed between DWR and controls (p = 0.001) There was a significant difference in superior RNFL thickness between DWR and DWOR (p = 0.032). The superior quadrant RNFL correlated with the maximum number of pupillometry parameters.

The amplitude and velocity of contraction are affected early in diabetic autonomic dysfunction. There is a relationship between RNFL thickness and pupillometry parameters in diabetic patients, indicating simultaneous neurodegeneration and autonomic neuropathy.