Pupillary light reflex using Dual Mode Confocal Scanning Laser Ophthalmoscope (cSLO) in patients with diabetic retinopathy

Abstract

Purpose: To measure pupillary light reflex (PLR) using a dual mode confocal Scanning Laser Ophthalmoscope (cSLO) in diabetic patients with varying degree of diabetic retinopathy (DR).

Methods: In this prospective case control study, 90 subjects aged 35-80 years with diabetes mellitus (DM) and varying grades of DR were recruited from a diabetic retinopathy clinic. Exclusion criteria included patients with any other eye conditions, intraocular surgeries/treatments interfering with the PLR recording. Patients were given 1% tropicamide for pupil dilation and dark adapted for 40 minutes before performing retinal imaging with cSLO (Heidelberg Retina Angiograph 2). Pupillometric measurements were obtained using the infra-red (IR) reflectance mode, allowing a high pupil-iris contrast. The photic stimulus was a blue laser light, projected repeatedly for 5 seconds every 5 second intervals for 3 minutes. Pupil IR images were captured every 1 second and 12 PLR parameters were analyzed. All subjects underwent standardized clinical examination and retinal photography which were graded for the presence and severity of DR using the modified Airlie House classification system.

Results: There were 40 subjects with no DR, 20 with mild DR, 15 with moderate DR and 15 with severe DR. Among the 12 parameters, 4 showed significant difference in patients with varying degrees of DR. In patients with severe DR there was a significant reduction of the pupil constriction (p=0.001) as well as pupil re-dilation (p=0.002) compared to patients with mild and moderate DR. Average pupil size in moderate DR patients was smaller compared to healthy controls (p=0.041), and patients with severe DR had the smallest ratio of pupil maxima/pupil minima.

Conclusions: Four out of twelve pupillary light reflex parameters recorded with dual mode cSLO showed significant associations with varying degree of DR. Future research is needed to establish whether dual mode cSLO could be implemented for the early detection of DR.

Keywords: 499 diabetic retinopathy • 550 imaging/image analysis: clinical • 668 pupillary reflex