Abstract
Purpose:
The aim of this study was to evaluate the ability of chromatic pupillometry, using a novel photic stimulation paradigm, to discriminate glaucoma patients from healthy controls, by detect functional loss of intrinsically photosensitive retinal ganglion cells (ipRGCs).
Methods:
In this cross-sectional study, we included 40 patients with primary open angle glaucoma (POAG) and 161 healthy controls, aged 50 and above. Pupillometry and standard ophthalmic examination were performed in all participants; POAG patients were also evaluated with standard automated perimetry (Humphrey Visual Field, HVF, Carl Zeiss Meditec, Dublin, CA) and scanning laser ophthalmoscopy (Heidelberg Retinal Tomography, HRT, Heidelberg Engineering, Heidelberg, Germany). Dose-response curves of the pupillary light responses (PLR) to narrowband blue light (469nm) or red light (631nm), at increasing corneal irradiances, over 2 minutes (7 to 14 log photons cm-2 s-1), were constructed. Pupil diameter was recorded using an infrared pupillography system.
Results:
The pupillary light reflex was reduced in patients with POAG at high irradiance levels, corresponding to the range of ipRGCs activation. Pupillary responses to high-irradiance blue light associated more strongly with disease severity compared with responses to red light, with a significant linear correlation observed between pupil diameter and HVF mean deviation (r = -0.44, p = 0.005) as well as HRT linear cup disc ratio (r = 0.61, p <0.001).
Conclusions:
This novel colour pupillometric test using exposure to continuously increasing blue light allows accurate discrimination of glaucomatous eyes from normal eyes. Further studies are needed to determine if this test may also estimate the degree of visual function loss in glaucoma.