Abstract
Cortical cholinergic deficiency is prominent in Alzheimer's disease (AD), and published findings of diminished pupil flash response in AD suggest that this deficiency may extend to the visual cortical areas and anterior eye. Pupillometry is a low-cost, noninvasive technique that may be useful for monitoring cholinergic deficits which generally lead to memory and cognitive disorders. The aim of the study was to evaluate pupillometry for early detection of AD by comparing the pupil flash response (PFR) in AD (N = 14) and cognitively normal healthy control (HC, N = 115) participants, with the HC group stratified according to high (N = 38) and low (N = 77) neocortical amyloid burden (NAB). Constriction phase PFR parameters were significantly reduced in AD compared to HC (maximum acceleration p < 0.05, maximum velocity p < 0.0005, average velocity p < 0.005, and constriction amplitude p < 0.00005). The high-NAB HC subgroup had reduced PFR response cross-sectionally, and also a greater decline longitudinally, compared to the low-NAB subgroup, suggesting changes to pupil response in preclinical AD. The results suggest that PFR changes may occur in the preclinical phase of AD. Hence, pupillometry has a potential as an adjunct for noninvasive, cost-effective screening for preclinical AD.
Highlights
The ocular pupil controls retinal illumination and responds dynamically to a bright flash of light by rapid constriction followed by redilation (Figure 1)
AIBL participants were excluded from the pupil response study if they did not have positron emission tomography (PET) data available; if they had pupillary malformations, severe cataract, self-reported history of glaucoma in either eye, penetrating eye wounds to both eyes, and eye surgery to both eyes that involved the muscle; if they used cholinesterase inhibitors or prescribed ocular medications; or if they were unable to complete the task without excessive blinking
Participants were excluded from the pupil response study if they had pupillary malformations, severe cataract (N = 5), self-reported history of glaucoma in either eye, penetrating eye wounds to both eyes, and eye surgery to both eyes that involved the muscle; if they used cholinesterase inhibitors or prescribed ocular medications (N = 36); or if they were unable to complete the task without excessive blinking (N = 10)
Summary
The ocular pupil controls retinal illumination and responds dynamically to a bright flash of light by rapid constriction followed by redilation (Figure 1). Pupillometry investigates this response by delivering a flash of light into the eye and accurately detecting and measuring pupil size changes over time. Pupil size and response are controlled by the opposing action of the sphincter and dilator muscles of the iris. Pupillometry provides a practical, noninvasive approach with which to evaluate cholinergic deficiency. Pupillometry has been used to identify a cholinergic deficiency in a number of disorders including Alzheimer’s
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
