Pupillometric Assessment of Cholinergic Functioning in People with Alzheimer Disease: A Study from India

Abstract

Background

Diagnosis of Alzheimer disease is mainly clinical, based on longitudinal history and clinical criteria due to lack of specific biochemical tests and neuroimaging studies. Deficient central cholinergic activity of AD pathology is said to be reflected as decreased peripheral cholinergic activity. Assessing peripheral cholinergic function with pupillometer for diagnostic and prognostic purpose may be beneficial, as it may be a non-invasive, acceptable, and easily administered diagnostic tool if proven so.

Method

This is a single point case control pilot study with sample size of 45 (25 AD patient and 20 controls). CAMDEX-R based interview, HMSE, and DSM-IV criteria were used for detailed assessment and diagnosis. The pupillometric parameters (Horizontal and vertical diameters of pupil) were measured by Oasis Colvard pupillometer (SKU-0401A) under three conditions namely after 5 minute of dark adaptation in dark room (PD-5min-DA i.e. Baseline PD); after 5 minutes (PD-5min-T) and 15 minutes (PD-15min-T) of instillation of 2–3 drops of 1.0% Tropicamide.

Results

There was no difference in baseline pupil diameter (horizontal + vertical) of AD patients and age matched healthy controls. 1% tropicamide induced significant increment in pupil diameters from baseline to after 5 (‘PD-5min-T’) and 15 minutes (‘PD-15min-T’) of its instillation in both AD patients and age matched healthy controls. But tropicamide induced increment in pupil diameters were approximately equal in cases and controls.

Conclusion

The study did not find the role of 1% tropicamide induced pupillary hypersensitivity in AD patients for diagnostic purpose.

Disclosure of interest

The authors have not supplied their declaration of competing interest.