Analysis for Extracted Features of Pupil Light Reflex to Chromatic Stimuli in Alzheimer’s Patients

Abstract

INTRODUCTION: Some Alzheimer's Disease (AD) patients respond to chromatic light stimulus, which may influence intrinsically photosensitive retinal ganglion cells (ipRGCs), due to factors common to both AD and Age-Related Macular Disease (AMD). OBJECTIVES: In this study, short light pulses of three colours were introduced to a novel diagnostic procesure for AD patients such as classification techniques using waveform features of pupil light reflexs (PLRs), and their prediction performances were evaluated. METHOD: PLRs to 1s pulses of red, blue and white stimuli shown at high and low photopic levels followed by a 7s restoration process were recorded after the stimuli were shown to 7 AD patients and 12 non-AD participants (aged 42-89). Features of waveform shapes of PLRs in 5 dimensions and 15 features of PLRs were extracted. RESULTS: In a classification analysis, most non-AD participants were correctly identified using the same level of performance we reported when PLRs for red and blue stimuli were used to measure the performance of AD patients. There were significant differences in some of the features of PLRs extracted from the two groups (AD and non-AD participants), particularly with the features for blue light stimuli in high brightness, which produced significant reactions in AD patients. The classification performance of using 15 features of the response to blue light stimuli was the highest among responses for all three colours, and was higher than the performance using the procedure in the previous study. Also, a few of the features extracted using the three colours of stimuli changed significantly across age ranges (70 and under, 71-80, and over 80), so these may indicate factors related to ageing. CONCLUSION: These results confirm that some specific features of PLRs, in particular the response to blue light, can indicate the existence of AD in patients. Also, a few of the features may reveal factors related to ageing during evaluations which use PLRs. This evidence may help in the better understanding of features of PLRs.

Detecting Symptoms of Dementia in Elderly Persons using Features of Pupil Light Reflex

“…The factor scores for blue but not red light pulses were selected once more for use in a regression model, following a stepwise procedure. The dominance of blue light pulses for the prediction was confirmed in a previous study [11], [12]. The possible reason for this may be based on the first hypothesis, which could not be confirmed according to the above evaluation, however.…”

Symptoms of Dementia in Elderly Persons Using Waveform Features of Pupil Light Reflex

“…If the participants have sensor impairments, it may not be possible to conduct these types of tests. In another procedural approach to diagnosis, participant's behavioural responses, acoustic features of their spoken voice [17,41,24], gait features [1], and oculo-motors [32,31] have been analysed technically. Some new measurements using vision functions are also being studied to introduce new diagnostic approaches [39,26,8].…”

“…Some characteristics of PLR waveforms are extracted and compared with light wavelengths of colours such as blue or red [9,42] as suggested in previous works [21,20,18]. Though some PLR-based diagnostic prediction procedure using features of the waveforms are proposed [32,31], key features of PLRs and the appropriate procedures have not yet been extracted. As the previous studies have produced various successful assessments, feature extraction approaches to ipRGC based PLRs will be discussed in this work, with the most appropriate observation procedure for a PLR based diagnostic prediction procedures also being considered.…”

“…The study of conventional PLR activity suggests that as this activity represents the visual information processing of retinal stimuli and the ability to activate neural signal transfers [12,5], it should be evaluated as an alternative means of diagnosing cognitive function impairment [26,3]. Also, PLR responses based on Melanopsin ganglion cells [15,21,40] can be applied to the study of Aged Macular Disease (AMD) and AD [15,21,8], and the possibility of their use in diagnosing these diseases has been studied [29,34,32,31]. A simple procedure to detect AMD and AD patients is required for medical and clinical staff who treat elderly people [33].…”

Classification of Alzheimer's disease patients using metrics of oculo-motors

“…Changes in the level of cognitive activity and mental workload handling ability are often assessed using pupillary changes [2], [3], [4]. The symptoms of AD and aged macular disease (AMD) are also detected using pupillary reactions to the pupil light reflex (PLR) [5], [6], [7].…”