ABSTRACT
The Queen Square Screening Test for Visual Deficits (QS test) screens for changes in visual processing. Our pilot study aimed to review the applicability of the QS test in individuals with dementia compared with those with normal cognition. Participants with major and minor neurocognitive disorder scored 50/71 (n=12) and 61/71 (n=10) respectively on the QS test, compared to 65/71 for age-matched healthy controls (n=11). The QS test score correlated with cognitive impairment as measured using the Rowland Universal Dementia Assessment Scale (r = 0.74). The QS test is an affordable and easy bedside screening test for visual processing changes.
KEYWORDS: Dementia, cognitive impairment, visual deficits, visuospatial, screening test
Introduction
Dementia is a neurocognitive disorder (NCD) that can cause deficits in visual processing. The American Psychiatry Association’s 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) categorises dementia as major and minor NCD.1 Major NCD is characterised by an interference to daily function due to impairments in complex attention, executive function, learning and memory, language, perceptual-motor function, or social cognition.1 In minor NCD these deficits do not interfere with daily activities. Individuals can be screened for cognitive impairment using several metrics. The Rowland Universal Dementia Scale (RUDAS) (Appendix 1) is one such screening test that is sensitive to early dementia, has good content validity, and is easy to administer in approximately 10 minutes.2 It also does not appear to be influenced by age, sex, or a person’s cultural and linguistic background.
Dementia poses a significant burden, affecting approximately 50 million individuals worldwide with 10 million new cases diagnosed each year.3 Dementia and its associated visual impairments are likely to present more frequently to clinicians in our ageing population. It would therefore be of clinical value to investigate visual testing as a method of screening and monitoring dementia.4
Despite increased research on the visual deficits in dementia, there is limited consensus on their specificity to the various dementia syndromes including Alzheimer’s disease (AD), Lewy body dementia (LBD), and posterior cortical atrophy (PCA). In AD, which accounts for the majority of cases, impairment of memory and executive function appear first, but visual processing may also be impaired in the early stages, manifesting as difficulties with reading, discriminating form and colour, perceiving contrast, perceiving visuospatial orientation and motion detection. This may progressively decline into visual agnosia and difficulty in developing visual strategies.5
These findings are consistent with pathological changes in AD that occur in the parieto-occipital regions responsible for processing visuospatial information.6–9 In AD, studies have identified amyloid beta plaques and neurofibrillary tangles in the eye, superior colliculus, pulvinar nucleus of the thalamus, and lateral geniculate nucleus, which can cause deficits in visuospatial attention and visual processing.9 However, this pathology has also been observed in the elderly with normal cognition without any clinical consequence.9
Individuals who develop visual processing deficits before other signs of dementia often seek an Ophthalmology opinion, but typically have normal results on standard tests of visual function and a diagnosis of dementia may not be suspected.6 Several metrics have been developed to analyse visual processing changes that can also be used in the context of dementia. Trobe and Butter developed tests of integrative visual function that assess the identification of forms and their spatial relationships including overlapping forms, masked forms, high density line cancellation, reading, and puzzle construction.6 A single subtest had a mean test time of 8 minutes and could identify more than 90% of patients with AD. Their battery was able to differentiate individuals with visual symptoms related to AD from those who had subnormal vision secondary to ocular or retrobulbar visual pathway diseases unrelated to AD.
The Visual Object and Space Perception (VOSP) test battery developed by Warrington and James examines object perception (incomplete letters, silhouettes, object decision, progressive silhouettes tests) and spatial perception (dot counting, position discrimination, number location, and cube analysis tests).10 It takes approximately 45 to 60 minutes to perform and costs £244.50. The test can be reused multiple times. It is based on the theory that object and spatial perception are functionally independent domains of visual processing and are dependent on the ventral (occipito-temporal) and dorsal (occipito-parietal) pathways respectively.11 AD patients perform poorly in all subtests of object perception, and the cube analysis and number location subtests of space perception.5 The VOSP test battery has been validated5,12 and assists in improving the characterisation and early diagnosis of neurocognitive disorders such as Huntington’s disease, LBD and atypical Parkinsonian syndromes.11
The Queen Square Screening Test for Visual Deficits (QS test) (Appendix 2) is a short booklet developed using remnant object and spatial perception tests from the validated VOSP test battery.13 It is a quick and easily accessible alternative to the VOSP test, requiring less than 10 minutes to perform and costs £10. The test can be reused multiple times. The QS test assesses early visual processing, object perception, space perception, face perception and reading. It has never been formally validated as a single test, but if validated, would serve as a time efficient method of screening for visual deficits within the constraints of a clinical consultation or outreach clinic. This would assist in better understanding the role of vision in dementia, diagnosing visual processing disorders earlier, and potentially developing interventions.14
Our study aimed to review the applicability of the QS test and examine the patterns of visual processing deficits it identified in individuals with dementia compared with those with normal cognition. It was hypothesised that patients with dementia will demonstrate deficits in object and space perception similar to the VOSP test battery.
Methods
Study design
We carried out a pilot study with two cross-sectional studies of participants with dementia (major NCD or minor NCD) and age-matched healthy controls. All participants were recruited from outpatient general Neurology and Geriatrics clinics and medically stable inpatients of the Neurology and Geriatrics department of a major tertiary hospital between December 2018 and March 2019. The diagnoses of dementia, its subtypes, and whether there was major or minor cognitive impairment, were made by the treating Neurologist or Geriatrician in accordance with the DSM-5.1
Individuals were included in this study if they completed more than 1 year of schooling, were more than 50 years of age, and had no uncorrected visual deficits on a reading acuity test. If they had been taking central nervous system acting drugs such as cholinesterase inhibitors and anti-depressants, then they must have been receiving a stable dose for at least 3 months. Furthermore, participants were included in the group with cognitive impairment if they had a clinical diagnosis of dementia. Participants were included in the normal cognition group if they were cognitively normal with RUDAS of 27 or more and were clinically unimpaired.
Participants with dementia were excluded from this study if they had severe language deficits, severe aphasia, uncorrected sensory deficits (visual or hearing), severe systemic diseases (metastatic cancer, terminal illnesses), or severe concomitant psychiatric conditions (psychosis). Participants were also excluded from the group with cognitive impairment if they had a RUDAS of less than 13 in order to exclude participants who may have difficulties with task comprehension and response. Participants were excluded from the normal cognition group if they had a previous history of major central nervous system diseases such as multiple sclerosis or stroke.
Standard protocol approvals, registrations, and patient consents
Ethics Approval was granted by the South Western Sydney Local Health District Human Research Ethics Committee (HREC/18/LPOOL/454). The study was therefore performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.
All participants gave their informed written consent prior to the inclusion in the study. Details that might disclose the identity of the subjects under study were omitted.
Data collection
Participant demographics and medical history were collected including age, sex, level of education, preferred language, ethnicity, and subtype of dementia diagnosed (if applicable).
A simple test of reading acuity (single letter naming at 30 cm) was performed using glasses if required to ensure participants could read the font of the book. Confrontation visual fields was performed using the examiner’s finger as a target to ensure there was no significant visual field defect.
Performance on the RUDAS and QS tests were measured.
Statistical analysis
All continuous variables were described using median and interquartile range, and categorical data as numbers and percentages. RUDAS and QS test scores were described using mean and 95% confidence interval. Statistical analysis was performed using IBM SPSS Statistics (IBM Corp. Released 2016. IBM SPSS Statistics for Windows, Version 24.0. Armonk, NYL IBM Corp.).
Results
Thirty-three participants were examined and their baseline characteristics are summarised in Table 1. The major NCD group consisted of patients with diagnoses of AD (n = 3), vascular dementia (n = 4), LBD (n = 1), mixed AD/vascular dementia (n = 1), and unspecified major neurocognitive disorder (n = 3). The ethnic background as identified by each participant were categorised geographically as follows for the normal cognition, minor NCD and major NCD groups: the United Kingdom (n = 6, n = 7, and n = 8 respectively), Europe (n = 2, n = 2, and n = 3 respectively), and Asia (n = 3, n = 1, and n = 1 respectively).
Table 1.
Baseline characteristics of the participants
| Variable | Cognitive impairment |
|||
|---|---|---|---|---|
| Overall (n = 33) |
Normal cognition (n = 11) |
Minor NCD (n = 10) |
Major NCD (n = 12) |
|
| Median age in years (IQR) | 83.0 (78.5–87.5) | 83.0 (79.0–88.0) | 80.0 (73.8–87.5) | 83.5 (81.0–87.8) |
| Numbers of males (%) | 18 (54.5%) | 5 (45.5%) | 7 (70.0%) | 6 (50.0%) |
| English as preferred language (%) | 26 (78.8%) | 9 (81.8%) | 9 (90.0%) | 8 (66.7%) |
| Median total years of education (IQR) | 10.0 (8.0–11.0) | 10.0 (7.0–11.0) | 10.0 (8.75–11.0) | 9.5 (6.50–12.0) |
IQR = interquartile range.
NCD = neurocognitive disorder.
The QS test took approximately 8 minutes to complete and was well tolerated by participants.
Figure 1 summarises the RUDAS and QS Test scores for each participant and stratified according to cognitive group. Pearson’s correlation coefficient for the RUDAS and QS Test scores was 0.74. The mean RUDAS and QS test score results for each cognitive group are summarised in Table 2.
Figure 1.
QS test and RUDAS scores for each participant, stratified by cognitive status. Note that there are two participants with RUDAS score of 27 and QS test score of 62
Table 2.
Mean RUDAS and QS Test scores, stratified by cognitive status
| Variable | Cognitive impairment |
||
|---|---|---|---|
| Normal cognition (n = 11) |
Minor NCD (n = 10) |
Major NCD (n = 12) |
|
| Mean RUDAS score | 28/30 (95% CI: 28–29; range: 27–30) |
25/30 (95% CI: 23–27; range: 22–28) |
17/30 (95% CI: 15–18; range: 13–20) |
| Mean QS Test score | 65/71 (95% CI: 62–67; range: 59–70) |
61/71 (95% CI: 55–67; range: 44–69) |
50/71 (95% CI: 43–56; range: 29–65) |
CI = confidence intervals.
NCD = neurocognitive disorder.
QS Test = Queen Square Screening Test for Visual Deficits.
RUDAS = Rowland Universal Dementia Assessment Scale.
The mean scores for each subset of the RUDAS are summarised in Appendix 3 and the mean scores for each subset of the QS test are summarised in Appendix 4.
Discussion
The QS test was easy to administer and revealed visual processing difficulties in patients with major NCD. Our study showed a pattern where patients with major NCD may have deficits in early visual processing, reading, and the perception of faces and objects – scoring 3.9 points, 3.7 points, 2.9 points, and 2.7 points less in the QS test than the normal cognition group respectively. This is important for clinicians to recognise, particularly when clinical signs do not match functional symptoms.
Each subset of the QS test provides insight into where lesions may appear in dementia to affect visual processing. Deficits in space perception is seen more in PCA as it localises to the right occipito-parietal (dorsal) region. This could explain why space perception was not markedly affected in our study as none of the participants had PCA. In contrast, object and face perception localise to the left occipito-temporal (ventral) region. Early visual processing is dependent on high order functions of both visual object and space perception, and reading ability is dependent on multiple areas.
Our results are consistent with the current literature in which individuals with AD exhibit deficits in complex visual function such as reading, visuospatial function, and object recognition.15–17 However, our pilot study was unable to be directly compared to the results of other studies that examined AD since our dementia group comprised of different aetiologies including AD, vascular dementia, mixed dementia, and LBD. The diagnosis of dementia is based on consensus criteria, which also introduces variability in sensitivity and specificity of selected patient populations of dementia subtypes in published studies.9 Although we are unable to directly compare our results to studies that examined AD, our study shows that the QS test may be useful in screening for cognitive impairment in the real world in patients with undifferentiated dementia.
The mean RUDAS score of each cognitive group in our study was in line with that of published data.2 We noted that the ‘visuospatial orientation’ score of the RUDAS was not different between the cognitive groups despite several QS subtest scores being different. The ‘visuospatial orientation’ component in the RUDAS tests body orientation, which may measure factors other than visual function despite being labelled as a visuospatial test. Regardless, it is the overall RUDAS score that our study used to determine cognitive status in our study. The interpretation of the specific body orientation task therefore does not affect our conclusions about the QS test.
The overall performance in the QS test was markedly abnormal in major NCD but was unable to differentiate between minor NCD and normal cognition. There was also a positive correlation between RUDAS and QS test scores (r = 0.74). These are interesting findings that would be worthwhile investigating further in future studies. The small sample size of our pilot study posed a challenge in accounting for potential confounding factors that could have contributed to the poor score for the major NCD group – for example, difficulties with task comprehension and response. Our study aimed to control such factors by excluding participants with a RUDAS of less than 13 and those with severe language deficits, severe aphasia, or uncorrected sensory deficits. Having said this, it is interesting to note that many studies examining vision and AD have utilised a sample of less than 25 participants in the current literature.14 Assessing a larger sample size is an improvement that can be made when the pilot study is extended in the future.
Minor NCD is challenging to define precisely but describes subnormal cognitive function that is not severe enough to impair routine day-to-day functioning. Visual deficits are often not recognised nor considered as a potential cause of functional impairment in these patients. Having said this, individuals with minor NCD progress to AD at a rate of 10–15% per year.2 The minor NCD group in our pilot study most likely represented a mix of individuals who may or may not be at risk of progression to dementia. Our pilot study is under-powered to determine how effective the QS test is in screening for visual deficits in patients with minor NCD who may be in the early stages of developing dementia. Patients with minor NCD and visuospatial symptoms may require more detailed visual testing to identify abnormalities.
There are potential influences of sociodemographic factors on the performance in the QS test. Herrera-Guzman et al. observed that age and sex were significant modifying factors in some subtests of both object and visual perception in the VOSP test battery, whilst education level was a significant predictive factor in some subtests of object perception.18 Similar findings have been observed by other authors.19 Meaningful conclusions on whether age, gender, fluency in English and education between the three cognitive groups in our study could not be reached due to the constraints of our sample size. This is an area that can be explored in future studies.
More than half of the participants in each cognitive group were from the United Kingdom. There is the possibility of own-race recognition bias in our study, given that the face perception subtests of the QS test were based on Caucasian faces including American and British famous persons. The historical reason for this is that the QS test was developed in the UK for a largely Anglo-Saxon population. Male Caucasian celebrities were chosen to prevent participants from guessing the famous person through ethnic or gender differences. However, own-race recognition bias has been demonstrated in other studies of facial recognition.20 Expanding our pilot study to recruit a more ethnically diverse study population would help to detect own-race recognition bias in the QS test, and more accurately assess its performance in multicultural populations.
The QS test is simple, inexpensive, and well tolerated by participants. In the real world, it is likely that factors such as hearing, vision, and cognitive impairment may affect an individual’s ability to comply with the QS test and confound test findings. Pye et al. reviewed cognitive screening tools for dementia that have been adapted for adults with acquired auditory or vision impairment.21 They identified several strategies to minimise the sensory bias of cognitive tests, for example, by optimising light levels in the examination room, reducing background noise, and use of sensory correction devices. These strategies could also be used for the QS test and this is an area for future research.
In conclusion, the results of our pilot study suggest that the QS test may be a promising screening tool for visual processing deficits in dementia. It is time efficient, easily accessible, and has a low utility cost. It can be easily adapted into clinical practice to alert clinicians to potential visual processing deficits in patients with cognitive impairment to improve the delivery of care to such patients.
Supplementary Material
Acknowledgments
Dr Rinaldo Gonzales, Dr David Conforti, and the Geriatrics and Neurology Departments at Liverpool Hospital for their assistance with patient recruitment and specialist opinion.
Declaration of interest statement
This study was conducted without any sponsorship or funding. The authors declare they have no financial relationships deemed relevant to the manuscript. None of the authors have any financial interest in the sale of the QS test.
Supplementary material
Supplemental data for this article can be accessed online at https://doi.org/10.1080/01658107.2021.1947324.
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