Color Vision Impairment Research Articles

Color vision abnormalities in type II diabetes: Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular Genetics Study II report no 2

Purpose:The purpose of this study is to assess color vision abnormalities in a cohort of subjects with type II diabetes and elucidate associated risk factors.Methods:Subjects were recruited from follow-up cohort of Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular Genetics Study I. Six hundred and seventy-three eyes of 343 subjects were included from this population-based study. All subjects underwent detailed ophthalmic evaluation, including the Farnsworth-Munsell 100 hue test.Results:The prevalence of impaired color vision (ICV) was 43% (CI: 39.2–46.7). Risk factors for ICV were higher heart rate (odds ratio [OR]: 1.043, [1.023–1.064]) and a higher intraocular pressure (IOP) (OR: 1.086, [1.012–1.165]). Subjects with clinically significant macular edema (CSME) had three times higher chance of having ICV. C1, C2, and C3 are the commonly found Early Treatment Diabetic Retinopathy Study (ETDRS) patterns. The moment of inertia method showed that the angle did not reveal any specific pattern of color vision defect. Although the major and minor radii were high in those with ICV, we did not observe polarity. Confusion index was high in subjects with ICV, indicating a severe color vision defect.Conclusions:The prevalence of ICV was 43% among subjects with type II diabetes. The most commonly observed patterns were increasing severities of the blue–yellow defect on ETDRS patterns, but no specific pattern was observed at the moment of inertia analysis. The presence of CSME, a higher heart rate, and IOP was significant risk factors for ICV. This functional impairment in color vision could significantly contribute to morbidity among subjects with diabetes.

Impaired colour vision in workers exposed to organic solvents: A systematic review

To evaluate recent evidence concerning the relationship between the exposure to organic solvents and the impairment of colour vision. A bibliographic search was conducted for scientific papers published in the last 15 years, in the LILACS, PubMed, Science Direct, EBSCO, and Cochrane databases that included observational studies assessing the relationship between impairment in colour vision and exposure to organic solvents. Eleven studies were selected that were performed on an economically active population and used the Lanthony D-15 desaturated test (D-15d), measured the exposure to organic solvents, and included unexposed controls. It was found that there is a statistically significant relationship between the exposure to organic solvents and the presence of an impairment in colour vision. The results support the hypothesis that exposure to organic solvents could induce acquired dyschromatopsia. The evaluation of colour vision with the D-15d test is simple and sensitive for diagnosis. More studies need to be conducted on this subject in order to better understand the relationship between impaired colour vision and more severe side effects caused by this exposure. Evaluar la evidencia reciente sobre la relación entre la exposición a solventes orgánicos y la alteración en la visión de colores. Se realizó una búsqueda bibliográfica de artículos científicos publicados en los últimos 15 años, en las bases de datos Lilacs, Pubmed, Science Direct, Cochrane y EBSCO de estudios observacionales que evaluaran la asociación entre las alteraciones en la visión de colores y la exposición a solventes orgánicos. En total se seleccionaron 11 estudios realizados en población laboralmente activa, que utilizaron el test de Lanthony desaturado D-15 (D-15d), midieron la exposición a solventes orgánicos e incluyeron controles no expuestos. Se encontró que existe una relación estadísticamente significativa entre la exposición a solventes orgánicos y la presencia de alteraciones en la visión de colores. Los resultados encontrados apoyan la hipótesis de que la exposición a solventes orgánicos podría inducir discromatopsias adquiridas. Evaluar la visión de colores con el test D-15d es simple y sensible para el diagnóstico. Se hace necesaria la realización de más estudios sobre el tema que ayuden a entender mejor la relación entre la alteración de la visión de colores y los efectos adversos más severos causados por esta exposición.

Innate Color Preference of Zebrafish and Its Use in Behavioral Analyses.

Although innate color preference of motile organisms may provide clues to behavioral biases, it has remained a longstanding question. In this study, we investigated innate color preference of zebrafish larvae. A cross maze with different color sleeves around each arm was used for the color preference test (R; red, G; green, B; blue, Y; yellow). The findings showed that 5 dpf zebrafish larvae preferred blue over other colors (B > R > G > Y). To study innate color recognition further, tyrosinase mutants were generated using CRISPR/Cas9 system. As a model for oculocutaneous albinism (OCA) and color vision impairment, tyrosinase mutants demonstrated diminished color sensation, indicated mainly by hypopigmentation of the retinal pigment epithelium (RPE). Due to its relative simplicity and ease, color preference screening using zebrafish larvae is suitable for high-throughput screening applications. This system may potentially be applied to the analysis of drug effects on larval behavior or the detection of sensory deficits in neurological disorder models, such as autism-related disorders, using mutant larvae generated by the CRISPR/Cas9 technique.

‘I cried for my lost sight.’ Vision and diabetes

‘I cried for my lost sight.’ Vision and diabetes

The Implementation of Elaborative Feedback for Qualitative Improvement of Shade Matching-A Randomized Study

The objective of this prospective learning research study is to examine the impact of structured elaborative feedback in practical skills teaching of visual and digital shade matching. A total of 60 preclinical dental students participated in the study. The mean average age was 23 years, of which 37 were female (61.7%) and 23 male (38.3%). The participants were randomly divided into a study and control group (n = 30 each). Recording of shade matching was carried out on the phantom patient using clinically simulated settings with elaborative feedback in the study group (T1). Nine items were recorded for visual shade matching and six items for digital shade-taking. The errors were coded. The lower the total (max. 30 points), the fewer the errors made by students during shade determination. The subject labeled the tooth color using VITA 3D-Master and VITA Easyshade (Vita Zahnfabrik, Bad Säckingen, Germany). On comparing the two groups, the study group and the control group showed a similar mean error value at reference time T1. After intervention (T2) it was possible to achieve a clear improvement in the rate of errors for study group. In the study group there was a significant difference between the ΔE values from time T1 and T2 of visual shade matching (p <0.05). The digital ΔE values show in total no significant changes. Elaborative feedback in conjunction with standardized checklists can lead to a substantial improvement among students in terms of visual shade matching. Correctly determining the tooth shade is an essential treatment step in esthetic reconstructive dentistry. Color is probably one of the most important determinants of esthetics in dentistry. Factors such as lighting conditions, gender, age, experience, and color vision impairment affect the process of shade matching. With an elaborative feedback in conjunction with standardized checklists can lead to a substantial improvement among students in terms of visual shade matching. (J Esthet Restor Dent 28:277-286, 2016).

A validation study regarding a generative approach in choosing appropriate colors for impaired users.

In many circumstances, concepts, ideas and emotions are mainly conveyed by colors. Color vision disorders can heavily limit the user experience in accessing Information Society. Therefore, color vision impairments should be taken into account in order to make information and services accessible to a broader audience. The task is not easy for designers that generally are not affected by any color vision disorder. In any case, the design of accessible user interfaces should not lead to to boring color schemes. The selection of appealing and harmonic color combinations should be preserved. In past research we investigated a generative approach led by evolutionary computing in supporting interface designers to make colors accessible to impaired users. This approach has also been followed by other authors. The contribution of this paper is to provide an experimental validation to the claim that this approach is actually beneficial to designers and users.

Idiopathic rapid eye movement sleep behaviour disorder: a potential gateway to the development of disease-modifying treatments in neurodegenerative disorders.

Idiopathic rapid eye movement (REM) sleep behavioural disorder (RBD) is classified as one of the REM parasomnias with clinical characteristics including unpleasant dreams, acting out of dreams, and loss of the typical muscle atonia during the REM phase of sleep. Other associated clinical features include olfactory loss, dysautonomia, colour vision impairment and subtle Parkinsonian signs. RBD has been shown to predict development of an alpha-synucleinopathy in 20–45 % of patients within 5 years, and up to 92 % within 14 years post-diagnosis. Hence, this disorder provides a potential opportunity for understanding the prodromal stages of the synucleinopathies and exploring efficacy of potential neuroprotective agents.

Discromatopsias y exposición a solventes orgánicos: una revisión sistemática

ObjectiveTo evaluate recent evidence concerning the relationship between the exposure to organic solvents and the impairment of colour vision. MethodsA bibliographic search was conducted for scientific papers published in the last 15 years, in the LILACS, PubMed, Science Direct, EBSCO, and Cochrane databases that included observational studies assessing the relationship between impairment in colour vision and exposure to organic solvents. ResultsEleven studies were selected that were performed on an economically active population and used the Lanthony D-15 desaturated test (D-15d), measured the exposure to organic solvents, and included unexposed controls.It was found that there is a statistically significant relationship between the exposure to organic solvents and the presence of an impairment in colour vision. ConclusionsThe results support the hypothesis that exposure to organic solvents could induce acquired dyschromatopsia. The evaluation of colour vision with the D-15d test is simple and sensitive for diagnosis. More studies need to be conducted on this subject in order to better understand the relationship between impaired colour vision and more severe side effects caused by this exposure.

Neuro-Ophthalmic and Clinical Characteristics of Brain Tumours in a Tertiary Hospital in Ghana.

Anecdotally, increasing number of patients are seen at Korle Bu Teaching Hospital (KBTH) with brain tumour. Neuro-ophthalmic symptoms and signs may help in timely diagnosis and intervention. To evaluate the neuro-ophthalmic and clinical characteristics of brain tumour in patients presenting at a tertiary hospital in Ghana. A prospective case series involving 36 consecutive patients newly diagnosed with brain tumour from November 2010 to October 2011, at the Ophthalmology, Neurosurgery and Endocrine units of KBTH, Ghana. All patients had clinical diagnosis of brain tumour with confirmation by computerized tomography (CT) or magnetic resonance imaging (MRI). Thirteen patients had histological confirmation of diagnosis. Presenting Visual acuity, Colour vision, Visual fields and Cranial nerve deficits. Data of 36 patients were analyzed. Ages ranged from 3 to 69 years, mean (SD) 42.56 (±16.6 years). Twenty-six (72%) were females. Tumours included pituitary adenoma (20, 55.5%), meningioma(10, 27.8%), choroid plexus tumour(1, 2.8%), medulloblastoma(1, 2.8%), craniopharyngioma(1, 2.8%), haemangioblastoma(1, 2.8%), thalamic tumour(1, 2.8%) and haemangioma(1, 2.8%). Histologically confirmed tumours included pituitary adenoma (9, 69.2%), meningioma (3, 23.1%), craniopharyngioma (1, 7.7%). One patient had both a pituitary adenoma and meningioma. Blurred vision (30, 83.3%), headache (28, 77.8%) and photophobia (13, 36.1%) were predominant symptoms. Commonest neuro-ophthalmic signs were impaired colour vision (62 eyes, 88.6%), optic atrophy (26, 74.3%), unilateral or bitemporal hemianopia (15, 41.5%) and relative afferent pupillary defect (12, 34.3%). Seven (19.4%) patients were visually impaired and nine (25%) blind. Thirty-three of 72 (45.8%) eyes had monocular blindness. Common neuro-ophthalmic characteristics were blurred vision, headache, impaired colour vision, optic atrophy, and relative afferent pupillary defect (RAPD). Significant numbers of patients were blind or visually impaired at presentation.

Long-Term Follow-up Investigation of Isolated Rapid Eye Movement Sleep Without Atonia Without Rapid Eye Movement Sleep Behavior Disorder: A Pilot Study.

Idiopathic rapid eye movement (REM) sleep behavior disorder (RBD) is a harbinger of synuclein-mediated neurodegenerative diseases. It is unknown if this also applies to isolated REM sleep without atonia (RWA). We performed a long-term follow-up investigation of subjects with isolated RWA. Participants were recruited from 50 subjects with isolated RWA who were identified at the sleep laboratory of the Department of Neurology at the Medical University of Innsbruck between 2003 and 2005. Eligible subjects underwent follow-up clinical examination, polysomnography, and assessment of neurodegenerative biomarkers (cognitive impairment, finger speed deficit, impaired color vision, olfactory dysfunction, orthostatic hypotension, and substantia nigra hyperechogenicity). After a mean of 8.6 ± 0.9 y, 1 of 14 participating subjects (7.3%) progressed to RBD. Ten of 14 RWA subjects (71.4%) were positive for at least one neurodegenerative biomarker. Substantia nigra hyperechogenicity and presence of mild cognitive impairment were both present in 4 of 14 subjects with isolated RWA. Electromyographic activity measures increased significantly from baseline to follow-up polysomnography ("any" mentalis and both anterior tibialis muscles: 32.5 ± 9.4 versus 52.2 ± 16.6%; p = 0.004). This study provides first evidence that isolated RWA is an early biomarker of synuclein-mediated neurodegeneration. These results will have to be replicated in larger studies with longer observational periods. If confirmed, these disease findings have implications for defining at-risk cohorts for Parkinson disease.

Colour Vision Impairment in Young Alcohol Consumers.

Alcohol consumption among young adults is widely accepted in modern society and may be the starting point for abusive use of alcohol at later stages of life. Chronic alcohol exposure can lead to visual function impairment. In the present study, we investigated the spatial luminance contrast sensitivity, colour arrangement ability, and colour discrimination thresholds on young adults that weekly consume alcoholic beverages without clinical concerns. Twenty-four young adults were evaluated by an ophthalmologist and performed three psychophysical tests to evaluate their vision functions. We estimated the spatial luminance contrast sensitivity function at 11 spatial frequencies ranging from 0.1 to 30 cycles/degree. No difference in contrast sensitivity was observed comparing alcohol consumers and control subjects. For the evaluation of colour vision, we used the Farnsworth-Munsell 100 hue test (FM 100 test) to test subject’s ability to perform a colour arrangement task and the Mollon-Reffin test (MR test) to measure subject’s colour discrimination thresholds. Alcohol consumers made more mistakes than controls in the FM100 test, and their mistakes were diffusely distributed in the FM colour space without any colour axis preference. Alcohol consumers also performed worse than controls in the MR test and had higher colour discrimination thresholds compared to controls around three different reference points of a perceptually homogeneous colour space, the CIE 1976 chromaticity diagram. There was no colour axis preference in the threshold elevation observed among alcoholic subjects. Young adult weekly alcohol consumers showed subclinical colour vision losses with preservation of spatial luminance contrast sensitivity. Adolescence and young adult age are periods of important neurological development and alcohol exposure during this period of life might be responsible for deficits in visual functions, especially colour vision that is very sensitive to neurotoxicants.

Difficulties in Daily Life Reported by Patients With Homonymous Visual Field Defects.

Homonymous visual field defects (HVFD) are common after postchiasmatic acquired brain injury and may have a significant impact on independent living and participation in society. Vision-related difficulties experienced in daily life are usually assessed using questionnaires. The current study 1) links the content of 3 of these questionnaires to the International Classification of Functioning, Disability and Health (ICF) and 2) provides analyses of vision-related difficulties reported by patients with HVFD and minimal comorbidities. Fifty-four patients with homonymous hemianopia or quadrantanopia were asked about difficulties experienced in daily life because of their HVFD. This was performed during a structured interview including 3 standardized questionnaires: National Eye Institute Visual Functioning Questionnaire, Independent Mobility Questionnaire, and Cerebral Visual Disorders Questionnaire. The reported difficulties were linked to the ICF according to the ICF linking rules. Main outcome measures were presence or absence of experienced difficulties. The ICF linking procedure resulted in a classification table that can be used in future studies of vision-related difficulties. Besides well-known difficulties related to reading, orientation, and mobility, a high proportion of patients with HVFD reported problems that previously have not been documented in the literature, such as impaired light sensitivity, color vision, and perception of depth. A systematic inventory of difficulties experienced in daily life by patients with HVFD was performed using the ICF. These findings have implications for future study, assessment and rehabilitation of patients with HVFD.

Color vision impairment in multiple sclerosis points to retinal ganglion cell damage.

Multiple Sclerosis (MS) results in color vision impairment regardless of optic neuritis (ON). The exact location of injury remains undefined. The objective of this study is to identify the region leading to dyschromatopsia in MS patients' NON-eyes. We evaluated Spearman correlations between color vision and measures of different regions in the afferent visual pathway in 106 MS patients. Regions with significant correlations were included in logistic regression models to assess their independent role in dyschromatopsia. We evaluated color vision with Hardy-Rand-Rittler plates and retinal damage using Optical Coherence Tomography. We ran SIENAX to measure Normalized Brain Parenchymal Volume (NBPV), FIRST for thalamus volume and Freesurfer for visual cortex areas. We found moderate, significant correlations between color vision and macular retinal nerve fiber layer (rho = 0.289, p = 0.003), ganglion cell complex (GCC = GCIP) (rho = 0.353, p < 0.001), thalamus (rho = 0.361, p < 0.001), and lesion volume within the optic radiations (rho = -0.230, p = 0.030). Only GCC thickness remained significant (p = 0.023) in the logistic regression model. In the final model including lesion load and NBPV as markers of diffuse neuroaxonal damage, GCC remained associated with dyschromatopsia [OR = 0.88 95 % CI (0.80-0.97) p = 0.016]. This association remained significant when we also added sex, age, and disease duration as covariates in the regression model. Dyschromatopsia in NON-eyes is due to damage of retinal ganglion cells (RGC) in MS. Color vision can serve as a marker of RGC damage in MS.

Impairment of Colour Vision in Diabetes with No Retinopathy: Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular Genetics Study (SNDREAMS- II, Report 3).

PurposeTo assess impairment of colour vision in type 2 diabetics with no diabetic retinopathy and elucidate associated risk factors in a population-based cross-sectional study.MethodsThis is part of Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular-genetics Study (SN-DREAMS II) which was conducted between 2007–2010. FM 100 hue-test was performed in 253 subjects with no clinical evidence of diabetic retinopathy. All subjects underwent detailed ophthalmic evaluation including cataract grading using LOCS III and 45° 4-field stereoscopic fundus photography. Various ocular and systemic risk factors for impairment of colour vision (ICV) were assessed in subjects with diabetes but no retinopathy. P value of < 0.05 was considered statistically significant.ResultsThe mean age of the study sample was 57.08 ± 9.21 (range: 44–86 years). Gender adjusted prevalence of ICV among subjects with diabetes with no retinopathy was 39.5% (CI: 33.5–45.5). The mean total error score in the study sample was 197.77 ± 100 (range: 19–583). The risk factors for ICV in the study were women OR: 1.79 (1.00–3.18), increased resting heart rate OR: 1.04 (1.01–1.07) and increased intraocular pressure OR: 1.12 (1.00–1.24). Significant protective factor was serum high-density lipoprotein OR: 0.96 (0.93–0.99).ConclusionsAcquired ICV is an early indicator of neurodegenerative changes in the retina. ICV found in diabetic subjects without retinopathy may be of non-vascular etiology.

Prevalence and gene frequency of color vision impairments among children of six populations from North Indian region

X-linked red–green color blindness is the most widespread form of vision impairment. The study aimed to determine the prevalence and gene frequencies of red–green color vision impairments among children of six different human populations of Jammu province. A total of 1028 healthy subjects (6–15 years of age) were selected from five Muslim populations and the color vision impairments were determined using the Ishihara's test of color deficiency. The gene frequency was calculated using Hardy–Weinberg equilibrium method. The prevalence of color vision deficiency (CVD) ranged from 5.26% to 11.36% among males and 0.00%–3.03% among females of six different populations. The gender based differences in the frequency of CVD was found to be statistically significant (p < 0.0001), with a higher prevalence among male (7.52%) as compared to female (0.83%) children. We observed high frequency of deutan as compared to protan defects. The incidences of deuteranomaly (5.68%) and deuteranopia (2.27%) were higher among male children of Syed population while the frequencies of protanomaly (1.94%), protanopia (1.28%) and achromacy (2.27%) were the highest among male subjects of Khan, Malik and Syed populations, respectively. The allele and genotype frequencies showed cogent differences among six populations. The population based assessment of CVDs help patients to follow adaptive strategies that could minimize the risks of the disease.

REM Sleep Behavior Disorder (RBD) as a marker of neurodegenerative disorders.

Rapid eye movement (REM) sleep behavior disorder (RBD) can occur in the absence of any other obvious associated neurologic disorder or in association with a neurodegenerative disease, in which case it is considered as symptomatic RBD. RBD is frequently associated with Parkinson's disease (PD), Lewy body dementia or multiple system atrophy (MSA), and in several cases may even antedate the occurrence of motor symptoms by decades. When no neurologic disorder is obvious, RBD can be considered as idiopathic (iRBD). Several studies have looked at neurophysiologic and neuropsychological functions in iRBD and have found evidence of CNS dysfunction during both wakefulness and sleep in a variable proportion of these patients, challenging the concept of iRBD. Identifying subjects with a high risk of developing a neurodegenerative process may be crucial in order to develop early intervention strategies. Some prospective results in iRBD showed that potential markers of neurodegeneration are the following: 1) marked EEG slowing on spectral analysis; 2) decreased striatal 123I-FPCIT; 3) impaired color vision.

REM Sleep Behavior Disorder (RBD) as a marker of neurodegenerative disorders

Rapid eye movement (REM) sleep behavior disorder (RBD) can occur in the absence of any other obvious asso- ciated neurologic disorder or in association with a neurodegenerative disease, in which case it is considered as symptomatic RBD. RBD is frequently associated with Parkinson’s disease (PD), Lewy body dementia or multiple system atrophy (MSA), and in several cases may even antedate the occurrence of motor symptoms by decades. When no neurologic disorder is obvious, RBD can be considered as idiopathic (iRBD). Several studies have looked at neurophysiologic and neuropsychological functions in iRBD and have found evidence of CNS dysfunc- tion during both wakefulness and sleep in a variable proportion of these patients, challenging the concept of iRBD. Identifying subjects with a high risk of developing a neurodegenerative process may be crucial in order to develop early intervention strategies. Some prospective results in iRBD showed that potential markers of neuro- degeneration are the following: 1) marked EEG slowing on spectral analysis; 2) decreased striatal 123I-FPCIT; 3) impaired color vision.

Migraine with aura is associated with impaired colour vision: Results from the cross-sectional German DMKG headache study.

Hypersensitivity to light, noise and odour are pivotal clinical characteristics of migraine associated with enhanced cortical excitability and dysfunctional habituation. However, little is known about the integrity of basic sensory functioning in migraine on a population-based level. A total of 129 participants with migraine (105 without aura, MwoA, 24 with aura, MA) and 522 healthy controls without headache 12 months prior to baseline were included from a sample of the DMKG study and underwent standardised clinical sensory testing of smell, taste, hearing and vision. After adjustment for age, sex, smoking status and history of head injuries, the chance of impaired colour perception was significantly higher in MA compared to controls (odds ratio, OR=3.20; 95% CI=1.20-8.53) and MwoA (OR=3.62; 95% CI=1.31-9.97). Compared to MwoA, MA also had an increased chance of smell (OR=3.20; 95% CI=0.98-10.42) and taste (OR=2.58; 95% CI=0.90-7.40) impairment. In this cross-sectional, population-based study on sensory functioning in migraine participants, colour vision was impaired interictally in MA compared to MwoA and controls.

Prevalence of optic neuropathy in alcoholic patients and predictive value of optic nerve alterations for its diagnosis

AbstractPurpose Optic neuropathy (ON) is one of the complications of alcohol. The aim of this study was to assess the prevalence of alcoholic ON in a cohort of patients hospitalized for alcohol withdrawal. Secondary objective was to explore the predictive value of optic nerve changes for diagnosis of ON.Methods This was a single‐center prospective study. A complete eye examination was performed during the patient's alcohol withdrawal. The definition of alcoholic ON used was an assocation of alterations of visual field with impaired color vision. Optic nerve function and morphology were assessed using visual evoked potentials, optical coherence tomography (OCT), Nerve Fiber Indicator from polarimetry (GDx) and Moorfields Regression Analysis of the Heidelberg Retina Tomograph II (MRA‐HRT II).Results Two hundred patients were included prospectively from January 2010 to June 2013 (145 men and 55 women) with a mean age of 47 ± 12 year. The average alcohol consumption was 220 ± 122 g/day. 46 patients (23%) responded to alcoholic ON defintion (13.5 % in both eyes and 9.5% in only one eye). Diagnostic sensitivity and specificity for visual evoked potentials were of 55.5% and 54.5% respectively; for GDx 18% and 97%, respectively; for OCT 38% and 92%, respectively; and for MRA‐HRT II 19% and 79%, respectively.Conclusion A high prevalence of alcoholic ON observed in this study should prompt screening and early treatment. From predictive value of objective optic nerve changes, we discuss the best couple of exams to complete the screening of alcoholic ON.

The Non-motor Features of Essential Tremor: A Primary Disease Feature or Just a Secondary Phenomenon?

Essential tremor (ET) is a pathologically heterogeneous neurodegenerative disorder with both motor and increasingly recognized non-motor features. It is debated whether the non-motor manifestations in ET result from widespread neurodegeneration or are merely secondary to impaired motor functions and decreased quality of life due to tremor. It is important to review these features to determine how to best treat the non-motor symptoms of patients and to understand the basic pathophysiology of the disease and develop appropriate pharmacotherapies. In this review, retrospective and prospective clinical studies were critically analyzed to identify possible correlations between the severities of non-motor features and tremor. We speculated that if such a correlation existed, the non-motor features were likely to be secondary to tremor. According to the current literature, the deficits in executive function, attention, concentration, and memory often observed in ET are likely to be a primary manifestation of the disease. It has also been documented that patients with ET often exhibit characteristic personality traits. However, it remains to be determined whether the other non-motor features often seen in ET, such as anxiety, depression, and sleep disturbances are primary or secondary to motor manifestations of ET and subsequent poor quality of life. Finally, there is evidence that patients with ET can also have impaired color vision, disturbances of olfaction, and hearing impairments, though there are few studies in these areas. Further investigations of large cohorts of patients with ET are required to understand the prevalence, nature, and true significance of the non-motor features in ET.