Schrimer test in Parkinson's disease

Ocular Surface Features in Patients with Parkinson Disease on and off Treatment: A Narrative Review

Parkinson disease (PD) is a progressive, neurodegenerative disease of the central nervous system. Visual disturbance is one of the most frequent nonmotor abnormalities referred to by patients suffering from PD at early stages. Furthermore, ocular surface alterations including mainly dry eye and blink reduction represent another common finding in patients with PD. Tears of PD patients show specific alterations related to protein composition, and in vivo confocal microscopy has demonstrated profound changes in different corneal layers in this setting. These changes can be attributed not only to the disease itself, but also to the medications used for its management. In particular, signs of corneal toxicity, both at epithelial and endothelial level, are well described in the literature in PD patients receiving amantadine. Management of PD patients from the ophthalmologist's side requires knowledge of the common, but often underdiagnosed, ocular surface alterations as well as of the signs of drug toxicity. Furthermore, ocular surface biomarkers can be useful for the early diagnosis of PD as well as for monitoring the degree of neural degeneration over time.

Undetected ophthalmological disorders in Parkinson's disease

Background

Ophthalmological disorders are common and frequently disabling for people with Parkinson’s disease (PD). However, details on the prevalence, severity and impact of ophthalmological disorders thus far lacking. We aimed to identify PD patients with undetected ophthalmological disorders in a large cross-sectional, observational study.

Methods

We previously delivered a screening questionnaire to detect ophthalmological symptoms (Visual impairment in PD questionnaire; VIPD-Q) to 848 patients. Here, we report on a subgroup of 102 patients who received complete ophthalmological assessment aimed at identifying clinically relevant ophthalmological diseases, which were classified as either vison-threatening or not. Impact on daily life functioning was measured using the visual functioning-25 questionnaire (VFQ-25) and fall frequency.

Results

Almost all patients (92%) had one or more clinically relevant ophthalmological disorders. Of those, 77% had a potentially vision-threatening disease, while 34% had a potentially treatable ophthalmological disease which impacted on quality of life. The most prevalent ophthalmological disorders were dry eyes (86%), ocular misalignment (50%) and convergence insufficiency (41%). We found a weak but significant association between clinically relevant ophthalmological diseases and both fall frequency (R² = 0.15, p = 0.037) and VFQ-25 score (R² = 0.15, p = 0.02). The VIPD-Q could not correctly identify patients with relevant ophthalmological disorders.

Conclusions

Surprisingly, in our study sample, many participants manifested previously undetected ophthalmological diseases, most of which threatened vision, impacted on daily life functioning and were amenable to treatment. Screening for these ophthalmological disorders using a questionnaire asking about symptoms seems insufficient. Instead, episodic ophthalmological assessments should be considered for PD patients, aiming to identify vision-threatening yet treatable diseases.

Trial registration

Dutch Trial Registration, NL7421.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-022-11014-0.

Identification of tear-based protein and non-protein biomarkers: Its application in diagnosis of human diseases using biosensors

Discovery of robust, selective and specific biomarkers are important for early diagnosis and monitor progression of human diseases. Eye being a common target for several human diseases, vision impediment and complications are often associated with systemic and ocular diseases. Tears are bodily fluids that are closest to eye and are rich in protein content and other metabolites. As a biomarker repository, it advantages over other bodily fluids due to the ability to collect it non-invasively. In this review, we highlight some recent advancements in identification of tear-based protein biomarkers like lacryglobin and cystatin SA for cancer; interleukin-6 and immunoglobulin-A antibody for COVID-19; tau, amyloid-β-42 and lysozyme-C for Alzheimer's disease; peroxiredoxin-6 and α-synuclein for Parkinson's disease; kallikrein, angiotensin converting enzyme and lipocalin-1 for glaucoma; lactotransferrin and lipophilin-A for diabetic retinopathy and zinc-alpha-2 glycoprotein-1, prolactin and calcium binding protein-A4 for eye thyroid disease. We also discussed identification of tear based non-protein biomarkers like lysophospholipids and acetylcarnitine for glaucoma, 8-hydroxy-2'-deoxyquanosine and malondialdehyde for thyroid eye disease. We elucidate technological advancement in developing tear-based biosensors for diagnosis and monitoring diseases such as diabetes, diabetic retinopathy and Alzheimer's disease. Altogether, the study of tears as potential biomarkers for early diagnosis of human diseases is promising.

Meibum Lipid Composition and Conformation in Parkinsonism

PURPOSE

Patients with Parkinson's disease (PD) exhibit unstable tear films. Tear film lipid composition and structure are related to tear film stability and dry eye and tear lipids have not been characterized in people with PD. The aim of this study is to characterize Meibum tear lipids in donors with PD using ¹H-NMR and infrared spectroscopy.

METHODS

Three cohorts were compared: meibum from donors with PD (Mp) n = 10, meibum from donors with PD and dry eye (Mpd) n = 3, meibum from donors without PD (Mn) n = 29.

RESULTS

There were no significant differences, P > 0.05, in hydrocarbon branching for Mp compared with Mn. Mn contained twice as much cholesteryl esters compared with Mp, P < 0.0001. The cooperativity of the phase transition was significantly 37% lower for Mp compared with Mn, P < 0.0001. Mpd was much more ordered (stiffer) with compared with Mp and Mn, P < 0.0001.

CONCLUSION

Changes in meibum lipid composition and structure could be a marker for and/or contribute to increase the susceptibility of dry eye in patients with PD. A less cooperative phase transition for Mp compared with Mn indicates that Mp was more heterogeneous and/or contained more contaminants than Mn. The data support the idea that more ordered lipid contributes to dry eye.

Biomarkers in Tears and Ocular Surface: A Window for Neurodegenerative Diseases

OBJECTIVES

The purpose of this review is to briefly outline current scientific evidence on the potential role of tear analysis and ocular surface evaluation in diagnosis and monitoring of neurodegenerative diseases, especially Alzheimer disease, Parkinson disease, and glaucoma.

METHODS

A systematic computerized search in the electronic databases PubMed, MEDLINE, and the Cochrane Collaborations was conducted to find eligible articles which their main topic was to investigate the tear and ocular surface in neurodegenerative diseases. After a first screening of titles and abstracts and a full-text review, 26 articles met the inclusion criteria (1 about the neurodegenerative diseases, 3 about the Alzheimer disease, 11 about the Parkinson disease, 11 about glaucoma, and 1 about amyotrophic lateral sclerosis).

RESULTS

The ocular surface picture seems to be altered in the setting of neurodegenerative diseases with specific characteristics according to each disease. They seem to be associated with reduced corneal sensitivity and abnormal tear function, and each one presents the expression of specific biomarkers in tears.

CONCLUSIONS

The study of tears and ocular surface appears to be a new and noninvasive promising way to assist in the diagnosis and monitoring of neurodegenerative diseases.

Tears - more to them than meets the eye: why tears are a good source of biomarkers in Parkinson's disease

Tears are a known source of biomarkers for both ocular and systemic diseases with particular advantages; specifically, the noninvasiveness of sample collection and a unique and increasingly better-defined protein composition. Here, we discuss our rationale for use of tears for discovery of biomarkers for Parkinson's disease (PD). These reasons include literature supporting changes in tear flow and composition in PD, and the interconnections between the ocular surface system and neurons affected in PD. We highlight recent data on the identification of tear biomarkers including oligomeric α-synuclein, associated with neuronal degeneration in PD, in tears of PD patients and discuss possible sources for its release into tears. Challenges and next steps for advancing such biomarkers to clinical usage are highlighted.

Towards seeing the visual impairments in Parkinson's disease: protocol for a multicentre observational, cross-sectional study

Background

Visual disorders are common in Parkinson’s disease (PD) but their exact frequency and severity are unknown. Good visual functioning is crucial for patients with PD, because of their need to compensate for loss of automated motor control and their postural instability, forcing patients to guide their movements visually. Here, we describe the study design of a cross-sectional, multi-centre study aiming to: (1) validate the Visual Impairment screening questionnaire (VIPD-Q, which aims to identify PD patients who should be referred to an ophthalmologist for further assessment); (2) study the prevalence of visual disorders in PD; (3) study the severity and clinical impact of different types of visual disorders in PD; and (4) explore treatment options for ophthalmologic disorders in PD, as a basis for future guideline development.

Methods

This study consists of two phases. In phase one, 750 PD patients and 250 healthy controls will be recruited to complete the VIPD-Q. In phase two, a subgroup of responders (n = 100) (with the highest and lowest scores on the VIPD-Q) will be invited for an extensive neurological and ophthalmological assessment. The in-depth ophthalmologic examination will serve as the “gold standard” for validating the VIPD-Q. Moreover, these assessments will be used to study associations between visual disorders and clinical presentation, in order to gain more insight in their clinical impact.

Discussion

Our study will heighten the awareness of visual problems in PD and offers a robust starting point to systematically approach this subject. In current daily practice, the association between visual problems and PD is far from obvious to both patients and clinicians. Consequently, patients may not adequately report visual problems themselves, while clinicians miss potentially treatable visual disorders. Routinely asking patients to complete a simple screening questionnaire could be an easy solution leading to timely identification of visual problems, tailored treatment, restored mobility, greater independence and improved quality of life.

Trial registration

Dutch Trial Registration, NL7421, Registered on 4 December 2018 – Retrospectively registered.

Electronic supplementary material

The online version of this article (10.1186/s12883-019-1365-8) contains supplementary material, which is available to authorized users.

Proteomic analysis of tear fluid reveals disease-specific patterns in patients with Parkinson's disease - A pilot study

BACKGROUND

The diagnosis of Parkinson's disease (PD) is still challenging and biomarkers could contribute to an improved diagnostic accuracy. Tear fluid (TF) is an easily accessible body fluid reflecting pathophysiological changes in systemic and ocular diseases and is already used as a biomarker source for several ophthalmological disorders. Here, we analyzed the TF of patients with PD and controls (CTR) to describe disease-related changes in TF and identify putative biomarkers for the diagnosis of PD.

METHODS

Unstimulated TF samples of a pilot cohort with 36 PD patients and 18 CTR were collected via Schirmer tear test strips and then analyzed via a Bottom-up liquid chromatography electrospray ionization tandem mass spectrometry (BULCMS) workflow, followed by functional analysis encompassing protein-protein interaction as well as cellular component and pathway analysis.

RESULTS

BULCMS analysis lead to the identification of 571 tear proteins (false discovery rate, FDR < 1%), whereby 31 proteins were exclusively detected in the PD group and 7 only in the CTR group. Whereas 21 proteins were significantly increased in the PD versus CTR groups, 19 proteins were significantly decreased. Core networks of proteins involved in immune response, lipid metabolism and oxidative stress were distinctly altered in PD patients.

CONCLUSIONS

To our best knowledge, this is the first description of TF proteome in PD patients. Tear protein level alterations suggest the contribution of different disease-related mechanisms in ocular pathology in PD and propose candidate proteins to be validated as potential biomarkers in larger cohorts.

Biochemical and Functional Changes in the Eye As a Manifestation of Systemic Degeneration of the Nervous System in Parkinsonism

Parkinson's disease (PD) is a systemic neurodegenerative condition caused by the death of dopaminergic neurons of the nigrostriatal system of the brain. This disease is diagnosed after most neurons have already been lost, which explains the low efficiency of treatment. Hope for increasing treatment efficiency rests in the development of new strategies for early diagnosis of PD based on a search for peripheral markers that appear as early changes in non-motor functions. Since impairment of the visual function is one of the manifestations of PD, the purpose of our work was to identify biochemical and physiological changes in a mouse's eye and eyelid in models of preclinical (presymptomatic) and clinical (symptomatic) stages of PD. We found that the norepinephrine, dopamine, and serotonin levels in the mouse eye reduced not only in the model of the early clinical stage, but also in the model of preclinical stage, an indication that pathological changes in the monoaminergic systems of the brain had affected the eye even before the motor disorders emerged. Moreover, in both models of PD, mice had increased intraocular pressure, indicating the development of both metabolic and functional impairments, which can be used as diagnostic markers. Unlike in the eye, the serotonin level in the eyelid was increased in mice at both parkinsonism stages and in presymptomatic mice to a much higher extent than in symptomatic ones. Given that serotonin is involved in the regulation of lacrimal glands of the eyelid, an increase in its level in parkinsonian mice should alter the composition of tear fluid, which could serve as a diagnostic marker of early stage of PD. Thus, the changes in the metabolism of monoamines in the eye and eyelid observed in mice at the early stage of parkinsonism are accompanied by changes in the function of these structures and, therefore, can be used as diagnostic markers of the early stage of PD.

Ocular and visual disorders in Parkinson's disease: Common but frequently overlooked

Patients with Parkinson's disease (PD) often compensate for their motor deficits by guiding their movements visually. A wide range of ocular and visual disorders threatens the patients' ability to benefit optimally from visual feedback. These disorders are common in patients with PD, yet they have received little attention in both research and clinical practice, leading to unnecessary - but possibly treatable - disability. Based on a literature search covering 50 years, we review the range of ocular and visual disorders in patients with PD, and classify these according to anatomical structures of the visual pathway. We discuss six common disorders in more detail: dry eyes; diplopia; glaucoma and glaucoma-like visual problems; impaired contrast and colour vision; visuospatial and visuoperceptual impairments; and visual hallucinations. In addition, we review the effects of PD-related pharmacological and surgical treatments on visual function, and we offer practical recommendations for clinical management. Greater awareness and early recognition of ocular and visual problems in PD might enable timely instalment of tailored treatments, leading to improved patient safety, greater independence, and better quality of life.

Evaluation of corneal parameters in patients with Parkinson's disease

The aim of this study was to evaluate blink rate (BR), tear tests and corneal parameters by Scheimpflug imaging and also to clarify the associations between the severity of disease and corneal parameters in patients with Parkinson's disease (PD). Forty patients with PD and 40 healthy subjects were included in this study. All participants underwent a detailed neurological and ophthalmological evaluation. The severity of disease was measured according to Hoehn-Yahr (H-Y) scale. BR was determined for participants. Corneal parameters were measured using Pentacam. Additionally, Schirmer test, tear break-up time (TBUT), corneal fluorescein staining, and Ocular Surface Disease Index (OSDI) scores were assessed. Corneal parameters were significantly different between the patients with PD and healthy controls. The mean central corneal thickness (538.95 ± 30.9 μm versus 557.60 ± 26.6 μm, p = 0.005) was significantly reduced in patients with PD compared to healthy controls. The BR and the values of TBUT and Schirmer test scores were significantly lower in patients with PD than in controls. Also, corneal fluorescein staining and OSDI scores were higher in patients with PD than in controls. The BR was significantly negative correlated with the severity of the disease. Factors related to the corneal thickness were BR, TBUT and Schirmer test (p < 0.05 for all). Corneal thickness may decrease in patients with PD which may be affected by reduced BR and tear dysfunction.

Tear Osmolarity, Break-up Time and Schirmer's Scores in Parkinson's Disease

OBJECTIVES

Dry eye is an important problem in Parkinson's disease (PD) with a potential to affect life quality. Tear osmolarity, accepted as the gold standard in dry eye diagnosis, has not been studied in this subset of patients so far. Therefore, in this study we aimed to evaluate tear osmolarity, Schirmer's test scores and tear film break-up time (TBUT) in PD patients.

MA­TE­RI­ALS AND MET­HODS

PD patients with a minimum follow-up of 1 year and healthy controls who admitted for refractive abnormalities were enrolled to the study. Subjects using any systemic medication with a possibility to affect tear tests were not included in the study. The presence of any ocular surface disorder, previous ocular surgery, previous dry eye diagnosis, any topical ophthalmic medication or contact lens use were other exclusion criteria. Age, gender, disease duration, and Hoehn and Yahr (H&Y) score for disease severity were noted, and blink rate (BR), Schirmer's test score, TBUT and tear osmolarity of the right eye were measured in both groups.

RE­SULTS

Thirty-seven PD patients and 37 controls were enrolled to the study. The groups were age and gender matched. The mean disease duration and H&Y score were 5.70±2.64 years and 1.70±0.93, respectively. H&Y staging and disease duration were not correlated to BR, Schirmer's scores, TBUT, or tear osmolarity (p>0.05). The mean BR was 8.54±4.99 blinks/minute in PD patients and 11.97±6.36 blinks/minute in the control group. Mean Schirmer's scores, TBUT and osmolarity values were 9.08±4.46 mm, 11.38±4.05 seconds and 306.43±12.63 mOsm/L in the PD group and 17.16±9.57 mm, 12.81±3.66 seconds and 303.81±16.13 mOsm/L in the control group. The differences were significant only in BR and Schirmer's scores.

CONCLUSION

BR and Schirmer's scores decreased significantly in PD patients. Although not significant, the demonstrated tear osmolarity increment might be important to document the dry eye and inflammatory process of the ocular surface in PD patients.

Ophthalmological features of Parkinson disease

Background

The aim of this study was to determine the type and frequency of ophthalmologic changes occurring in patients with Parkinson disease (PD).

Material/Methods

One hundred consecutive patients (196 eyes) with idiopathic PD and a control group consisting of 100 healthy patients (196 eyes) matched for age and sex underwent a complete ophthalmological examination of both eyes, including assessment of patient medical history, dry eye questionare, and visual hallucinations questionnaire, distance and near best corrected visual acuity (DBCVA, NBCVA), color vision, distance photopic contrast sensitivity, near point of convergence, slit lamp examination of the eye anterior segment, tear film osmolarity and breakup time, aqueous tear production, and intraocular pressure, as well as fundus examination and evaluation of the perimacular retinal thickness (RT) and peripapillary retinal nerve fiber layer (RNFL) thickness.

Results

In the eyes of PD patients DBCVA, NBCVA, contrast sensitivity, and color discrimination were significantly reduced. We also detected increased frequency of convergence insufficiency, seborrhoic blepharitis, meibomian gland disease (MGD), dry eye syndrome, nuclear and posterior subcapsular cataract, and glaucoma (p<0.05). However, intraocular pressure (IOP) was significantly lower in the PD group compared to controls. The frequency of visual hallucinations, age-related macular degeneration (ARMD), and other ophthalmological diseases, as well as RT and RNFL thickness, did not significantly differ between investigated groups.

Conclusions

Clinicians need to be aware of the association between PD and ophthalmological changes. Restoration of good-quality vision has a great impact on PD patients’ quality of life, reduction of costs of treatment and care, and rehabilitation.

Tear levels of tumor necrosis factor-alpha in patients with Parkinson's disease

Neuroinflammatory events mediated by the pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-α) cause progressive neurodegeneration in dopaminergic neurons, and play an important role in the pathogenesis of Parkinson's disease (PD). The purpose of this study was to determine TNF-α levels in tear samples obtained from patients with PD and to analyze the relationship between TNF-α values and PD characteristics. Eighteen patients with PD and 17 healthy control subjects were included in the study. We examined the patient demographics, modified Hoehn and Yahr Staging Scale (mHY) stages, Unified Parkinson's disease rating scale (UPDRS) II and III scores, Mini Mental State Examination (MMSE) scores, and the predominant symptoms. We measured TNF-α using the multiplex immunobead assay in unstimulated tear samples, and determined the Schirmer's test and blink rate for each subject. Tear TNF-α values were significantly higher in patients with PD (196.9 ± 121.2 pg/ml) than in control subjects (110.7 ± 87.2 pg/ml; p=0.02). We identified no relationship between tear TNF-α levels and age, sex, age at onset, PD duration, mHY stages, UPDRS II, UPDRS III, or MMSE scores. The higher TNF-α levels observed in the tears of patients with PD suggests neuroinflammation and TNF-α plays a role in the pathogenesis of PD. Tear TNF-α levels, however, were not related to the duration or severity of PD. Tears are a suitable method for measuring TNF-α levels, and can be used as a diagnostic measure to evaluate biomarkers in PD.

The Definition and Classification of Dry Eye Disease: Report of the Definition and Classification Subcommittee of the International Dry Eye Workshop (2007)

The aim of the DEWS Definition and Classification Subcommittee was to provide a contemporary definition of dry eye disease, supported within a comprehensive classification framework. A new definition of dry eye was developed to reflect current understanding of the disease, and the committee recommended a three-part classification system. The first part is etiopathogenic and illustrates the multiple causes of dry eye. The second is mechanistic and shows how each cause of dry eye may act through a common pathway. It is stressed that any form of dry eye can interact with and exacerbate other forms of dry eye, as part of a vicious circle. Finally, a scheme is presented, based on the severity of the dry eye disease, which is expected to provide a rational basis for therapy. These guidelines are not intended to override the clinical assessment and judgment of an expert clinician in individual cases, but they should prove helpful in the conduct of clinical practice and research.

Tear film tests in Parkinson's disease patients

OBJECTIVE

Parkinson's disease (PD) has both motor and nonmotor features. Parkinson's disease patients are prone to dry eye due to both autonomic dysfunction and motor symptoms affecting blinking. This study was conducted to investigate the changes in tear functions in PD patients.

DESIGN

Nonrandomized, prospective, clinical study.

PARTICIPANTS

Fifty-six eyes of 56 consecutive patients with PD were studied. Thirty-six eyes of age-matched non-PD patients without pathology affecting tear tests were examined as control subjects.

INTERVENTION

Modified Hoehn-Yahr (H-Y) scale, blink rate (BR), and tear tests were examined.

MAIN OUTCOME MEASURES

Modified H-Y scale, BR, dry eye assessment questionnaire, meibomian gland evaluation, tear meniscus height, tear breakup time, fluorescein stain, rose bengal stain, Schirmer's test, and phenol red thread test.

RESULTS

Overall tear function abnormalities were significantly more common in PD patients (P = 0.001, Mann-Whitney U test). Each test was found to be significantly disturbed in PD patients relative to controls (P<0.05, Mann-Whitney U test). Each PD patient had at least 1 abnormal test. Overall tear function abnormalities as assessed by the total abnormal test count correlated with the H-Y score (P<0.001, Spearman rho correlation). Parkinson's disease patients' mean BR (12.7+/-7.42 per minute) was significantly less than the controls' (21.8+/-7.37) (P<0.01, Student's t test). The abnormality in each tear test, except those for meibomian gland function and tear meniscus height, was significantly related to the H-Y scores (P<0.05, chi2 linear-by-linear association).

CONCLUSION

The results of this study indicate that PD is associated with disturbances in tear function. With the exception of meibomian gland disease and tear meniscus height, the tests were found to have a linear association with the H-Y scale, which may be attributed to associated dysfunctions of PD.