An observational study in Parkinson Disease, sponsored by University of Valencia. Completed at 1 site in Spain. Open to participants aged 30 Years to 100 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-05-04.
Sponsored by University of Valencia · Observational
Parkinson's disease (PD) is the second most common neurodegenerative condition worldwide, characterised by motor symptoms, but with other symptoms such as visual impairment.
The aim is to compare visual function between PD patients and healthy subjects in order to adequately characterise the visual capabilities of the PD population and perform oculomotor or perceptual therapy to find optometric solutions to slow down the visual impairment they suffer from or minimise their visual symptoms.
In the first phase, non-invasive tests will be carried out, such as measuring visual acuity, refraction, pupil diameter in different lighting conditions, sensory dominance, contrast sensitivity, colour vision, stereopsis, reading speed, binocular vision, eye movements and influence on quality of life.
In the second, visual oculomotor or perceptual exercises will be performed in a group of PD patients to assess whether there is stabilisation of impairment or improvement of these visual skills. These will be performed in a non-invasive way using simple and easy-to-use instruments or an application on an electronic device could be used.
Finally, in the third phase, those visual skills that have been treated will be re-evaluated to assess possible changes, compared with a group of PD patients who have not undergone the visual exercises.
Parkinson's disease (PD) is the second most common neurodegenerative condition worldwide. It is a movement disorder characterised by tremor, rigidity, bradykinesia and postural instability. However, 78% of PD patients report visual problems such as dry eye, reduced visual acuity, visual field defects, impaired contrast sensitivity (CS), impaired eye movements, diplopia, convergence insufficiency, impaired colour vision, visual hallucinations and problems in visual-spatial orientation. In fact, visual dysfunction is one of the initial symptoms of PD. A recent study has found that dopaminergic neurons affected in PD show physiological dysfunctions, but do not die. Currently, there is no cure for PD; treatments consist of controlling symptoms, and the earlier the disease is detected and administered, the more effective they are.
It is hypothesised that a programme of visual oculomotor therapy and/or visual perceptual learning (VPL) could slow or halt the deterioration of oculomotor ability and/or CS in these patients. Visual perceptual learning or VPL is a long-term improvement in performance on a visual task, any relatively permanent change in perception that arises from visual experience. Contrast Sensitivity or CS is the ability of the visual system to differentiate an object from the background in which it is located by the difference in contrast. It is the ability to detect differences in luminance between adjacent areas in an image.
If the results confirm the hypothesis, this study will have a great impact on the PD population because it could slow down the deterioration of oculomotor ability that 75% of them suffer from. It could also slow down the decline in CS that they suffer, as demonstrated by several studies. Consequently, patients would also experience an improvement in their quality of life, as they would be able to continue to perform activities of daily living that are affected by visual impairment such as walking, reading, driving and cooking. This would have a major impact on society as PD affects many people worldwide. In Europe, the prevalence and incidence rates of PD are estimated to be approximately 108-257/100 000 and 11-19/100 000 per year, respectively. Furthermore, this project would expand scientific knowledge because to date there is no literature that has evaluated VPL in patients with PD. However, there is research on amblyopia, Stargardt's disease and other neural pathologies, such as Huntington's disease. Likewise, with regard to oculomotor therapy, there is still a lot of research to be done, as there are few studies on this subject.
This is an analytical, longitudinal, prospective and observational study. In the first phase, to characterise the vision of the population with Parkinson's disease, non-invasive tests would be performed, such as measuring visual acuity, refraction, contrast sensitivity, colour vision, depth vision, the state of binocular vision and visual pathways and eye movements. Simultaneously, a control population will be measured to compare the data obtained in PD patients.
In a second phase, visual oculomotor and/or perceptual exercises would be performed in a group of PD patients to assess whether there is stabilisation of the impairment and/or improvement of these visual skills.
Finally, in the third phase, those visual skills that have been treated would be re-evaluated to assess possible changes, compared with a group of PD patients who have not undergone the visual exercises.
The research will be carried out at the Laboratory of Vision and Colour Sciences of the Department of Optics, Optometry and Vision Sciences of the University of Valencia, at the Arnau de Vilanova Hospital and at the Parkinson's Association of Valencia. These are the institutions from which the participants who take part in the study will come. They will do so voluntarily, will not be coerced to participate in any way and will be free to choose whether they want to participate or not, after having been explained to them what this project consists of. Furthermore, they will be able to revoke their signed consent at any time, so that they will automatically be excluded from the study and their data will not be used in the study if the patient so wishes. Furthermore, this project does not harm the patient's health and does not bring any financial benefit to the patient.
Only the members of the project will have access to the original study data. These data will be collected on paper, and the original source will be kept under lock and key in the laboratory of Vision and Colour Sciences of the Department of Optics, Optometry and Vision Sciences of the University of Valencia. For data analysis, the principal investigator will extract the data into a computer document in which each patient will be identified by a two-letter code (GP: control group; PD: Parkinson's patient) and three numbers. Not even the initials of the name will appear. Under this code, the data of each patient will be entered. This is the data that the rest of the group will see and have access to. Adverse event reporting and change management will be carried out through the Reservio platform, which will be used for appointment planning and online booking.
Data analysis will be carried out using the SPSS (Statistical Package for Social Sciences) statistical software and the Matlab numerical calculation system. The statistical analysis plan is as follows: the mean, standard deviation and normality of the samples will be performed with the Shapiro-Wilk test. Statistical comparison between groups will be performed with Student's t-test if the data follow a normal distribution or with the U-Mann-Whitney test otherwise. The statistical test used for qualitative variables will be Pearson's chi-square test.
4,487 studies on the registry are indexed under Parkinson Disease; 1,082 are open to participants now.
This study's enrollment of 160 is above the median of 96 across 1,057 observational studies indexed under Parkinson Disease.
Browse Parkinson Disease studies →University of Valencia is the lead sponsor of 349 studies on the registry; 73 are open to participants now.
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Patients with Parkinson's Disease.
Exclusion Criteria:
1. Anamnesis 2. Measurement of best visual acuity with an EDTRS (Early Treatment Diabetic Retinopathy Study) test 3. Measurement of refraction with trial frame refraction 4. Measurement of pupillary diameter under photopic and mesopic illumination conditions using a specific millimetric ruler 5. Measurement of ocular sensory dominance with the red filter test 6. Measurement of binocular vision status with the Cover Test, prism bar and Maddox wing 7. Photopic and mesopic achromatic contrast sensitivity using the Functional Test Analyzer device 8. Stereopsis using the Titmus Test 9. Colour vision using the Farnsworth-Munsell 100 Hue sorting test 10. Measurement of eye movements with aDEMd (adult Developmental Eye Movement) test and NSUCO (Northeastern State University College of Optometry) 11. Measurement of reading speed with Radner-Vissum test 12. National Eye Institute Visual Functioning Questionnaire-25 (NEI VFQ-25)
Other: Clinical measurements
1. Anamnesis: name, sex, date of birth, contact, family contact, medical report, Hoehn \& Yahr classification, medication, systemic, ocular and family history, consumption of tobacco, alcohol, drugs, coffee, physical activity, eye colour, other observations 2. Measurement of best visual acuity with an EDTRS test 3. Measurement of refraction with trial frame refraction 4. Measurement of pupillary diameter under photopic and mesopic illumination conditions using a specific millimetric ruler 5. Measurement of ocular sensory dominance with the red filter test 6. Measurement of binocular vision status with the Cover Test, prism bar and Maddox wing 7. Photopic and mesopic achromatic contrast sensitivity using the Functional Test Analyzer device 8. Stereopsis using the Titmus Test 9. Colour vision using the Farnsworth-Munsell 100 Hue sorting test 10. Measurement of eye movements with aDEMd test and NSUCO 11. Measurement of reading speed with Radner-Vissum test 12. NEI VFQ-25
Other: Clinical measurements
Oculomotor exercises such as tracking eye movements, saccadic eye movements and fixations will be performed. These exercises will be performed in a non-invasive manner using simple and easy-to-use instruments. An application on an electronic device, namely the virtual reality software Visionary, could also be used. If financial resources allow, the intention is to use tablets or computers for this purpose. Perceptual learning exercises will also be carried out on an electronic device. The following variables will be collected from these exercises: time taken to carry out the tests, errors made, speed of completion, latency, etc. These will be compared before and after the exercises in the third phase. In addition, the patients will be given indications for working on these exercises at home.
Other: Oculomotor or perceptual therapy
These patients will not receive oculomotor or perceptual therapy. They will be evaluated in the same manner as patients who will receive therapy, both at the beginning and at the end of therapy in the other group.
Other: Clinical measurements
Optometric measurements
Oculomotor or perceptual visual learning exercices
Anamnesis
Ocular and perceptual characterization of Parkinson's Disease visual capabilities with the following measurements (1-12). Anamnesis: Asking age, allergies, ocular and systemic pathologies, family background, current treatment (if proceed), consumption of tobacco, alcohol, drugs, coffee, tea, performance of physical activity, state on the Hoehn \& Yahr classification, date of Parkinson's diagnosis and other observations.
Time frame: 1 year
Visual Acuity
Using an EDTRS (Early Treatment Diabetic Retinopathy Study) test for distance and near vision with the patient's optical correction, scale: LogMAR.
Time frame: 1 year
Refraction
Doing ocular compensation with trial frame refraction, units: diopters (D).
Time frame: 1 year
Pupillary diameter
Under photopic and mesopic illumination conditions using a specific millimetric ruler, units: millimeters (mm).
Time frame: 1 year
Ocular sensory dominance
Using the red filter test.
Time frame: 1 year
Binocular vision status
Using the Cover Test Cover Test, Modified Thorington Test Card to phoria measurement and fusional vergence measurement with prism bar, units: prismatic diopters (Δ).
Time frame: 1 year
Achromatic CSF (Contrast Sensitivity Funtion)
Under photopic and mesopic illumination conditions using the FACT (Funtional Acuity Contrast Test) test of the FVA (Functional Visual Analyzer) device of Stereo Optical Co., Inc.
Time frame: 1 year
Stereopsis
Using the Wirth points of the Titmus test, units: seconds of arc (").
Time frame: 1 year
Colour vision
Using the Farnsworth-Munsell 100 Hue sorting test and the Chromatic Threshold Measurement test.
Time frame: 1 year
Eye movements quality
Using aDEMd (adult Developmental Eye Movement with distractors) test and NSUCO (Northeastern State University College of Optometry) test. Units: seconds (s).
Time frame: 1 year
Reading speed
Using Radner-Vissum test, units: seconds (s).
Time frame: 1 year
Life quality assessment
Scoring the National Eye Institute Visual Functioning Questionnaire-25 (NEI VFQ-25). Higher scores mean a better outcome. Minimum value: 0, maximum value: 100.
Time frame: 1 year
Pursuit eye movements
Would be performed noninvasively using simple, easy-to-use instruments such as flashlights, pointers, slates, Marsden's ball, rotating devices and Groffman's visual tracing test. If financial resources permit, an application on an electronic device could also be used. From these exercises, the following variables will be collected: time spent in the performance of the exercises in seconds (s) and errors made. These will be compared before and after the therapy. In addition, the patients would be given indications for the work of these exercises at home.
Time frame: 1 year
Saccadic eye movements
Would be performed noninvasively using simple, easy-to-use instruments such as flashlights, pointers, slates, Hart's charts, ARB charts and Ann Arbor tracing sheets. If financial resources permit, an application on an electronic device could also be used. From these exercises, the following variables will be collected: time spent in the performance of the exercises in seconds (s) and errors made. These will be compared before and after the therapy. In addition, the patients would be given indications for the work of these exercises at home.
Time frame: 1 year
Perceptual learning technique
Perceptual learning exercises could also be performed on an electronic device with a program that displays Gabor patches. This technique consists of a task with low-contrast, progressively decreasing, sustained attention, demanding and repetitive stimuli.
Time frame: 1 year
Plan to share: No
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