The 6-Item Vision-Related Quality of Life and Limitations Questionnaire: Evaluation of Psychometric Properties.

Purpose: We developed the Vision-related Quality of life and Limitations Questionnaire (VQL-6), a screening instrument to signal a need for additional care resulting from reduced vision-related quality of life in patients with chronic ophthalmic diseases. The aim of the present study was to evaluate psychometric properties. Methods: A Dutch population-based sample of 2032 participants (mean age, 55 ± 19 years) completed the VQL-6 and other questionnaires on vision-related quality of life, executive functioning, attention, mental health, and symptom validity. In addition, we recruited a sample of 208 ophthalmic patients (mean age, 72 ± 12 years) and 98 age and gender similar controls (mean age, 69 ± 11 years) who completed the VQL-6 and the National Eye Institute Visual Function Questionnaire-25. We studied the factor structure, internal consistency, convergent and divergent validity, and known-groups validity. Results: For the factor analyses, the population-based sample was split randomly in two subsamples. Exploratory factor analysis on the first subsample suggested a two-factor model (visual limitations and general health and quality of life), which was supported by confirmatory factor analyses on the second subsample, and on the patients. The VQL-6 demonstrated good internal consistency within each factor (0.78-0.89), sufficient convergent (r2= 55%) and divergent validity (r2 = 11%-24%), and good known-groups validity (Cohen's r = 0.57; P < 0.001). Conclusions: The VQL-6 has a robust two-factor structure and seems to be a valid tool to assess vision-related quality of life. Additional validation is needed in patients with chronic ophthalmic diseases. Translational Relevance: Future research is needed to determine if the VQL-6 can be used to identify patients with chronic ophthalmic diseases who are in need of additional care.

Reading Difficulties in Parkinson's Disease: A Stepped Care Model for Neurovisual Rehabilitation.

BACKGROUND: People with Parkinson's disease (PD) frequently experience reading difficulties. Little is known about what functional impairments distinguish people with PD with and without reading difficulties and how these should guide rehabilitation. OBJECTIVE: To provide concrete advice for an efficient stepped care model for reading difficulties in PD, based on extensive functional assessments. METHODS: This study included 74 people with PD in a neurovisual rehabilitation setting who underwent assessment of visual, visuoperceptual, and cognitive functions. Outcomes were compared between those with frequent (RD+; N = 55) and infrequent reading difficulties (RD-; N = 19). Aids and advice provided during rehabilitation were registered. RESULTS: Only a few functions appeared to distinguish RD+ and RD-. Visual functions (i.e., contrast sensitivity, g = 0.76; reading acuity, g = 0.66; visual acuity, g = 0.54) and visuoperceptual functions (i.e., visual attention, g = 0.58, visual motor speed, g = 0.56) showed significant worse scores in RD+ compared to RD-. Aids and advice applied consisted mainly of optimizing refraction, improving lighting, and optimizing text size and spacing. CONCLUSION: The test battery showed significant differences between RD+ and RD-on only a few tests on visual and visuoperceptual functions. The applied aids and advice matched well with these impairments. Therefore, we recommend a stepped care model, starting with a short test battery on these functions. If this battery indicates functional impairments, this can be followed by standard aids and advice to improve reading. Only in case of insufficient effect additional testing should take place.

Eye Movement Evaluation in Multiple Sclerosis and Parkinson's Disease Using a Standardized Oculomotor and Neuro-Ophthalmic Disorder Assessment (SONDA).

Evaluating the state of the oculomotor system of a patient is one of the fundamental tests done in neuro-ophthalmology. However, up to date, very few quantitative standardized tests of eye movements' quality exist, limiting this assessment to confrontational tests reliant on subjective interpretation. Furthermore, quantitative tests relying on eye movement properties, such as pursuit gain and saccade dynamics are often insufficient to capture the complexity of the underlying disorders and are often (too) long and tiring. In this study, we present SONDA (Standardized Oculomotor and Neurological Disorder Assessment): this test is based on analyzing eye tracking recorded during a short and intuitive continuous tracking task. We tested patients affected by Multiple Sclerosis (MS) and Parkinson's Disease (PD) and find that: (1) the saccadic dynamics of the main sequence alone are not sufficient to separate patients from healthy controls; (2) the combination of spatio-temporal and statistical properties of saccades and saccadic dynamics enables an identification of oculomotor abnormalities in both MS and PD patients. We conclude that SONDA constitutes a powerful screening tool that allows an in-depth evaluation of (deviant) oculomotor behavior in a few minutes of non-invasive testing.

The development of the Screening of Visual Complaints questionnaire for patients with neurodegenerative disorders: Evaluation of psychometric features in a community sample.

BACKGROUND AND OBJECTIVES: Patients with neurodegenerative disorders often experience impairments in visual function. In research and clinical care, visual problems are primarily understood as objective visual impairments. Subjective complaints, referring to complaints from a patient's perspective, receive less attention, while they are of utmost clinical importance to guide assessment and rehabilitation. A 21-item Screening of Visual Complaints questionnaire (SVC) was developed for the assessment of subjective visual complaints in patients with neurodegenerative disorders. This prospective study aims to evaluate the psychometric properties of the SVC in a large community sample. METHODS: A stratified convenience sample of 1,461 healthy Dutch participants (18-95 years) without severe self-reported neurological, ophthalmological or psychiatric conditions completed the SVC, Cerebral Visual Complaints questionnaire (CVC-q), National Eye Institute Visual Function Questionnaire-25 (NEI-VFQ-25), Behavior Rating Inventory of Executive Function-A (BRIEF-A), Questionnaire for Experiences of Attention Deficits (Fragebogen erlebter Defizite der Aufmerkzamkeit; FEDA), Depression Anxiety Stress Scale-21 (DASS-21) and the Structured Inventory for Malingered Symptomatology (SIMS) online. After two weeks, 66 participants completed the SVC again. We evaluated the factor structure, internal consistency, convergent and divergent validity, and test-retest reliability of the SVC. RESULTS: The sample was split in two subsamples to perform exploratory and confirmatory factor analyses. In the first subsample, the exploratory factor analysis extracted three factors from the SVC: diminished visual perception, altered visual perception and ocular discomfort. The confirmatory factor analysis showed this model to be valid in the second subsample. The SVC showed satisfactory convergent validity (NEI-VFQ-25: r = -0.71; CVC-q: r = 0.84) and divergent validity (SIMS: r = 0.26; BRIEF-A: r = 0.29; FEDA: r = 0.40; DASS-21: r = 0.34) and good internal consistency (Cronbach's alpha = 0.85) and test-retest reliability (ICC = 0.82). CONCLUSIONS: The SVC is a valid and reliable tool for the assessment of subjective visual complaints in a community sample and appears promising for clinical use in patients with neurodegenerative disorders.

Haptic discrimination and matching of viscosity.

In three experiments, viscosity perception of liquids using the sense of touch was studied. The first two were discrimination experiments in which Weber fractions were determined for a number of viscosities spanning the range of what is encountered in daily life, and for two ways of perceiving viscosity (stirring with a spatula or with the index finger). For high viscosities, Weber fractions were around 0.3, whereas they increased for lower viscosities. For low viscosities, discrimination performance was much worse with the finger than with the spatula. In the third experiment, subjects matched liquids perceived with these two methods, which resulted in biases of around 80. Control experiments and force measurements were performed to find an explanation for these results. It was concluded that the relationship between perceived and physical viscosity is steeper for stirring liquids with a spatula than stirring with the finger.

An extended 15 Hz ERG protocol (1): the contributions of primary and secondary rod pathways and the cone pathway.

The minimum in the amplitude versus flash strength curve of dark-adapted 15 Hz electroretinograms (ERGs) has been attributed to interactions between the primary and secondary rod pathways. The 15 Hz ERGs can be used to examine the two rod pathways in patients. However, previous studies suggested that the cone-driven pathway also contributes to the 15 Hz ERGs for flash strengths just above that of the minimum. We investigated cone pathway contributions to improve upon the interpretation of (abnormal) 15 Hz ERGs measured in patients. We recorded 15 Hz ERGs in five healthy volunteers, using a range of flash strengths that we extended to high values. The stimuli were varied in both colour (blue, green, amber, and red) and flash duration (short flash and square wave) in order to stimulate rods and cones in various ways. The differences in the responses to the four colours could be fully explained by the spectral sensitivity of rods for flash strengths up to approximately 12.5 log quanta·deg(-2). At higher flash strengths, higher-order harmonics appeared in the responses which could be attributed to cones being more sensitive than rods to higher frequencies. Furthermore, the amplitude curves of the blue and green responses showed a second minimum suggesting rod to cone interactions. We present a descriptive model of the contributions of the rod and cone pathways. In clinical application, we would advise using the short flash flicker instead of the square wave flicker, as the responses are of larger amplitude, and cone pathway contributions can be recognized from large higher-order harmonics.

Clinical validation of point-source corneal topography in keratoplasty.

PURPOSE: To validate the clinical performance of point-source corneal topography (PCT) in postpenetrating keratoplasty (PKP) eyes and to compare it with conventional Placido-based topography. METHODS: Corneal elevation maps of the anterior corneal surface were obtained from 20 post-PKP corneas using PCT (VU topographer, prototype; VU University Medical Center, Amsterdam, The Netherlands) and Placido-based topography (Keratron, Optikon 2000, Rome, Italy). Corneal surface parameters are calculated in terms of radius and asphericity. Corneal aberrations were characterized using standard Zernike convention. An artificial surface with quadrafoil feature (SUMIPRO, Almelo, The Netherlands) was measured and used as a reference to assess instrument performance compared with the gold standard. RESULTS: The differences (mean ± std of PCT - Placido) found between the two types of topographers in measurements of post-PKP eyes are 0.02 ± 0.21 mm (p=0.64) for radius of curvature, 0.14 ± 0.49 (p=0.23) for asphericity, -0.19 ± 1.67 µm (p=0.61) for corneal astigmatism, -0.25 ± 1.34 µm (p=0.41) for corneal coma, 0.23 ± 0.82 µm (p=0.23) for corneal trefoil, and 0.15 ± 0.28 µm (p=0.02) for corneal quadrafoil. The PCT measured the artificial surface more accurate (rms error 0.16 µm; 0.12 eq. Dpt.) than the Placido-based topographer (rms error 1.50 µm; 1.15 eq. Dpt.). CONCLUSIONS: PCT is more accurate than Placido-based topography in measuring quadrafoil aberration.