Capturing saccades in multiple sclerosis with a digitized test of rapid number naming

Effect of methylphenidate on oculomotor function in individuals with multiple sclerosis: a pilot randomized placebo-controlled trial

Introduction

Individuals with multiple sclerosis (MS) frequently experience visual and oculomotor symptoms that may impact and confound neuropsychological assessments of information processing speed (IPS). In this study, we examined the effect of the psychostimulant methylphenidate on oculomotor function and the association between change in oculomotor speed and change in information processing speed.

Methods

We used a repeated measures crossover design in which a sample of 11 participants with MS were randomly assigned to one of two treatment arms: one that received methylphenidate for 4 weeks and another that received a placebo for 4 weeks. After a 7-day washout period, the treatments were crossed over. The King Devick test, the Symbol Digit Modalities Test, and the Paced Auditory Serial Addition Test were administered at baseline and after each of the two study arms.

Results

We found a significant improvement in oculomotor speed in the methylphenidate condition as compared to placebo. This improvement was significantly correlated with improvement on a visuomotor assessment of IPS (Symbol Digit Modalities Test), but no such association was found for an auditory-verbal assessment of IPS (Paced Auditory Serial Addition Test).

Discussion

These findings suggest that individuals with MS experience improved oculomotor speed while taking methylphenidate, which may, in turn, improve performance on assessments of IPS with visuomotor demands.

Developmental Eye Movement (DEM) and King-Devick (K-D) Performance in Multiple Sclerosis

Eye movement disorders have been reported in patients with multiple sclerosis (MS) as saccadic disturbances. Several methods have been described for the assessment of saccades, including the K-D and DEM tests. The performance of these tests also involves attention, language, and other brain areas which have been reported to be altered in MS patients. The aim of the study was to determine how developmental eye movement (DEM) and King-Devick (K-D) tests are affected in MS-patients. It was also to analyze whether a resolved episode of optic neuritis (ON) has a negative influence. Subjects with MS showed worse outcomes (higher times) in DEM test (72 (26) s and a K-D test (56 (22) s compared to healthy subjects (64 (7) s and 55 (11) s, respectively). However, a previous ON episode did not worsen the MS-times of DEM (80 (33) s or of K-D (62 (33) s. Horizontal saccades with the DEM showed differences between subjects with MS (with and without ON) and healthy ones (p < 0.05), whereas no such differences were found in the vertical saccades. According to the DEM instructions, MS patients would present heterogeneous oculomotor and non-visual disturbances. Regarding the K-D test, only the third card (the most complex one) showed differences (p < 0.05) between groups. These tests can capture impairment of attention, language, and other areas that correlate with suboptimal brain function in addition to the oculomotor dysfunctions present in subjects with MS.

Are near visual signs and symptoms in multiple sclerosis compatible with convergence insufficiency?

CLINICAL RELEVANCE

Optometric management of neurodegenerative diseases is essential since visual signs, such as double vision, visual acuity reduction, or oculomotricity dysfunctions, are usually present in these subjects over the course of the disease. The present paper can guide clinicians in better managing their patients with multiple sclerosis.

BACKGROUND

Patients with multiple sclerosis present near vision symptoms that may be related to binocular anomalies, but these symptoms have not been investigated and related to specific signs. The aim of the present study was to evaluate the binocular vision in subjects with multiple sclerosis, and to analyse if the near visual signs and symptoms observed are compatible with those found in convergence insufficiency, as occurs in other neurodegenerative diseases.

METHODS

A total of 57 multiple sclerosis patients and 26 healthy controls were examined and classified as potentially compatible with convergence insufficiency according to the signs and symptoms. Clinical diagnosis of convergence insufficiency was established when subjects met the following criteria: NPC breakpoint more than 6 cm, PFV ≤ than 15^Δ (base-out), and exophoria greater at near than at distance at least 4^Δ. Convergence Insufficiency Symptom Survey (CISS) was administered to assess the symptomatology considering a score ≥16 as positive.

RESULTS

According to the CISS score, 54,4% of the multiple sclerosis subjects revised showed a suspect of convergence insufficiency, with a median score of 27 (IQR 9), whereas only one subject from control group (3.8%) showed this suspect. According to the diagnostic criteria based on signs, only 15.8% of multiple sclerosis patients had a real diagnosis of convergence insufficiency.

CONCLUSION

Multiple sclerosis patients showed symptomatology compatible with convergence insufficiency, but this was not supported by the signs which showed a more esophoric tendency. The discrepancies between the signs and symptoms could be due to the questionnaire used including items that are also related to the cognitive function and other ocular abnormalities.

Correlation of Visual Quality of Life With Clinical and Visual Status in Friedreich Ataxia

BACKGROUND

The primary objective was to determine the association of patient-reported vision-specific quality of life to disease status and visual function in patients with Friedreich's ataxia (FRDA).

METHODS

Patients with FRDA were assessed with the 25-Item National Eye Institute Visual Functioning Questionnaire (NEI-VFQ-25) along with measures of disease status (ataxia stage) and visual function (low- and high-contrast letter acuity scores). The relations of NEI-VFQ-25 scores to those for disease status and visual function were examined.

RESULTS

Scores for the NEI-VFQ-25 were lower in patients with FRDA (n = 99) compared with published disease-free controls, particularly reduced in a subgroup of FRDA patients with features of early onset, older age, and abnormal visual function.

CONCLUSIONS

The NEI-VFQ-25 captures the subjective component of visual function in patients with FRDA.

Detection of normal and slow saccades using implicit piecewise polynomial approximation

The quantitative analysis of saccades in eye movement data unveils information associated with intention, cognition, and health status. Abnormally slow saccades are indicative of neurological disorders and often imply a specific pathological disturbance. However, conventional saccade detection algorithms are not designed to detect slow saccades, and are correspondingly unreliable when saccades are unusually slow. In this article, we propose an algorithm that is effective for the detection of both normal and slow saccades. The proposed algorithm is partly based on modeling saccadic waveforms as piecewise-quadratic signals. The algorithm first decreases noise in acquired eye-tracking data using optimization to minimize a prescribed objective function, then uses velocity thresholding to detect saccades. Using both simulated saccades and real saccades generated by healthy subjects and patients, we evaluate the performance of the proposed algorithm and 10 other detection algorithms. We show the proposed algorithm is more accurate in detecting both normal and slow saccades than other algorithms.

Visual and motor confounds on the symbol digit modalities test

BACKGROUND

Slowed information processing speed is the most prevalent cognitive symptom in persons with multiple sclerosis (MS). The most commonly used instrument to measure information processing speed in MS is the Symbol Digit Modalities Test (SDMT). However, visual, oculomotor, and oralmotor deficits are frequently observed in persons with MS, and performance on the SDMT relies on these visual and motor functions, in addition to cognition.

METHODS

The current study examined the relationship between the SDMT and the King-Devick Test (KDT). The KDT encompasses similar oculomotor and oralmotor demands as the SDMT but requires a smaller attentional load. One hundred and thirty participants with MS completed the oral version of the SDMT and the KDT. Ordinary nonparametric bootstrapped regression models were performed with 1000 bootstrapped samples. Bootstrapped confidence intervals (CIs) were bias-corrected.

RESULTS

KDT performance explained 31% (bootstrapped CI: 18 - 43%) of the variance of SDMT performance (moderate correlation), much more than demographic and disease-related variables (0.7% and 10%, respectively).

CONCLUSIONS

Visual, oralmotor, and oculomotor functions contributed significantly to SDMT performance. Therefore, these sensory and motor functions must be taken into account when interpreting SDMT scores.

Multiple sclerosis in ophthalmology: beyond optic neuritis

Disorders of the visual system are one of the main features of multiple sclerosis (MS), and have a great impact on the quality of life of patients. Although optic neuritis is the most frequent manifestation, there are other ophthalmological processes not related to neuritis, a knowledge of which is very useful in the management of patients with MS. These abnormalities are described, grouped into impairments of the afferent pathway, efferent pathway, or upper cerebral areas. Additionally, the main ophthalmological side effects of the drugs currently used in the control of MS are described.

Binocular, Accommodative and Oculomotor Alterations In Multiple Sclerosis: A Review

Multiple sclerosis (MS) is an acquired demyelinating and inflammatory neurodegenerative disease affecting the central nervous system (CNS). Clinical and subclinical ocular disturbances occur in almost all patients with MS. The objective of this narrative review was to collect and summarize the available scientific information on oculomotor, accommodative and binocular alterations that have been reported in MS. A systematic search strategy with the following descriptors was carried out: multiple sclerosis, ocular motility disorders, internuclear ophthalmoplegia, nystagmus, vergences, fixation, pupil reflex, accommodation and stereopsis. According to the search, some oculomotor alterations were found to be commonly reported in MS, such as alterations in saccades and nystagmus. In contrast, accommodative, vergence and stereopsis alterations have not been comprehensively studied despite their relevance, with only minimal evidence showing a potential negative impact of the disease on these aspects. In conclusion, oculomotor impairment is a common component of disability in MS patients and should be considered when managing this type of patients. More research is still needed to know the real impact of this disease on binocular vision and accommodation.

Evaluation of the Commercial, Off-the-Shelf (COTS) King-Devick Eye Tracking System

Concussion biomarkers are important guides for diagnosis and return-to-duty decisions. Recent literature describes the King-Devick (KD) test as a sensitive sports-related concussion screener. This test involves timing an individual reading aloud 120 digits printed on three test cards. The test is commonly considered to evaluate the effects of concussion and other factors on reading-related eye movements (EMs). However, the extent to which the KD test reflects EMs remains a matter of conjecture since the test reports only reading speed and number of errors. An off-the-shelf, computerized KD with eye tracking system recently became commercially available. Two early model KD with eye tracking systems were purchased in 2015 and evaluated before deploying them for research. The evaluation consisted of two studies; one with 20 volunteers assessing the comparability of the two systems and the other with 5 volunteers to quantify the systems' stability and repeatability over 5 successive days. The results showed that several of the systems' reported EM response parameters lacked face validity; consequently, the systems could not be used for scientific research. This conclusion emphasizes the importance of systematic test and evaluation of new equipment before it is used for research.

Mobile Universal Lexicon Evaluation System (MULES) in MS: Evaluation of a new visual test of rapid picture naming

OBJECTIVE

The Mobile Universal Lexicon Evaluation System (MULES) is a test of rapid picture naming that is under investigation for concussion. MULES captures an extensive visual network, including pathways for eye movements, color perception, memory and object recognition. The purpose of this study was to introduce the MULES to visual assessment of patients with MS, and to examine associations with other tests of afferent and efferent visual function.

METHODS

We administered the MULES in addition to binocular measures of low-contrast letter acuity (LCLA), high-contrast visual acuity (VA) and the King-Devick (K-D) test of rapid number naming in an MS cohort and in a group of disease-free controls.

RESULTS

Among 24 patients with MS (median age 36 years, range 20-72, 64% female) and 22 disease-free controls (median age 34 years, range 19-59, 57% female), MULES test times were greater (worse) among the patients (60.0 vs. 40.0 s). Accounting for age, MS vs. control status was a predictor of MULES test times (P = .01, logistic regression). Faster testing times were noted among patients with MS who had greater (better) performance on binocular LCLA at 2.5% contrast (P < .001, linear regression, accounting for age), binocular high-contrast VA (P < .001), and K-D testing (P < .001). Both groups demonstrated approximately 10-s improvements in MULES test times between trials 1 and 2 (P < .0001, paired t-tests).

CONCLUSION

The MULES test, a complex task of rapid picture naming involves an extensive visual network that captures eye movements, color perception and the characterization of objects. Color recognition, a key component of this novel assessment, is early in object processing and requires area V4 and the inferior temporal projections. MULES scores reflect performance of LCLA, a widely-used measure of visual function in MS clinical trials. These results provide evidence that the MULES test can add efficient visual screening to the assessment of patients with MS.

EVALUATION OF VERTICAL AND HORIZONTAL SACCADES USING THE DEVELOPMENTAL EYE MOVEMENT TEST COMPARED TO THE KING-DEVICK TEST

BACKGROUND

Oculomotor function is impaired when an individual has a concussion and as such, it is important to identify tests that are able to assess oculomotor impairment. The King-Devick (K-D) test assesses horizontal saccadic eye movement and attention. The Developmental Eye Movement (DEM) test is designed to identify oculomotor dysfunction in children. It measures both horizontal and vertical saccades. The K-D test shows promise as a concussion-screening tool and part of a multifactorial assessment. The DEM has not been tested as a concussion assessment tool, but the neuroanatomical control of horizontal and vertical saccades originates from different areas of the brain, so one might expect to see differences in performance on the K-D and DEM tests when administered to concussed patients. First, it is important to determine if performance on the DEM and K-D tests, particularly with respect to the measurement of vertical and horizontal saccades, is similar in a healthy population.Hypothesis/Purpose: The primary purpose was to evaluate the relationship between horizontal and vertical saccade tests over repeated trials in normal, healthy subjects. A secondary purpose of this study was to determine the number of trials needed to reach a performance plateau for both the DEM and K-D tests.Study Design: This study used a prospective cohort research design.

METHODS

Forty-two healthy non-concussed participants (22 males, 20 females; mean age, 24.2 ± 2.92 years) completed six repeated trials of both the DEM, and then six trials of the K-D test in a single testing session. Trials within each test were performed in random order and participants were offered short rest breaks as needed between test administrations.

RESULTS

Results indicated strong correlations, r=.67, or greater, between measurements of horizontal and vertical saccades. Performance plateaued on the K-D at trial three and on the DEM at trial two for both horizontal and vertical saccades.

CONCLUSION

It appears that the DEM and K-D tests measure similar constructs in healthy individuals and that no additional information is provided by assessment of vertical saccades. Additional studies are required to investigate the usefulness of the DEM in concussed individuals.

LEVEL OF EVIDENCE

3: Laboratory study with repeated measures.

Visual Pathway Measures are Associated with Neuropsychological Function in Multiple Sclerosis

PURPOSE

To determine the relationships between visual function and ganglion cell and inner plexiform layer thickness and neuropsychological measures in multiple sclerosis (MS).

METHODS

Ninety-five relapsing-remitting MS (RRMS) and 36 progressive MS patients underwent 100%-contrast visual acuity (VA), 2.5%- and 1.25%-contrast letter acuity (LA) testing, Cirrus-HD-optical coherence tomography, and neuropsychological assessments. Mixed-effects regression models were used to assess relationships.

RESULTS

Across the cohort, 1.25%-contrast LA was associated with Symbol Digit Modalities Test (SDMT; β = 2.17, p = 0.005) and Brief Visuospatial Memory Test-Revised (BVMT-R) total recall (TR) and delayed recall (DR) scores (β = 0.31, p < 0.001; β = 0.15, p = 0.039, respectively). 2.5%-contrast LA was associated with BVMT-R TR scores (β = 0.27, p = 0.006). In the RRMS cohort, 1.25%-contrast LA was generally more significantly associated with cognitive measures: SDMT (β = 2.97, p = 0.001) and BVMT-R TR (β = 0.32, p < 0.001) and DR (β = 0.22, p = 0.012).

CONCLUSION

This study suggests that visual pathway measures, particularly visual function measures, reflect aspects of cognitive function in MS, further supporting their roles as complementary outcomes in MS neuroprotection trials.

Slower saccadic reading in Parkinson's disease

Idiopathic Parkinson's Disease (PD) is characterized by degeneration of dopaminergic and other neurons, leading to motor and non-motor deficits. Abnormal eye movements in PD, including fixations, saccades, and convergence, are well described. However, saccadic reading, which requires serial and alternating saccades and fixations, is not well studied, despite its obvious impact on the quality of life. In this study, we assessed saccadic reading using variations of the King-Devick (KD) test, a rapid single digit number naming test, as a way to assess the ability to make serial left-to-right ocular motor movements necessary for reading. We recruited 42 treated PD patients and 80 age-matched controls and compared their reading times with a variety of measures, including age, duration of disease, Unified Parkinson's Disease Rating Scale (UPDRS), the National Eye Institute 25-Item Visual Functioning Questionnaire 25 (VFQ-25), and Montreal Cognitive assessment (MoCA) test. The subjects performed 4 trials of reading 120 single digit numbers aloud as fast as possible without making errors. In each trial, they read 3 pages (KD1, KD2, and KD3), and each page contained 40 numbers per page in 8 lines with 5 numbers/line. We found that PD patients read about 20% slower than controls on all tests (KD1, 2, and 3 tests) (p < 0.02), and both groups read irregularly spaced numbers slower than regularly spaced numbers. Having lines between numbers to guide reading (KD1 tests) did not impact reading time in both PD and controls, but increased visual crowding as a result of decreased spacing between numbers (KD3 tests) was associated with significantly slower reading times in both PD and control groups. Our study revealed that saccadic reading is slower in PD, but controls and PD patients are both impacted by visuospatial planning challenges posed by increased visual crowding and irregularity of number spacing. Reading time did not correlate with UPDRS or MoCA scores in PD patients but significantly correlated with age, duration of disease, and VFQ-25 scores. The presence of convergence insufficiency did not significantly correlate with reading time in PD patients, although on average there was slower reading time in those with convergence insufficiency by 8 s (p = 0.2613). We propose that a simple reading task using 120 single-digit numbers can be used as a screening tool in the clinical setting to assess functional ocular motor difficulties in Parkinson's disease that can have a profound impact on quality of life.

A nonlinear generalization of the Savitzky-Golay filter and the quantitative analysis of saccades

The Savitzky-Golay (SG) filter is widely used to smooth and differentiate time series, especially biomedical data. However, time series that exhibit abrupt departures from their typical trends, such as sharp waves or steps, which are of physiological interest, tend to be oversmoothed by the SG filter. Hence, the SG filter tends to systematically underestimate physiological parameters in certain situations. This article proposes a generalization of the SG filter to more accurately track abrupt deviations in time series, leading to more accurate parameter estimates (e.g., peak velocity of saccadic eye movements). The proposed filtering methodology models a time series as the sum of two component time series: a low-frequency time series for which the conventional SG filter is well suited, and a second time series that exhibits instantaneous deviations (e.g., sharp waves, steps, or more generally, discontinuities in a higher order derivative). The generalized SG filter is then applied to the quantitative analysis of saccadic eye movements. It is demonstrated that (a) the conventional SG filter underestimates the peak velocity of saccades, especially those of small amplitude, and (b) the generalized SG filter estimates peak saccadic velocity more accurately than the conventional filter.