The effect of contrast on monocular versus binocular reading performance.

The binocular advantage in reading performance is typically small. On the other hand research shows binocular reading to be remarkably robust to degraded stimulus properties. We hypothesized that this robustness may stem from an increasing binocular contribution. The main objective was to compare monocular and binocular performance at different stimulus contrasts and assess the level of binocular superiority. A secondary objective was to assess any asymmetry in performance related to ocular dominance. In a balanced repeated measures experiment 18 subjects read texts at three levels of contrast monocularly and binocularly while their eye movements were recorded. The binocular advantage increased with reduced contrast producing a 7% slower monocular reading at 40% contrast, 9% slower at 20% contrast, and 21% slower at 10% contrast. A statistically significant interaction effect was found in fixation duration displaying a more adverse effect in the monocular condition at lowest contrast. No significant effects of ocular dominance were observed. The outcome suggests that binocularity contributes increasingly to reading performance as stimulus contrast decreases. The strongest difference between monocular and binocular performance was due to fixation duration. The findings may pose a clinical point that it may be necessary to consider tests at different contrast levels when estimating reading performance.

Motion perception in children with foetal alcohol syndrome.

AIM: To evaluate the visual magnocellular pathway by a coherent motion perception test in children with foetal alcohol syndrome (FAS). METHODS: Eighty-nine children (49 with verified FAS and 40 without FAS) aged from 10 to 16 years were included into the study. Both the study and the control group were children living in orphanages. A coherent motion perception test was used. The test consisted of 150 white moving dots on a black background presented in different signal-to-noise ratio conditions. The task was direction detection of the coherently moving dots whose percentage decreased at each step. RESULTS: A significant difference between the two groups was found (p = 0.018). Children with FAS had lower coherent motion perception ability in all the signal-to-noise ratio conditions. A significant difference between difficulty levels (p < 0.001) was found for all subjects in both groups - decreasing the stimulus signal-to-noise level decreased the motion perception score. In both groups, the motion perception score differed for vertical and horizontal stimuli (p = 0.003) with better performance with vertical stimuli. CONCLUSION: Impaired motion perception in FAS children could be indicative of a dorsal stream developmental dysfunction resulting from alcohol brain damage.

How to assess visual function in acquired brain injury-Asking is not enough.

BACKGROUND: Acquired brain injury affects many brain areas and causes a range of dysfunctions including vision-related issues. These issues can have negative impacts on rehabilitation progress and activities of daily life but may easily be overlooked. There is no common recommendation about how to assess visual impairments after ABI. The purpose of this study was to estimate the frequency of objectively measures oculomotor dysfunctions, and also how these findings are related to two inventories intended to support detection of visual impairment. METHODS: The study was cross-sectional and included 73 outpatients. In addition to the standard evaluation program, the patients went through a comprehensive optometric examination. The inventories used were the Vision Interview (VI) and the Convergence Insufficiency Symptom Survey (CISS). RESULTS: All three types of examinations showed a high proportion vision-related symptoms. Fusion vergence was the most common objectively measured finding, 83%. There were seven statistically significant associations between five VI items and five visual deficits. The strength of associations was moderate (Phi 0.261-0.487, p < .05). The sensitivity and specificity of the CISS were moderate. CONCLUSION: We found high percentages of the patients with visual symptoms and dysfunctions. Due to the complexity of visual symptoms and functional deficits in ABI, we find it necessary to combine both symptom assessment and vision examination in order to capture visual function issues.

Evaluation of an international benchmarking initiative in nine eye hospitals.

BACKGROUND: Benchmarking has become very popular among managers to improve quality in the private and public sector, but little is known about its applicability in international hospital settings. PURPOSE: The purpose of this study was to evaluate the applicability of an international benchmarking initiative in eye hospitals. METHODOLOGY: To assess the applicability, an evaluation frame was constructed on the basis of a systematic literature review. The frame was applied longitudinally to a case study of nine eye hospitals that used a set of performance indicators for benchmarking. Document analysis, nine questionnaires, and 26 semistructured interviews with stakeholders in each hospital were used for qualitative analysis. FINDINGS: The evaluation frame consisted of four areas with key conditions for benchmarking: purposes of benchmarking, performance indicators, participating organizations, and performance management systems. This study showed that the international benchmarking between eye hospitals scarcely met these conditions. The used indicators were not incorporated in a performance management system in any of the hospitals. Despite the apparent homogeneity of the participants and the absence of competition, differences in ownership, governance structure, reimbursement, and market orientation made comparisons difficult. Benchmarking, however, stimulated learning and exchange of knowledge. It encouraged interaction and thereby learning on the tactical and operational levels, which is also an incentive to attract and motivate staff. PRACTICE IMPLICATIONS: Although international hospital benchmarking seems to be a rational process of sharing performance data, this case study showed that it is highly dependent on social processes and a learning environment. It can be useful for diagnostics, helping local hospitals to catalyze performance improvements.

Vision-related symptoms after acquired brain injury and the association with mental fatigue, anxiety and depression.

BACKGROUND: Brain injury causes multiple symptoms. Among these, visual disturbances are common; 50-70% of patients experience some change in vision after injury/illness. Other very common and disabling symptoms are fatigue, anxiety and depression. This study examines whether levels of fatigue, anxiety and depression are increased if the patients also experience vision disorders. MATERIALS AND METHODS: A total of 123 patients enrolled in day care rehabilitation unit for medium-to-severe brain injury completed questionnaires about self-experienced fatigue, anxiety, depression and self-experienced level and type of visual disturbances. Symptoms of fatigue, anxiety and depression were compared with the occurrence of visual disturbances. Analyses were performed using binary logistic regression. RESULTS: An association was found between visual symptoms and fatigue, but not between visual symptoms and anxiety/depression. However, some visual symptoms, such as glare, blurred vision and reading difficulties, showed great differences between patients with or without anxiety/depression. CONCLUSION: Vision rehabilitation may be a tool for mitigating fatigue after acquired brain injury.

Strabismus, binocular functions and ocular motility in children with hydrocephalus.

PURPOSE: To investigate heterotropia, heterophoria, head posture, nystagmus, stereo acuity, ocular motility and near point of convergence (NPC) in children with hydrocephalus treated surgically before 1 year of age. In addition, the effects of being born with hydrocephalus, the effect of the etiology of hydrocephalus, number of shunt revisions and the size of the ventricles on these variables were studied. METHODS: A population-based study was performed in 75 children and the results were compared with the results of an age- and sex-matched group (comp group) (n = 140). RESULTS: Heterotropia 68.9% (comp group 3.6%; p < 0.001), abnormal head posture 41.3% (comp group 0; p < 0.001), nystagmus 44.0% (comp group 0; p < 0.001), stereo acuity < or =60'' 33.8% (comp group 97.1%; p < 0.001) and ocular motility defects 69.7% (comp group 0.7%; p < 0.001) were more common among children with hydrocephalus than in the comparison group. Children with overt hydrocephalus at birth had significantly more heterotropia (p = 0.0006), esotropia (p = 0.002), abnormal head posture (p = 0.02) and motility defects (p = 0.003) compared to those with hydrocephalus developing during the first year of life. The etiology, number of shunt revisions and the size of the ventricles had no significant effect on any of the investigated variables. CONCLUSIONS: Children with hydrocephalus surgically treated before the age of one year commonly present orthoptic abnormalities. The etiology of hydrocephalus, number of shunt revisions and ventricle size seem to be of minor importance compared with the age of onset of hydrocephalus with regard to the risk for orthoptic abnormalities.

Visual dysfunction is underestimated in patients with acquired brain injury.

OBJECTIVES: More than 50% of human cerebral activity is related to vision. Visual impairments are therefore common after acquired brain injury, although they are often overlooked. In order to evaluate the prevalence of visual deficits in our Out-patient Brain Injury Program, a structured screening questionnaire, the Visual Interview, was administered. METHODS: A total of 170 patients with acquired brain injury, mean age 47 years, who were enrolled in the programme during 2010-12, underwent the Visual Interview. The interview consists of 18 questions concerning visual impairment and was performed on admission. The different types of visual impairment were compared with regard to sex and diagnosis. RESULTS: Fifty-four percent of the patients reported visual changes, mainly reading difficulties, photosensitivity, blurred vision and disorders of the visual field. Sixteen patients who did not experience visual changes also reported visual symptoms in 4-9 questions. Only slight differences were noted in the occurrence of visual symptoms when correlated with sex or diagnosis. CONCLUSION: Visual impairments are common after acquired brain injury, but some patients do not define their problems as vision-related. A structured questionnaire, covering the most common visual symptoms, is helpful for the rehabilitation team to facilitate assessment of visual changes.

Progressive brain calcifications and signs in a family with the L9R mutation in the PDGFB gene.

Primary familial brain calcifications (PFBC) are a heterogeneous group of rare autosomal dominant disorders. Mutations in the PDGFB gene are the second most common cause of PFBC. A model for PDGFB-associated PFBC, hypomorphic PDGFB (ret/ret) mouse, displays impaired blood-brain barrier (BBB), progressive brain calcifications and increased flux of the oxysterol 24S-hydroxycholesterol from the brain into the circulation.(1,2) Only 8 families and 2 sporadic cases with PDGFB mutations have been identified so far, one of them a Swedish-Finnish family previously described as F13.(1,3-6) Very little is known about the natural history of PDGFB-associated PFBC. Here, we provide a comprehensive long-term follow-up of the F13 family.

Screening for Dyslexia Using Eye Tracking during Reading.

Dyslexia is a neurodevelopmental reading disability estimated to affect 5-10% of the population. While there is yet no full understanding of the cause of dyslexia, or agreement on its precise definition, it is certain that many individuals suffer persistent problems in learning to read for no apparent reason. Although it is generally agreed that early intervention is the best form of support for children with dyslexia, there is still a lack of efficient and objective means to help identify those at risk during the early years of school. Here we show that it is possible to identify 9-10 year old individuals at risk of persistent reading difficulties by using eye tracking during reading to probe the processes that underlie reading ability. In contrast to current screening methods, which rely on oral or written tests, eye tracking does not depend on the subject to produce some overt verbal response and thus provides a natural means to objectively assess the reading process as it unfolds in real-time. Our study is based on a sample of 97 high-risk subjects with early identified word decoding difficulties and a control group of 88 low-risk subjects. These subjects were selected from a larger population of 2165 school children attending second grade. Using predictive modeling and statistical resampling techniques, we develop classification models from eye tracking records less than one minute in duration and show that the models are able to differentiate high-risk subjects from low-risk subjects with high accuracy. Although dyslexia is fundamentally a language-based learning disability, our results suggest that eye movements in reading can be highly predictive of individual reading ability and that eye tracking can be an efficient means to identify children at risk of long-term reading difficulties.

Fixation stability in normal children.

Fixation stability was found to increase with increasing age (4-15 years) in normal children, but there was no directional preponderance in fixation location.

Drift in ocular counterrolling during static head tilt.

A decreasing drift of the counter-rolled eye position (OCR) during head tilt was recently described. The underlying mechanism is not known. OCR in eleven healthy subjects was recorded (Search coil, Skalar) during a head tilt paradigm in two test conditions. The head was tilted with a velocity below (test 1) and above (test 2) detection threshold for the semicircular canals (SC) and held static for eight minutes. A significant drift of OCR was revealed in test 2 (P = .0006, ANOVA) and close to significant in test 1 (P = .07). No statistical difference was found between the two test conditions. The results suggest that the OCR drift was not caused by the SC complex merely.

Drift in ocular torsion during sustained head tilt.

PURPOSE: A head tilt towards the shoulder (roll) induces an ocular counter-roll (OCR), i.e. torsion in the opposite direction to the head. How this counter-rolled position is maintained during a static head tilt is in debate. In a previous study, we reported an OCR-increasing drift subsequent to the head tilt. This finding is in contrast to other reports where no such response was found. The primary aim of this study was to repeat the experiment during a prolonged head-tilt test and to describe the OCR characteristics. A secondary aim was to investigate the influence of spatial visual cues on OCR. METHODS: Five male subjects performed a head tilt (30 degrees ) towards the right shoulder while the eye position was recorded during a 10-minute interval. In test 1, the subjects viewed a target with no cues for spatial orientation. The same head-tilt paradigm was repeated in test 2 with a visual target with spatial cues. Two samples of data were extracted from the start and the end of the recordings for statistical analysis. RESULTS: Subsequent to the head tilt, a slow OCR-increasing drift in the opposite direction to the head roll was found in all subjects. On average, this drift lasted for 30 sec (+/- 5) in test 1 and for 55 sec (+/- 18) in test 2. The drift was then found to change its direction, i.e. the eyes were rotated in the same direction as the head roll. When measured after 10 minutes, the OCR was significantly decreased. CONCLUSIONS: The OCR during static head tilt is not constant. During the first minute there is a gradually increasing OCR. Thereafter, the amplitude of the OCR decreases gradually. These changes are influenced to some extent by spatial visual cues. Possible mechanisms are adaptive responses in otolithic afferents as well as central nervous memory functions related to the semicircular canal system.

Strabismus and binocular functions in a sample of Swedish children aged 4-15 years.

PURPOSE: To investigate strabismus, head posture, nystagmus, stereoacuity, ocular motility, near point of convergence (NPC) and accommodative convergence to accommodation ratio (AC/A) in a sample of Swedish children. METHODS: A prospective cross-sectional study was carried out on 143 children, 4-15 years of age. RESULTS: Heterotropia was found in five children (3.5%), four with esotropia and one with exotropia. One child with esotropia had a slight overaction of both inferior oblique muscles. Heterophoria was found in 37 children (26%) at near and/or distance fixation and it was four times more common at near than at distance. In 29 children, heterophoria was found at one distance only and orthophoria at the other. Orthophoria at both near and distance fixation was noted in 101 children (70.5%). The near point of convergence was < or =6 cm in 97% of the children and 97% had stereoacuity of 60" or better. In the whole group, the median AC/A ratio calculated with the heterophoria method was 5.6/1 prism diopters/diopters (PD/D) and with the gradient method, 1.3/1 PD/D. No anomalous head postures or nystagmus were observed and all children had normal versions. CONCLUSION: In this study, 143 well-defined children were investigated with a battery of accurately described tests, commonly used in clinical practice. These results are in agreement with those of other studies examining one or few variables in larger populations and the authors therefore conclude that their results may be used for comparisons with different patient groups.

Ocular Motor Score (OMS): a clinical tool to evaluating ocular motor functions in children. Intrarater and inter-rater agreement.

PURPOSE: Ocular motor score (OMS) is a new clinical test protocol for evaluating ocular motor functions in children and young adults. OMS is a set of 15 important and relevant non-invasive ocular motor function parameters derived from clinical practice. The aim of the study was to evaluate OMS according to intrarater and inter-rater agreement. METHODS: Forty children aged 4-10 years, 23 girls median age 6.5 (range 4.3-9.3) and 17 boys median age 5.8 (range 4.1-9.8) were included. The ocular motor functions were assessed and scored according to the OMS protocol. The examinations were videotaped. To obtain the intrarater agreement, the first author examined and scored the children twice, first in the clinic and 2 weeks later by watching the videotape. To obtain the inter-rater agreement, three other raters independently scored the ocular motor function of the children by watching the videotapes. RESULTS: The overall observed intrarater agreement was 88%, and the observed inter-rater agreement between the three raters was 80%. For none of the subtests was there an observed intrarater agreement lower than 65%. Three of the subtests had an observed inter-rater agreement of 65% or below. CONCLUSION: Overall there was high observed intra- and inter-rater agreement for the OMS test protocol. Subtests such as saccades and smooth pursuit were more difficult for raters to score similarly according the clinical OMS test protocol.

Conjugacy of torsional eye movements in response to a head tilt paradigm.

PURPOSE: Vertically skewed eye movements are induced by head tilt toward the shoulder (roll). Because vertical and torsional eye movements are tightly coupled both mechanically and neuronally, the purpose of the present study was to investigate the conjugacy of torsional eye movements during the Bielschowsky head tilt test (BHTT). Furthermore, the purpose was to investigate the influence of different visual and viewing condition on torsional conjugacy. The issue has clinical relevance in interpreting the outcome of the BHTT. METHODS: Eye movement recordings were performed using the infrared three-dimensional video-oculography (3D-VOG) technique. Objective cycloposition of 20 healthy individuals was measured in presumed primary position and in head tilt positions of 15 degrees, 30 degrees, and 45 degrees to the right and left, respectively. The same paradigm was performed under three different viewing conditions: binocularly without spatial orientation and both binocularly and monocularly with spatial orientation. The stimulus used with spatial orientation was a photographic picture of a historic building, whereas the stimulus with no spatial cues consisted of concentric circles. RESULTS: Consistent excyclovergence occurred in all subjects in head tilt. The relative amount increased with head tilt, regardless of the visual stimulus. Maximum excyclovergence was 0.7 degrees in 45 degrees head tilt during monocular fixation. Binocular viewing enhanced the torsion conjugacy by means of vergence stability (SD), whereas spatial visual cues improved the torsional conjugacy only slightly. CONCLUSIONS: Consistent excyclovergence was induced in head tilt. A vestibular origin seems to provide a plausible explanation of the induced torsional disconjugacy, whereas visual feed-back seems plausible in explaining the better conjugacy in binocular viewing.

Torsional and vertical eye movements during head tilt dynamic characteristics.

PURPOSE: As the first response to a Bielschowsky head tilt test (BHTT), a fast transient torsional eye movement in the same direction as the head tilt has been shown with the three-dimensional (3D)-video oculography (3D-VOG) technique, and this movement is paralleled by a transient vertical vergence shift inducing a physiological skew deviation. The purpose of the present study was to investigate these dynamic eye movements further in response to a BHTT paradigm with the magnetic search coil technique. METHODS: Ten healthy subjects performed a BHTT (15 degrees, 30 degrees, and 45 degrees) toward each shoulder while (search coil) the monocular eye and head positions were recorded. The same head tilt paradigm was repeated in a second test while (3D-VOG) the binocular eye position was recorded. RESULTS: Subsequent to the initiation of the head tilt (latency, approximately 160 ms) a rapid torsional eye movement (mean peak velocity: 40 deg/s; mean amplitude: 4 degrees) was seen in the same direction as the head movement, followed by a somewhat slower return movement. This torsion was synchronous with a vertical vergence eye movement (mean amplitude 3 degrees). The vertical vergence was always with left eye over right eye in the rightward head tilt and in head straightening from the left shoulder. In the left head tilt and in the head straightening from the right shoulder, this movement was always with the right eye over the left eye. CONCLUSIONS: A torsional and vertical vergence back-and-forth eye movement induced by a BHTT was confirmed with the search coil technique. Utricular inertia due to an interaural head translation, combined with a stimulation of the vertical semicircular canals, seems to be a plausible explanation for these eye movements.

Assessment of ocular counterroll during head tilt using binocular video oculography.

PURPOSE: According to recent literature, the presence and the amount of true compensatory ocular counterroll is still debatable. The purpose of the current study was to assess compensatory counterroll in response to lateral head tilt using a new noninvasive recording technique, and, furthermore, to find out whether the amount of counterroll is influenced by the presence or absence of spatial orientation. METHODS: Eye movement recordings were performed using the infrared three-dimensional video oculography (3D-VOG) technique. Objective cycloposition of five healthy individuals was measured in presumed primary position and in head tilt positions of 15 degrees, 30 degrees, and 45 degrees to the right and left. The same paradigm was performed under three viewing conditions: binocularly without spatial orientation and both binocularly and monocularly with spatial orientation. RESULTS: A consistent ocular counterroll corresponding to the amount of head tilt was observed in all subjects. Maximum torsional amplitude was 10 degrees at a 45-degree head tilt. The relative amount of compensation ranged between 13% and 22% of the actual head tilt, decreasing with increasing head tilt. Compensatory counterroll and torsional conjugacy between both eyes revealed minor differences between the experimental paradigms. Incomplete cycloductional reorientation in primary position after head tilt was detected in all subjects, regardless of the stimulus. CONCLUSIONS: A consistent compensatory ocular counterroll was demonstrated in response to static lateral tilting of the head in healthy individuals. The amplitude of counterroll and the gain of compensatory cycloversion were higher than has been generally reported. Infrared 3D-VOG technique was a reliable and comfortable method for the assessment of ocular cycloduction. It can be considered to be a promising tool for advanced evaluation of disturbances of the oblique eye muscles.