Contrast sensitivity of patients with severe motor and intellectual disabilities and cerebral visual impairment

The Multidisciplinary Guidelines for Diagnosis and Referral in Cerebral Visual Impairment

Introduction

Cerebral visual impairment (CVI) is an important cause of visual impairment in western countries. Perinatal hypoxic-ischemic damage is the most frequent cause of CVI but CVI can also be the result of a genetic disorder. The majority of children with CVI have cerebral palsy and/or developmental delay. Early diagnosis is crucial; however, there is a need for consensus on evidence based diagnostic tools and referral criteria. The aim of this study is to develop guidelines for diagnosis and referral in CVI according to the grade method.

Patients and Methods

We developed the guidelines according to the GRADE method 5 searches on CVI (children, developmental age ≤ 18 years) were performed in the databases Medline, Embase, and Psychinfo, each with a distinct topic.

Results

Based on evidence articles were selected on five topics: 1. Medical history and CVI-questionnaires 23 (out of 1,007). 2. Ophthalmological and orthoptic assessment 37 (out of 816). 3. Neuropsychological assessment 5 (out of 716). 4. Neuroradiological evaluation and magnetic resonance imaging (MRI) 9 (out of 723). 5. Genetic assessment 5 (out of 458).

Conclusion

In medical history taking, prematurity low birth weight and APGAR (Appearance, Pulse, Grimace, Activity, Respiration) Scores (<5) are important. Different questionnaires are advised for children under the age of 3 years, older children and for specific risk groups (extremely preterm). In ophthalmological examination, eye movements, specially saccades, accommodation, crowding, contrast sensitivity and visual fields should be evaluated. OCT can show objective signs of trans-synaptic degeneration and abnormalities in fixation and saccades can be measured with eye tracking. Screening of visual perceptive functioning is recommended and can be directive for further assessment. MRI findings in CVI in Cerebral Palsy can be structured in five groups: Brain maldevelopment, white and gray matter lesions, postnatal lesions and a normal MRI. In children with CVI and periventricular leukomalacia, brain lesion severity correlates with visual function impairment. A differentiation can be made between cortical and subcortical damage and related visual function impairment. Additional assessments (neurological or genetic) can be necessary to complete the diagnosis of CVI and/or to reveal the etiology.

Standalone cooperation-free OKN-based low vision contrast sensitivity estimation in VR - a pilot study

BACKGROUND

In low vision patients, the assessment of contrast sensitivity is an essential tool to determine the stage of visual impairment. However, traditional contrast sensitivity tests rely on verbal feedback, and the expertise of the examiner.

OBJECTIVE

In the current study, a fast, OKN-based virtual diagnosis tool was developed estimating contrast sensitivity automatically without active cooperation of the patient as well as the practitioner within 3.5 minutes.

METHODS

In a HTC Vive headset with an SMI-eye tracker, a virtual rotating drum was implemented, and an algorithm was developed, evaluating the occurrence of an OKN. The tool was evaluated in healthy subjects as well as under low vision simulation for two spatial frequencies and four contrasts. It was then compared to two contrast sensitivity estimates based on manual report on the orientation of static gratings as well as the movement direction of translating gratings.

RESULTS

An algorithm was developed, which matched ground truth ratings of occurrence of OKN with an accuracy of 88 %. Furthermore, known differences in contrast sensitivity between healthy and low vision conditions as well as a decrease in contrast sensitivity for lower spatial frequencies was successfully reproduced in the developed tool.

CONCLUSIONS

The developed OKN-based sensitivity test represents a reliable proof of concept for technology readiness of virtual reality-based screening tools of visual function in practice, specifically in patients with difficulties to report perception verbally, or under conditions, where no experienced examiner is present.

Microswitch Technology to Promote Adaptive Responses and Reduce Mouthing in Two Children with Multiple Disabilities

This study assessed the viability of using microswitch clusters (combinations of microswitches) plus contingent stimulation to promote adaptive responding and to reduce aberrant behavior in two children with multiple disabilities. The results revealed that both children increased their adaptive responses, learned to perform these responses free from aberrant behavior, and maintained this level of performance three months later.

Is there consensus in defining childhood cerebral visual impairment? A systematic review of terminology and definitions

The childhood condition of visual difficulties caused by brain damage, commonly termed cortical or cerebral visual impairment (CVI), is well established but has no internationally accepted definition. Clarification of its core features is required to advance research and clinical practice. This systematic review aimed to identify the definitions of childhood CVI in the original scientific literature to describe and critically appraise a consensual definition of the condition. MEDLINE, EMBASE, PsychINFO, CINAHL and AMED databases were searched in January 2017. Studies were included if they (1) were published original research, (2) contained a childhood CVI sample, (3) contained a definition of CVI and (4) described their CVI identification/diagnostic method. Thematic analysis identified concepts within definitions and narrative synthesis was conducted. Of 1150 articles, 51 met inclusion criteria. Definitions were subdivided according to detail (descriptive definition, description not reaching definition status and diagnostic/operationalising criteria). Three themes concerning visual deficits, eye health and brain integrity were identified (each containing subthemes) and analysed individually across definitions. The most common themes were ‘visual impairment’ (n=20), ‘retrochiasmatic pathway damage’(n=13) and ‘normal/near normal eye health’ (n=15). The most consensual definition identified here may not be the best quality for advancing our understanding of CVI. We argue for the alternative definition: CVI is a verifiable visual dysfunction which cannot be attributed to disorders of the anterior visual pathways or any potentially co-occurring ocular impairment. We propose reporting guidelines to permit comparison across studies and increase the evidence base for more reliable clinical assessment and diagnosis.

Persons with multiple disabilities accessing stimulation and requesting social contact via microswitch and VOCA devices: new research evaluation and social validation

The first of these two studies assessed whether 11 participants with multiple disabilities of 5.3-18.2 (M=10.7) years of age would succeed in combining a microswitch for accessing preferred environmental stimuli and a Voice Output Communication Aid (VOCA) for requesting social contact. The second study conducted a social validation assessment of the aforementioned microswitch-VOCA combination. Data showed that all participants learned to use the microswitch and the VOCA. Moreover, the 10 participants, who received a 1-month post-intervention check, largely maintained their responding. The social validation assessment indicated that the raters (i.e., 110 university psychology students) favored the combination of microswitch and VOCA over the microswitch or the VOCA alone, and hypothetical combinations of microswitches or VOCAs.

Students with multiple disabilities using technology-based programs to choose and access stimulus events alone or with caregiver participation

The first of these two studies extended preliminary evidence on the use of technology-based programs for enabling students with severe and profound multiple disabilities to choose and access environmental stimuli on their own. Each of the three participants had two microswitches linked to specific sets of stimuli through a computer system. The activation of one of the microswitches triggered the computer system to present a sample of one of the stimuli. If the student chose it, the computer system turned it on for a specific time interval. The second study tested a new technology that allowed the students to choose and access the chosen stimuli with the involvement of the caregiver. The two participants had three microswitches linked to a computer system. The participants' choice of a stimulus alerted the caregiver who then got involved in the stimulation process. The results of both studies showed that the participants learned to activate the basic microswitches consistently, had high percentages of choice for the stimulus samples presented by the computer but with wide differences across stimuli, and largely maintained this performance at a 2-month post-intervention check. These findings were analyzed in terms of the usability of the two types of programs, the role they may play within educational and living contexts, and their innovative technical dimensions.

Assisting persons with multiple disabilities to move through simple occupational activities with automatic prompting

The present study assessed the possibility of assisting four persons with multiple disabilities to move through and perform simple occupational activities arranged within a room with the help of automatic prompting. The study involved two multiple probe designs across participants. The first multiple probe concerned the two participants with blindness or minimal vision and deafness, who received air blowing as a prompt. The second multiple probe concerned the two participants with blindness and typical hearing who received a voice calling as a prompt. Initially, all participants had baseline sessions. Then intervention started with the first participant of each dyad. When their performance was consolidated, new baseline and intervention occurred with the second participant of each dyad. Finally, all four participants were exposed to a second intervention phase, in which the number of activities per session doubled (i.e., from 8 to 16). Data showed that all four participants: (a) learned to move across and perform the activities available with the help of automatic prompting and (b) remained highly successful through the second intervention phase when the sessions were extended. Implications of the findings are discussed.

Visual function of a patient with advanced adrenoleukodystrophy: comparison of luminance and color contrast sensitivities

We assessed achromatic luminance and isoluminant chromatic contrast sensitivity functions of a 20-year-old male. He showed severe motor and intellectual disabilities after advanced adrenoleukodystrophy, which started at the age of 7. Optokinetic nystagmus (OKN) to drifting gratings was used to assess his contrast sensitivities. Although the achromatic luminance contrast sensitivities were lower over the entire range of spatial frequencies tested than those of the healthy adults, they were preserved to the level comparable to healthy 7-year-old children, except for the frequency of 1 and 4 cycles/degree. In contrast, both of the red-green and blue chromatic contrast sensitivities were remarkably lower in all frequency range compare to healthy children and adults. These results indicate that it is possible for even an advanced case of ALD to show residual visual capacity that was preserved to a remarkable extent.

Assessing the effects of stimulation versus microswitch-based programmes on indices of happiness of students with multiple disabilities

BACKGROUND

Stimulation and microswitch-based programmes are considered main strategies to promote indices of happiness in students with multiple disabilities. However, only limited attempts have been made to assess the relative effects of the two programmes. This study conducted such an assessment with seven students with multiple disabilities.

METHODS

The first four phases of the study served to: (1) provide the students with a systematic exposure to each of the programmes; and (2) measure the programmes' effects on indices of happiness by comparing them with baseline levels. The fifth phase served to compare the programmes with each other.

RESULTS

The first four phases of the study showed that the microswitch-based programme produced a significant increase in indices of happiness for all seven students, and the stimulation programme produced a significant increase for six students. During the fifth phase of the study (i.e. when the two programmes were alternated), the microswitch-based programme promoted significantly higher indices of happiness than the stimulation programme for four of the seven students.

CONCLUSIONS

Microswitch-based programmes might be deemed preferable to stimulation programmes because they can promote higher or comparable indices of happiness while promoting the acquisition of adaptive responses and self-determination.

Relationship between optokinetic nystagmus response and recognition visual acuity

PURPOSE

The aim of this study was to investigate the relation between recognition visual acuity (RVA) and optokinetic nystagmus (OKN) response exhibited to different bar sizes with varying contrast.

METHODS

OKN testing was performed in 52 children aged between 3 and 11 years. The children were evaluated in two groups according to their RVA. Group I consisted of 22 eyes with RVA equal to or better than 0.1 logMAR units. Group II consisted of 30 eyes with RVA 0.2-1 logMAR units. Each subject was seated 60 cm from the screen of Ophthimus device, and was exposed to consecutive black and white stripes of seven different spatial frequencies (0.08-1.6 cycle/degree). The narrowest bar that elicited OKN was identified, and then the OKN contrast threshold at this bar size was established.

RESULTS

Twenty-one of the 22 eyes in Group I, and 26 of the 30 eyes in Group II exhibited 1.6 cycle/degree spatial frequency (P=0.287). In Group II, 88.9% of the 18 eyes with RVA 0.2-0.5 logMAR responded at this maximum spatial frequency, whereas the corresponding figure for the 12 eyes with RVA 0.6-1 logMAR was 83.3% (P=0.531). Contrast sensitivity (CS) significantly changed with age in Group I (P=0.006). When the eyes that responded at maximum spatial frequency in the two groups were compared, the mean CS in Group II was significantly lower than that in Group I (P=0.005).

CONCLUSIONS

The results indicate no relation between spatial frequency threshold for OKN response and RVA in children. However, the children with RVA deficits had significantly lower CS.