Rana Arham Raashid

Developmental Trajectory of McGurk Effect Susceptibility in Children and Adults With Amblyopia

PURPOSE The McGurk effect is an audiovisual illusion that involves the concurrent presentation of a phoneme (auditory syllable) and an incongruent viseme (visual syllable). Adults with amblyopia show less susceptibility to this illusion than visually normal controls, even when viewing binocularly. The present study investigated the developmental trajectory of McGurk effect susceptibility in adults, older children (10-17 years), and younger children (4-9 years) with amblyopia. METHODS A total of 62 participants with amblyopia (22 adults, 12 older children, 28 younger children) and 66 visually normal controls (25 adults, 17 older children, 24 younger children) viewed videos that combined phonemes and visemes, and were asked to report what they heard. Videos with congruent (auditory and visual matching) and incongruent (auditory and visual not matching) stimuli were presented. Incorrect responses on incongruent trials correspond to high McGurk effect susceptibility, indicating that the viseme influenced the phoneme. RESULTS Participants with amblyopia (28.0% ± 3.3%) demonstrated a less consistent McGurk effect than visually normal controls (15.2% ± 2.3%) across all age groups (P = 0.0024). Effect susceptibility increased with age (P = 0.0003) for amblyopic participants and controls. Both groups showed a similar response pattern to different speakers and syllables, but amblyopic participants invariably demonstrated a less consistent effect. CONCLUSIONS Amblyopia is associated with reduced McGurk effect susceptibility in children and adults. Our findings indicate that the differences do not simply indicate delayed development in children with amblyopia; rather, they represent permanent alterations that persist into adulthood.

Short-Term Saccadic Adaptation in Patients With Anisometropic Amblyopia

PURPOSE Amblyopia is a developmental disorder characterized by impairment of spatiotemporal visual processing that also affects oculomotor and manual motor function. We investigated the effects of amblyopia on short-term visuomotor adaptation using a saccadic adaptation paradigm. METHODS A total of 8 patients with anisometropic amblyopia and 11 visually-normal controls participated. Saccadic adaptation was induced using a double-step paradigm that displaced a saccadic visual target (at ±19°) back toward central fixation by 4.2° during the ongoing saccade. Three test blocks, preadaptation, adaptation, and postadaptation, were performed sequentially while participants viewed binocularly and monocularly with the amblyopic and fellow eyes (nondominant and dominant eyes in controls) in three separate sessions. The spatial and temporal characteristics of saccadic adaptation were measured. RESULTS Patients exhibited diminished saccadic gain adaptation. The percentage change in saccadic gain was lower in patients during amblyopic eye and binocular viewing compared to controls. Saccadic latencies were longer, and saccadic gains and latencies were more variable in patients during amblyopic eye viewing. The time constants of adaptation were comparable between controls and patients under all viewing conditions. CONCLUSIONS The short-term adaptation of saccadic gain was weaker and more variable in patients during amblyopic eye and binocular viewing. Our findings suggest that visual error information necessary for adaptation is imprecise in amblyopia, leading to reduced modulation of saccadic gain, and support the proposal that the error signal driving saccadic adaptation is visual.

The Initiation of Smooth Pursuit is Delayed in Anisometropic Amblyopia

Purpose Several behavioral studies have shown that the reaction times of visually guided movements are slower in people with amblyopia, particularly during amblyopic eye viewing. Here, we tested the hypothesis that the initiation of smooth pursuit eye movements, which are responsible for accurately keeping moving objects on the fovea, is delayed in people with anisometropic amblyopia. Methods Eleven participants with anisometropic amblyopia and 14 visually normal observers were asked to track a step-ramp target moving at ±15°/s horizontally as quickly and as accurately as possible. The experiment was conducted under three viewing conditions: amblyopic/nondominant eye, binocular, and fellow/dominant eye viewing. Outcome measures were smooth pursuit latency, open-loop gain, steady state gain, and catch-up saccade frequency. Results Participants with anisometropic amblyopia initiated smooth pursuit significantly slower during amblyopic eye viewing (206 ± 20 ms) than visually normal observers viewing with their nondominant eye (183 ± 17 ms, P = 0.002). However, mean pursuit latency in the anisometropic amblyopia group during binocular and monocular fellow eye viewing was comparable to the visually normal group. Mean open-loop gain, steady state gain, and catch-up saccade frequency were similar between the two groups, but participants with anisometropic amblyopia exhibited more variable steady state gain (P = 0.045). Conclusions This study provides evidence of temporally delayed smooth pursuit initiation in anisometropic amblyopia. After initiation, the smooth pursuit velocity profile in anisometropic amblyopia participants is similar to visually normal controls. This finding differs from what has been observed previously in participants with strabismic amblyopia who exhibit reduced smooth pursuit velocity gains with more catch-up saccades.

Paediatric vision screening in the primary care setting in Ontario

Objectives Early intervention is critical to prevent treatable causes of vision loss in children. The objectives of the current study are: (1) to assess how well primary care physicians in Ontario follow the vision screening guidelines for children as recommended by the Canadian Paediatric Society and the Rourke Baby Record and (2) to identify barriers to vision screening in the primary care setting. Design Cross-sectional survey. Methods A 19-question survey was mailed out to 1000 randomly selected family physicians (family MDs), 1000 general practitioners (GPs) and 1000 paediatricians in Ontario as listed in the 2013 Canadian Medical Directory. Results A total of 719 completed surveys were included in the analysis (449 from family MDs/GPs and 270 from paediatricians). Vision screening was reported to be performed by 65% of family MDs/GPs and 52% of general paediatricians at every well child visit. While red reflex was reported to be checked by 94% of all physicians in children under 3, it was only performed by 25% of respondents for children over 3. Thirty seven percent of all physicians reported never performing a visual acuity test in any age group. When asked about the obstacles preventing them from performing vision screening, lack of training (family MDs/GPs: 50%, paediatricians: 42%), time constraints (family MDs/GPs: 42%; paediatricians: 40%) and inadequate reimbursement (family MDs/GPs: 17%; paediatricians: 15%) were the most commonly cited reasons. Conclusions Strategies to improve vision screening are necessary given that early intervention is crucial to prevent treatable causes of vision loss in children.