The role of oculoproprioception in the neural control of ocular alignment: Understanding disease mechanisms in strabismus
Strabismus (squint or crossed eyes), specifically Partially Accommodative Esotropia (PAE) and Fully Accommodative Esotropia (FAE).
This is an observational study, there is no intervention. Below is a description of the measurements. The study assesses oculoproprioceptive function in children with primary accommodative esotropia (PAE) through two experiments. Performance of children with PAE is compared with two control groups: children with fully corrected accommodative esotropia (FAE) and healthy controls. The three groups are matched for age and refractive error. Each child completes two behavioural tasks, with a planned sample of 34 children per group. Prior to testing, the children are shown a short instructional video explaining the task in simple terms, and the parents are trained on administering the eyelid press (explained below). Experiment 1a: Oculoproprioceptive accuracy Oculoproprioceptive accuracy is measured using an established task (Balslev et al., 2012) adapted for children. Children are seated on their parent’s lap in a darkened room, with their head stabilised using a chin rest and cheek pads. One eye is patched while the other is open. The children view the target (a red butterfly) on a computer screen. The children use left and right response buttons to move the target on the screen until it appears directly in front of their nose. During some trials, the parent gently presses the child’s closed eyelid for a brief, duration (<1 second) in response to an auditory cue, causing a small passive movement of the eyeball. The child then moves the target to the perceived straight ahead position. The experimenter records the final target location using a key press, and a new trial begins. There are a total of 10 trials (excluding 2 dummy trials). In children with normal oculoproprioception, as in healthy adults, no difference is expected between conditions with and without eye press. Experiment 1b: Oculoproprioceptive coupling Oculoproprioceptive coupling between the two eyes is measured by recording the movement of one eye while the other eye is gently and briefly moved using
For the children with strabismus: 1. Diagnosis – FAE or PAE For All Children: 1. Hyperopia corrected to normal using glasses 2. Age 4- to 5-years-old 3. No previous surgery on the eye muscles
1. No underlying neurological disease such as a brain lesion or extraocular muscle paresis 2. The parents do not have the capacity to give informed consent, and the child has the capacity to assent. 3. Inability to speak English 4. Previous surgery on the extraocular muscles