When should they hold their head still…
The development of the visual system in children is much discussed. The AOA offers time lines which have development of eye movement continuing to improve at 36 months. This development is dependent upon many factors including the development of the brain as whole and the vestibular, and proprioceptive systems. The development of these systems is inter-dependent. Problems in the visual system will affect development of the vestibular and other systems and impact the developmental movement sequence. This is why the first eye exam is recommended at 6 months of age.
In the birth to 3 three year old, developmental delays would most likely include tracking and saccades problems, particularly when neurological problems (seizures, anoxia, CP, etc) are present. As therapists, our treatments should should stimulate as many sensory systems at possible, including vision.
Eye Movement norms
The best information on the development of eye movement accuracy comes from the NSUCO Ocular motor norms. The NSUCO protocol looks at ability to perform the movement, accuracy of the movement, amount of head movement present and the amount of body movement present during the testing of tracking and saccades. Each of these skills is rated 1-5 with each score defined in the above referenced article. This is the standard way saccades and tracking are quantified by ODs. Each movement would include 4 numbers describing the child ability to perform the movement. This is a somewhat subjective test, much as our manual muscle testing is somewhat subjective. It is most important for the therapist to recognize the errors and refer to the doctor for scoring, then be able to interpret the score as provided by the doctor.
The norms begin at age 5 and support the idea of a constantly improving ocular motor system until full maturity at the age of the 10. The paper further references minimal standards from age 5 to 10 to help identify less than age appropriate eye movement accuracy.
The Therapist’s job
We should be screening these eye movement on all of our patients. Children with developmental delays have a high incidence of ocular motor problems which affect balance, reading, spatial awareness, fine motor and visual motor integration development. These ocular motor problems are influencing the outcomes of our interventions so being testing them should be a part of every OT and PTs evaluation process.