Final answer:
The school nurse would suspect strabismus when a child cannot maintain proper eye alignment and coordinated movements, especially if one eye fails to follow a moving object smoothly in conjunction with the other, potentially leading to double vision or diplopia.
Step-by-step explanation:
The school nurse would suspect strabismus when the child exhibits difficulties in maintaining proper eye alignment and movement. One test that may be used is having the child track the movement of a pen or another object with their eyes without turning their head. During this testing of eye movement, it is important to observe if the eyes move in conjugate (well-coordinated) fashion.
A key sign that suggests strabismus is if one eye fails to move in harmony with the other when following a moving object (internuclear ophthalmoplegia) and this can lead to symptoms such as diplopia, or double vision. This occurs because the child's eyes are temporarily pointed at different stimuli, and it suggests that the extraocular muscles are not functioning in conjunction. In a broader context, similar tests for visual field deficits can alert healthcare providers to issues beyond strabismus, such as a growth affecting the optic chiasm and leading to loss of peripheral vision known as bilateral hemianopia.