You should consider use of a cycloplegic agent to give:

1. an accurate assessment of the refractive error, which is the major factor in amblyopia or squint
2. the best possible view of the fundus, within the limits of the co-operation of the child.

When possible, you should use a line or array of letters, pictures or symbols to measure morphoscopic acuity, or some other method that induces crowding. This is because the use of single optotypes to measure visual acuity may overestimate the degree of visual acuity in patients with some amblyopias. Acuity charts, utilising crowding and logMAR letter-by-letter scoring, are recommended.