Binocular Vision and Paediatric Assessment
Sensory and motor testing
Establish whether a deviation is latent, intermittent, constant, unilateral or alternating using cover/uncover and alternate cover tests, and quantify it with a prism bar. Hirschberg and Krimsky give a rapid estimate in uncooperative children (roughly 1 mm of corneal displacement equals about 2 degrees, or 4 prism dioptres). Then assess near point of convergence, amplitude of accommodation, accommodative facility, vergence break and recovery points, stereopsis and, where indicated, Worth four-dot and Maddox rod.
Paediatric assessment
Match the test to the developmental stage: fixation preference and Bruckner red reflex in infants, preferential looking or picture tests in toddlers, matching letter or symbol tests in pre-schoolers, and logMAR in school-age children. Cycloplegic refraction with cyclopentolate is essential when strabismus or amblyopia is suspected, because children accommodate powerfully and mask hyperopia. Amblyopia management corrects refractive error first, then adds occlusion or atropine penalisation with clear monitoring and review.
Traps
Reporting "no strabismus" from one cover test in a child fixating on the target; performing retinoscopy without cycloplegia in a suspected esotrope; missing anisometropic amblyopia because the child reads monocularly "fine"; and dismissing reduced stereoacuity as a test artefact rather than a genuine binocular defect.
Rule of thumb
An NPC break beyond about 6 cm with recovery beyond 10 cm, together with reduced base-out fusional reserves, supports convergence insufficiency; a normal NPC should be reproducible close to the nose.