Amblyopia is poor vision caused by abnormal visual stimulation during early visual development. The abnormal visual stimulation disrupts neurodevelopment of visual centers in the brain. Abnormal stimulation can arise from a blurred retinal image, or strabismus with strong fi xation preference for one eye and cortical suppression of the nondominant eye. Children under 8 years of age are capable of strong cortical suppression and hence can eliminate double vision. Children who alternate fi xation and use either eye will alternate suppression and do not develop amblyopia. The vertical prism induced tropia test can be used to determine fi xation preference and diagnose unilateral amblyopia in preverbal children with straight eyes or small angle strabismus.1 This test is performed by placing a vertically oriented 10 PD prism over one eye, either base down or base up. The vertical prism induces a hypertropia allowing evaluation of fi xation preference. Strong fi xation preference for one eye is indicative of amblyopia.2 Amblyopia can be bilateral in children with bilateral blurred retinal images (e.g., bilateral congenital cataracts, or bilateral high hypermetropia >+5.00 sphere).


Refractive Error Optical Correction Strabismus Surgery Binocular Fusion Occlusion Therapy 
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