Clinical Pearl: The "Rule of 8".

Preschool-aged children typically perform worse than 20/20 on visual acuity testing in the absence of ocular or visual pathway abnormalities due to non-ocular issues, including concentration, cooperation, and/or confidence. As a result, vision screening for this age group can be a challenge. The "Rule of 8" is an easy-to-remember, highly effective mnemonic that clinicians can use to help differentiate children who are performing visual acuity testing at age-appropriate levels from those who may need further evaluation. [J Pediatric Ophthalmol Strabismus. 2017;54:e75-e76.].