Figure 3-19 Binocular balancing by prism dissociation from patient perspective. (Courtesy of Tommy Korn, MD.)

Cycloplegic and Noncycloplegic Refraction

Ideally, refractive error is measured with accommodation relaxed. The amount of habitual accommodative tone varies from person to person, and even within an individual it varies at times and with age. Because determining this variable may not always be possible, cycloplegic drugs are sometimes used. The indication and appropriate dosage for a specific cycloplegic drug depend on the patient’s age, accommodative amplitude, and refractive error.

A practical approach to obtaining satisfactory refraction is to perform a careful noncycloplegic (or manifest) refraction, ensuring relaxed accommodation with fogging or other nonpharmacologic techniques. If the results are inconsistent or variable, a cycloplegic refraction should be performed. If the findings of these 2 refractions are similar, the prescription may be based on the manifest refraction. If there is a disparity, a postcycloplegic evaluation may be necessary. Most children