Traditional methods of visual assessment in preverbal pediatric patients rely on refined but subjective measurement techniques. A standard ophthalmologic examination includes evaluation of a child's fixation patterns, with performance ranked on the basis of ability to fix and follow an object (F & F) or maintain central, steady fixation (CSM). In the hands of a skilled clinician, these evaluations are important for diagnosis and treatment. Documentation of quantitative changes in visual abilities of preverbal patients, however, has only recently become feasible. We began using the acuity card procedure in our pediatric clinical practice more than 3 years ago. This assessment, a modified version of the standard Forced-Choice Preferential Looking paradigm (FPL), provides quantitative evaluation of visual functioning in preverbal patients. The total number of patients assessed on one or more occasions exceeds 900. Of this group, we followed 83 patients with at least four acuity card evaluations on separate visits. Thirty of these patients, all with different diseases, have been evaluated with acuity cards on six or more visits. We found the information provided by the acuity card assessments extremely helpful in quantifying the developmental and therapeutic changes in vision, previously monitored only qualitatively.