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Patients with sufficient verbal communication who know the alphabet can be tested using a Snellen chart. If difficulties are encountered, an assessment of visual acuity may include the following methods:¾3. Ocular Motility and AlignmentDeficiencies in ocular motility have been associated with learning problems.105-112 Ocular motility is typically evaluated by chairside testsof fixation stability, and of saccadic and smooth pursuit eye movements.105,In addition to investigation of basic neurologicaland extraocular muscle function in patients with learning related vision problems, qualitative analysis of their ocular motility is necessary. Although almost all learning tasks require sequences of fixation-saccade-fixation, and hence the emphasis on saccades, there are several important reasons for also testing pursuit eye movements: (1) Pursuits are vital for visually guided movement.115 (2) An important part of the neurological control process for smooth pursuit eye movements – detection of stimulus motion -- is deficient in individuals with reading disabilities.116 (3) To successfully maintain the target, a sustained level of attention is required.117,118 (4) Difficulties encountered in crossing the midline may signal problems with visual spatial orientation.119 The ability to maintain steady fixation a stationary target can also be deficient.120The following standardized observational rating systems have been developed:¾ NSUCO (Northeastern State University College of Optometry)¾ SCCO 4+ (Southern California College of Optometry)For smooth pursuit testing, both of these systems involve tracking a target moving in a circle. Evaluation of performance is by gain (eye velocity in relation to target velocity) and the number of catch-up saccades to reacquire the target.Both systems investigate predictive saccades between two fixed targets positioned centrally, equidistant from the midline. Hypometric inaccuracies are commonly found in individuals with poor saccadic eye movement control. Excessive head and body movements (motor overflow) frequently accompany ocular motility deficiencies. The1• Having deficient ball-playing skillsAssessment tools are available for a more quantitative evaluation, albeit indirect, of saccadic eye movements.121,122 These tests simulate reading, using a rapid number-naming strategy in which numbers are placed in horizontal spatial arrays to be read in the left-to-right and top-down fashion of normal reading. The time to complete the task and the number of errors are the clinical outcomes. Presumably, slower and/or error-prone performance would indicate poor saccadic eye movement control.
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