Visual field testing in children is limited to detecting altitudi-nal and hemianopic defects [bitemporal, homonymous). In children as young as 6 months of age, visual field testing can be accomplished by observing reflex eye movements to a visual stimulus. The technique is performed by having the examiner first attract the child's attention, and then a toy or some other interesting target is moved in quietly from the periphery. If the child makes an eye movement to fixate on the target, this is evi dence that the peripheral field is intact (Fig. 2-9). This technique is quite useful in detecting homonymous and bitemporal hemianopias. It is less useful in altitudinal defects. In children as young as 2 years, "finger mimicking" visual fields can be
obtained. Using this technique the child is asked to copy what the examiner is doing. Having the child display one, five, or no fingers by "mimicking" the examiner is a fairly reliable way to assess visual fields (Fig. 2-10). The numbers two, three, and four should be avoided as they are somewhat confusing at times. The fingers should be flashed quickly to avoid erroneous results obtained by the child fixating on the hand instead of the examiner.
Fixation is often difficult to control and is the major problem with this technique. A useful maneuver when attempting to evaluate the temporal visual field is to place the child's eye in full abduction; this prevents further eye movement laterally and minimizes a fixation artifact. This move cannot be done nasally as the nose blocks visual field assessment. Binocular visual field defects should be assessed first as the child may not cooperate for monocular testing because of the necessary eye occlusion. Finger "counting" visual fields can be performed in children over 3 years of age. The technique is similar to finger mimicking; however, the child "counts" the number of fingers presented. Simultaneous presentation in both hemifields is now possible, and subtler field defects can be detected. As before, the fingers should be flashed quickly and the numbers kept to one, five, or none. Alti-
tudinal field defects are easier to test in this age group, and very reliable information can be obtained by this technique.
Goldman and automated perimetry can be performed on the child aged 6 to 7. Often children are playing sophisticated video games at home, and the test can be explained using such terms. Testing, however, should be kept simple because patience and fatigue are factors. Fixation is still a problem at this age, and constant surveillance is necessary to obtain a reliable field. When using the Goldman perimeter, two isopters are all that are necessary to detect most neuro-ophthalmic visual defects in children (V4e, II4e).16 Automated perimetry is more difficult because the control programs are written to detect subtle field defects in adults and take more time than most children will tolerate. Before using more sophisticated tests, the examiner should begin with a simple confrontation technique to assess reliability. Visual field constriction is a common artifact because the child is hesitant to "make a mistake." This tendency tends to decrease with age.
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