Info

Observe: blink response to visual threat, reaching for objects, PL (TAC), OKN, VEP

Observe: blink response to visual threat, reaching for objects, PL (TAC), OKN, VEP

6-18 months

>0.5

PL (TAC, Cardiff-Cards), OKN, VEP

Observe: blinks at visual threats -fixes and follows objects (faces!) PL (TAC, Cardiff Cards), OKN, VEP

18-36 months

>0.6

PL (Cardiff Cards), LEA-Test VEP

PL (TAC, Cardiff Cards), OKN, VEP Reaches for small, hard candy spheres (1 mm to 1 cm in size)

3-5 years

>0.6

Tumbling Es, Landolt rings, Lea test VEP (and mfERG) when functional visual loss is suspected

PL (TAC, Cardiff Cards), VEP Reaches for small, hard candy spheres (1 mm to 1 cm in size)

>6 years

VEP and mfERG (when functional visual loss is suspected

PL (TAC, Cardiff Cards), OKN, VEP, Lea test Reaches for small, hard candy spheres (1 mm to 1 cm in size)

Tests written in italics are those of lower or limited use

When using the Cardiff-Cards, one will commonly find an overestimation of acuity

TACTeller Acuity Cards, OKN optokinetic nystagmus, VEP visually evoked potentials, PL preferential looking, mfERG multifocal ERG

Tests written in italics are those of lower or limited use

When using the Cardiff-Cards, one will commonly find an overestimation of acuity

TACTeller Acuity Cards, OKN optokinetic nystagmus, VEP visually evoked potentials, PL preferential looking, mfERG multifocal ERG

Visual Testing

The important elements of pediatric vision testing are listed in ■ Table 19.4, and ■ Table 19.5 and provide a summary of the most appropriate methods, based on the child's age or level of development.

Preferential-looking methods are now established as conventional tests. Teller Acuity Cards (TAC) measure spatial acuity by grating resolution. In children with strabismic amblyopia, this method can produce an overestimate of function. In addition, the grating acuity cannot be reliably transposed into a Snellen acuity level. Grating test object methods measure a recognition function that is not strictly comparable with the results of conventional spatial acuity testing. For older children, the Cardiff Cards have proven to be effective (■ Fig. 19.1 a). Testing with sequential rows of alphabetical characters, e.g., the C chart according to Haase or the Lea character sequence cards (■ Fig. 19.1 b) allows for a distinction between acuity reductions because of a microstrabismus on the one hand, and a developmental central scotoma caused by diseases in the retrobulbar visual pathways on the other. This is because of the crowding phenomenon, which causes acuity levels for identification of single optotypes to be significantly better than those obtained by testing with rows of letters.

Reliable results, when testing children's visual function, require the use of trained personnel who are familiar with the specific techniques suited to the neuro-ophthalmic examination of children.

Fig. 19.1. a Acuity testing of small children. Cardiff Cards. The vertical orientation of the test characters has the advantage that the results will not be affected by horizontal but by vertical, motility disturbances. Visual function may be overestimated by this method, but it allows for a valid determination of interocular differences in preverbal children in whom the Teller Acuity Cards have already become uninteresting (i.e., from about 12 to 18 months of age).

Fig. 19.1. a Acuity testing of small children. Cardiff Cards. The vertical orientation of the test characters has the advantage that the results will not be affected by horizontal but by vertical, motility disturbances. Visual function may be overestimated by this method, but it allows for a valid determination of interocular differences in preverbal children in whom the Teller Acuity Cards have already become uninteresting (i.e., from about 12 to 18 months of age).

b Vision tests for small children. Starting at about 24 months of age, comparison tests become useful. The Lea test has proven itself effective for both distant and near testing, including measures of the crowding phenomenon. Thus, it is useful for differentiating strabismic amblyopia on one hand from an acuity loss caused by an optic neuropathy on the other b Vision tests for small children. Starting at about 24 months of age, comparison tests become useful. The Lea test has proven itself effective for both distant and near testing, including measures of the crowding phenomenon. Thus, it is useful for differentiating strabismic amblyopia on one hand from an acuity loss caused by an optic neuropathy on the other

Only specifically trained technical personnel should be permitted to record visual acuities. They must have specific knowledge of neuro-ophthalmic disorders and of the methods of testing suited to the examination of children.

Pupillomotor Testing

The testing of pupillary motility (see Chap. 5) is mandatory but is often neglected. The following discussion covers a few of the unique aspects of pupillary testing in children.

It is particularly easy to miss a strictly (or very strongly) unilateral loss of afferent function. The swinging flashlight test is difficult to use with children, particularly those with darkly pigmented irises. As an alternative to the swinging flashlight test, one can use monocular occlusion. The eye with an afferent deficit will show pupillary dilation ("escape") when the contralateral eye is occluded. The parents can help in such cases when specifically asked, by confirming that during patching of the dominant eye, the pupil of the strabismic eye is consistently and strikingly larger than when both eyes are open. (A typical example is the unrecognized optic disc hypoplasia of the strabismic eye).

A manifest anisocoria is not produced by a relative afferent pupillary defect, but rather reflects an efferent (auto-nomic) motor deficit.

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