Figure 1-4 Teller Acuity Cards can be used to measure visual acuity in a preverbal child. (Courtesy of John W. Simon, MD.)

Visually evoked potential

A special form of visually evoked potential (VEP), a sweep VEP, can also be used to assess visual acuity in preverbal patients. In this test, electrodes are placed over the occipital lobe. The child views a stimulus with a series of bar or grid patterns. If the stripes are large enough for the child to discriminate, a visual impulse is recorded by the electrodes. The stripe width narrows to the point that the stimulus appears uniformly gray, at which point no impulse is recorded. Visual acuity is estimated based on the smallest line width that produces a response.

Red Reflex Examination (Brückner Test)

The Brückner test is performed in a semidark room using a direct ophthalmoscope to assess the red reflex from both eyes simultaneously at a distance of approximately 1 m. Most infants and children will look toward the light from the direct ophthalmoscope. The clinician can quickly determine the clarity and symmetry of the red reflex and identify significant or asymmetric refractive errors and ocular misalignment. This is an essential technique for pediatricians and pediatric primary care providers.

Dynamic Retinoscopy

Dynamic retinoscopy is a useful measure of accommodation. The child is given a distance fixation target and then quickly switched to a near fixation target while the retinoscopic reflex is observed. A

child with normal accommodation will neutralize the reflex at near focus. A poor accommodation reflex indicates a possible need for bifocal or reading glasses. Hypoaccommodation occurs more frequently in children with Down syndrome or cerebral palsy.

Visual Field Testing

Visual field information can be obtained in very young patients, once they have developed visual fixation (usually by 4 months of age), by presenting a peripheral target while the child fixates on an interesting central target. Movement of the eyes toward the peripheral target (an evoked saccade) confirms the field. Visual fields can be approximated by confrontation in children old enough to count or match fingers placed in each quadrant. School-aged children can often be evaluated with manual or automated perimetry testing.

Pupil Testing

The pupillary light reflex is not reliably present until approximately 30 weeks’ gestational age. Newborns usually have a miotic pupil that gradually increases in size until the preteen years. Accurate pupil testing in young children is complicated by the smaller pupil and difficulty controlling accommodation with near focus response to a test light. Careful observation, remote or foot control of the room lights for continued observation during changes in room illumination, and use of appropriate distance fixation targets greatly facilitate pupil evaluation. Digital photography can be useful for accurate assessment and documentation.

Anterior Segment Examination

In children, a successful anterior segment examination is usually possible but often requires persistence and different techniques. Children old enough to sit by themselves can usually be enticed to hold the “motorcycle handles” of the slit lamp and place their chin on the “pillow” long enough for a brief examination of both eyes. Longer looks are possible if, while at the slit lamp, they watch a cartoon behind the examiner. Younger children may also be placed at the slit lamp while in a parent’s lap or held with the chin positioned in the chin rest. Children unable or unwilling to cooperate with standard slit-lamp examination can be examined with a portable slit lamp, surgical loupes, or a 20 D or 28 D handheld lens used with an indirect ophthalmoscope. Children with suspicious findings who cannot be adequately assessed with these techniques may require a restrained or sedated examination.

Intraocular Pressure Measurement

It is not easy or always possible to perform formal tonometry in children. Ocular palpation, though not quantitative, can allow a gross assessment of whether pressure is normal or abnormal. This requires practice involving correlation with formal tonometry performed on the same patient. Formal tonometry requires a noncrying, relaxed patient. With a non-threatening approach and practice, the practitioner may find that many young children permit accurate testing when handheld devices such as the Tono-Pen (Reichert Ophthalmic Instruments, Depew, NY) or Icare (Icare Finland Oy, Helsinki, Finland) are used. The Tono-Pen or the Perkins Tonometer (Haag-Streit USA, Mason, OH) may be used to test infants when they are sleeping or feeding in the supine position. Children at risk for glaucoma may require sedated examination if accurate readings cannot be obtained in the clinic.

Cycloplegic Refraction

Because of the relationship between accommodation and ocular convergence, one of the most important tests in the evaluation of any patient with issues relating to binocular vision and ocular

motility is refraction with cycloplegic agents. Cyclopentolate (1.0%) is the preferred drug for routine use in children, especially when combined with phenylephrine, which has no cycloplegic effect. Use of 0.5% concentration is suggested in infants. The clinician should remember that adverse effects may occur in children receiving cyclopentolate. Homatropine (5.0%) and scopolamine (0.25%) are occasionally used instead of cyclopentolate, but neither is as rapid acting or as effective. Tropicamide (0.5% or 1.0%) is usually not strong enough for effective cycloplegia in children. Some ophthalmologists use a combination of cyclopentolate and tropicamide to achieve maximum dilatation. Some ophthalmologists use atropine (1.0%) drops or ointment, but this drug causes prolonged blurring and is more often associated with adverse effects (see the section “Adverse effects”). Nonetheless, 1.0% atropine drops are frequently used without problems in the treatment of amblyopia (see Chapter 4).

Table 1-2 shows the schedule of administration and duration of action for commonly used cycloplegics. The duration of action varies greatly, and the pupillary effect occurs earlier and lasts longer than the cycloplegic effect, so a dilated pupil does not necessarily indicate complete cycloplegia. For patients with accommodative esodeviations, frequent cycloplegic examinations are essential when control is precarious. Having the patient fixate at distance helps prevent false readings due to residual accommodative effort.

Table 1-2

Eyedrops in children

Almost all children are apprehensive about eyedrops. There are many approaches to giving eyedrops. If possible, someone other than the examining physician should administer the drops. Some practitioners use a cycloplegic spray, some use a topical anesthetic drop first, and some simply use the cycloplegic drops. The drops can be described as being “like a splash of swimming pool water” that will “feel funny for about 30 seconds.” Do not give children a long time to think about it. Dark irides are more difficult to dilate. In some cases, the parent can put the cycloplegic drops in at home. See also BCSC Section 2, Fundamentals and Principles of Ophthalmology.

Adverse effects

Adverse reactions to cycloplegic agents include allergic (or hypersensitivity) reaction with conjunctivitis, edematous eyelids, and dermatitis. These reactions are more frequent with atropine than with any of the other agents. Atropine drops may also cause systemic symptoms, including fever, dry mouth, flushing of the face, rapid pulse, nausea, dizziness, delirium, and erythema. Treatment is discontinuation of the medicine, with supportive measures as necessary. If the reaction is severe, physostigmine may be given. The ophthalmologist should remember that 1 drop of 1.0% atropine is 0.5 mg atropine. In addition, hypnotic effects can be seen with scopolamine and occasionally with cyclopentolate or homatropine.

Refraction technique

Refraction is generally performed after cycloplegia. The ophthalmologist’s working distance and the child’s visual axis are important considerations. Retinoscopy must be performed on axis in order to provide accurate refraction information. The 2 main methods for refraction are loose lenses for infants and younger children and the phoropter for those old enough to sit in an exam chair. A