Examination of the Eye

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Chapter 611 Examination of the Eye

Scott E. Olitsky, Denise Hug, Laura S. Plummer, Merrill Stass-Isern

Examination of the eyes is a routine part of the periodic pediatric assessment beginning in the newborn period. The primary care physician is very important in detecting both obvious and insidious asymptomatic eye diseases. Screening by lay persons in schools and community programs can also be effective in detecting problems early. The best method of screening (ages 3-5 yrs) is currently being investigated. The American Academy of Ophthalmology recommend preschool vision screening as a means of reducing preventable visual loss (Table 611-1). This testing should also be done by pediatricians during well child visits. Children should be examined by an ophthalmologist whenever a significant ocular abnormality or vision defect is noted or suspected. Children who are at high risk of ophthalmologic problems, such as genetically inherited ocular conditions and various systemic disorders, should also be examined by an ophthalmologist.

Table 611-1 VISION SCREENING GUIDELINES*

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Basic examination, whether done by a pediatrician or an ophthalmologist, must include evaluation of visual acuity and the visual fields, assessment of the pupils, ocular motility and alignment, a general external examination, and an ophthalmoscopic examination of the media and fundi. When indicated, biomicroscopy (slit-lamp examination), cycloplegic refraction, and tonometry are performed by an ophthalmologist. Special diagnostic procedures, such as ultrasonic examination, fluorescein angiography, electroretinography, or visual evoked response (VER) testing, are also indicated for specific conditions.

Visual Acuity

There are many tests of visual acuity. Which test is used depends on a child’s age and ability to cooperate, as well as a clinician’s preference and experience with each test. The most common visual acuity test in infants is an assessment of their ability to fixate and follow a target. If appropriate targets are used, this reflex can be demonstrated by about 6 weeks of age. The test is performed by seating the child comfortably in the caretaker’s lap. The object of visual interest, usually a bright-colored toy, is slowly moved to the right and to the left. The examiner observes whether the infant’s eyes turn toward the object and follow its movements. The examiner can use a thumb to occlude one of the infant’s eyes and test each eye separately. Although a sound-producing object might compromise the purity of the visual stimulus, in practice, toys that squeak or rattle heighten an infant’s awareness and interest in the test.

The human face is a better target than test objects. The examiner can exploit this by moving his or her face slowly in front of the infant’s face. If the appropriate following movements are not elicited, the test should be repeated with the caretaker’s face as the test stimulus. It should be remembered that even children with poor vision can follow a large object without apparent difficulty, especially if only one eye is affected.

An objective measurement of visual acuity is usually possible when children reach 2.5-3 years of age. Children this age are tested using a schematic picture or other illiterate eye chart. Each eye should be tested separately. It is essential to prevent peeking. The examiner should hold the occluder in place and observe the child throughout the test. The child should be reassured and encouraged throughout the test because many children are intimidated by the procedure and fear a “bad grade” or punishment for errors.

The E test, in which a child points in the direction of the letter, is the most widely used visual acuity test for preschool children. Right-left presentations are more confusing than up-down presentations. With pretest practice, this test can be performed by most children 3-4 years of age.

An adult-type Snellen acuity chart can be used at about 5 or 6 years of age if the child knows letters. An acuity of 20/40 is generally accepted as normal for 3 yr old children. At 4 yr of age, 20/30 is typical. By 5 or 6 years of age, most children attain 20/20 vision.

Optokinetic nystagmus (the response to a sequence of moving targets; “railroad” nystagmus) can also be used to assess vision; this can be calibrated by targets of various sizes (stripes or dots) or by a rotating drum at specified distances. The VER, an electrophysiologic method of evaluating the response to light and special visual stimuli, such as calibrated stripes or a checkerboard pattern, can also be used to study visual function in selected cases. Preferential looking tests are also used for evaluating vision in infants and children who cannot respond to standard acuity tests. This is a behavioral technique based on the observation that given a choice, an infant prefers to look at patterned rather than unpatterned stimuli. Because these tests require the presence of a skilled examiner, their use is often limited to research protocols involving preverbal children.

Visual Field Assessment

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