Introduction

Proper performance of the pediatric eye examination is both a challenging and rewarding experience. Abnormal visual experiences early in life may have devastating and long-lasting effects. The pediatrician plays an important role in identifying those patients who may need consultation with an ophthalmologist. The screening process may utilize only simple tools and techniques or can take advantage of some of the new technological advances presently available to help achieve optimal results, particularly regarding vision screening and ophthalmoscopy. The importance of recognition of any ocular abnormalities that require referral cannot be overemphasized.

Ocular examination

The performance of an eye examination in an infant or young child requires flexibility in approach and a willingness to modify the sequence of the examination according to the age and cooperative ability of the child. Nevertheless, there are essential aspects of the examination such as the testing for a ‘red reflex’ during the neonatal period. The pediatrician must determine what information is critical to achieve an accurate diagnosis in the individual

child, and then complete an examination and determine treatment or referral options. Early detection and prompt treatment of ocular disorders in children are critical since infants are susceptible to the development of deprivation amblyopia in cases of unilateral visual axis obstruction, and nystagmus as a result of bilateral visual deprivation.

A chief complaint and a detailed history of the present illness are obtained from the parents or guardian.This should also be obtained from the verbal child, as this may also provide useful information. This time is also useful for attempting to establish good rapport with the child. As in any examination, information as to past medical history, including birth weight, allergies, and medications taken is essential. Familial history is particularly important in suspected multisystem and genetic disorders.

General inspection of the child’s overall appearance and body habitus may provide an immediate diagnosis in some specific syndromes. Obvious external features such as ptosis, blepharophimosis, and lid and iris colobomas should be noted. Signs of conjunctival discharge and vascular injection may indicate infection or intraocular inflammation. Corneal edema or opacification may indicate congenital glaucoma (10). Palpation of the lacrimal sac area may produce a mucoid discharge from the puncta, indicating a nasolacrimal duct obstruction (11). The pupils

10 Corneal opacity in the right eye secondary to acute corneal edema in congenital glaucoma.

11 Expression of mucoid discharge from the lacrimal puncta in an infant with a congenital nasolacrimal duct obstruction.

can be checked for reactivity to light and near targets and for the presence of an afferent pupillary defect. The latter is diagnosed with a swinging flashlight test. As the light is directed from the normal eye to the eye with the afferent defect in the visual pathway, both pupils will dilate. This indicates an abnormality in the afferent limb of the pupillomotor response.

The ‘red reflex’

Every child should receive his/her first eye exam in the newborn nursery. Evaluation for a normal red reflex in the newborn eye can help to eliminate several potentially vision-, and even life-threatening, ocular disorders. Red reflex testing can also be performed at any time later in life.

The ‘red reflex’ test is best performed in a room with the lights turned down. The examiner looks through a direct ophthalmoscope and initially focuses on each pupil from a distance of about 12–18 inches (30–45 cm). It is also useful to focus on both pupils simultaneously from a distance of 24–36 inches (60–90 cm). The examiner should observe a bright reddish-yellow or a light gray reflex in more darkly pigmented eyes. It is important that the reflex appears symmetric and is not blunted or dull. Linear or diffuse dark spots with a surrounding bright reflex may indicate a partial corneal or lenticular opacity. Absence of a reflex may indicate a total lenticular opacity. A white reflex or leukocoria may be seen in eyes with retinoblastomas or large chorioretinal colobomas. Performance of the simultaneous red reflex test or Bruckner Test may detect asymmetric reflexes that could indicate amblyogenic factors such as differences in refractive error between the eyes. It is not necessary to dilate the pupils pharmacologically to appreciate a red reflex. As mentioned, dulling the room lights is very useful. If pupillary dilation is desired it is safest to use 2.5% phenylephrine drops.1

It is important that the pediatrician records his/her observations from the red reflex exam performed during the first 3 months of life and at other visits up to 3 years of age.

Assessment of vision and visual acuity

Recently, emphasis has been placed on vision screening being performed by pediatricians and other primary health care providers. They have been instructed to screen both for visual acuity and for ocular alignment using either a unilateral cover test at 3 m (10 feet) or a Random-dot-E stereo test at 40 cm (630 seconds of arc). The age-specific guidelines developed by the American Academy of Pediatrics, Section on Ophthalmology, are listed in Table 2 (overleaf).

With the possible exception of red reflex testing in infants, the single most important aspect of the pediatric eye examination is the assessment of visual acuity in each eye. Most significant ocular disease will produce a reduction of visual acuity in one or both eyes.

Infants begin to smile to a human face around 6 weeks of age and follow objects in the environment starting around 8 weeks.2 Clinically, one can stimulate a child’s interest in a colorful toy or object and observe his or her fixation behavior. Under binocular conditions the child is observed for the presence of nystagmus or torticollis. It is well recognized that children with good vision in only one eye may function and behave as well as a child with excellent binocular visual acuity. Therefore, it is imperative to assess the vision independently in each eye. Fixation of each eye can be evaluated by the ‘CSM’ formula: (1) central, if not eccentric; (2) steady; and (3) maintained, if the fixation does not revert to the fellow eye as in a strabismic child.

Comments

1.Tests are listed in decreasing order of cognitive difficulty; the highest test that the child is capable of performing

should be used; in general, the tumbling E or the HOTV test should be used for children 3–5 years of age and Snellen letters or numbers for children 6 years and older

2.Testing distance of 10 ft (3 m) is recommended for all visual acuity tests

3.A line of figures is preferred over single figures

4.The nontested eye should be covered by an occluder held by the examiner

or by an adhesive occluder patch applied to the eye; the examiner must ensure that it is not possible to peek with the nontested eye

Direct ophthalmoscope, darkened room. View eyes separately at 12–18 inch (30–45 cm); white reflex indicates possible retinoblastoma

12 Child’s attention is obtained with a toy.

The examiner covers one eye (usually with the hand, thumb, or occluder) and notes whether the infant looks steadily at a light or fixation target. The eye is then uncovered. (12, 13). A strabismic patient who strongly prefers the eye just uncovered will switch fixation to that eye. A child with poor vision in the absence of strabismus may react strongly to occlusion of the better-seeing eye. The anxiety and avoidance maneuvers precipitated by the occlusion may provide evidence of poor visual acuity in the uncovered eye.

Cross-fixation may be observed in infants with large angle esotropia and equal visual acuity. These children find it more convenient to follow objects to their right with the esotropic left eye and vice versa. This produces an apparent diminished ability to abduct either eye and a pseudoparesis of the lateral rectus muscles. Temporary occlusion of either eye or rotating the baby in a chair on an adult’s lap will usually demonstrate that abduction is present.

This part of the examination is best performed during the initial part of the evaluation of the child, as it requires good cooperation from the child and can be fatiguing to both the patient and doctor. In many cases, the infant or child is brought to the pediatric ophthalmologist specifically for this evaluation. The earliest age that objective visual acuity testing with input from the child can be accomplished is approximately 2.5–3 years of age. It is always useful to measure visual acuity binocularly since this reflects how the child is seeing in normal viewing conditions. It is well

13 Examiner covers the left eye and observes the child’s ability to maintain fixation with the right eye.

recognized that children with latent nystagmus (nystagmus that is present when one eye is covered) may see dramatically better binocularly than with either eye individually. Furthermore, in the binocular state, compensatory head postures for nystagmus with a null zone or torticollis from paralytic strabismus can be appreciated. In fact, occlusion of one eye may eliminate a compensatory face position in some cases of paralytic strabismus. This finding may help to distinguish an ocular from a nonocular cause of torticollis.3

Distance visual acuity is most useful and ideally should be measured at 6 m (20 feet). Instruments and charts can be calibrated for distances down to 3 m (10 feet) to accommodate smaller examination rooms. There are a number of symbols or optotypes available. Line tests with 0.1 log unit differences between the lines should be used.4 Picture charts or symbols such as HOTV are useful for children who have not learned to recognize the standard Snellen letters or numbers. The HOTV test consists of a wall chart composed only of Hs, Os, Ts, and Vs. The child is provided with a card containing a large H, O, T, and V and is asked to indicate or match the correct symbol visualized at distance. Most practitioners do not use the tumbling-E (or illiterate-E) test since many preschool children find it confusing. The LH or Lea optotypes are very useful for vision screening (14). These optotypes, which include a circle, apple, square, and house, all blur to a circle beyond the child’s threshold acuity.5

Visual acuity measured at 0.33 m (13 inches) is not an essential part of the pediatric eye examination although assessment of the near point of accommodation is useful. Other than an unusual child with accommodative insufficiency, there are very few conditions in which a child will have normal distance acuity with subnormal near acuity. Single optotype visual acuity cards used at near fixation or standard near cards should be reserved for situations in which distance acuity testing is not possible. Pathologic vision loss diminishes acuity both for near and distance, therefore near visual acuity testing is appropriate in emergency situations.

Presentation of a full line of optotypes eliminates the crowding phenomenon present in many amblyopic eyes. Children with amblyopia will be able to recognize smaller optotypes when presented individually. Whatever ‘eye chart’ is used, care must be taken to occlude the nontested eye totally (15, 16). Children frequently peek around the hand-held occluder and must be monitored carefully (17). It may be useful to occlude the eye with a strip of inexpensive 5 cm (2-inch) tape (e.g. 3M-Micropore) (18). Those experienced in assessing visual acuity in the preschool verbal age group understand the individual variability and necessity of being

14

14Visual acuity testing chart using‘Lea’ optotypes.

flexible in examination technique. A great deal of effort is often expended in persuading the child to allow the occlusion and subsequently coaxing from him or her, an appropriate response. The time and effort are necessary, however, and the ability to assess the visual acuity accurately in this age group is the prerequisite of a good eye examination.