Five steps to: Paediatric vision screening

Paediatric vision screening is an important component of well-child visits to detect and refer vision threatening conditions. Over 80% of a child’s learning is based on vision, and good vision is crucial for both physical and emotional development (1). Untreated visual abnormalities in childhood cause permanently reduced visual acuity (VA) (amblyopia) (2). Recent studies suggest that the prevalence of poor vision in the Canadian elementary school population is at least 16.1% (3). Further, evidence suggests that medical graduates do not feel adequately trained or comfortable performing ocular examinations (4,5).

The objective of this article is to provide a quick and straightforward approach to paediatric vision screening with practical tips that are easy to remember using the mnemonic PROVE. It is intended for residents and staff physicians in various settings (i.e., emergency department, family medicine clinic, paediatrician’s office) to identify any vision threatening conditions, and make appropriate and timely referrals.

GENERAL TIPS

1. Prepare a good fixation target. Children are often uncooperative and have a difficult time fixating. Generally, large, bright toys or videos of the child’s favourite show on a phone or tablet work well.

2. Be quick! Children have short attention spans. Thus, it is important to finish the exam efficiently.

3. Use light last. It can be distressing to some children. The chances of finishing the screening will be less once the child starts crying.

4. Involve the parents. Ensure they are in the room and able to comfort the child.

5. Be creative, playful, and make the exam fun. For instance, if a toy is being used as the fixation target, make a story related to it (i.e., “Look it’s Dora, where is she going?”).

APPROACH TO PAEDIATRIC VISION SCREENING

Mnemonic – Remember ‘PROVE’

• Pupils

• Red reflex

• Ocular Alignment

• Vision Assessment

• External Ocular Examination

Note: The mnemonic is simply an aid to remember the essential components of a paediatric screening exam. The ocular exam should be performed in reverse order of the mnemonic (as listed below) to have the components of the exam with light sources directly aimed at the eye performed last (i.e., external ocular examination first and pupils last).

EXTERNAL OCULAR EXAM

Use a light source to examine various parts of the eye including eyelids, orbit, sclera, conjunctiva, iris and cornea. Look for asymmetry, identify any surface irregularities such as lumps and bumps, and help diagnose any sight-threatening disorders such as congenital glaucoma (i.e., corneal clouding, epiphora [tearing], buphthalmos [enlarged eye]) and amblyopia (caused by sensory deprivation, i.e., ptosis or cataract). Any abnormal finding(s) should be referred.

VA ASSESSMENT

To begin, questions on history such as ‘Is your child able to reach out to or grab objects?’ or ‘Does your child bump into walls?’ can help assess any concerns with vision or stereopsis. Vision assessment in children will vary based on age (1). Assessment of VA cannot begin prior to 3 to 4 months of age as the fovea has not completely matured (3). Other parts of the ocular exam, however, can be performed such as red reflex and external ocular exam. In preverbal or nonverbal children VA can be assessed using the central, steady, maintained (CSM) method (6). This is performed by assessing the following three components: 1) Is the corneal light reflex central (C) and symmetrical in both eyes? 2) Is fixation steady under monocular conditions i.e. no evidence of latent nystagmus when contralateral eye is occluded? and 3) Is fixation maintained? The child must be able to fix and follow a target (generally a few seconds). Tip: An important clue to amblyopia during CSM testing in younger children would be a child’s resistance to covering of one eye more than the other (i.e., occlusion behaviour), this should prompt a referral. For those over 3 years of age, VA charts can be used. Picture charts and matching charts (i.e., HOTV) can be helpful in preliterate children. For those who can read letters, a Snellen or ETDRS chart can be used. VA less than 20/40 (depending on age, see Table 1) and significant asymmetry (two lines on chart) between eyes at any age are concerning and warrant a referral (3). Tip: Ensure that the child is not peeking or memorizing if using VA charts.

Table 1.

Canadian Paediatric Society vision screening recommendations at infant and well-child visits

	Reason for referral	Newborn to 3 months	6–12 months	3–5 years‡
External eye examination	Structural abnormalities	x	x	x
Red reflex	Decreased, absence, leukocoria, asymmetry	x	x	x
Family history of hereditary diseases*	Positive history of ocular diseases	x	x	x
Corneal reflex test	Asymmetric or displaced		x	x
Fix and follow	Inability to fix and follow		x
Cover-uncover test	Refixation			x
Visual acuity testing†	20/50 or worse (age 3–4 years) 20/40 or worse (age 4–5 years)			x

Data taken from ref. (1).

*For high risk newborns (i.e., prematurity).

^†With age appropriate charts as outlined in the article.

^‡After 5 years of age, they should be examined with routine health examination or as complaints occur.

OCULAR ALIGNMENT

Corneal light reflex (Hirschberg test)

Alignment can be assessed quickly using the corneal light reflex. The child fixates on a target, and light will be directed at both eyes at midline from 0.5 to 1.0 m away. The corneal light reflex should be at the slightly nasal to the centre of each pupil. If the light reflex is off centre, it may imply a misalignment of the eye (strabismus).

Cover tests

The cover tests are additional tests to measure ocular alignment (7). The presence of a misalignment (i.e., strabismus) warrants a referral. These tests are done on both eyes while the child fixates on a target (7). The cover test reveals a manifest deviation (tropia). One eye is occluded, and the uncovered (tested) eye is checked for correction from deviated position to fixation. If the eye moves from outward to central for fixation, then the child has an exotropia and if the eye moves from inward to central then the child has esotropia. The alternate cover test reveals total deviation (manifest plus latent deviation). Provide a fixation target and cover each eye for 1 to 2 seconds, while moving the cover back and forth between each eye observe the unoccluded eye for any movement to central position. Some children will have poor fusional mechanisms that keep the eyes straight, and this can be made apparent with the alternate cover test. Any misalignment noted should be referred for further workup as strabismus can lead to amblyopia.

RED REFLEX

The ophthalmoscope is directed at the eye individually 50 cm away from the patient in a dark room (5). The red reflex should be bright, red and symmetric between the two eyes. Abnormal findings (i.e., dark spots, diminished or increased reflex, white reflex [leukocoria] and asymmetry) can implicate any of the structures of the visual pathway, or indicate high or asymmetric refractive error, and should invoke referral for further workup.

PUPILS

Using a bright light source check for equal, reactive and consensual responses of pupils in light and in dark. Using swinging flashlight test check for relative afferent pupillary defect (RAPD). Swing the light between one eye to the next at 1 Hz. Each time the light hits the pupil, it should constrict. If, for example, the left pupil dilates when swung from right to left, there is a left RAPD. The presence of a RAPD indicates a unilateral or asymmetrical pathology of the retina or optic nerve, which should prompt a referral. In cases of irregular shape or unequal pupils (anisocoria), the child should be referred for further workup. If the anisocoria is less than 1 mm and there are no other ocular abnormalities, it is likely to be physiologic in nature, which accounts for 20% of anisocoria (4). Tip: Pupils can also be assessed while viewing the red reflex through a direct ophthalmoscope (i.e., look for shape and symmetry).

Conflict of interest and financial disclosure

None.