Conducting Screening Tests

Fatigue, hunger, anxiety, and environmental distractions can interfere with vision testing. Testing should always precede the administration of immunizations or any procedure that might cause discomfort. While testing, observe children for behavior indicating that they are having difficulty, such as straining, squinting, excessive blinking, head tilting or shaking, or thrusting the trunk or head forward. The tendency to peek out from behind the eye shield may or may not reflect difficulty; the child may do so out of a desire to be successful and please the tester. The examiner should resist the tendency to correct a mistake or give the child nonverbal clues that can influence the results. Three-year-old children who have difficulty performing any of the vision tests in the PCP’s office should be tested again within 6 months; those unable to perform when older than 4 years of age should be retested in 1 month (AAP et al, 2007). A child who is uncooperative on the second attempt should be referred for a formal examination (AAPOS and AAO, 2007).

Red Light Reflex

The red light reflex should be tested at every well examination, including the initial newborn examination. Performing an adequate red light reflex test (Bruchner test) allows the clinician to detect the presence of asymmetric refractive errors, strabismic deviations, and abnormalities in the ocular media (e.g., cataracts, corneal abnormalities, RB). Disease processes involving the cornea, lens, vitreous, or retina block the light from entering or exiting the pupil and result in an abnormal red light reflex. The recommended technique follows:

• Darken the examination room (a lighted room causes the pupils to constrict, resulting in a poor red reflex). The darker the room, the easier it is to detect more subtle asymmetries between the red reflexes.

• Stand an arm-length away from the infant or child and use the ophthalmoscope light set at 0 or +1 to illuminate the face.

• Look at both pupils simultaneously and separately. Examining the red reflex slightly off axis to the center of the pupil enhances the color (ask a child to look to one side or use a distraction; infants can be approached from the side). In children with fair skin pigmentation, the red reflex is bright red-orange; in those with darker pigmentation, the red reflex is dark red-brown.

• The red reflexes should be symmetric; any asymmetry, dark or white spots, opacities, or leukokoria (white pupillary reflex) requires either:

Prompt referral to an ophthalmologist, or

Dilation of the pupils. Dilation may be used to enhance the examination in questionable situations. In infants younger than 9 months, use 0.25% cyclopentolate with 2.5% phenylephrine. In infants older than 9 months, use the cyclopentolate/phenylephrine drops or 1% tropicamide ophthalmic drops (AAP et al, 2008). One or 2 drops are instilled in each eye at least 15 minutes prior to the examination. Rare side effects to these medications include tachycardia, hypertension, urticaria, cardiac arrhythmias, or contact dermatitis.

Photoscreening, in which a calibrated camera takes a photograph under prescribed lighting conditions, may be used to assess the red light reflex and screen for ambylopia, although more research is indicated before this technique is a consistently reliable method of screening children because results vary among photoscreening apparatus and operators (AAP, 2008a). Medial opacities and refractive errors can also be discerned using this technique, particularly in preverbal or developmentally delayed children.

Infants with a positive family history of RB should be referred to an ophthalmologist familiar with the disease for examinations under anesthesia or dilation starting at 1 to 6 weeks old. Infants with a history of or with a relative having congenital cataracts, congenital retinal dystrophies (e.g., Leber congenital amaurosis, retinitis pigmentosa), malformation of the eye and related brain structures (e.g., coloboma, microphthalmia, anophthalmia, optic nerve hypoplasia), metabolic disorders (e.g., albinism, Hurler syndrome, Tay-Sachs disease), or other retinal or lenticular problems should also be referred to an ophthalmologist for a dilated examination (AAP, 2008b; Teplin et al, 2009).

Some pediatric ophthalmologists recommend routine dilation at the 2-month well-child examination, instilling the drops as the infant is weighed. Adequate dilation is achieved within 15 to 30 minutes, in time for the physical examination. Such dilation also enhances the detection of infantile cataracts (Murphee and Christensen, 2003).

Visual Acuity Testing

Visual acuity screening (see Tables 28-2 and 28-3), for both near and distance vision, should be performed on all children during routine physical examinations, when problems with visual acuity are suspected, and/or when eye trauma occurs. The American Optometric Association recommends comprehensive examinations at 6 months, 2 and 4 years, and every 2 years afterward (AOA, 2002). The AAO recommends a formal screening by the age of 5 years and sees no added benefit in having comprehensive examinations for asymptomatic children (AAPOS and AAO, 2007). If the child wears eyeglasses or contact lenses, visual acuity measurement must be obtained with correction.

Color Vision Testing

The human retina contains 6 million red and green cones and approximately 1 million blue cones. Alterations in color vision occur when the normal photopigments in the photoreceptor cones are replaced with different ones. Color ranges are then interpreted or perceived differently.

Red-green color deficiency is an X-linked inherited disorder or may indicate optic nerve disease. Inherited color deficiencies are more common in males and affect up to 8% of males and 5% of females (Tomsak, 2008). Color vision deficiency may also be acquired. A patient with acquired deficiency may have had normal color vision and then experienced color changes and losses. Diabetes, infections, optic neuritis, and toxins are systemic conditions that can lead to such losses. Blue-yellow deficiency is the most common type of acquired color deficiency.

Significant color blindness can affect school performance; can have safety implications, in that the child may be unable to distinguish traffic or vehicle brake lights; and can affect career choices. Color vision is tested by using the Richmond pseudoisochromatic plates (formerly Hardy-Rand-Rittler plates) or Ishihara plates. Children 3 to 4 years old are usually able to comply with testing directions, but the test does not routinely need to be administered (parents may request testing when their child is young and makes errors when asked to identify colors). In a child who is truly color deficient, the colors are not misnamed.

Peripheral Vision Testing

Examination of peripheral visual fields provides information about retinal function, the neuronal visual pathway to the brain, and the function of CN II (optic nerve). In an infant, assessment is limited to a rough estimate of peripheral visual fields by watching the child’s response to a familiar object (e.g., bottle, toy) or a threatening gesture as it is brought into each of the four quadrants. In children mature enough to cooperate, peripheral visual fields can be measured by confrontation or by finger counting. Peripheral visual fields should be approximately 50 degrees upward, 70 degrees downward, 60 degrees medially (toward the nose), and 90 degrees laterally.

Testing for Ocular Mobility and Alignment

The Hirschberg test (also called the corneal light reflex) evaluates extraocular muscle function by projecting a small light source onto the cornea of the eye with the child looking straight ahead. A normal test reveals the reflected light as a small white dot symmetrically located in the same position of each eye (often slightly nasal of center). The cover-uncover test and the alternating cover test should be performed with the child fixating straight ahead, first on a near point object and then on a far point object about 20 feet away (Fig. 28-3). The process is sometimes aided by asking the child questions about the object (e.g., “How many cows do you see?” in a picture that has been placed for this purpose on the wall). During the alternating cover test, the examiner rapidly covers and uncovers the eye while shifting between the two eyes. Any orbital movement is an indication of misalignment.

FIGURE 28-3 Extraocular muscle function testing (corneal light reflex and cover test).

(From Jarvis C: Physical examination and health assessment, ed 2, Philadelphia, 1996, Saunders.)

Assessment of Visual Loss

If significant visual disturbance is suspected, the following functional vision assessments should be performed, the results documented, and the child referred immediately to an ophthalmologist:

Laboratory and Imaging Studies

Cultures and Gram stain of eye discharge are done if identification of infection or particular organisms would be helpful in guiding management. Ultrasound (not to be used in cases of a suspected ruptured globe), computed tomography (CT), or magnetic resonance imaging (MRI) are sometimes useful in determining a diagnosis of orbital cellulitis, trauma, or tumor, or in substantiating a concern about the central nervous system (CNS). An MRI should not be used in the case of a suspected intraocular metal foreign body.

Fluorescein Staining

Fluorescein staining may be used to determine the extent of damage to the corneal or conjunctival epithelium as a result of trauma, infection, or exposure to a foreign body. Moisten a small strip of fluorescein tape with sterile water and place it in the lower conjunctival cul-de-sac. Allow the fluorescein to mix with tears. Examine the cornea with a cobalt blue filter light; any injury will take up the fluorescein stain and appear as a greenish area. Too much of the stain will cloud the entire cornea.

Other Visual Testing Tools

Three primary visual electrodiagnostic or electrophysiologic tests are used by ophthalmologists to provide insight into the functioning of the visual pathway. Preferential looking, or forced choice preferential looking (FPL), testing can be done in the PCP’s office (requires use of special black-and-white and gray-striped cards to provide the spatial frequencies). A digital camera can be used to take images of the pupillary and red reflexes. The various visual screening procedures done in ambulatory and school settings are being evaluated by a three-phase Vision in Preschoolers (VIP) study sponsored by the National Eye Institute. Results of the study will more definitively indicate which of 11 different vision screening tests are more sensitive and specific for targeting preschoolers with amblyopia, strabismus, refractive errors, and/or idiopathic decreased visual acuity (National Eye Institute, 2010).

Occlusion

Various techniques may be used to treat strabismus and improve or prevent amblyopia by blocking vision in the sound eye. These include occlusion (patching), occlusive contact lens (a last resort method), optical penalization (overplusses the lens on the sound eye), or pharmacologic penalization with 0.5% or 1% atropine (not used in infants).

Corrective lenses

In children, eyeglasses are used to correct refractive errors. Gas-permeable or soft contact lenses can be successfully worn by children as young as 8 years (Jones et al, 2009). Keratorefractive (laser-assisted in situ keratomileusis [LASIK]) surgery is undergoing worldwide research for its applicability in children with low to moderate myopia, severe anisometropia, bilateral high ametropia, and refractive amblyopia; however, its use remains controversial (Daoud et al, 2009; Fecarotta et al, 2010). The AAO discourages LASIK surgery in individuals younger than 18 years old and provides guidelines regarding suitable candidates for the procedure (AAO, 2007a, 2008a).

General guidelines for glasses and contact lenses can be found in Box 28-1. Glasses must be changed frequently in children because of head growth. Because the child may be reluctant to wear eyeglasses that hurt or pinch, parents should assess the fit of the eyeglasses on a monthly basis and watch for behavior that indicates discomfort in a preverbal child (e.g., constantly removing glasses, rubbing at the frames or face).

Contact lenses (includes daily wear [hard lenses] and soft, extended and/or disposable wear lenses), in addition to the cosmetic benefit, can provide better refractive error correction than eyeglasses, thereby enhancing visual acuity and the total corrected field of vision. Studies have also shown that their use improves how children feel about their appearance, athletic abilities, and what friends think of them (Jones-Jordan et al, 2010). Eye health can be promoted by reinforcing instructions regarding proper contact lens care and reminding the patient that contact lenses should not be worn when the eye is inflamed or topical ophthalmic medications are being used.

Until recently “plano” (noncorrective, decorative, or theatrical contact lenses used for cosmetic purposes) have been available for purchase from non-vision care resources. Severe eye injuries (including blindness) resulted when people bypassed the usual regulatory safeguards (proper fit, adequate instruction on use, and hygiene). Such cases prompted the AAO to sponsor legislation that required the U.S. Food and Drug Administration (FDA) to regulate the lenses as medical devices (AAO, 2005). The law requires that these types of lenses be properly fitted and dispensed by prescription only from a qualified eye care professional. Another type of plano lens includes those with light-filtering tints. These block or enhance certain colors and are designed for sports use by tennis players, golfers, baseball players, spectators, trapshooters, and skiers.

Topical Antibiotics

Prescription of topical antibiotics is ideally based on empirical evidence of infection. The best choice of a topical antibiotic is one that is not often prescribed for problems in other body systems. Topical ophthalmologic preparations, such as fluoroquinolones, sulfacetamide, and trimethoprim/polymyxin B, are effective and rarely produce a hypersensitivity reaction. Topical penicillins, on the other hand, are to be avoided. The pros and cons of these antibiotics are addressed in later sections of this chapter. Ophthalmic ointments are generally preferred over solutions for use in children, especially infants, because they last longer, do not sting, do not need to be given as often, and are less likely to be absorbed into the lacrimal passage. However, they do temporarily interfere with vision because they coat the eye, and they can cause contact dermatitis. Special care must be taken to ensure that the tip of the tube or dropper is not contaminated. Ophthalmic ointment should be transferred from the tube to moistened cotton swabs (one for each eye) and then rolled into the lower portion of each conjunctival sac.

Ophthalmic Corticosteroids

Although ophthalmic corticosteroids are effective in the treatment of ocular inflammation and traumatic iritis (excluding ocular allergy), a patient with a condition severe enough to warrant consideration of corticosteroid use should be referred to an ophthalmologist. Steroids are associated with numerous complications, such as an increased incidence of herpes simplex keratitis and corneal ulcers, fungal keratitis, corneal perforation and intraocular sepsis, glaucoma, slowed healing of corneal abrasions and wounds, increased IOP, cataract formation, and permanent loss of sight. They should be used only for significant ocular allergy, anterior uveitis, external eye inflammatory diseases associated with some infections, ocular cicatricial pemphigoid, and following some types of eye surgery. They should never be used for suspected eye infections, for red eye of unknown origin, or in immunocompromised children. A child receiving long-term ophthalmologic steroids should be assessed frequently for signs of adrenal suppression or other side effects. Encourage parents to keep scheduled tonometry appointments at 2- to 3-month intervals.

Other Topical Preparations

Topical decongestants or antihistamines or a combination of the two, mast cell stabilizers, and nonsteroidal antiinflammatory drugs (NSAIDs) are used in treating various ophthalmologic conditions such as allergic conjunctivitis. Over-the-counter vasoconstrictors or vasoconstrictor-antihistamine preparations can be tried first for mild allergic conjunctivitis. Cycloplegic agents are used for iritis.

Systemic Medications

In ocular infections involving the posterior segment and the orbit, systemic antibiotic preparations are necessary. A combination of topical and systemic antibiotics can also be used. In general, these conditions warrant referral to an ophthalmologist. Systemic drugs may also cause damage to the eyes (Table 28-5).

TABLE 28-5 Systemic Drugs, Herbs, and Nutritional Supplements That Can Cause Ocular Side Effects

Data from Anderson AC: Ocular toxicology. In Shannon MW, Borron SW, Burns MJ, editors: Haddad and Winchester’s clinical management of poisoning and drug overdose, ed 4, Philadelphia, 2007, Saunders; National Registry of Drug-Induced Ocular Side-Effects: 2006 AAO syllabus. Available at www.piodr.sterling.net (accessed Jan 6, 2007); Reed Brandon, Hua Len: Potential ocular side effects of select systemic drugs. Faculty Scholarship, paper 3, 2010. Available at www.commons.pacificu.edu/cgi/viewcontent.cgi?article=1002&context=coofac (accessed Nov 14, 2010); Trobe J: The physician’s guide to eye care, San Francisco, 2001, The Foundation of the American Academy of Ophthalmology.

Sunglasses

Ultraviolet (UV) A and UVB radiation from the sun can damage the lens and retina of the eye and cause cataracts and other conditions harmful to vision later in life (e.g., macular degeneration). Sunlight has more UVA than UVB, but UVB is more damaging. Sunglasses should be used to minimize such damage by absorbing these light wavelengths, even if wearing UV-treated contact lenses. It is never too early to start wearing sunglasses. Wearing a hat with a wide (3-inch) brim only cuts the radiation exposure in half.

Sunglasses that have large-framed wraparound lenses with side shields provide the best protection. They should provide 99% to 100% protection from the UVA and UVB short waves, which range from 280 nanometers (nm) to 380 nm or more (Prevent Blindness America, 2008). The lens and frame should be constructed of nonbreakable plastic or polycarbonate. The protection comes from the chemical coating on top of, or incorporated into, the lenses. Gray, brown, and green colors are sufficient for general purposes and lead to minimal color distortion. Darker colors or polarized lenses alone do not offer the protection that is needed unless they specifically state otherwise. Sunglasses that are for fashion purposes or that do not list the UV protective wave spectrum should be avoided. Lenses should only be purchased if they carry the American National Standards Institute (ANSI) label or American Optometry Association (AOA) notation. ANSI communicates their standards by labeling their lenses Z80.3 and “general purpose,” “special purpose” (for snow and water sports), and “cosmetic use” (lowest protection) (Bishop et al, 2009). In addition to the requisite UVA and UVB protection, the AOA recommends purchasing only lenses that state that they screen out 75% to 90% of visible light, are gray (for best color perception), and cause no distortion in vision (AOA, 2008).

Sports Protection

Eye protection is recommended for any child or adolescent participating in sports that have a high eye injury rate. Protective glasses or goggles are mandatory for all functionally one-eyed individuals (with best corrected vision worse than 20/40 in the poorer-seeing eye) or for any athlete who has had eye surgery or trauma or whose ophthalmologist recommends eye protection (AAO, 2003; Prevent Blindness American, 2008). Additionally, these children or adolescents should not participate in boxing or full-contact martial arts. Caution is also recommended in these individuals if they choose to wrestle, even though there is a low rate of reported injury. Specific protective eyewear is available; however, there are no standards for eyewear in this sport. Eye protection is also recommended for hockey, fencing, boxing, full-contact martial arts, racquetball, lacrosse, squash, basketball, baseball, tennis, badminton, soccer, volleyball, water polo, fishing, golf, field hockey, paintball games, pool activities, and football.

Protective eyewear should be properly fitted and selected specifically for the sport. A complete list of recommended eyewear for each sport is available online from the AAO website (www.aao.org). The list serves as a useful handout for parents. A headband or wraparound earpieces should be used to secure the glasses. Parents should only buy the protective eyewear certified by American Society for Testing and Materials (ASTM), the Hockey Equipment Certification Council (HECC), Canadian Standards Association (CSA), Protective Eyewear Certification Council (PECC), or National Operating Committee on Standards for Athletic Equipment (NOCSAE) for use in the particular sport. Fashion or street-wear glasses are inadequate, as is safety eyewear that carries an ANSI Z87.1 rating. Sports eye guards should have protective lenses designed to stay in place or pop outward in case of a blow to the eye (Prevent Blindness America, 2008).

Athletes who need prescription eyewear can either choose polycarbonate lenses in a sports frame that is ASTM F803 rated for the specific sport, wear polycarbonate contact lenses plus the appropriate protective eyewear, or wear an attached over-the-glasses eye guard that also meets specifications of ASTM F803. Younger children who do not fit into manufactured protective eyewear may be fitted with 3-mm polycarbonate lenses with ANSI Z87.1 rating. However, adequate protection cannot be guaranteed and perhaps another choice of sport should be discussed.

Laser Pointers

Lasers are rated on a scale of I to IV, with class I lasers used in laser printers and class IV used in research lasers. The FDA strengthened its message to manufacturers regarding the labeling and safety of laser pointers in 2009, stating class IIIa lasers may be used as pointers, but class IIIb (laser light shows, industrial lasers) and class IV lasers should not be used (FDA, 2009). Lasers traditionally available to the public had a maximum output of from 1 to 5 milliwatts (mW). Although harmless when used as intended by lecturers, potential injury from direct, intentional, prolonged exposure to the retina is of concern if the pointers are used as toys. A literature review found that these types of retinal injuries are not common and that exposure from a brief sweep across the eye by a class II or IIIa laser causes no injury (Ajudua and Mello, 2007). However, there are case reports of children and adolescents buying high-powered lasers from the Internet (with outputs ranging from 150 to 700 mW) and suffering permanent retinal injury and vision loss after playing with them (Wyrsch et al, 2010). It is recommended that laser devices not be made available as toys to children and adolescents.