Vision Testing in Children
Estimates of visual acuity at birth range from 20/2000 to 20/400. A newborn starts fixating and regarding the mother's face by 2 weeks of age. Between 8 and 10 weeks of age, a normal infant can generally fix and follow a large object over an arc of 180°. A visual problem exists if an infant cannot fix and follow a lighted toy by 3 months of age.
Normal ranges of visual acuity in children vary based on age. Methods to measure visual acuity are also age-dependent. In general, recognition acuity measures are favored over other methods (see "Recognition acuity tests: Allen pictures, HOTV and Snellen letters," p. 380). To assess visual acuity in a preverbal child, motor behavioral responses can be used, such as optokinetic nystagmus or preferential looking tests. When needed, a visual evoked potential test can quantify the visual sensory response. Table 29-1 lists normal ranges of visual acuity by age using the preferential looking test or visual evoked potentials. When children are old enough to verbalize their responses, visual acuity is done by recognition acuity testing. If a child is too shy to talk, he or she can be asked to match pictures or letters with a hand-held card.
Table 29–1. Estimates of Visual Acuity by Age ||Download (.pdf)
Table 29–1. Estimates of Visual Acuity by Age
|Test||Age 2 mo||Age 6 mo||Age 12 mo||Attainment of 20/20 vision (mo)|
|Forced choice preferential looking test||20/400||20/200||20/50||18-24|
|Visual evoked response test||20/200||20/60-20/20||20/40-20/20||6-12|
Examination Procedures and Guidelines for Referral
This test consists of a cylindrical drum with alternating black and white rectangular stripes. The drum is rotated in the infant's visual field while the examiner observes for smooth pursuit eye movements in the direction of the rotating drum followed by saccadic eye movements in the opposite direction. Horizontal saccades can be elicited at birth in a full-term child, but vertical saccades do not develop until 4 to 6 weeks of age.
Using scalp electrodes, electroencephalographic activity can be assessed while showing a child a specific visual pattern. Waveforms are compared to age-matched controls.
Preferential Looking Test
Infants prefer to look toward a pattern stimulus over a nonpattern homogenous single color (Figure 29-1). For this test, an operator holds a large card that carries a pattern on one side and is blank on the other. Through a central viewer the infant's fixation movement can be observed—higher the grating (thinner the stripes of the pattern), the better the visual acuity measured.
Preferential looking test.
Finding and Following Objects
A simple way of assessing visual function is to show a child a small toy or a familiar object such as a colorful piece of cereal. The examiner elicits the child's determination to reach for the object of regard as well as the child's ability to fix and follow the object as it is moved about in space. Fixation behavior can be assessed separately for each eye by using an eye patch.
Recognition Acuity Tests: Allen Pictures, Hotv, and Snellen Letters
Generally beginning at 2 to 3 years of age, a child can name or point to a matching card of familiar pictures (Lea symbols or Allen pictures). Older children can do this with the letters H, O, T, and V (Figure 29-2). Once children learn the alphabet, their vision can be assessed with the Snellen visual acuity chart. A visual acuity of 20/30 signifies that a child can identify a letter at 20 feet that a normal child, or adult, could identify at 30 feet.
Child matching the letter H on the screen with one on the card.
Reasons for Referral to an Ophthalmologist
The basic eye examination for the non-ophthalmologist should include gross vision testing, external ocular examination, assessment of the red reflex, and the position of the corneal light reflex. Any abnormality of these tests should prompt a referral to an ophthalmologist. Checking for a red reflex is best performed with the examiner holding a direct ophthalmoscope about 30 cm away from the baby's face and setting the dial on the ophthalmoscope at +8. The infant can be rocked gently or given a bottle to encourage opening of the eyes. Setting the ophthalmoscope to a slit beam sometimes gives a reflex that is easier to evaluate. A normal red reflex is bright orange in a blond infant and brownish-orange in a darkly pigmented infant. If the reflex is difficult to see because of a small pupil, the instillation of dilating drops can facilitate the examination.
Assessment of the corneal light reflex is done by holding a light source (preferably next to a toy to attract the child's attention) and looking at the position of the light reflexes on the cornea. In a normal child the light will fall symmetrically on the nasal border of the pupil in each eye. If there is a strabismus present (see "Disorders of Ocular Motility" later in the chapter), the corneal light reflex will be asymmetrically located between the two eyes.
A particular condition that warrants referral to an ophthalmologist is nystagmus—an involuntary, rhythmic oscillatory movement of the eyes. The most benign form is congenital motor nystagmus that begins soon after birth and is not associated with a visual or neurological disorder. A sensory nystagmus is due to a visual pathway dysfunction, usually due to an abnormality of the retina or optic nerve as detected by a dilated eye examination. In the rare cases where the dilated eye examination is normal, an electroretinogram (ERG) may assist in the diagnosis. New-onset nystagmus requires neuroimaging.3
General aspects of the eye examination that can be performed by a non-ophthalmologist are outlined in Table 29-2.
Table 29–2. Eye Tests in Children ||Download (.pdf)
Table 29–2. Eye Tests in Children
|Test||Age||When to Refer|
|Assessment of red reflex||Newborn-3 y||Abnormal or asymmetric light reflex|
|Corneal light reflex||2 mo-5 y||Constant strabismus prior to 6 mo, or any strabismus beyond 6 mo|
|Gross examination||Every visit||Eye structure anomaly|
|Discharge or eyelid matting|
|Pupillary examination||Every visit||Pupils unequal or not round; poor response to light; presence of a relative afferent pupillary defect|
|Occlusion of each eye||6 mo-3 y||Unequal objection to occlusion|
|Fix and follow||6 mo-3 y||Inability to fix and follow in either eye|
|Visual acuity||Older than 3 y||Unequal vision (≥ 2 lines) or vision worse than 20/40 in either eye|
Ocular Causes of Decreased Visual Acuity in Children
Based on data from the American Schools for the Blind, in the United States the most common causes of poor vision in children are cortical visual impairment (19%), retinopathy of prematurity (13%), and optic nerve hypoplasia (5%). In developing countries, the World Health Organization estimates that 500,000 people are born blind each year, of which 50% to 90% die mostly due to malnutrition. Thirty percent to seventy percent of childhood blindness is preventable, and the leading causes are corneal opacities or other anterior segment anomalies due to systemic diseases such as measles, congenital rubella, ophthalmia neonaturum, vitamin A deficiency, or side effects from traditional eye medications.4
Anomalies of the Anterior Segment of the Eye
The anterior segment of the eye consists of the cornea, anterior chamber, iris, and crystalline lens. The main function of these structures is to focus light onto the retina. Refractive errors or opacities in the media result in a blurred image. It is important to diagnose and treat these problems at an early age to prevent amblyopia. A congenital cataract that is visually significant should be surgically treated in the first few months of life to prevent severe visual loss and nystagmus. An excellent screening test for media opacities in children is assessing the red reflex (Table 29-3, Figure 29-3). Corneal infections, such as with herpes simplex virus, or trauma resulting in corneal scarring can also result in decreased visual acuity in children, and these problems can be compounded by amblyopia (see section entitled "Amblyopia," p. 384).
Table 29–3. Causes of Abnormal Red Reflex ||Download (.pdf)
Table 29–3. Causes of Abnormal Red Reflex
|Anterior Visual System|
|Cloudy cornea: congenital glaucoma, metabolic abnormalities, anterior segment dysgenesis|
|Cataract: idiopathic, familial, associated with genetic or metabolic syndromes (Figure 29-3).|
|Intraocular tumors (eg, retinoblastoma)|
|Retinopathy of prematurity|
Cataract in the left eye, showing leucokoria and exotropia.
A cataract is an opacification of the crystalline lens. It occurs in 1 in 4000 to 10,000 live-born infants. It may be unilateral or bilateral, and may be part of an ocular or systemic syndrome. Surgical removal is warranted when the cataract is visually significant (ie, when the opacity is central and larger than 3 mm in size). Smaller partial cataracts may be managed with pharmacologic pupillary dilation. The visual outcome of congenital cataracts has significantly improved over the past few decades with the advent of newer surgical techniques. Surgery should be performed as soon as the diagnosis is made to prevent irreversible, severe amblyopia. Congenital cataracts may be a familial condition; therefore screening the proband's family members (especially young siblings) for an asymptomatic cataract is recommended. Screening for galactosemia, a treatable systemic disease, is advisable in cases of a congenital cataract. However, routine testing for toxoplasmosis, other agents, rubella, cytomegalovirus, and herpes simplex (TORCH) is controversial and recommended by some only if there are systemic findings suggestive of an infection.5
Glaucoma is an increase in the intraocular pressure causing damage to the optic nerve. Untreated it may cause irreversible vision loss. The most common type of pediatric glaucoma is primary congenital glaucoma, which has an incidence of 1 in 10,000. The primary pathology in congenital glaucoma is intrinsic disease of the aqueous outflow system. A child with congenital glaucoma will present with a large and cloudy cornea, tearing (epiphora), and photophobia. However, the symptoms may vary in severity ranging from pure tearing and photophobia to a very large, cloudy cornea (bupophthalmos).5,6
A coloboma is caused by a failure of the embryonic fissure to close. It may involve the eyelid, anterior segment, retina, or optic nerve. Not all colobomas lead to visual impairment. For example, an iris coloboma results in a keyhole-shaped pupil with no reduction in vision. In comparison, a coloboma of the fundus will often have associated visual impairment because of retinal dysplasia, particularly if the macula is involved. Patients with retinal colobomas are advised to have a dilated eye examination twice a year because of an increased risk for retinal holes and detachments. Colobomas may be part of the CHARGE syndrome (coloboma, heart anomalies, choanal atresia, retardation of growth and development, and genital and ear anomalies), an autosomal dominant disorder.5
Other Rare Anterior Segment Anomalies
Anomalies of the anterior segment of the eye can be isolated or accompanied by systemic abnormalities. There will be a blunted red reflex similar to a congenital cataract. Persistant hyperplastic primary vitreous can be seen in children born of mothers who have consumed cocaine. It often presents as a small eye with a unilateral cataract, microcephaly, and mental retardation. Anterior segment dysgenesis is a spectrum of abnormalities involving the cornea, iris, and lens due to dysembryogenensis associated with systemic findings such as facial dysmorphism, skin and dental abnormalities, and chromosomal anomalies. A dermoid is a white, elevated lesion that can encroach on the cornea, causing astigmatism or occlusion of the visual axis. It may be a manifestation of Goldenhar syndrome (oculo–auricular–vertebral syndrome), consisting of vertebral anomalies, small ears with skin tags, and facial dysmorphism. Aniridia (absence of the iris) may be associated with multiple ocular anomalies including glaucoma, macular hypoplasia, and nystagmus. It can have a familial autosomal dominant or sporadic inheritance pattern. The sporadic type may be associated with Wilms tumor, genitourinary anomalies, and mental retardation (WAGR syndrome). Microphthalmia is defined as a small eyeball with no structural defect. Vision is often affected because of the presence of other ocular anomalies. Microphthalmia can be a manifestation of an intrauterine infection or trisomy 13 or 18.5
Anomalies of the Vitreous and Retina
The main chamber of the eye is the vitreous cavity, which is filled with a jelly-like substance called the vitreous. The retina is the neurosensory structure of the eye that captures light and transmits a signal to the brain through the optic nerves.
There are multiple causes of a vitreous hemorrhage, but in children the most common causes are retinopathy of prematurity, retinal vessel pathology, ocular trauma, shaken baby syndrome, or an intracranial hemorrhage (Terson syndrome). A vitreous hemorrhage becomes visually significant when it blocks the visual axis. It often resolves spontaneously over several months, but observation is warranted to prevent amblyopia. In persistent cases a vitrectomy is performed. The final visual outcome is dependent on the extent of the disease, with penetrating eye trauma carrying the worst prognosis.7
Retinitis pigmentosa (RP) is a term used for a broad category of diseases affecting the retinal photoreceptor cells (rods and cones). The incidence of primary photoreceptor cell anomalies is 1 in 3000 to 5000. More than 100 genes have been implicated in RP. Of the inherited RP syndromes, recessive X-linked RP is the most common inheritance pattern seen.8 Typically, visual dysfunction begins with night blindness (nyctalopia) and visual field constriction progressing to decreased central visual acuity. Pigment deposits in a "bone spicule" formation are often seen in the peripheral retina. An ERG can help establish the diagnosis and monitor disease progression. Although there is no cure, vitamin A, palmitate, and omega-3-rich fish may slow the progression of the disease. Systemic diseases associated with RP include Usher syndrome, Laurence-Moon-Bardet-Biedl syndrome, and Kearns-Sayre syndrome. Usher syndrome is characterized by sensorineural hearing loss of variable severity and onset. Patients with Laurence-Moon-Bardet-Biedl syndrome have truncal obesity, renal dysfunction, polydactyly, and short stature. Kearns-Sayre syndrome is a mitochondrial myopathy characterized by external ophthalmolplegia, ptosis, and cardiac conduction block.8 Congenital stationary night blindness (CSNB) is a retinal dystrophy characterized by decreased vision at night. It is associated with high myopia and fundus pigmentation that is similar to RP; however, CSNB is a nonprogressive disorder.9
Leber congenital amaurosis (LCA) is an autosomal recessive disorder characterized by blindness before 6 months of age. It is the cause of approximately 10% to 18% of cases of congenital blindness. The ERG is severely attenuated. Final visual acuity in LCA patients ranges from no light perception to 20/200. Systemic findings in children with LCA include polycystic kidneys, osteoporosis, cleft palate, and skeletal and brain anomalies.9,10
Retinopathy of Prematurity
Retinopathy of prematurity (ROP) affects premature and low birth weight babies of less than 32 weeks gestation or less than 1251 g, respectively. It is a complex disorder of prematurity caused by the disruption of the normal intrauterine growth of the retina. Management of ROP starts in the nursery with a screening examination to monitor the growth of the retinal vessels. In appropriate cases, treatment is initiated with laser photoablation to the peripheral retina to decrease the probability of a retinal detachment. A vitrectomy is often indicated in cases of severe disease and retinal detachment.
Genetic and Metabolic Disorders Causing a Decrease in Vision
Sometimes, clinical symptoms and findings on ocular examination may provide clues to the presence of a genetic or metabolic disease. Many metabolic diseases can manifest with accumulation of toxic by-products in the cornea, lens, or retina.
The cornea may become opacified in a variety of genetic disorders. In mucopolysaccharidoses (MPS), the cornea is cloudy due to the deposition of glycosaminoglycans in the corneal stroma. Corneal transplant may be required in MPS IV (Morquio), MPS VI (Maroteaux-Lamy), and less commonly in MPS III (Sanfilippo).11 Other disorders known to cause deposits in the cornea include mucoliposes, Gaucher disease, cystinosis, tyrosinemia, and sphingolipidoses including the juvenile form of metachromatic leukodystrophy. In Wilson disease, alkaptonuria and dyslipoproteinemias deposits occur at the corneal limbus with no effect on vision.
Corneal opacification can be seen in a number of hereditary corneal dystrophies that do not have systemic manifestations (eg, congenital hereditary corneal dystrophies). They usually manifest in late childhood and are characterized by deposits in the cornea that progressively affect vision.
Enlargement of the cornea (megalocornea) can be seen in Marfan syndrome or Ehlers-Danlos syndrome. An abnormally shaped cornea (keratoconus) causing severe astigmatism and scarring is associated with osteogenesis imperfecta and Ehlers-Danlos syndrome.
The cornea is a very sensitive structure and disorders causing corneal exposure or dryness must be managed very carefully to prevent excessive corneal dryness and subsequent infections, scarring, and vision loss.
The lens may opacify due to a variety of metabolic disorders, such as diabetes mellitus, galactosemia, galactokinase deficiency, and Fabry syndrome. Marfan syndrome and homocystenuria is associated with subluxation of the lens.
The macular area is devoid of ganglion cells; therefore, in cases of lipid accumulation or edema of the ganglion cell layer, the macula still displays a red choroidal color, giving the look of a red spot surrounded by white retina—clinically described as a cherry red spot. A cherry red spot is most commonly seen following an ischemic or vaso-occlusive event in both adults and children but may also be seen in Tay-Sachs or Sandhoff disease, metachromatic leukodystrophy, and Niemann-Pick disease. Mucopolysccharidoses, mucolipidosis, gangliosidoses, and peroxisomal disorders can also show retinal pigment changes similar to RP.12
Congenital Optic Nerve Anomalies
Congenital optic nerve disorders include but are not limited to optic nerve hypoplasia, autosomal dominant optic atrophy, hereditary optic neuropathy of Leber, and morning glory disc anomaly. Children with an optic nerve anomaly may have vision ranging from normal to complete blindness. Anomalies of the optic nerve may be associated with anterior segment, retinal, brain, or other systemic abnormalities.
Optic nerve hypoplasia (ONH) is the most common congenital optic nerve anomaly. In addition to the appearance of a small nerve, signs of ONH on examination include a "double ring" sign (with the larger ring being the scleral canal and the smaller ring the actual nerve tissue) and anomalous vascular branching pattern. Patients might be asymptomatic in mild cases or they may present with poor vision, nystagmus, strabismus, or a combination of these. Bilateral cases, more commonly than unilateral cases, are associated with congenital malformation of the central nervous system and pituitary axis (septo-optic dysplasia). In these cases, magnetic resonance imaging (MRI) may show an absent infundibular stalk, ectopic bright spot in the hypothalamus, and an absent corpus callosum and septum pellucidum. A particular syndrome associated with ONH is DeMorsier syndrome, which is characterized by a combination of septo-optic dysplasia, facial dysmorphism, and an open anterior fontanel. Patients with DeMorsier syndrome may present with pituitary axis disruption including sudden death due to corticotropin deficiency.5,13
Morning Glory Disc Anomaly
Usually a unilateral condition, a morning glory disc is an enlarged optic nerve in the shape of a funnel with an indistinct border surrounded by depigmented areas, giving the appearance of the morning glory flower. It may be associated with a basal encephalocele in patients with midline defects, Moyamoya vascular disorder,14 and papillorenal disorder. The presentation and management of morning glory disc is similar to ONH.5,13
Autosomal Dominant Optic Atrophy
Autosomal dominant optic atrophy (ADOA) presents with vision loss in the first or second decade of life. Visual acuity may range from 20/20 to 20/200, with some affected individuals visually asymptomatic. Patients with ADOA may have a concomitant blue-yellow color blindness (tritanopia) and visual field testing showing a centrocecal or paracentral scotoma.5
Autosomal Recessive Optic Atrophy
Autosomal recessive optic atrophy (AROA) is a more severe condition than ADOA. It presents in infancy with rapid, progressive vision loss followed by a stabilization of visual acuity. Although it can be isolated, AROA is usually associated with other neurological disorders such as Behr and Costeff syndromes. Behr syndrome manifests with AROA associated with ataxia, spinocerebellar degeneration, and mental retardation. Costeff optic atrophy syndrome or type III 3-methyglucaconic aciduria presents with bilateral optic atrophy, spasticity, extrapyramidal dysfunction, and cognitive dysfunction.5
The causes of amblyopia are ocular but pathophysiology is within the central nervous system. Amblyopia is defined as a decrease in visual acuity despite best refractive correction with no organic ocular abnormality seen on examination. Amblyopia can be unilateral or bilateral, and is caused by the lack of a clear image directed onto the retina during visual development. Image blur can be refractive, strabismic, or anatomic in origin. Refractive amblyopia is due to an uncorrected refractive error in one or both eyes, or a difference in refractive error between the two eyes (anisometropia). Strabismic amblyopia is due to early-onset strabismus (see "Disorders of Ocular Motility" later in the chapter) resulting in visual suppression. Deprivational amblyopia is due to ptosis or media opacity of the cornea, lens, or vitreous.
Young children (under the age of 8) are the most susceptible to amblyopia. Congenital media opacities should be treated as early as possible to prevent severe visual loss. Children usually do not complain of decreased vision, especially when it is unilateral; therefore, amblyopia can be overlooked and only detected when there is a noticeable strabismus or during a screening eye examination.
Treatment of amblyopia begins by removing any media opacity and providing the appropriate refractive correction in spectacles. The mainstay of amblyopia treatment is penalization of the fellow eye, either by patching or by cycloplegia with atropine eye drops (Figure 29-4). One large study showed that children with amblyopia may still respond to treatment up to age 17 years, especially if they have not been previously treated.15 However, results are generally better when treatment is started at younger ages.16
Child wearing an eye patch for amblyopia treatment.
One should keep in mind that early-onset eye trauma or infection causing a disturbance to the visual axis (eg, corneal scar or cataract) can be a cause of amblyopia. Prompt referral to an ophthalmologist with close follow-up is indicated in these cases.
Neurological Causes for Decreased Visual Acuity
Cortical Visual Impairment
Cortical visual impairment (CVI) is defined as a decrease in visual function due to an insult to the cerebral cortex. It can be congenital or acquired. The two most common causes of CVI are perinatal hypoxia and prematurity.17 CVI can also be due to an intrauterine infection, brain malformation, seizure, intracranial bleeding, hydrocephalus, meningitis, encephalitis, and accidental or non-accidental trauma. Children with CVI often have other associated neurological abnormalities due the primary insult extending beyond the affected visual pathways. Visual impairment in patients with CVI can vary in severity.
One common behavior in children with CVI is intermittent visual attention demonstrated by a child reacting positively to visual cues on some occasions and not on others. It has been hypothesized that the main visual disturbance in CVI is not central vision but rather visual difficulties in perception, integration, orientation, focusing on more than one object at a time, facial recognition, tracking moving targets, color discrimination, and depth perception. In CVI, the ocular examination may be normal if the condition is isolated, but neuroimaging often shows damage to the geniculate or extrageniculate visual pathways. The neurological damage is usually permanent and stable but children can show improved visual behavior with age.18 Commonly, these patients also have associated ocular abnormalities including strabismus, optic atrophy, and significant refractive errors, although the ocular problems are not at a significant level to explain the severity of the visual loss.17
Delayed Visual Maturation
Sometimes a child fails to fix and follow by 3 months of age and has a normal eye examination without a specific cause for visual cortical dysfunction. In most cases this finding is due to delayed visual maturation (DVM). It is hypothesized that DVM results from a delay in the myelination of the visual pathways despite the fact that there is no evidence that the primary visual pathway is involved. Some experts believe that the disorder might be a primary visual inattention disorder. Usually fixation behavior starts to improve between 4 and 12 months of age, and final visual outcome is excellent. If visual attentiveness is not normal by 12 months of age, then CVI should be suspected. Children with DVM have a higher rate of learning disabilities, attention deficit disorders, seizures, autism, and other psychiatric disorders.19
Optic nerve glioma is a low-grade pilocytic astrocytoma representing 5% of all intracranial tumors in children. It can involve the optic nerve, optic chiasm, or both. Clinical presentation is prior to 12 years of age. Approximately 50% of optic nerve gliomas are associated with neurofibromatosis type I. Fifteen percent of patients with neurofibromatosis type I will develop an optic nerve glioma at some point in their life. Children with optic nerve gliomas usually present with decreased visual acuity, proptosis, and a relative afferent pupillary defect. Chemotherapy has evolved over the past decade to become the treatment of choice. Radiotherapy or surgical excision is reserved for chemoresistant cases.20
Optic neuritis is an inflammatory demyelinating condition of the optic nerve. Presentation is acute in onset with rapidly progressive loss of vision associated with pain on eye movement, decreased color perception, poor contrast sensitivity, and a relative afferent pupillary defect. Retrobulbar optic neuritis refers to a normal appearing optic nerve with the pathologic process affecting the posterior or retrobulbar portion of the optic nerve. Neuroretinitis, commonly seen in cat scratch disease, refers to optic nerve edema associated with macular exudates in a star-like pattern.
Optic neuritis may occur in children or adults as an isolated condition or part of a systemic demyelinating disorder such as multiple sclerosis or Devic disease (neuromyelitis optica). Other optic neuropathies in the differential diagnosis of optic neuritis include viral or bacterial infection (cat scratch disease, toxoplasmosis, toxocara, Lyme disease, and syphilis), postimmunization, exposure to an exogenous toxin such as lead, or prolonged treatment with medications such as chloramphenicol or vincristine.
The initial evaluation of a child with an acute inflammatory demyelinating optic neuritis includes a MRI of the brain and spine, lumbar puncture with opening pressure, and cerebrospinal fluid analysis. Visual symptoms generally start improving spontaneously 1 to 4 weeks after onset, and recovery is usually almost complete. Intravenous corticosteroids can improve the rate of visual recovery but have been shown to have no affect on the final visual outcome. It has been stated that children who present with optic neuritis are at less risk of developing multiple sclerosis than adults. This premise is controversial and has not been well studied, in part because optic neuritis is relatively uncommon in children.21,22
Papilledema is swelling of the optic nerve head secondary to increased intracranial pressure. Clinical signs and symptoms include headaches, transient visual obscurations, or a sixth-nerve palsy. Visual acuity is not acutely affected by papilledema although the visual field may show an enlarged blind spot. On fundus examination the optic nerve is edematous, elevated, congested, and hyperemic. The disc margins are blurred and there is loss of spontaneous venous pulsations and obliteration of the optic cup. Severe papilledema may also show disc hemorrhages, peripapillary exudates, or macular swelling with exudates. Untreated chronic papilledema results in optic nerve damage as manifested by a pale atrophic optic disc, severe peripheral vision loss, and reduced central visual acuity.
Common etiologies of papilledema in children include intracranial tumors, idiopathic intracranial hypertension, obstructive hypdrocephalus, trauma, venous sinus thrombosis, intracranial hemorrhage, and encephalopathy.
Management of papilledema involves treating the underlying cause and decreasing the intracranial pressure either pharmacologically with acetazolamide, or surgically with a cerebrospinal fluid diversion procedure. Optic nerve sheath fenestration is reserved for cases of vision loss unresponsive to intracranial pressure reduction.23
Homonymous hemianopia can occur in children and has the same clinical features as in adults. However, in children the most common causes are traumatic brain injuries and brain tumors. Following trauma, visual fields have been found to improve in 33% to 50% of cases, generally within the first 3 months after the injury.24
Children usually do not complain of visual field loss and formal visual field testing can be very challenging at a young age. The examiner may grossly assess the status of the peripheral vision by using a toy or a familiar object (like a bottle) for fixation, and then slowly bringing into the child's field of view another object of equal interest. Older children can perform standardized visual field tests (static or dynamic perimetery). These tests require the child to sit behind a screen and signal when the incoming light from the screen is seen. Standardized visual field testing is usually not reliable before the age of 8 years. The pattern of visual field loss can indicate the location of the lesion along the visual pathway (Figure 29-5).
Visual field defects caused by various brain lesions.