Ординатура / Офтальмология / Английские материалы / Pediatric Ophthalmology for Primary Care 3rd edition_Wright, Farzavandi_2008
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Hereditary Optic Atrophy
Hereditary optic atrophy with blindness in the neonatal period is usually autosomal recessive optic atrophy. This is a rare form of bilateral severe optic atrophy, often causing nystagmus in half of the patients. Ophthalmoscopic examination shows pale optic nerves and vascular attenuation. Retinal func tions are normal, as the electroretinograph shows normal amplitudes. Behr syndrome may be associated with mental retardation, spasticity, and cer ebellar ataxia. Other forms of optic atrophy have a later onset in late infancy or early childhood (see Chapter 7).
Cortical Blindness
Cortical blindness is caused by injury to the optic radiations or the visual cortex in the occipital lobe. The occipital cortex is extremely sensitive to hypoxia because it is in the watershed area of the cerebral vessels. Neonatal hypotension and birth asphyxia are important causes of neonatal cortical blindness. Hydrocephalus, stroke, intracranial hemorrhages, direct trauma, and congenital aplasia in the occipital cortex are other causes. In contrast to the previously listed causes for neonatal blindness, cortical blindness is usu ally associated with normal ocular examination, and nystagmus is not pres ent. Stimulation with an optokinetic nystagmus stimulus, even in cortically blind children, usually produces a response. In addition, pupillary responses are brisk in contrast to pupillary responses associated with optic nerve or retinal diseases. If the occipital damage is severe and widespread and occurs within a few weeks of birth, retrograde transsynaptic degeneration of optic nerve axons can occur and result in optic atrophy. Acute hypoxia associated with cardiac bypass surgery can result in transient cortical blindness. The majority of these patients will show spontaneous improvement over several weeks. An MRI scan of the visual pathways and cortex often aids in the diag nosis of cortical blindness.
Chapter 7
Acquired Visual Loss
in Childhood
In this chapter, causes of acquired visual loss after 1 year of age, associated with a normal red reflex, are discussed. Disorders are classified as follows: optic nerve disease, retinal disease, and neurodegenerative disorders.
Optic Nerve Disease
Juvenile Onset Glaucoma
Glaucoma is defined as optic nerve damage from increased intraocular pressure (usually >22 mm Hg). Glaucoma is rare in children but when present can cause visual loss and blindness. Juvenile onset glaucoma is usually asymp tomatic, in contrast to congenital glaucoma (see Chapter 12), which is almost always associated with large corneas, corneal edema, and tearing. In some cases, if the intraocular pressure is extremely high (>35–40 mm Hg), symp toms of tearing, corneal edema, red eye, and pain may occur. There are various forms of juvenile onset glaucoma, some hereditary and others sporadic. See Chapter 12 for systemic diseases associated with pediatric glaucoma.
Leber Hereditary Optic Neuropathy
This is inherited through a mitochondrial DNA point mutation that results in defective oxidative phosphorylation. Over time, this metabolic abnormality results in optic neuropathy with acute or subacute severe, painless visual loss. Visual loss can start in one eye and then subsequently go to the other eye, or the patient may present with bilateral simultaneous visual loss. Visual loss is in the range of 20/200 or worse and is associated with poor red/green color
vision. Patients are usually male and lose vision between 10 and 13 years of age.
Visual acuity has been reported to improve in anywhere from 5% to 30% of patients after the acute episode.
The classic fundus appearance of the acute phase consists of telangiectatic microangiopathy around the optic disc and blurred disc margins (pseudopa pilledema) (Figure 7 1). Later, the optic disc will turn pale and lose its normal
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Figure 7 1.
Leber hereditary optic neuropathy.
pink appearance (Figure 7 2). Leber hereditary optic neuropathy has been associated with cardiac arrhythmia syndromes such as Wolff Parkinson White. A definitive diagnosis can be made by genetic analysis of leukocyte mitochondrial DNA. Currently, there is no effective treatment for Leber hereditary optic neuropathy.
Dominant Optic Atrophy
Dominant optic atrophy is associated with slow, insidious, bilateral visual loss, usually beginning around 10 years of age. In some cases, visual acuity can remain quite good, even in the range of 20/25 or 20/30. In other cases, visual acuity is as poor as 20/100. Color vision is significantly affected. Direct oph thalmoscopy reveals temporal optic disc pallor.
Recessive Optic Atrophy
Recessive optic atrophy is associated with severe bilateral visual loss, often with nystagmus. Visual loss occurs before age 5 years, often in infancy.
Optic Neuritis
Optic neuritis is inflammation of the optic nerve or chiasm. Inflammation is usually caused by an autoimmune post viral syndrome associated with a systemic infection such as measles, mumps, chickenpox, nonspecific viral
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Figure 7 2.
Optic atrophy. Note the optic nerve is pale, especially in the temporal area of the disc.
disease, or immunizations. Children often present with a headache, nausea, pain on eye movements, bilateral optic disc swelling (papillitis) (Figure 7 3), and acute visual loss (20/200 or worse) (also see Chapter 9). If the inflamma tion is isolated to the posterior optic nerve, the optic disc may appear normal; however, vision will be affected. Spontaneous recovery with visual improve ment usually occurs after 1 to 2 weeks; however, permanent visual loss can occur. In children, the majority of cases are secondary to an autoimmune post viral syndrome; however, there is a risk for developing demyelinating disease (multiple sclerosis [MS]). Unilateral optic neuritis has a higher risk of being associated with MS than bilateral optic neuritis. Initial evaluation should include a full physical examination, Venereal Disease Research Laboratory test, and fluorescent treponemal antibody absorption test—both for syphilis; cat scratch skin test and magnetic resonance imaging if the diagnosis is in question and to rule out MS. Treatment with high dose intravenous (IV) cor ticosteroids may speed up visual acuity recovery but probably does not have an effect on the final visual acuity outcome. A multicenter adult trial showed that IV corticosteroids may decrease the incidence of late multiple sclerosis; however, oral corticosteroids may increase the incidence of the development of demyelinating disease. If visual improvement does not start within the first
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3 weeks or if vision worsens after treatment, neuroimaging and a workup for sarcoidosis, Lyme disease, and autoimmune vasculitis (lupus) are indicated.
Macular Stellate Neuroretinitis
Optic disc edema may be extensive enough to leak into the macula and cause macular edema and exudates, producing a macular star (Figure 7 3). This form of optic neuritis is called macular stellate neuroretinitis. It is unilateral in 80% of cases and is associated with viral illness, cat scratch disease, lepto spirosis, Lyme disease, sarcoidosis, and toxoplasmosis.
Devic Neuromyelitis Optica
This is bilateral optic neuritis followed by a transverse myelitis.
Optic Nerve Glioma
In contrast to the rare malignant glioblastoma in adults, optic nerve gliomas in children are histologically very benign and are termed juvenile pilocytic astrocytoma. They occur along the optic nerve and more commonly in the chiasm, causing a fusiform enlargement of the optic nerve as it diffusely replaces normal neuronal architecture. Posterior tumors can bring about a slow diencephalic syndrome with diabetes insipidus, failure to thrive after a normal growth period, hyperactivity, changes in skin pallor, hypotension,
Figure 7 3.
Papillitis with optic disc swelling similar to papilledema. Note the macular star pattern that represents fluid and lipid exudates.
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and hypoglycemia. Tumors can occur anywhere along the optic nerves, chiasm, and optic tract (Figure 7 4). Optic nerve and chiasmal gliomas are slow growing, and patients present with proptosis, unilateral or bilateral visual loss, strabismus, optic atrophy, or nystagmus. The nystagmus is simi lar to spasmus nutans, a unilateral or asymmetrical shimmering pendular nystagmus (see Chapter 8). Optic nerve gliomas are most common in chil dren younger than 10 years and represent two thirds of all primary optic nerve tumors.
There is an important association with neurofibromatosis—it is reported that anywhere from 10% to 70% of optic nerve gliomas are associated with neurofibromatosis type 1 (NF1). Likewise, approximately 15% of patients with NF1 will develop an optic nerve glioma. The treatment of optic nerve gliomas remains controversial because the natural history is unknown.
Figure 7 4.
Magnetic resonance imaging scan of patient with right optic nerve glioma; note extensive involvement of the contralateral nerve, chiasm (white arrows), and the optic tract (black arrows).
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Some studies have reported an overall benign course; however, other studies indicate that 50% show progressive enlargement with visual loss. Obtain ing serial ocular examinations and neuroimaging are important to moni tor the tumor progress. Neuroimaging should be performed at least every
6 months and visual acuity with visual field testing at approximately 3 month intervals, at least for the first year after the tumor is diagnosed. Progres sive visual loss and enlargement of the tumor are indications for therapy.
If the tumor is localized to one optic nerve, many advocate removal of the optic nerve. Bilateral optic nerve involvement and chiasmal involvement are usually treated with radiation therapy. In children younger than 4 years, chemotherapy with vincristine and carboplatin is often preferred over radia tion therapy. Usually a biopsy is not necessary; however, a biopsy may be performed in cases of chiasmal glioma when there is a need to debulk an exophytic portion of the tumor because of secondary compression of sur rounding structures.
Craniopharyngioma
Craniopharyngioma arises from squamous epithelial cells that are remnants from the Rathke pouch. It is the third most common brain tumor found
in children. These tumors may be solid or cystic, often containing necrotic blood, epithelium, and cholesterol crystals. Children often present with nonspecific complaints of headaches or progressive visual loss of unknown etiology. It is important to consider the diagnosis of craniopharyngioma in children who have decreased vision of unknown cause. Children may also present with endocrine dysfunction consisting of pituitary deficiency.
Optic atrophy occurs in 60% of patients and papilledema in 65% of patients. Acquired nystagmus (see saw nystagmus) and bitemporal hemianopsia may result from large parasellar tumors expanding within the third ventricle. The treatment of craniopharyngioma involves removing the tumor completely, if possible. Often, complete resection is not possible. Repeat neuroimag ing is important to follow the progress of the tumor. Unfortunately, most children with visual loss and optic atrophy at the time of their presentation will not show significant visual acuity improvement after surgery; however, decompression stops further visual loss. Recurrences usually occur 1 to 2 years after the primary procedure. Radiotherapy may be employed in older children and teenagers.
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Retinal Disease
Retinal Toxicosis
Several medications have retinal toxicity as a side effect. These medications include chloroquine (Aralene), hydroxychloroquine (Plaquenil), thiorida zine (Mellaril), chlorpromazine (Thorazine), tamoxifen (Nolvadex), nico tinic acid (Niacin), and canthaxanthine.
Chloroquine and hydroxychloroquine were first used in the treatment of malaria and are currently used for treating connective tissue diseases. Both drugs produce identical retinopathies that progress from mild macular pigmentary abnormalities to severe central maculopathies with loss of cen tral vision. The classic appearance of the maculopathy is that of a bull’s eye, consisting of a central foveal area of hyperpigmentation surrounded by hypopigmentation (Figure 7 5). Toxicosis usually does not occur until the cumulative dose is greater than 100 grams. Follow up ocular examinations should be obtained on patients undergoing chloroquine or hydroxychloro quine therapy. Ocular examinations should occur every 4 to 6 months and include testing visual acuity, checking the central visual field with an Amsler grid, and performing funduscopic examination. It is important to note that
Figure 7 5.
Bull’s-eye macular lesion in a 28-year-old patient who had received a cumulative dose of almost 700 g chloroquine over 6 years. The pigmentary changes in the macular area remain, even after discontinuation of the drug.
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once toxicosis is diagnosed, progression can be seen even after discontinuing the medication.
Hereditary Retinal Disorders
Stargardt Disease Fundus Flavimaculatus
The most common hereditary macular dystrophy is Stargardt disease fundus flavimaculatus. Typically, it is inherited as an autosomal recessive trait that results in a progressive macular degeneration. Stargardt disease begins in adolescence with complaints of slowly progressive, decreased visual acuity and mild loss of color vision. In its late stages, visual acuity drops to a range of 20/200 and patients may complain of poor night vision (nyctalopia). Macular appearance is that of beaten bronze, then changes to show areas of retinal pigment epithelial atrophy, which are seen as whitish yellow flecks (Figure 7 6). Unfortunately, there is no treatment.
Best Disease
Best disease is an autosomal dominant retinal dystrophy that affects central vision and causes dystrophic changes in the macula. During early child hood to the mid teens, patients develop a yellowish macular lesion. This
Figure 7 6.
Fundus flavimaculatus in a 42-year-old patient with 20/100 vision. Color photograph showing multiple yellow flecks at the level of the retinal pigment epithelium, visible throughout the posterior pole.
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is a well circumscribed round lesion in the macula, approximately 1 to 2 disc diameters in size. The lesion has a distinct appearance, that of an egg yolk, and is termed vitelliform macular lesion (Figure 7 7). Over time the lesion represents abnormal accumulation of lipofuscin granules within the retinal pigment epithelium. The yellowish egg yolk lesion breaks up and creates a scrambled egg appearance that will ultimately result in an area of retinal atrophy. Visual acuity is fairly well preserved, in the range of 20/40 to 20/100. Late complications of retinal scarring and retinal vascularization, however, can lead to legal blindness.
X linked Retinoschisis
X linked retinoschisis is an X linked recessive retinal dystrophy that affects both the fovea and peripheral retina. This disorder consists of a splitting of the retina (schisis) at the level of the nerve fiber layer (inner retina). Unlike the previously described retinal dystrophies, this retinal dystrophy does not primarily affect the retinal pigment epithelium (outer pigment layer). In the fovea, there are small cystic cavities that form a spoke like pattern
(Figure 7 8). Fine folds in the area of the fovea occur overlying these micro cysts. In the periphery, large areas of retinoschisis occur, usually involving
Figure 7 7.
The vitelliform macular lesion of Best disease is an accumulation of lipofuscin within the retinal pigment epithelium. At a later stage, the egg yolk may be partially reabsorbed, producing a scrambled egg appearance.