Ординатура / Офтальмология / Английские материалы / Pediatric Ophthalmology for Primary Care 3rd edition_Wright, Farzavandi_2008

Jansky Bielschowsky Disease

Jansky Bielschowsky disease is an NCL that has a later onset, between 2 and 4 years of age, with patients often presenting with seizures. This pro gresses with visual loss (optic atrophy and retinal pigmentary degeneration), ataxia, loss of developmental milestones, and eventually decerebrate rigidity and death.

Spielmeyer Batten Vogt Disease

Spielmeyer Batten Vogt disease is an NCL that differs because of its

later onset and that visual loss (retinal degeneration) often presents before neurologic deterioration occurs. Visual loss first occurs between 3 and 7 years of age, and death from progressive neurologic deterioration occurs by age 20 years.

Peroxisomal Disorders

Peroxisomes are small single membrane bound organelles that contain enzymes responsible for catabolism of long chain fatty acids. There are 3 peroxisomal disorders that can cause blindness in the neonate. These are Zellweger syndrome, neonatal adrenoleukodystrophy, and Refsum disease. All are autosomal recessive and are associated with progressive pigmentary retinopathy, optic atrophy, and neurologic deterioration sec

ondary to massive and progressive white matter degeneration. Over time, quadriparesis, dysphagia, and finally death occur. Adrenoleukodystrophy and Zellweger syndrome have an onset during early infancy, while infantile Refsum disease has a later onset.

Zellweger Syndrome

Zellweger syndrome causes the most rapid deterioration of vision of all the peroxisomal diseases. Patients are born with dysmorphic features including prominent forehead, hypertelorism, epicanthal folds, hypoplastic supraor bital ridge, and a high arched palate. Neonates have hypotonia, seizures, severe psychomotor retardation, deafness, and spastic contracture of the limbs. Ocular features include pigmentary retinopathy and optic atrophy that result in early visual loss. Cataracts, corneal clouding, and glaucoma also occur. Visceral involvement includes polycystic kidneys, cardiac ven tricular septal defects, and intrahepatic biliary dysgenesis. Currently, there is no treatment, and death often occurs in the first year of life.

Neonatal Adrenoleukodystrophy

Neonatal adrenoleukodystrophy is associated with early visual loss second ary to retinal pigment epithelial degeneration. At birth, infants are severely hypotonic and develop uncontrollable infantile seizures. Adrenal insuffi ciency occurs late in the disease and causes increased pigmentation of

the skin. Death usually occurs by 3 years of age.

X linked Adrenoleukodystrophy

X linked adrenoleukodystrophy is a peroxisomal disease occurring in males between 4 and 8 years of age. As with any leukodystrophy, there is massive and progressive white matter degeneration. It is associated with adrenal insufficiency, bronzing of the skin, personality changes, and intellectual decline. Neurologic deterioration is progressive with dysphagia, quadripare sis, and death occurring around age 8 to 12 years. Initial visual loss is from cortical pathology; later, optic nerve involvement leads to optic atrophy.

Mitochondrial Diseases (Table 7 3)

Mitochondrial DNA is transmitted exclusively by the mother via the mito chondria found in the egg. Sperm are almost devoid of mitochondria; there fore, sperm does not transmit mitochondrial DNA.

Chronic Progressive External Ophthalmoplegia

Chronic progressive external ophthalmoplegia (CPEO) is a disease of pro gressive limited eye movements, ptosis, retinal pigmentary degeneration, and heart block. Onset can occur in childhood but often occurs in the sec ond or third decade of life. Patients often present with ptosis and diplopia. The retinal degeneration consists of pigmentary alterations that have a salt and pepper appearance. About 40% of affected patients will experience decreased visual acuity or night blindness. Cardiac abnormalities include conduction defects and heart block. Red ragged fibers of skeletal and cardiac muscles are present, and patients are frequently managed with a cardiac pacemaker. Other systemic findings include decreased brain stem ventila tory response to hypoxia and possible sudden death, cerebellar ataxia, deaf ness, vestibular dysfunction, loss of intelligence, and multiple endocrine abnormalities including diabetes mellitus, growth hormone deficiency, adre nal dysfunction, and hypoparathyroidism. Endocrine dysfunction may be

triggered by corticosteroids and hypersensitivity to anesthetic that may even precipitate a fatal event.

The majority of patients with CPEO are sporadic; however, when famil ial, the disease is transmitted maternally via mitochondrial DNA.

There are many types of CPEO, with the most well known of the syn dromes considered to be a subset of CPEO—Kearns Sayre syndrome. Its unique phenotype notwithstanding, Kearns Sayre syndrome may be one particular manifestation of a larger group of abnormalities, all caused by deletions of mitochondrial DNA. Deletions lead to similar biochemical abnormalities that are found to produce clinical syndromes that differ. Diagnostic criteria include 2 obligatory features: early onset CPEO (prior to age 20 years) and retinal pigmentary degeneration, plus 1 of the following 3: heart block, cerebrospinal fluid protein greater than 100 mg/dL, or cer ebellar syndrome.

MELAS Syndrome

(Mitochondrial myopathy, Encephalopathy, Lactic Acidosis, and Stroke like episodes)

MELAS syndrome is characterized by seizures, vomiting, and lactic acidosis occurring during the first few years of life. Patients with MELAS syndrome may experience vision loss secondary to cortical blindness; however, they do not develop progressive retinal degeneration. The disorder is secondary to respiratory dysfunction of cortical neurons caused by the mitochondrial dysfunction. Patients experience problems with autoregulation of blood flow at the level of the pial arterioles. Although stroke like episodes occur, the patient usually recovers. Hemianopsia, cortical visual loss, and intermittent hemiparesis may occur. Unlike other mitochondrial diseases, muscle weak ness is not a prominent feature of MELAS syndrome; however, the patient does have ragged red fibers of skeletal and cardiac muscle.

MERRF Syndrome—Fukuhara Disease

(Myoclonus Epilepsy With Ragged, Red Fibers)

MERRF syndrome is a generalized seizure disorder with patients presenting in the second decade with myoclonus. Severe visual loss may be secondary to optic atrophy; however, retinal degeneration is not a prominent feature. Over time, patients develop ataxia and muscle weakness.

Chapter 8

Nystagmus

(Oscillating Eyes)

Nystagmus is defined as involuntary rhythmic oscillations of the eye. The movements can be described as either pendular or jerk. Pendular nystagmus occurs when the movements have equal velocity in each direction, whereas jerk nystagmus is defined by a fast eye movement in one direction and a slow eye movement in the opposite direction. The direction of jerk nystagmus

is determined by the direction of the fast component. Figure 8 1 depicts a right jerk horizontal nystagmus in primary gaze that increases in right gaze and diminishes in left gaze. Nystagmus can be horizontal (sideways move ment), vertical (up and down movement), or rotary (twisting of the eye or torsion). The oscillations can be described in regard to their amplitude (dis tance the eye travels) and the frequency (number of oscillations per second).

Figure 8 1.

Nystagmus notation. The above schema are useful in describing a patient’s nystagmus. Directional arrows are used to indicate the direction of the nystagmus and its basic characteristics. Multiple arrows and the length of the arrow can be used to indicate frequency and amplitude, respectively.

In most cases, there is a position of gaze where the nystagmus dimin ishes, referred to as the null point. Patients with nystagmus often adopt a compensatory face turn to place the eyes at the null point to enhance visual acuity. Figure 8 2A shows a patient with a null point in right gaze. The patient turns his face to the left to place the eyes at the null point in right gaze.

Latent nystagmus is a special form of nystagmus where the nystagmus increases when one eye is covered. Latent nystagmus is often associated with congenital nystagmus and congenital esotropia. Patients with latent nystagmus usually perform poorly on vision testing because the examiner routinely covers one eye, making the nystagmus worse. To assess the best visual potential in a patient with nystagmus, test vision with both eyes open and allow the patient to adopt a compensatory face turn.

It is helpful to classify nystagmus as either congenital or acquired. It is important to recognize acquired nystagmus because it maybe a sign of a significant central nervous system disease.

Congenital Nystagmus

Congenital nystagmus is nystagmus with onset by 6 to 8 weeks of age. Because of the early onset, infants are able to cortically suppress the motion and do not perceive oscillopsia (ie, perception of cyclic motion associated with nystagmus). Only patients with acquired nystagmus will experience oscillopsia, as they do not have the cortical plasticity to suppress the shaking image. There are 2 basic types of congenital nystagmus: (1) congenital motor nystagmus and (2) sensory nystagmus.

Patients with congenital nystagmus should be referred for full ocular evaluation.

Congenital Motor Nystagmus

Congenital motor nystagmus is bilateral and symmetrical and occurs in the first month of life. The cause of congenital motor nystagmus remains unknown. It is often inherited as an X linked recessive trait; however, other modes of inheritance have been documented. By 2 to 4 months of age, the child often establishes a face turn to place the eyes in a position to minimize the nystagmus (null point). Patients with congenital motor nystagmus have

A B

Figure 8 2.

A, Patient with a face turn to the left, eyes right to damp nystagmus and improve visual acuity. B, Same patient after Kestenbaum surgical eye muscle procedure to relocate the null point to the primary position. After surgery, the null point is in primary position and the face turn is improved.

relatively good visual potential (usually around 20/50 or better), and the face turn posturing is used to optimize their vision.

Treatment of motor nystagmus and face turn is the Kestenbaum eye muscle surgery. This surgery moves the null point to primary position (straight ahead gaze), thus correcting the face turn (Figure 8 2B). Patients with motor nystagmus and no face turn usually do not require surgery; however, some have advocated eye muscle surgery to reduce the nystagmus. Eye muscle surgery for nystagmus without a face turn is controversial.

Sensory Nystagmus

Sensory nystagmus is caused by lack of development of the fixation reflex secondary to neonatal blindness. Any disease that results in bilateral blind ness, such as congenital cataracts, congenital optic nerve atrophy, and congenital retinal disorders, can cause sensory nystagmus (see Chapter 6). Table 8 1 lists the more common causes of sensory nystagmus. The pattern

116 Pediatric Ophthalmology for Primary Care

Table 8-1. Causes of Sensory Nystagmus

of sensory nystagmus is usually indistinguishable from congenital motor nystagmus, except that the nystagmus has a larger amplitude and the eye movements show poor fixation with a searching character. The onset of the nystagmus is later than congenital motor nystagmus, usually occurring after 6 to 8 weeks. Patients with sensory nystagmus rarely adopt a compensatory face turn. In those cases of sensory nystagmus and face turn (eg, albinism) the Kestenbaum eye muscle surgery is indicated to correct the face turn.

Acquired Nystagmus

Acquired nystagmus, even if acquired in infancy, may be a sign of a serious neurologic condition. Neurologic disease involving the midbrain, cerebellum, vestibular system, and areas throughout the brain stem can cause nystagmus. Table 8 2 lists types of nystagmus associated with neuro

anatomic etiology. In contrast to congenital nystagmus, acquired nystagmus is often associated with the perception of the environment moving or oscil lopsia. Oscillopsia, therefore, is an important indication that the nystagmus is acquired.

Spasmus Nutans

This is an acquired pendular nystagmus that develops between 3 and

18 months of age and is usually asymmetrical and rarely unilateral. The nys tagmus appears as shimmering, small amplitude, pendular eye movements. A distinctive feature of spasmus nutans is the presence of head nodding.

Children with this disorder nod their heads in a rhythmic manner. The

Table 8-2. Types and Characteristics of Nystagmus

primary form of spasmus nutans is a benign disorder that spontaneously disappears by around 3 to 4 years of age. This is an important type of nystag mus, as several cases of spasmus nutans have been associated with chiasmal or suprachiasmal tumors. Patients with spasmus nutans should have neu roimaging to rule out a central nervous system tumor, even if the nystagmus is the only presenting sign.