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

Inner retinal layer

Outer retinal layer

“Cartwheel” macular change

Figure 7 8.

X-linked retinoschisis. The splitting occurs at the nerve fiber layer.

the inferior temporal quadrant. Schisis can be difficult to see if the retinal separation is shallow. Late in the disease, secondary retinal pigment epithe lial changes can occur, and pigment can sometimes take on the appearance of retinitis pigmentosa. Vision often remains in the range of 20/70; however, vitreous hemorrhages can occur in areas of schisis, and the retina can detach in some patients, resulting in very poor vision.

Congenital Stationary Night Blindness

Congenital stationary night blindness is a hereditary, nonprogressive disor der of night vision. It can be inherited as autosomal dominant, autosomal recessive, or X linked. The autosomal recessive pattern is rare and usually associated with consanguineous relationships or found in Jewish families. Visual acuity may be normal, although many cases have poor vision. Poor vision can be secondary to myopia, as patients with congenital night blind ness are highly myopic. The night blindness usually occurs during the first

decade of life as an isolated complaint. Color vision, visual field, and fundus examinations are normal. There are 2 distinct variants, however, that have fundus findings. These are Oguchi disease and fundus albipunctatus, both autosomal recessive. They are stable, nonprogressive disorders and have no known treatment.

Cone Dystrophy

Cone dystrophy is a rare retinal dystrophy that preferentially affects cones more than rods. It is typically an autosomal dominant disorder; however, autosomal recessive and X linked varieties have been described. This cone dystrophy usually presents during the first 3 decades of life, caus ing decreased central visual acuity. Other symptoms include photophobia (hypersensitivity to light), dark to light adaptation difficulty, and a history of better vision at night versus during the day. Color vision is significantly affected early in the development of the disorder. Visual fields demonstrate a central scotoma. Cone dystrophy, in most cases, is isolated to the retina

without systemic involvement; however, renal retinal dysplasia, which pref erentially involves cone photoreceptors, has been described. The course of the disease is progressive and can be quite variable even among members of the same family. Vision often declines to the 20/200 level by the end of the third decade. For those experiencing photophobia, tinted lenses may help reduce the symptoms.

Retinitis Pigmentosa

Retinitis pigmentosa is an overall description for a large group of inher ited disorders that affect the retinal pigment epithelium (outer pigmented layer of the retina). The retinal pigment epithelium is critical to the health of the neurosensory retina, as the retinal pigment epithelium nourishes and revitalizes the outer segments of the rods and cones. Diseases of the outer segments of the rods and cones and the retinal pigment epithelium result in decreased function of the rods and cones and ultimately, over time, can cause blindness. These inherited diseases may be confined to the eye; however, many are associated with systemic abnormalities. Retinitis pig mentosa is a major health problem, as approximately 1 in 4,000 individuals are affected. The inheritance pattern is 20% autosomal dominant, 20% auto somal recessive, 10% X linked recessive, and 50% sporadic. The autosomal

recessive and X linked recessive forms tend to develop early in childhood or adolescent years and have a rapid, progressive course. Autosomal dominant cases tend to occur later in adulthood and have a slower, milder course.

The cause of progressive, retinal pigmentary epithelial atrophy has undergone intensive study. Recent molecular biological breakthroughs have shown the primary defect in many types of retinitis pigmentosa is a point mutation in the rhodopsin gene. Rhodopsin is a critical protein in the outer segments of the rods. Over time, the abnormal protein builds up and results in rod death and secondary retinal pigment epithelial atrophy. Retinitis pig mentosa is mostly a rod disease and first affects the peripheral retina where the rod concentration is very high. Some types of retinitis pigmentosa affect both rods and cones, while other inherited retinal diseases preferentially affect cones.

Symptoms associated with retinitis pigmentosa include poor night vision with abnormal dark adaptation. Rods are responsible for our night vision (scotopic vision), and loss of rods first affects our ability to adapt to dark conditions. Patients also experience peripheral visual field loss and develop tunnel vision. Late in the disease, the tunnel vision can be so severe that it greatly restricts patient activity. Central visual acuity loss can occur late in the disease.

Ophthalmoscopic findings are peripheral bone spicule hyperpigmenta tion (Figure 7 9). This is an area of clumped pigmentation with adjacent areas of hypopigmentation and retinal pigment epithelial atrophy. The optic nerve will take on a waxy pallor and the retinal vessels will be significantly attenuated. Electrophysiologic testing is important to document decreased electroretinogram from poor dark adaptation.

Systemic Diseases Associated With Retinitis Pigmentosa (Table 7 1)

Usher Syndrome

Usher syndrome is an autosomal recessive form of retinitis pigmentosa (Figure 7 9) associated with sensorineural deafness. In some cases, the deafness is associated with abnormal vestibular function. The combination of visual and auditory deprivation has devastating social implications, and affected individuals often have severe psychologic problems.

Figure 7 9.

Usher syndrome. Fundus photograph showing typical retinitis pigmentosa findings of bone spicule hyperpigmentary changes, attenuated retinal vessels, and optic disc pallor (atrophy).

Refsum Syndrome

Refsum syndrome is an autosomal recessive defect in fatty acid metabolism that results in increased phytanic acid throughout the body. This metabolic defect results in peripheral neuropathy, cerebellar ataxia, deafness, and reti nitis pigmentosa. The time of onset is usually in the third decade. The diag nosis is confirmed by the presence of elevated levels of phytanic acid in the serum. Restricting dietary phytanic acid early in life may slow the progres sion of the disease.

Bassen Kornzweig Syndrome (Abetalipoproteinemia)

Bassen Kornzweig syndrome is a rare autosomal recessive disorder caused by malabsorption of intestinal fat. Patients have decreased serum levels of cholesterol, triglycerides, and fat soluble vitamins A, E, and K. Diagnosis is confirmed by very low serum cholesterol. Patients present with steatorrhea, acanthocytosis (a thorny or spiny erythrocyte characterized by multiple spiny cytoplasmic projections), ataxia, and childhood onset retinitis pigmen tosa. Dietary supplementation with vitamin E can be helpful.

Table 7.1. Neurologic Disorders Accompanying Retinitis Pigmentosa

Errors in Lipid Metabolism 3-Hydroxydicarboxylic aciduria Abetalipoproteinemia

Refsum disease

Neuronal ceroid lipofuscinosis Infantile form

Late infantile form Juvenile form

Errors in Mucopolysaccharide Metabolism Hurler disease (MPS IH)

Hunter disease (MPS II) Scheie disease (MPS IS)

Peroxisomal Disorders Zellweger disease

Neonatal adrenoleukodystrophy Infantile Refsum disease

Mitochondrial Disorders Kearns-Sayre syndrome

Heredodegenerative Disease Friedreich ataxia Cerebellar ataxia, dominant Familial spastic paraplegia Hallervorden-Spatz disease Cockayne syndromes Chédiak-Higashi syndrome Hallgren syndrome

Other Hereditary Disorders

Gyrate atrophy due to ornithine aminotransferase deficiency Sjögren-Larsson syndrome

Laurence-Moon syndrome Alström syndrome

Usher syndrome

Laurence Moon Bardet Biedl Syndrome

Laurence Moon Bardet Biedl syndrome is a disorder consisting of obe sity, mental retardation, hypogenitalism, and retinitis pigmentosa. This syndrome has been divided into 2 forms: the Laurence Moon syndrome, which is associated with spinocerebellar ataxia, hypogonadism, and spastic paraplegia, and the Bardet Biedl syndrome, which includes polydactyly. Bardet Biedl syndrome is autosomal recessive. These patients may have subtle findings and the diagnosis may be overlooked. Examination of feet

and hands may require radiography to determine polydactyly or brachydac tyly. Recently, the genotype of Bardet Biedl syndrome has been mapped to chromosome 16.

Renal Retinal Syndromes

Retinitis pigmentosa is associated with certain renal diseases including

Senior Loken syndrome and Maldino Mainzer syndrome. These are usu ally autosomal recessively inherited and feature retinal pigment epithelial degeneration. Senior Loken syndrome consists of juvenile renal failure, often leading to transplantation and progressive retinitis pigmentosa.

Neurodegenerative Disorders Associated With

Vision Loss (Tables 7 2 and 7 3)

Neurodegenerative disease can cause visual loss through retinal degenera tion, optic neuropathy, or cortical blindness.

Neuronal Ceroid Lipofuscinosis

Batten Disease

Neuronal ceroid lipofuscinosis (NCL) refers to a group of lysosomal storage disorders of lipopigments with secondary neuronal degeneration. Neonates are not blind at birth, but start losing milestones between 6 months and 3 years of age. These are autosomal recessive generalized disorders with pro gressive psychomotor delay, seizures, and choreoathetosis. Patients develop a retinal degeneration that leads to blindness and an attenuated or extin guished electroretinogram. Intracellular inclusions can be seen by electron microscopy in neurons, pericytes, macrophages, smooth muscle cells, lipo cytes, and capillary endothelial cells. Diagnosis is made by biopsy of the skin and rectum. Conjunctival biopsy may also be helpful.

Haltia Santavuori Disease

Haltia Santavuori disease is an infantile form of NCL characterized by nor mal development until 6 months of age. Then progressive regression with loss of psychomotor milestones, onset of seizures, pigmentary retinal degen eration, and optic atrophy occur. Patients are usually blind by 2 to 3 years of age, and death occurs around 6 to 7 years of age.