Ординатура / Офтальмология / Английские материалы / Visual Fields Examination and Interpretation_Walsh_2011

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Figure 7-1. (Continued)

findings, such as posterior staphyloma or choroidal neovascular membrane (Figure 7-4,7-5).

AMD may show nonspecific changes in the central or paracentral visual field that correlate with the structural damage to the retina and choroid (see Figure 7-1). Geographic atrophy in dry AMD can cause a dense scotoma correlated with the pattern of the atrophy. Choroidal neovascular membranes can cause a depression in the correlating visual field due to edema or hemorrhage. Disciform scars in endstage AMD can also cause a dense scotoma (see Figure 7-2).

Macular holes may cause a small central scotoma (Figure 7-3). Pattern dystrophies are a family of disorders with a common pathology at the level of the RPE. Butterfly dystrophy, an autosomal dominant disorder, and Sjögren reticular dystrophy, an autosomal recessive disorder, are two examples of pattern dystrophies. Often, patients with pattern dystrophies maintain excellent vision, unless atrophy compromises their central visual field. Electrophysiologic testing often shows normal electroretinographic (ERG) testing with mildly abnormal electro-oculo- graphy (EOG) results, reflecting the RPE disturbance. Pathologic myopia has a field defect that is correlated with fundus lesions (see Figures 7-4 and 7-5).

7-3 VASCULAR DISEASES

Vascular diseases can present with more localizing defects. Artery and vein occlusions will have defects that correlate with the area that has abnormal circulation. Macular edema caused by diabetic retinopathy or vein occlusions will cause a central or paracentral defect (Figures 7-6 through 7-8). Macroaneurysms can cause localized changes from blockage from hemorrhage or edema. Retinal emboli, regardless of composition (fibrin, cholesterol, or calcium), may cause anything from a sectoral to a full field defect.

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Figure 7-2. (Continued)

7-4 CONGENITAL AND GENETIC DISEASES

Retinitis pigmentosa (RP) represents a family of diseases with variable inheritance (autosomal dominant, autosomal recessive, or X-linked). Patients with RP may have poor vision in dim light, rod and cone dysfunction by ERG, and bone spicules in the periphery. Patients classically present with mid peripheral scotomas that coalesce into a ring-shaped scotoma. Later in the course of the disease, the scotoma progresses and involves the central vision or leaves a small central visual field. This pattern can be seen in patients who have the typical bone spicules and in those who do not (sine pigmente). Cystoid macular edema may be associated with RP and will cause changes to the central or paracentral visual field. Because of the progressive degenerative changes and the significant impact of the disease, it is important to evaluate patients suspected of having RP to rule out masqueraders such as syphilis, uveitis, old vascular occlusion, or drug toxicity. It is also important to evaluate patients for systemic metabolic disorders, particularly treatable conditions such as Refsum disease or abetalipoproteinemia.

Choroideremia, an X-linked recessive disease, is characterized in the advanced stages by total atrophy of the choriocapillaris, choroid, and RPE. Fundus changes begin with pigmentary mottling at the equator that evolve into atrophy and migrate peripherally as well as centrally. Patients often have diffuse peripheral visual field defects with central sparing until late in the course of the disease (Figure 7-9). ERG recordings are reduced and progress to unrecordable in the late stages.

Gyrate atrophy, a rare autosomal recessive disorder, causes choroidal and retinal atrophy with progressive loss of peripheral and central vision. The defective gene, ornithine aminotransferase, leads to high levels of serum ornithine. Treatment is targeted at reducing ornithine levels such as through an arginine-restricted diet.1 Such treatment has been shown to slow the progression of disease as measured by serial visual field testing and ERG.

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Figure 7-3. (Continued).

Fundus flavimaculatus, or Stargardt disease, is an autosomal recessive disease that has been localized to mutations in the ABCR gene, which encodes a transmembrane transporter protein in the rod outer segment. Patients with early stages of Stargardt disease can have central scotomas despite minimal findings on ophthalmoscopy. Patients can have a primarily macular presentation or peripheral changes, or a combination of both. Patches of atrophy can give a beaten bronze appearance of the macula. Pisciform flecks can be found in the macula or in the periphery. Fluorescein angiography can be helpful with the classic finding known as a “silent choroid.” Advanced disease can show peripheral degenerative changes that are reflected in depressed ERG testing.

Vitelliform dystrophy, or Best disease, often have well-preserved central vision despite abnormal appearing maculae. Typically of dominant inheritance, the mutation is identified on the VMD2 gene on chromosome 11. The initial appearance of a yellow macular lesion is often associated with good vision, until

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Figure 7-4. (Continued)

atrophy causes a central scotoma. ERG testing is usually normal; however, Best disease classically has an abnormal EOG with an Arden ratio of less than 1.5. A distinction is made between Best disease and adult-onset vitelliform lesions, such as adult vitelliform foveomacular dystrophy, which is also characterized by bilateral yellow subfoveal lesions but with normal ERG and EOG testing. Patients usually are asymptomatic or have mild metamorphopsia. Distinguishing these diseases is important for genetic counseling.

Ocular albinism presents clinically with photophobia and on examination shows iris tranillumination defects as well as a hypoplastic fundus and fovea (Figure 7-10). Visual field defects are associated with the areas of hypoplasia, notably in the peripapillary distribution. A hallmark of the disease is the presence of abnormal retinogeniculostriate projections of temporal nerve fibers traveling to the contralateral hemisphere. One study indicated that there is no abnormality in visual field testing associated with the projection abnormality.2 In pathologic studies, oculocutaneous albinism is associated with a reduction in the amount of melanin in melanosomes, whereas ocular albinism has a reduction in the total number of melanosomes. Oculocutaneous albinism is usually inherited in an autosomal recessive pattern, although ocular albinism is often X-linked. There are two systemic conditions associated with albinism—Chediak-Higashi syndrome, which is associated with increased susceptibility to infections, and Hermansky-Pudlak syndrome, which is common in children of Puerto Rican descent and is characterized by platelet abnormalities. It is important to clinically distinguish these two syndromes so that appropriate hematologic consultation can be arranged.

Patients with cone dystrophy may present with a central field defect (Figure 7-11).