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

Figure 5-2 shows a central scotoma in a patient with ONH.

Pediatric patients with unilateral or segmental ONH and with normal growth and development should undergo regular ophthalmic and pediatric examinations. Those with bilateral ONH should undergo neuroimaging (magnetic resonance imaging [MRI]) and endocrine evaluation. ONH discovered in neurologically intact adults requires no further workup.8

Figure 5-2. Central scotoma in a patient with optic nerve hypoplasia.

5-2-2 Optic Nerve Colobomas and Pits. Colobomas or pits are congenital malformations that enlarge or distort the nerve head circumference and shape. In most cases, the enlarged peripapillary area is irregularly pigmented with the presence of anomalous vessels. Colobomas are usually unilateral and sporadic.10

The morning glory anomaly is an enlarged, relatively round disc filled with retained embriogenic glial and vascular remnants (Figure 5-3). It often projects forward as a funnel and can be surrounded by an elevated annulus of chorioretinal pigment. When associated with congenital forebrain anomalies, including basal

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Figure 5-3. Morning glory syndrome.

Figure 5-4. Optic disc pit.

encephaloceles (spheno-orbital, transsphenoidal, or frontoethmoidal), it is termed “morning glory syndrome.” The majority of patients with this syndrome have marked visual loss and amblyopia.11

Patients with congenital disc malformations may complain of transient obscurations of vision, lasting seconds to minutes, but the mechanism of the disturbance is not known.10 Pits of the optic disc are intrapapillary pearly gray slits containing pale glial material (Figure 5-4). They are usually located within the scleral rim of the disc margin and can extend for up to one third of a disc diameter. The disc border is usually distorted, and mild pigment epithelial

changes may be present. Pits are usually unilateral and temporally located. There is a positive association with serous detachment of the macula in up to 50% of the cases.12,13

Visual field changes include the following:

5-2-3 Anomalous Disc Elevations: Pseudopapilledema With or Without Hyaline Bodies (Drusen). Pseudopapilledema are congenitally elevated discs that may present with or without hyaline bodies. Disc hyaline bodies are acellular laminated concretions of unknown origin, often partially calcified. They are possibly related to the accumulation of axoplasmic derivatives from degenerating retinal nerve fibers, in which orthograde axoplasmic flow has been obliterated due to an abnormally narrow scleral canal. These hyaline bodies slowly become visible, as they enlarge toward the disc surface and margin; the overlying retinal nerve fibers also become progressively thinner. Usually they become visible in the early teens. They are usually inherited as autosomal dominant trait. They present in two thirds of cases bilaterally and are not necessarily symmetric. When there is uncertainty between true edema and pseudopapilledema, examination of family members may be helpful.15-17 Hyaline bodies may become symptomatic by insidious visual field loss or spontaneous hemorrhage.18

Visual field defects are usually in the form of:

1.Blind spot enlargement, reflecting absence of functioning photoreceptors mechanically disrupted by the expanding adjacent ONH.

2.Arcuate, which is actually a mild form of an altitudinal defect. It does not involve fixation but rather the areas just peripheral to it.

3.Other nerve fiber bundle patterns, such as altitudinal or nasal step.

4.Other less commonly irregular peripheral constriction that may occur. Normally, these defects progress slowly, with a predilection for involvement of the inferior nasal quadrant.19

Drusen are not an uncommon condition and may be seen in up to 2% of patients.15 Figure 5-5 shows optic disc drusen, and Figure 5-6 shows a central visual field defect (blind spot enlargement) in optic disc drusen.

5-2-4 Tilted Disc and Crescents. Tilted discs usually present with depigmented peripapillary crescents. The most common variety of crescent is that located inferiorly (Fuchs colobomata), usually with inferonasal retinal quadrant involvement and superior temporal field defect without respect for either vertical or horizontal.20, 21 In bilateral cases, visual field shows bitemporal hemianopia, which does not respect the vertical meridian.22

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Figure 5-5. Optic disc drusen.

Figure 5-6. Central visual field defect (blind spot enlargement) in optic disc drusen.

5-3 HEREDODEGENERATIVE OPTIC ATROPHIES

Heredodegenerative inherited optic neuropathies fall under the rubric of metabolic optic neuropathies. Metabolic optic neuropathies share many common pathophysiologic and clinical characteristics. Most metabolic optic neuropathies involve derangements that affect mitochondria and oxidative phosphorylation. Common hereditary optic neuropathies include Leber’s hereditary optic neuropathy (LHON), dominant optic atrophy (DOA), and congenital recessive optic atrophy (ROA). Like most acquired metabolic optic neuropathies, inherited optic neuropathies all involve mitochondria function. In all cases, mitochondria are impaired either by mutations of their own DNA (mtDNA) or by mutations of nuclear DNA involved in the transcription of mitochondrial proteins or substrates.

The presentation is usually symmetric visual loss with dyschromatopsia and central or cecocentral visual field defects, which involve the optic disc and

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A

B

Figure 5-7. Right and left eyes of a patient with Leber’s hereditary optic neuropathy. Fundus photographs of both eyes demonstrate hyperemic optic nerve heads, with dilated tortuous vessels, and swollen retinal nerve fiber layer (pseudoedema of the optic disc). Note also the telangectatic vessels.

There are a few reports of spontaneous recovery, especially with the 14484/ND6 mutation (up to 60% of cases) and in younger patients. Most often, the visual loss progressing to total optic atrophy over time stabilizes within 1 year, with the early development of temporal optic atrophy.

There is currently no clinical evidence for an efficacious treatment to reverse vision loss in LHON. Theoretical considerations have led to the use of several agents involved with mitochondrial energy production and with antioxidant capabilities, such as coenzyme Q10 (or its analogues), succinate, L-carnitine, vitamins K1, K3, C, and B12, folate, and thiamine. It remains unlikely that any of these agents alone or in combination will prove consistently useful in the treatment of acute visual loss in LHON or in the prophylactic therapy in asymptomatic family members at risk.23,27,28,31

However, it is prudent to recommend the avoidance of agents that might induce oxidative stress or impair mitochondrial energy production. Most specifically, it is imperative to avoid exposure to smoke and alcohol because these environmental factors can trigger the loss of vision in susceptible individuals.34

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Figure 5-8. Dense central visual field defect in patient with Leber’s hereditary optic neuropathy.

5-3-2 Dominant Optic Atrophy. DOA, or Kjer’s optic neuropathy, is one of the most common forms of hereditary optic atrophies. Presentation usually occurs at latency age (7-10 years old). It often presents with an imperceptible onset and a slowly progressive course and results in mild to moderate visual impairment (20/40 to 20/400). The inheritance of DOA is autosomal dominant. Despite the variability in expression, the penetrance is actually very high. DOA presents as mild, bilateral, sometimes asymmetric loss of visual acuity. On examination, there is temporal