Ординатура / Офтальмология / Английские материалы / Field of Vision A Manual and Atlas of Perimetry_Barton, Benatar_2003

DISCUSSION

Field description: Central scotoma with subtle inferior wedge defect OS.

Localization: Retrobulbar optic nerve.

Pathology: Retrobulbar optic neuritis.

Confrontation testing showed an inferonasal step to a red target and a temporal decrease in the perifoveal field to face comparison.

The central hole in the patient’s field is obvious. Inferior to the disc is a wedge defect. While this is fairly narrow with the I2e target, with the smaller 03e isopter it widens to approach the temporal horizontal meridian on one side and arches nearly to the nasal horizontal meridian on the other.

Sagittal FLAIR MRI demonstrated multiple areas of signal hyperintensity that appear to arise from the corpus callosum and extend out radially toward the cortical surface. These are areas of perivenular demyelination (known as Dawson fingers) and are one of the characteristic patterns of demyelination seen in MS.

In someone who may be presenting with a first neurologic episode, the location as well as the number of MRI lesions may be helpful in predicting whether the individual will develop MS. One study (39) identified four critical features: gadolinium enhancement of one or more white matter lesions, location of white matter lesions adjacent to the cortical gray matter (i.e., “juxtacortical”), periventricular white matter lesions, and infratentorial lesions, in the brain stem or cerebellum. With no such lesions, the calculated risk of MS in a patient’s median follow-up period of about 3 years was only 14%, and with all four criteria met, the risk was 84% (see graph).

HISTORY AND EXAM

This 38-yr-old man had 6 weeks of “decreased contrast” in vision OS, “like a bad photocopy,” with fading of colors and darkening. The other eye was fine. Two years earlier he had been hospitalized with numbness progressing from his feet to his buttocks over a few days, which resolved almost completely over several weeks. A year earlier he had

similar temporary numbness of the right face. Acuity was 20/20 OD and 20/40 OS, with Ishihara color scores of 13/14 OD and 2/14 OS. There was a small RAPD OS. Fundi were normal OU. He had a comitant exotropia. The left hand had a mild pronator drift and clumsiness.

DISCUSSION

Field description: Generalized depression OS and inferior arcuate defect OD. Localization: Retrobulbar optic nerves, bilateral.

Pathology: Retrobulbar optic neuritis, MS.

Confrontation fields showed generalized red desaturation OS.

The patient’s field in the symptomatic eye shows no particular pattern, just a diffuse variable depression, which was actually the most common finding on automated perimetry in the ONTT, occurring in half the patients (30). However, he has a lot of false negative errors, which implies that his defect is not as severe as his responses indicate on automated perimetry. Indeed, Goldmann perimetry 30 min later showed a less impressive (but more classic) moderate relative central scotoma. (This does raise the question of how many of the diffuse defects on automated perimetry in the ONTT (30) may also have been central defects, if they had been examined with other techniques.) The arcuate defect in the asymptomatic eye cannot be dated, but the ONTT did show that such defects in the fellow eye occur in half or more of patients, with peripheral rim defects and diffuse loss

the most common patterns (30,40). Fellow eye defects are more common in patients with more severe loss in the symptomatic eye (acuity <20/200) but, counter-intuitively, do not correlate with associated clinical or radiologic signs of demyelination (40).

This patient already has a history of relapsing neurologic dysfunction. A thoracic spine MRI done 2 years earlier showed a demyelinative lesion (arrow). Thus, he already has clinically definite MS. The prognostic aspects of MRI and long-term effects of methylprednisolone found by the ONTT in patients with no earlier neurologic history do not apply to him. He was referred for β-interferon treatment.

HISTORY AND EXAM

A 40-yr-old man had 3 weeks of bilateral orbital pain with eye movement and 6 days of progressive deterioration in acuity and color vision in both eyes, the right more than the left. He could see hand motion only with the right eye. Acuity of the left eye was

20/25, and the Ishihara color score with this eye was reduced at 5/14. Optic discs were mildly hyperemic and swollen OU.

DISCUSSION

Field description: Large cecocentral scotoma OD, inferior arcuate defect OS. Localization: Bilateral anterior optic nerves.

Pathology: Bilateral papillitis.

Confrontation testing showed dense central defect to finger motion OD, and inferior arcuate defect to finger counting and red targets OS.

Note how the defect OS arches from the blind spot to form a step at the nasal horizontal meridian. Subacute onset of visual loss and pain with eye movement suggest an inflammatory process. T1-weighted MRI of the orbits showed bilateral optic nerve enhancement with gadolinium (right image is enhanced).

Does enhancement of the optic nerve provide any useful prognostic information? The answer is probably no. Enhancement is common in idiopathic optic neuritis and does

not necessarily indicate a different diagnosis (41). Furthermore, neither the length of enhancement nor the involvement of the intracanalicular nerve predicted degree of recovery or response to steroids (42). This patient had an excellent clinical response to 3 days of iv methylprednisolone. Automated perimetry 2 weeks later demonstrated mild residual central depression on the right and inferior arcuate defect on the left, which resolved completely over the ensuing months.

More important, the patient’s brain MRI was normal. Bilateral simultaneous optic neuritis carries a low risk of future MS, probably about 20% over 30 years (43,44), in contrast to bilateral sequential optic neuritis. About another 20% of cases can be due to Leber’s hereditary optic neuropathy (LHON) (44). In the absence of other inflammatory conditions such as sarcoidosis, one might speculate that this presentation is some postviral event. Four years later, he remains free of neurologic events.

HISTORY AND EXAM

This 29-yr-old woman with chronic headaches had 2 weeks of blurred vision OD and fever. For 3 weeks she had noted small round lesions on her shins. Acuity was 20/200 OD and 20/20 OS. There was an RAPD OD. Fundoscopy showed disc edema OD with a mac-

ular star. The skin lesions were diagnosed as erythema nodosum. She was treated with 80 mg of prednisone, and 4 months later acuity had improved to 20/50 OD, with the field below.

DISCUSSION

Field description: Superior and inferior arcuate defects with superior nasal step OD.

Localization: Anterior optic nerve. Pathology: Probable sarcoidosis.

Other features: Macular star (see fundus photograph below).

The patient’s field OD is complex, with a superior defect that points to the location of the blind spot, and approaches an incomplete altitudinal defect in its extent. The smaller isopters align at the nasal horizontal meridian. Inferiorly there is a scotoma (shaded spot) in the course of the inferior arcuate bundle. There is also a depression in the central 5°, consistent with her reduced acuity.

She had an MRI showing enlargement and enhancement of the right intracranial optic nerve and chiasm, as well as enhancement lining the base of the brain and third ventricle (shown here), all of which resolved after 3 months of steroids. Chest X-ray, bronchoscopy, and cerebrospinal fluid (CSF) were normal.

Optic neuropathy in sarcoidosis can be either a chronic form that responds poorly to steroids or, as here, an acute form with rapid improvement with treatment (45). Features that distinguish acute sarcoid optic neuropathy from idiopathic demyelinating optic neuritis include progression beyond the first week, more extensive peripheral field loss, and “steroid dependency”, i.e., relapse of visual loss when steroids are tapered and stopped (45,46). The macular star indicates neuroretinitis and is so unusual for idiopathic optic neuritis that it can be considered evidence against MS (47). Basilar meningeal enhancement on MRI is not a feature of MS but of sarcoidosis (46,48).

DISCUSSION

Field description: Inferonasal step OS. Localization: Anterior optic nerve.

Pathology: Anterior ischemic optic neuropathy (AION) (nonarteritic). Confrontation testing showed decreased hand and color comparison in the inferior

hemifield OS.

The patient presents with a classic inferior arcuate defect and segmental disc edema. The disc edema with sudden nonprogressive visual loss in a man of his age points to ischemia of the optic disc (AION), which is supplied by the posterior ciliary arteries (see Chapter 2). The most important initial step in the evaluation and management of AION is the determination of whether the cause is arteritic (i.e., giant cell arteritis) or nonarteritic (49), the latter usually related to microvascular disease from diabetes, hypertension, or old age. Symptoms in favor of arteritis include preceding amaurosis fugax, headache,

fever, jaw claudication, and scalp tenderness, the latter due to ischemia distal to the external carotid artery (49). Signs suggestive of arteritis are more severe visual loss, with 60% of patients having acuities of less than 20/200 in the affected eye, and a pale chalky color to the swollen disc (49). Less severe loss with segmental rather than diffuse disc edema favors the nonarteritic form, as here. The erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are typically elevated in arteritic AION (50), with the ESR usually above 70 mm/h, but normal in up to 16% of biopsy-proven cases. Poor or absent filling of the choroid on fluorescein angiography also points to arteritic AION. Giant cell arteritis is confirmed by positive temporal artery biopsy, but the false negative rate of biopsy has been estimated as between 5 and 8% (50). Diagnosis of arteritic AION needs to be made promptly, in order to begin steroid treatment to prevent possible imminent loss of the second eye’s vision.