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

DISCUSSION

Field description: Spiraling.

Localization: Functional deficit. Pathology: Psychogenic.

Confrontation fields with varying viewing distance showed cylindrical tunnel vision OU.

The patient displays two classic functional patterns on visual field testing: cylindrical tunnel vision on confrontation testing (see Chapter 3), and functional spiraling on kinetic perimetry. In spiraling, the first test location is usually seen in the midperiphery (point A). If the examiner maintains an orderly test sequence, moving, say, in a counterclockwise direction (as in her field), the eccentricity at which the target is seen gradually decreases. The result is that when the examiner has completed a full circle and is back testing at the first location, the target cannot be seen until it is much closer to fixation (point B) than when it was perceived at the start of the test. As the examiner continues in a second

counterclockwise circle, this can be shown for the rest of the points as well. It is as if the patient is losing vision during the actual test!

So what does this mean about her vision? Clearly, at least part of her deficit is functional, but given her history she could still have a mild optic neuropathy with some nerve fiber layer field defect. It is just that the functional defect makes it that much harder to discern any signs of true pathology that might be present. Functional and organic defects can coexist and often do in other neurologic arenas, the combination of pseudo-seizures and seizures being one such example (175). At the least, in this patient the lack of optic atrophy argues against a severe neuropathy. Evoked potentials may or may not help; it is possible to create artifactual abnormalities on such testing by poor fixation or defocusing one’s eyes (176). Evidence that this patient has MS will have to come from avenues other than the eye clinic. Unfortunately, the rest of her neurologic examination also shows functional elements.

HISTORY AND EXAM

This 47-yr-old school bus driver had an accident, hitting her head, but without loss of consciousness. Since then she had been unable to see to the right with her right eye. Acuity

was 20/20 OU, Ishihara color scores were 13/14 OU, and there was no RAPD. Fundoscopy was normal OU.

DISCUSSION

Field description: Monocular temporal hemianopia.

Localization: Functional.

Pathology: Psychogenic (“hysterical hemianopia”).

The patient’s monocular visual fields suggest a unilateral temporal hemianopia in the right eye, respecting the vertical meridian. This is a puzzling defect—rare monocular nasal hemianopias have been described with lateral chiasmal compression; however, it is

virtually impossible for lesions affecting the crossing fibers to eliminate one temporal hemifield entirely and spare the other temporal hemifield. This raises suspicion of a functional hemianopia, which is one of the few clinical settings in which perimetry with both eyes open is useful. When tested with both eyes viewing, as shown on this page, the patient still fails to see in the right hemifield, despite the fact that her normal left eye is now open. Some call this the “missing half” field defect (177). Not surprisingly, she was applying for disability after 25 years of ferrying screaming children to and from school.

HISTORY AND EXAM

This 49-yr-old woman had 20 years of “eye strain” impairing reading, shopping, and looking at people. A prior examination had found latent hyperopia, and her symptoms had responded 16 years before to clonazepam. She had a long history of depression.

Acuity was 20/20 OU with correction, and Ishihara color scores were 14/14 OU. There was no RAPD. She had small optic disks with minimal cups. Neurologic examination was normal.

DISCUSSION

Field description: Flat thresholds across entire field, OS.

Localization: Functional defect.

Pathology: Depression.

Confrontation field were normal.

Note that the patient’s entire field has nearly the same thresholds, 17–20 dB, which correspond to fairly bright lights of 100–200 asb. Apart from being a tour de force of functional consistency, this performance is physiologically implausible. A global reduc-

tion from physiologic causes should still preserve a hill-like shape to the visual field, with decreasing sensitivity in more eccentric retina.

This patient has a history of depression. However, serious psychopathology is unusual among patients with functional visual loss, with only half meriting a psychiatric diagnosis on follow-up (178). Unfortunately, visual complaints resolve in only about a quarter, despite reassurance and encouragement. Nevertheless, the social and functional consequences of the visual aspect of their problems are minimal (179).

HISTORY AND EXAM

Two years earlier, this 40-yr-old woman had painless loss of vision in the left eye that progressed to almost no light perception over a week. MRI showed an enlarged and enhancing intraorbital optic nerve. She was treated with iv methylprednisolone and oral prednisone tapered gradually over 3 to 4 months, with slow visual improvement. One year

later she developed painful swelling of multiple joints and erythema nodosum. Chest X- ray revealed hilar adenopathy and ESR was 48 mm/h. These findings resolved with a further course of prednisone. At her most recent evaluation, visual acuity and color vision were normal OU, but there was a left RAPD and the left optic disk was pale.

DISCUSSION

Field description: Inferior arcuate defect, with dense inferonasal scotoma OS.

Localization: Optic nerve.

Pathology: Sarcoidosis.

Confrontation testing showed inferior paracentral scotoma to color and hand comparisons.

Automated perimetry shows a defect that arches out of the blind spot to end in a dense defect just below the nasal horizontal meridian—note that the visual sensitivities in this region are very low (2–6 dB). Goldmann perimetry done 10 months earlier showed exactly the same arcuate defect, with the same dense hole between 15 and 30° eccentric-

ity nasally, a nice example of the correlation of the two techniques. The presence of optic disk pallor implies that the optic neuropathy is not new.

After the facial nerve, the optic nerve is the second most commonly affected cranial nerve in sarcoidosis, being involved in about 5% of patients with this disorder (180). Although unusual, this disease can present as an isolated optic neuritis (45,181). In this patient, an atypical optic neuritis must have been suspected initially, given the unusually long course of steroids. The subsequent development of erythema nodosum and hilar lymphadenopathy confirmed the diagnosis. While this patient did well with steroids, some cases can relapse when steroids are withdrawn—“steroid-dependent” optic neuropathy (182). Immunosuppression with azathioprine may be required in such cases.

DISCUSSION

Field description: Superior temporal hemifield defects OU, with inferior arcuate defect and nasal step OS.

Localization: Optic chiasm and left intracranial optic nerve. Pathology: Pituitary macroadenoma complicated by apoplexy.

Confrontation fields showed a mild temporal step defect to red comparison in the upper fields of both eyes.

The superior temporal field depressions OU point to a lesion of the inferior chiasm. The inferior nasal step defect OS, seen in both the I2e and 03e isopters, indicates left optic

neuropathy. This combination has an inverted resemblance to the right eye of Case 68, in which the compression was from above the chiasm.

The sudden severe headache should have been a red flag for some intracranial bleed, such as a subarachnoid hemorrhage or pituitary apoplexy. Acute hypopituitarism is a medical emergency (108). Fortunately, the patient survived until its belated discovery and responded well to replacement with desmopressin, cortisone, thyroid hormone, and testosterone patch. He had resection of the tumor with no change in his fields over the next 2 years.

HISTORY AND EXAM

This 36-yr-old woman, seen for headache, had long-standing poor vision OS. Previous neurologists had also questioned a left VI nerve palsy because of esotropia with limited

abduction OS. Acuity was 20/20 OD and hand motion at 6′ OS. Ishihara color score was 14/14 OD. There was a large RAPD OS and mild limitation of abduction OS.