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

DISCUSSION

Field description: Mildly incongruous left homonymous partial superior quadrantanopia.

Localization: Right temporal optic radiation.

Pathology: Resection.

Confrontation fields were normal OU.

The patient has a subtle relative depression of the superior field, more OD, and not extending close to the horizontal meridian or fixation.

Field defects from temporal lobe resections are homonymous and always begin at the vertical meridian. The degree to which they spread toward the horizontal meridian varies with the posterior extent of the resection. Hence, the vertical meridian is the area to concentrate field testing in these patients. This subtle defect was missed on confrontation testing, but careful probing of the vertical meridian with Goldmann perimetry shows the defect. MRI shows the resection, which extends about 4 cm from where the anterior temporal pole had been. The classic neurosurgical series reported that field defects were produced when resections extended at least 4 cm posteriorly from the temporal pole (128,129). Lesions extending beyond 8 cm tend to produce complete hemianopia (128,130).

HISTORY AND EXAM

This 40-yr-old man had complex partial seizures since age 19, sometimes followed by a period of postictal psychosis. There was a history of complex febrile seizures as a child. video-electroencephalogram (EEG) telemetry showed that the seizures arose from the left temporal lobe. MRI demonstrated scarring in the white matter lateral to the temporal horn

of the lateral ventricle, and the left temporal lobe was smaller than the right. His visual fields at that time were normal. He had a left anterior temporal lobectomy, which showed hippocampal (mesial temporal) sclerosis. Acuity was 20/20 OU and fundoscopy was normal.

DISCUSSION

Field description: Mildly incongruous right homonymous partial superior quadrantanopia.

Localization: Left temporal optic radiation.

Pathology: Resection.

Confrontation testing with hand motion did not show the defect, but careful searching with a moving finger along the vertical meridian did.

The patient’s defect is more extensive than that of Case 73. It extends to fixation in the smaller isopters but still does not quite reach the horizontal meridian with the larger isopters. Postoperative MRI shows a resection of about 5.5 cm, consistent with the degree

of resection thought to encroach on Meyer’s loop. The preoperative MRI abnormality is consistent with mesial temporal sclerosis, the most common pathologic finding in patients with refractory temporal lobe epilepsy who undergo surgical resection for seizure control. The exact relation of mesial temporal sclerosis to seizures is still debated. Childhood complex febrile seizures may injure the medial temporal lobe, or the medial temporal lobe injury may occur first and cause subsequent seizures. The pathogenetic story may be even more complicated; a subtle brain anomaly may predispose to febrile seizures, which themselves may induce further injury and cause hippocampal sclerosis and, ultimately, adult complex partial seizures (131–133).

DISCUSSION

Field description: Moderately incongruous, nearly complete homonymous right superior quadrantanopia.

Localization: Left temporal optic radiation.

Pathology: Resection.

Confrontation fields showed greater incongruity, with no hand motions seen in the whole upper quadrant OS, but some preserved finger counting ability in this quadrant OD.

Automated perimetry shows a quadrantic defect that aligns at the horizontal meridian, with perhaps slight sparing at the macula. The incongruity is best appreciated in the sensitivity plot and gray scale, where more scattered locations with some residual sensitivity

(i.e., >0 dB) are found OD than OS. There are scattered reductions in sensitivity inferiorly, more so on the right eye, but these do not respect the vertical meridian and are not confluent with the quadrantanopia, and thus are not likely due to the resection, which MRI showed to be extensive, involving the anterior 5.3 cm of the temporal lobe. Goldmann perimetry confirmed normal inferior fields (shown here).

Surgery is being used more frequently in the treatment of epilepsy. A recent randomized trial (134) of 80 patients showed that 58% of surgical patients remained free of complex partial seizures at 1 year of follow-up, compared with 8% of patients treated medically. Evaluation for surgery should probably not be delayed by prolonged and numerous trials of drugs if seizures are poorly controlled.

HISTORY AND EXAM

This 74-yr-old woman suddenly lost vision on the right while at the circus with her grand-daughter. She found her reading slow, often having to re-read lines. She reported no problems with face or object recognition. Examination in the emergency room showed a right hemifield defect, normal acuity, no RAPD, and normal color scores with Ishihara

plates. However, within the remaining seeing regions of the right hemifield, she was unable to distinguish one color from another. She was in atrial fibrillation, which was treated with amiodarone and anticoagulation with coumadin.

DISCUSSION

Field description: Congruous right homonymous superior quadrantanopia plus. Localization: Left striate cortex.

Pathology: Posterior cerebral arterial infarct, cardioembolic. Other features: Right hemidyschromatopsia.

Confrontation testing with hand motions showed the same defect, involving the macula and upper part of the inferior quadrant.

Hemi-dyschromatopsia is impaired color vision in the hemifield contralateral to the lesion. It is often not spontaneously noticed by patients (135,136). The diagnosis requires an inability to discriminate among colors. Color naming may or may not be impaired,

depending on the severity of the color defect. Lesions of the lingual and fusiform gyri in the ventromedial occipital lobe are responsible (137). Achromatopsia affecting the entire visual field is always apparent to the patient and requires bilateral occipital lesions. FLAIR axial MRI demonstrates a left posterior cerebral artery territory infarction that involves the fusiform gyrus. This patient’s stroke is likely due to emboli from her atrial fibrillation. The risk of stroke with this disorder is high. It is one of the few scenarios for which a prospective double-blind, placebo-controlled trial (138) has proven that coumadin reduces the annual risk of recurrent stroke from 12 to 4%. The target INR in the study was 2.5–4.0.

HISTORY AND EXAM

This 75-yr-old man with coronary artery disease and hypercholesterolemia had 2 years of bilaterally decreased vision and was referred because of homonymous defects on automated perimetry shown here. He was known to have mild cataracts and macular changes

attributed to a valsalva retinopathy. Visual acuity was 20/25 OU, and Ishihara color scores were 13/14 OU. There was no RAPD. He had mild cataracts and macular pigmentary changes and drusen that were worse OS, but normal optic disks.

DISCUSSION

Field description: Incongruous right homonymous superior quadrantic defects, with possible extension into lower field OS, complicated by poor reliability.

Localization: Distal optic radiation. Pathology: Subcortical infarction.

Confrontation fields were normal, even though the results of perimetry were known.

Both right and left fields clearly show in the upper right quadrant a zone in which no target is seen at all (values of 0 dB on visual sensitivity plot). The rest of the right eye’s field is normal, and the three reliability indices are excellent. In the left eye, which was tested second, the first thing to note is the poor fixation index of “6/21 xx,” and the comment of

“low patient reliability,” in the upper left part of the printout. This makes the patchy, less severe reductions in threshold flagged in the lower quadrants (both left and right!) more dubious. Poor fixation may have been related to the patient’s macular disease. Goldmann perimetry 2 weeks later (see Goldmann field below) showed a congruous homonymous right superior quadrant scotoma, confirming that the inferior field defects were factitious.

MRI showed scattered white matter T2 hyperintensities with one large lesion near the trigone of the left lateral ventricle, likely involving the optic radiation. Patients with isolated quadrantanopic defects are most likely to have lesions in the occipital lobe. Isolated superior quadrantanopia may also result from a temporal lobe lesion (139), as in cases 73 to 75.

HISTORY AND EXAM

This 60-yr-old man with long-standing hypertension had sudden frontal headache with left-sided visual loss. Over the ensuing week images in the left field of vision appeared to be moving or jumping. Findings on neurologic examination included visual acuity of

20/20 OU, Ishihara color scores of 13/14 OU, and preserved recognition of famous faces. Optic disks were normal. Saccadic eye movements to the left were hypometric.