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

DISCUSSION

Field description: Superior altitudinal loss and marked constriction OD, superior parafoveal relative scotoma OS.

Localization: Retrobulbar optic nerves, bilateral. Pathology: Metastatic cancer.

Confrontation testing showed a superior altitudinal defect OD to hand motion, with only hand motion left in the inferior field. OS was normal.

There is severe visual loss OD, with only an island of inferior vision. The apparent displacement of this from the horizontal meridian may be an artifact of displaced fixation of an eye with severely reduced acuity. More important, the other eye has a subtle problem, with depression of the superior central field, on testing with the smallest I2e target.

A unilateral altitudinal defect would suggest ischemic optic neuropathy, for which the patient’s hypertension is a risk factor, but ischemia usually causes optic disk edema acutely. Without edema, with some defect in the other eye, and her cancer history, carci-

nomatous optic neuropathy was suspected instead. However, her initial MRI was normal, as were two CSF examinations. Her vision continued to worsen to no light perception OD and increased superior field loss OS 2 weeks later (shown here). Repeat MRI showed enhancement of the intracranial optic nerves (arrows), consistent with leptomeningeal carcinomatosis. She was treated with cranial irradiation, but died 3 months later.

Meningeal spread is most common with breast and lung cancer, melanoma, nonHodgkin lymphoma, and leukemia. Although the setting and subsequent course in this case made cancer likely, it illustrates the difficulty in confirming meningeal carcinomatosis. With solid tumors, a single CSF examination has positive cytology only 50% of the time (86). Three or more spinal taps are recommended to increase the yield to about 90% in suspicious cases. The value of maintaining a high index of suspicion and repeating initially negative investigations is evident. The life expectancy with meningeal cancer is about 4–6 months, with current therapy having a very modest impact on survival (86,87).

HISTORY AND EXAM

This 55-yr-old man suddenly noted decreased vision in the right eye when he incidentally covered his left eye one day a month earlier. Over this time, the vision in the right eye became progressively more blurry and he was bumping into people on his right side.

Visual acuity was 20/25 OD and 20/15 OS, and color vision was 12/14 OD and 13.5/14 OS. There was an RAPD OD. Fundoscopy demonstrated optic disk drusen OU. There was a slight proptosis OD.

DISCUSSION

Field description: Inferior arcuate defect with inferonasal step OD. Localization: Right optic nerve.

Pathology: Drusen, optic nerve sheath meningioma.

Confrontation testing showed inferior altitudinal defect for hand motion and comparison.

The patient’s inferior field loss is a complete altitudinal defect for the smallest target, but for the largest it is mainly an inferonasal step defect. The predominant fibers affected would thus be the superior arcuate fibers.

He has an optic neuropathy, and a visible candidate for cause in the optic disk drusen (see Case 56). However, the question of slight proptosis and his insistence that the field loss had progressed over a month led to further investigations. T1-weighted MRI showed “tram-track” enhancement and enlargement of the intraorbital optic nerve, persisting in repeated imaging over 2.5 years, consistent with optic nerve sheath meningioma. His vision continued to deteriorate over the next 2 years, to an acuity of hand motions only OD (field A, this page).

The goals of treatment are to improve vision and prevent intracranial spread. Traditional surgery usually results in loss of all vision of the eye, and since these tumors are rarely aggressive, there has been controversy over whether they should be resected and, if so, when (88,89). Stereotactic radiosurgery is a recent potential advance on this dilemma (90,91). This patient subsequently had stereotactic radiosurgery, with dramatic improvement in his visual acuity to 20/25 OD and expansion in his field (field B, this page).

DISCUSSION

Field description: Inferonasal defect as well as a small superior nasal arcuate defect OS. Localization: Left intraorbital optic nerve.

Pathology: Orbital fracture.

Other features: Ophthalmoparesis.

Confrontation testing was normal.

The left eye shows an extensive inferonasal defect, and a milder superior arcuate defect, with some reduction in the central field as well.

CT scan confirmed a blowout fracture of the medial and inferior walls of the orbit. The axial section shown depicts the resulting opacification of the ethmoid sinuses, air within the orbit, and orbital edema, causing proptosis. The patient’s visual dysfunction is likely the result of a traumatic optic neuropathy. The limited range of adduction and depression indicate medial and inferior rectus paresis due to either intraorbital third nerve damage or injury to the muscles, with or without entrapment by the orbital wall fractures.

Traumatic optic neuropathy should be suspected in any patient with a severe head injury or periorbital trauma. With midfacial fractures, the likelihood of visual loss correlates with the extent and severity of bony damage (92). Most often, the optic nerve is injured indirectly as a result of the concussive forces to the head that produce both mechanical and ischemic insult. Surgery is indicated if imaging reveals compression of the nerve by bony fragments or an optic nerve sheath hematoma, which usually presents with delayed worsening of vision (93).

HISTORY AND EXAM

This 23-yr-old man suffered an accident while bicycling without a helmet. He had a severe closed head injury with loss of consciousness and a post-traumatic amnesia spanning a period of a few days. On regaining consciousness, he noted visual loss and was

treated with iv steroids for 2 days. Six days after the head injury, visual acuity was 20/40 OD and 20/20 OS with Ishihara color scores of 13/14 OD (slow responses) and 14/14 OS. There was RAPD OD. Fundoscopy was normal.

DISCUSSION

Field description: Combination of a superotemporal wedge defect, a central scotoma, and a mild relative inferior arcuate defect OD.

Localization: Optic nerve. Pathology: Trauma.

Confrontation fields showed a decrease in the superior temporal quadrant OD.

The patient has lost much of the superotemporal quadrant, extending to a relative depression of the central field. Inferiorly, the smallest isopter shows a temporal peak and a notch between 10 and 20° in the inferior nasal quadrant, both marking a depression in the course of an arcuate nerve fiber bundle. Head CT was normal, showing no evidence of bony fracture.

In at least one series, bicycle accidents were the most common cause of indirect optic nerve injury (94). Fractures through the optic canal were seen in a minority, but the visual

prognosis did not differ between those with and without such fractures, nor did it correlate with the state of consciousness at injury, unlike other neurologic sequelae. The treatment options are high-dose iv steroids and/or optic canal decompression. While a meta-analysis suggested potential benefit with these (95), the International Optic Nerve Trauma Study did not find convincing evidence of efficacy for either treatment over observation alone (96).

There is no specific visual field defect for traumatic optic neuropathy, although some clinicians have noted that isolated involvement of the superior visual field is rare (97). This is thought to reflect the fact that the inferior optic nerve is less tightly bound than the superior nerve to the optic canal, which is presumed to be the most likely site of transmission of shearing and compressive forces to the optic nerve (98).

HISTORY AND EXAM

This 54-yr-old woman suddenly noticed blurred vision and impaired reading OD 6 months earlier. Vision was impaired centrally and inferiorly, like a “clear mesh.” Two months after onset, an optometrist noted optic atrophy OD. Her acuity then was 20/60

OD. Over the next few months her vision worsened, and she had a continuous dull retro-orbital ache. Acuity was now 20/100 OD and 20/20 OS. Ishihara color scores were 0/14 OD and 13/14 OS. There was a moderate RAPD OD, with temporal disk pallor OD.

DISCUSSION

Field description: Superior paracentral scotoma, inferior scotoma in the Bjerrum area, and inferior temporal defect extending to the blind spot OD.

Localization: Optic nerve OD.

Pathology: Optic canal meningioma.

This is a complex defect in one eye, with patchy involvement of multiple nerve fiber groups. The inferior temporal field is most affected, with deep paracentral and central scotomata. In addition, there is a superior paracentral U-shaped defect, with depression of the isopters peripheral to this spot.

AION was initially suspected at the patient’s optometric assessment, which is possible since the disk edema of AION usually resolves into optic atrophy over a few months. (The same can be said of the retinal pallor of CRAO.) Without documentation of disk edema in the acute phase, however, the diagnosis of AION cannot be confirmed. Sudden (ischemic) visual loss may then be confused with suddenly noticed (compressive) loss, as was the case here. The subsequent progression of visual loss by symptoms and measurements over some months raised the suspicion of a compressive lesion. This small optic canal meningioma (arrow) could easily have been missed on routine MRI of the brain and illustrates the value of MRI focused on the orbit, with coronal views, as shown here on the T1-weighted image.

HISTORY AND EXAM

This 51-yr-old woman first noted 2 months earlier that her left eye could not see to the left during a driver’s license test. This defect gradually enlarged to eliminate the temporal half and lower nasal field of vision in that eye alone, without pain or proptosis. She had had a left VII nerve palsy 22 years earlier, which partially recovered, leaving chronic

facial pain. A brain MRI 12 years earlier was normal. Acuity was 20/20 OD and count fingers at 4′ OS eccentrically. Ishihara color score was 14/14 OD. There was a large RAPD OS and severe optic disk pallor OS. She had mild left facial weakness with aberrant regeneration, and decreased hearing on the left.