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

DISCUSSION

Field description: Inferior altitudinal defect, splitting macula OS. Localization: Anterior optic nerve.

Pathology: AION, nonarteritic.

Confrontation testing showed near complete inferior altitudinal defect to hand motion.

Altitudinal defects are the classic pattern associated with AION. The patient’s defect is typical, with sharp demarcation at the nasal horizontal meridian and some partial sparing of the temporal field of the affected half. Her macula is split in half by the field defect, but this central region can be spared or involved completely by an altitudinal defect (see Case 35).

Disk edema fades over the first 1 to 2 mo, and about 40% of patients may have some mild improvement when this occurs (51). Interestingly, this patient’s disc hyperemia was in the normally functioning inferior half (serving the superior field), suggesting that this

may be an unusual luxury hyperperfusion of the remaining disc rather than persistent edema (52). The other disc was small and lacked a central cup; such “crowded” discs are considered a risk factor for AION, the “disk at risk” (53). Indeed, 3 mo later she had a second episode OD, with an inferior altitudinal defect, and then progressive constriction of both eyes that eventually stabilized after a few months. ESR and temporal artery biopsies were normal.

The early course of nonarteritic AION is usually static with little or no change in the initial visual loss. More unusual is a progressive form, in which vision continues to decline over weeks to months before eventual stabilization. Although optic nerve sheath fenestration was once promoted as a treatment for this form, it remains unclear whether there is benefit from the procedure. For AION in general, the procedure worsens vision (51). Progressive AION can sometimes improve spontaneously (54).

HISTORY AND EXAM

This 71-yr-old man awoke one morning and noticed a dark spot in the right eye. There was no change in his symptoms over the following mo. When examined a month after onset, visual acuity was 20/20 OU, but there was an RAPD OD. Ishihara color scores

were 12/14 OD and 11/14 OS. The optic disc OD was diffusely swollen, and the optic disc OS had a minimal central cup. The remainder of the examination was normal.

DISCUSSION

Field description: Inferior and superior arcuate defects OD. Localization: Anterior optic nerve.

Pathology: AION, nonarteritic.

Confrontation testing showed decreased finger counting in the inferonasal sector and decreased color in all except the superior temporal quadrant OD.

There is a relative nasal constriction to the large (V4e) isopter. Within this, the I4e isopter is indented above and below center, leading to depressed valleys of the smallest isopter that curve into the blind spot, leaving a small central island of better vision. ESR was 32 mm/h and CRP was <0.4 mg/dL, and the patient was diagnosed with a nonarteritic AION. He returned 2 months later and reported that his vision had deteriorated further, but he could not identify any time of sudden worsening. Examination revealed a visual acuity

of 20/40 on the right and 20/100 on the left. Color vision was markedly impaired in both eyes. Fundoscopy demonstrated optic atrophy on the right and mild disc edema on the left. Visual fields, shown below, revealed some minor evolution of the prior arcuate defects on the right as well as a new centrocecal scotoma and inferior arcuate defects on the left.

The optic disc in the eye contralateral to that with nonarteritic AION is typically small in diameter and the physiological cup is often either small or absent (53) (see Case 33). This can be associated with a small degree of hyperopia (55). The term disc at risk has been used to describe these crowded discs and their risk for AION. Structural crowding of the disc at the level of the cribriform plate may contribute to microvascular compression and render the optic disc vulnerable to ischemia. The finding of such a “disk at risk” in the contralateral eye may, therefore, sometimes assist in making the diagnosis of nonarteritic AION in the affected eye.

HISTORY AND EXAM

This 78-yr-old woman had sudden visual loss in the left eye 4 months earlier. Her ophthalmologist saw disc edema with a nerve fiber layer hemorrhage OS. She denied jaw claudication, headache, or scalp tenderness. ESR was 12 mm/h and CRP was <0.4 mg/dL.

She had 6 years of hypertension, treated with a diuretic. Acuity was 20/20 OU, and Ishihara color scores 13/14 OD and 8/14 OS. There was an RAPD OS. She had a normal optic disc OD but temporal pallor of the disc OS.

DISCUSSION

Field description: Superior incomplete altitudinal and inferior arcuate defects, with superonasal step, OS.

Localization: Anterior optic nerve. Pathology: AION, nonarteritic.

Confrontation testing showed superonasal step defect to a red target.

The best way to approach this patient’s complex defect is to divide the field in vertical halves. In the top half, she has an incomplete altitudinal defect, sparing some of the temporal field as well as the macula. Inferiorly there is a less severe arcuate defect arching out of the blind spot toward the nasal field, and also some depression in the temporal field immediately adjacent to the optic disc.

The documentation of disc edema in the acute phase is key to diagnosing AION. At this late stage, the patient has only nonspecific optic atrophy (shown here OS), which is

the end stage of any number of pathologic processes. Without knowledge of her earlier disc edema, one would have to consider other disorders, including the suddenly noted visual loss of a compressive optic neuropathy (see Case 52).

Arteritic AION is an occlusive disease, which is reflected in large areas of choroidal nonperfusion on fluorescein angiogram. Nonarteritic AION is usually a hypoperfusion event affecting the watersheds among different posterior ciliary arteries in the same eye (56). Microvascular disease due to long-standing hypertension or diabetes increases the vulnerability of the discs during episodes of hypotension. The normal nadir of blood pressure in early morning hours may explain why many patients first note visual loss on awakening (57). This nocturnal hypotension can be aggravated by the use of antihypertensive medication in the evening. Unlike the situation with central retinal artery occlusion, carotid atherosclerosis is not a major risk factor for AION (58).

HISTORY AND EXAM

This 65-yr-old man had 1 week of painless nonprogressive blurry vision OS. One year earlier he had awakened with painless visual loss OD that persisted. He had hypertension and diabetes for 10 years, and was taking ASA. Acuity was count fingers at 8 ft OD and

20/80 OS with eccentric fixation. There was an RAPD OD. Fundoscopy showed severe optic disc pallor OD and diffuse disc edema OS, with peripapillary nerve fiber layer hemorrhages. His ESR was 10 mm/h and CRP <0.4 mg/dL.

DISCUSSION

Field description: Complete inferior altitudinal defect with general constriction OD; incomplete superior altitudinal defect with central depression OS.

Localization: Bilateral optic nerves, anterior OS. Pathology: Bilateral sequential nonarteritic AION.

Confrontation testing showed an inferior altitudinal defect for hand motion OD and a superonasal step defect for hand and color comparisons OS.

The patient has only a sliver of remaining superior vision OD, which lies completely above the horizontal meridian. In the other eye, he has lost almost all of the superonasal quadrant, with a relative depression of both the superotemporal quadrant and the central region, so that he can see only the smallest target when it is just below center (this accords with his reduced acuity). Note how the largest V4e isopter “points” to the blind spot, in arcuate fashion.

Foster Kennedy syndrome combines optic atrophy in one eye with papilledema in the other (59). The classic cause is an orbitofrontal mass such as a meningioma causing an ipsilateral compressive optic neuropathy and contralateral papilledema from raised intracranial pressure (not expressed in the ipsilateral eye because of the atrophy). Usually this presents with progressive visual loss in the ipsilateral eye and no visual change other than an enlarged blind spot in the other eye.

Like all classic signs, its mimics are more common than the real thing. Bilateral sequential AION or optic neuritis is more frequent than the neoplastic version of Foster Kennedy syndrome (60). The difference is that the edematous eye in ischemic or inflammatory conditions has significant visual loss, and the deficit in the other eye is static rather than progressive.

In nonarteritic AION, about 20% of patients develop a second episode over the next 5 years (61). There is some marginal evidence that aspirin might reduce this risk by about half.

HISTORY AND EXAM

This 47-yr-old man with 9 years of known hypertension was hospitalized with a severe hemorrhage from an ulcer, precipitated by the use of ibuprofen and requiring transfusion with 6 units of blood. At this time he rapidly developed bilateral visual loss, which improved slightly 4 days later. When reviewed 6 months later, he had visual acuity of

20/30 OD and no light perception OS. Ishihara color score was 0/14 OD. There was a large RAPD OS, with some weak light reaction still present OS. There was diffuse pallor of both optic discs, worse OS.

DISCUSSION

Field description: Superior arcuate defect and inferior nasal step extending to inferior macula OD, complete loss OS.

Localization: Bilateral optic nerves. Pathology: Ischemic optic neuropathy.

Confrontation testing showed preserved superior and inferior temporal islands of vision to light OD.

The patient’s defect OD is complex. The superior defect begins at the disc as a zone of relative depression but quickly becomes a dense arch heading to the nasal meridian, in which the V4e isopter is not seen in the zone between 10 and 25° eccentricity. Inferiorly there is a dense nasal step defect, merging into an inferior hemimacular hole. Although he cannot see the V4e target OS, confrontation testing shows some residual glimmer of perception when a light is shone into the eye rather than projected onto a screen. This residual vision also explains the persisting weak pupillary light reaction and reminds us that

one cannot conclude total blindness just because a patient cannot see the biggest target in a perimetric test.

Severe hypotension or blood loss can precipitate ischemic optic neuropathy, particularly in patients with hypertension, as here, or atherosclerosis. Ischemia may occur either at the disc (AION) or behind it (posterior ischemic optic neuropathy [PION]) (62,63). The difference is that acutely the former has edematous optic discs, whereas the latter has normal discs. After a few months, both resolve into optic atrophy, as seen here. Since no one bothered to record this patient’s fundoscopic findings in the hospital, we do not know which he had.

Besides gastrointestinal bleeding, other high-risk situations for this complication include cardiac surgery and lumbar spine surgery. Bilateral visual loss in the setting of hypotension could also be caused by occipital ischemia but would cause homonymous bilateral hemianopic defects without RAPD or optic atrophy, which is not the pattern in this case.

HISTORY AND EXAM

This 39-yr-old woman had a gradual decline in visual acuity over the course of many years, with the right eye worse than the left. She did not smoke or drink and was not a vegetarian. Visual acuity was 20/30 OD and 20/20 OS. Ishihara color plates were 2/14 OD

and 13.5/14 OS. There was a small RAPD OD. Optic discs were large and mildly pale. The remainder of the examination was normal.