Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota.
Address correspondence to James A. Garrity, MD, Mayo Clinic, 200 First Street SW, Rochester, MN 55905; E-mail: email@example.com
A 60-year-old man with worsening Graves ophthalmopathy complained of complete loss of vision in the left eye on upgaze (“gaze-evoked amaurosis” [GEA]). Examination disclosed congestive orbital signs bilaterally. Upon upgaze, intraocular rose from 18 to 35 mm Hg in the left eye and visual acuity fell in that eye from 20/25 to no light perception. Evidence of optic nerve dysfunction and a swollen optic disc were present in the affected eye, and CT showed enlarged extraocular muscles with apical orbital compression of the optic nerve. Fundus photography performed during GEA disclosed blanching of the optic disc surface vessels in the affected eye. Surgical orbital decompression alleviated the congestive features and optic neuropathy and eliminated the GEA. This is the second case of GEA to be reported in Graves ophthalmopathy and the first to document blanching of optic disc vessels. The presumed mechanism of GEA in this patient is optic nerve ischemia, perhaps provoked by an elevation in intraocular pressure in a congested optic disc.
A 60-year-old man noted simultaneous onset of hyperthyroidism and orbital swelling. He was treated with radioactive iodine 1 month later, followed by oral replacement thyroid hormone. The orbital swelling was progressive such that 60 mg/day prednisone was started and tapered over 1 month. The orbital manifestations improved, only to worsen when the prednisone was tapered. Having been a heavy cigarette smoker, he had stopped completely 3 months later.
Our initial examination, 8 months after discontinuation of prednisone, disclosed a best-corrected visual acuity of 20/25 in each eye. The pupils were of normal size and reactivity and color vision (by Ishihara plates) was normal. The eyelids were mildly edematous and erythematous, and the conjunctiva and episclera were injected over the rectus muscle insertions. Each caruncle was mildly chemotic, as was the lateral conjunctiva bilaterally. Exophthalmometry was 25 mm bilaterally with moderate nontender resistance to retropulsion. Diplopia was present at the extremes of gaze. Ocular ductions were normal in adduction, mildly reduced in abduction, and severely reduced in supraduction bilaterally. There was some discomfort with eye movement. Each optic disc appeared normal with a small cup. There were no choroidal folds. There was no evidence of pretibial myxedema or thyroid acropachy. No therapy was given.
When we reexamined him 2 months later, he reported more painful eye movements and complete loss of vision in the left eye when he looked upward. The visual loss began with peripheral constriction and progressed to no light perception in the left eye. With return to primary gaze, the visual recovery began from the center and would be complete within 30 seconds.
Best-corrected visual acuity was 20/25 in both eyes but there was a trace left afferent pupillary defect while the eyes were in primary position. He could identify all Ishihara color plates with either eye but was more hesitant when viewing with the left eye. There was now more evidence of congestion and injection of the conjunctiva in both eyes. Exophthalmometry had increased to 27 mm bilaterally.
Ophthalmoscopy disclosed choroidal folds extending across each fovea. The right optic disc was mildly swollen (Fig. 1A); the left optic disc was massively swollen (Fig. 1B). In primary gaze position, the intraocular pressure was 18 mmHg bilaterally. In upgaze and during the visual loss, it was 33 mmHg in the right eye and 35 mmHg in the left eye as measured by a Perkins tonometer. The left optic disc blanched markedly during the visual loss, a feature confirmed with fundus photography (Fig. 1C). It resumed its baseline swollen appearance 2 minutes after the patient's eyes had returned to primary position (Fig. 1D).
Automated visual fields showed nerve fiber bundle defects that were more pronounced in the inferior visual field in both eyes and in the left than the right eye (Fig. 2). Orbital CT showed symmetric enlargement of all the rectus muscles with apical crowding bilaterally (Fig. 3).
The patient underwent bilateral transantral orbital decompression. The gaze-evoked amaurosis (GEA) ceased almost immediately. When he was reexamined 6 weeks later, visual acuity was 20/20 in each eye. There was a 5-mm reduction in proptosis. Bilateral medial rectus recession led to resolution of the diplopia. Follow-up visual field examination showed marked improvement in both eyes (FIG. 4).
Our patient manifested GEA, an uncommon symptom in which transient visual loss occurs when the affected eye is voluntarily moved into eccentric gaze. The GEA in the left eye consisted of a reduction of vision to no light perception and occurred in upgaze, when the intraocular pressure rose from 18 to 35 mmHg. During the GEA, the optic disc surface vessels, but not the retinal arteries, blanched, indicating a diminution in blood flow to the optic nerve.
Our patient manifested massive optic disc edema and optic nerve dysfunction in the affected eye (afferent pupil defect and visual field loss) attributed to apical orbital compression from enlarged extraocular muscles. After surgical orbital decompression, all manifestations, including the GEA, resolved.
In most reported cases, GEA has occurred in association with an intraorbital process (1), but it has been reported in Graves ophthalmopathy only once (2). The other reported case was a letter to the journal editor regarding a 62-year-old smoker with thyroid eye disease and bilateral GEA occurring on upgaze. This patient did not have evidence of optic neuropathy and was treated with corticosteroids, which resulted in resolution of the amaurosis.
First described 30 years ago (3), GEA usually results from intraconal orbital masses such as optic nerve sheath meningiomas (3-8) and cavernous hemangiomas (9-11) and less commonly from retained metallic foreign body (12), orbital metastasis from renal cell carcinoma (13), traumatic hemorrhagic cyst (3), optic nerve glioma (6,7), granular cell myoblastoma (7), and neurofibromatosis type II (14). There are a few reported cases of GEA due to pseudotumor cerebri (15,16) and with extraconal processes such as a juvenile nasopharyngeal angiofibroma (17), medial wall fracture (17), and osteoma (18).
The mechanism of GEA is thought to be ischemic (8). Wright et al (3) reported absence of retinal arterial blood flow on fluorescein angiography in a single patient with GEA from an optic nerve meningioma. In a case of GEA from a varix with hemorrhage, Knapp et al (4) demonstrated a complete absence of the arterial waveform in the central retinal artery during eccentric gaze that caused a decrease in vision to no light perception.
Our patient is unique in that we were able to demonstrate photographically a blanching of the optic nerve surface vessels but not the retinal vessels during GEA. Presumably the increased intraocular pressure associated with upgaze exceeded the intraocular perfusion pressure, leading to reversible optic nerve ischemia.
Our patient with GEA in Graves ophthalmopathy had evidence of optic nerve dysfunction. In the majority of the reported patients with GEA, baseline optic nerve dysfunction is present. In many of these patients, an afferent pupillary defect became more prominent in the eccentric gaze position that resulted in amaurosis. GEA has rarely been reported in patients with normal optic nerve function (1,2).
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