Gaze-Evoked Amaurosis
Article summary goes here.
Disease Entity
Gaze-Evoked Amaurosis
Disease
Gaze-evoked amaurosis (GEA) is a unique cause of transient vision loss whereby patients experience vision loss only in a particular direction of eccentric gaze, almost always caused by intraconal tumors causing position-dependent compression of the optic nerve.[1]
Etiology
When a history of gaze-evoked amaurosis is elicited, or if it can be demonstrated on exam, a search for orbital pathology should be conducted. In over 80% of reported cases, intraconal pathology is the cause. Examples of reported compressive pathologies that cause GEA include foreign bodies, facial fractures,[2] and tumors such as optic sheath meningiomas, cavernous hemangiomas, or optic nerve gliomas,[3] as well as inflammatory conditions like sarcoidosis.[4] Extraconal pathologies, though less common, may also cause gaze-evoked amaurosis if large enough to put pressure on the optic nerve.[2] A case of idiopathic intracranial hypertension causing GEA was reported, in which it was proposed that in an eccentric position of gaze, ischemic compression of a tense dilated optic nerve sheath can result in further elevation of intrasheath pressure, compromising blood flow to the retina. [5]
Pathophysiology
The exact mechanism behind gaze-evoked amaurosis has not been clearly defined. It seems most likely that position-dependent compression of the optic nerve results in inhibition of axonal impulse propagation through the nerve, causing transient vision loss. Another theory that has been postulated is that compression causes optic nerve ischemia, which results in temporary vision loss.[1]
History
Some patients may not initially notice their visual symptoms, especially because the amaurosis is only exacerbated in specific gaze positions. However, with a directed history patients may report vision loss when turning their heads and maintaining eccentric gaze, such as when driving or shaving one’s armpits. The vision loss returns to baseline when gaze is returned to primary position.
Physical examination
Examination should start with assessing vision, pupils, pressure, and color in primary gaze for an established baseline. From there, evaluating sustained eccentric gaze in the different cardinal positions should be performed for at least 10-15 seconds. If gaze-evoked amaurosis is elicited, patients will likely subjectively complain of central vision loss, visual field defect, or color desaturation. An afferent pupillary defect may be present in eccentric gaze only. Though one should try to spare prolonged optic nerve compression, if intraocular pressures are taken in the gaze of amaurosis, they may reveal elevated readings.[3] On return to primary gaze, the findings should resolve to baseline within a few seconds.
Most commonly, having a patient look the opposite direction to where the pathology is located elicits amaurosis; for example, a patient would experience vision loss when abducting their eye if the lesion was medial to the nerve. However, this is not always a consistent finding and should not be used to localize the disease.[2]
Depending on the degree of baseline optic neuropathy, central vision, color vision, and visual fields may be variably affected. Dilated fundus exam often reveals a swollen optic disc given the most found intraconal optic nerve compression.
Management
Treatment of amaurosis is aimed at its underlying etiology. If an orbital mass is found on imaging, depending on size and clinical presentation, an orbitotomy may be indicated to remove the mass and assess its pathology. If imaging reveals a displaced fracture, repair of the fracture is usually indicated. Following treatment of the underlying cause, most patients experience resolution of the gaze-evoked amaurosis and its other manifestations (APD, decreased visual acuity, color desaturation, etc.)
Prognosis
The presence of gaze-evoked amaurosis is not predictive of permanent vision loss. Most patients who receive treatment for the underlying cause of their amaurosis will experience a return to visual baseline and resolution of abnormal exam findings.[3]
References
- ↑ 1.0 1.1 Orcutt JC, Tucker WM, Mills RP, Smith CH. Gaze-evoked amaurosis. Ophthalmology. 1987;94(3):213-218.
- ↑ 2.0 2.1 2.2 Otto CS, Coppit GL, Mazzoli RA, et al. Gaze-evoked amaurosis: a report of five cases. Ophthalmology. 2003;110(2):322-326.
- ↑ 3.0 3.1 3.2 Bradbury PG, Levy IS, McDonald WI. Transient uniocular visual loss on deviation of the eye in association with intraorbital tumours. J Neurol Neurosurg Psychiatry. 1987;50(5):615-619.
- ↑ Sheth HG, O’Sullivan EP, Graham EM, Plant GT. Gaze-evoked amaurosis in optic neuropathy due to probable sarcoidosis. Eye . 2006;20(9):1078-1080.
- ↑ O’Duffy D, James B, Elston J. Idiopathic intracranial hypertension presenting with gaze-evoked amaurosis. Acta Ophthalmol Scand. 1998;76(1):119-120.
