Gaze-evoked amaurosis

Key points at a glance

Key points of this disease

• Gaze-evoked amaurosis (GEA) is a condition in which transient vision loss occurs only when the eye is in a specific eccentric position.
• More than 80% of reported cases are caused by intraconal lesions (lesions within the orbital muscle cone).
• When the eye returns to the primary position (straight ahead), vision recovers to baseline within seconds.
• Relative afferent pupillary defect (RAPD) may appear only in the deviated eye position.
• Contrast-enhanced orbital MRI or orbital CT is essential for diagnosis, and identification of the causative lesion determines the treatment strategy.
• After treatment of the underlying disease, GEA and related findings disappear in most patients.

1. What is Gaze-Evoked Amaurosis?

Gaze-Evoked Amaurosis (GEA) is a specific cause of transient vision loss, where visual impairment is experienced only when the eyes are in a particular deviated position.

It is characterized by decreased vision only when the eye is turned in a specific direction (deviated eye position), with recovery upon returning to the primary position. Typically, it is caused by an intraconal tumor compressing the optic nerve in a gaze-dependent manner. In over 80% of reported cases, an intraconal lesion is involved.

Specific epidemiological data are not available in the literature, and this is known as a rare condition.

Q What is gaze-evoked amaurosis?

A

This is a condition in which transient vision loss occurs only when the eye is in a specific deviated position. The main cause is compression of the optic nerve by an orbital tumor or inflammatory lesion that depends on eye position, and vision recovers when the eye returns to the primary position.

2. Main symptoms and clinical findings

Subjective symptoms

• Transient vision loss: Vision decreases only in a specific deviated eye position and recovers when the eye returns to the primary position.
• Central vision loss / visual field defect: Noticed when amaurosis is induced.
• Color desaturation: May be accompanied by a sensation that colors appear less vivid.
• Difficulty noticing symptoms: Some patients do not notice visual symptoms initially because they are only triggered in certain eye positions.
• Triggers in daily life: Examples include noticing vision loss while looking sideways during driving or while shaving armpit hair, when maintaining a deviated eye position by turning the head or eyes.

Q In what situations are symptoms often noticed?

A

It is often noticed during daily activities such as turning the head to the side while driving or shaving armpit hair, when the head or eyes are turned in a specific direction and the deviated eye position is maintained. Because it is only triggered in certain eye positions, some patients do not notice symptoms initially.

Clinical Findings (Findings Confirmed by the Doctor During Examination)

During the examination, a baseline evaluation is performed in the primary position, followed by assessment of changes after maintaining each eccentric gaze position for 10 to 15 seconds.

• Baseline evaluation in primary position: Measure visual acuity, pupils, intraocular pressure, and color vision.
• Evaluation in eccentric gaze positions: Assess after maintaining an eccentric gaze position for at least 10 to 15 seconds in different basic gaze positions.
• RAPD (Relative Afferent Pupillary Defect): May be observed only in eccentric gaze positions.
• Elevated intraocular pressure: Intraocular pressure measured in the gaze position where amaurosis occurs may show elevated values (return to primary position promptly to avoid prolonged optic nerve compression).
• Recovery confirmation: When the eye returns to the primary position, visual acuity, pupil, and intraocular pressure findings recover to baseline within seconds.
• Relationship between eye position and lesion: Most commonly, amaurosis is induced when looking in the direction opposite to the lesion (though not always consistent).
• Optic disc edema: Fundus examination under mydriasis often reveals disc edema due to compression of the optic nerve within the muscle cone.
• Baseline optic neuropathy findings: Depending on the degree of compression, central visual acuity, color vision, and visual field may be variably affected.

3. Causes and Risk Factors

Lesions causing GEA are intraconal in more than 80% of cases. Extraconal lesions can also be a cause, but are less frequent.

Intraconal Lesions

Optic nerve sheath meningioma: A benign tumor arising from the optic nerve sheath. One of the most typical causes of GEA.

Cavernous hemangioma: An intraorbital vascular tumor. Also common within the intraconal space in Japan.

Optic nerve glioma: A glial cell tumor originating from the optic nerve.

Thyroid eye disease: Enlargement of extraocular muscles compresses the optic nerve within the intraconal space.

Sarcoidosis, idiopathic orbital inflammation, myositis: Compression due to inflammatory lesions.

Foreign body/facial fracture: Compression due to foreign bodies or bone fragments within the muscle cone caused by trauma.

Extraconal and other causes

Extraconal lesions: Although rare, they can cause GEA when large enough to compress the optic nerve.

Idiopathic intracranial hypertension (IIH): In deviated eye positions, the tense and distended optic nerve sheath becomes compressed, increasing intrasheath pressure and impairing retinal blood flow.

Cavernous sinus meningioma: There are case reports of compression of the carotid artery leading to decreased ophthalmic artery perfusion during abduction.

In Japan, the frequency of orbital tumors shows that lymphoproliferative diseases account for 50–60% of all cases, followed by cavernous hemangioma/capillary hemangioma, dermoid cyst, and pleomorphic adenoma of the lacrimal gland. Common intraconal tumors include vascular tumors (cavernous hemangioma, lymphangioma) and neural tumors (schwannoma, optic nerve sheath meningioma).

Common causes of compressive optic neuropathy include orbital apex lesions, such as thyroid eye disease, rhinogenic optic neuropathy, hemangioma, and lymphoma.

Q What is the most common lesion causing gaze-evoked amaurosis?

A

Over 80% of reported cases are due to intraconal lesions, with optic nerve sheath meningioma, cavernous hemangioma, optic glioma, and thyroid eye disease being typical causes. Extraconal lesions can also be responsible, but are less frequent.

4. Diagnosis and Examination Methods

History Taking

Confirm whether vision loss occurs when maintaining the deviated eye position. Carefully inquire about visual symptoms during daily activities (e.g., driving, specific movements).

Examination Procedure

1. Perform baseline evaluation (visual acuity, pupil, intraocular pressure, color vision) in primary gaze.
2. Evaluate sustained deviation in each cardinal gaze position for 10–15 seconds.
3. Check for RAPD appearance, intraocular pressure elevation, visual acuity decrease, and color desaturation in the deviated gaze.
4. Confirm recovery upon returning to primary gaze.

Imaging Tests

• Orbital MRI (with and without contrast): Best for identifying the causative lesion. Allows detailed evaluation of intra- and extraconal tumors, inflammatory lesions, and the optic nerve.
• Orbital CT (with contrast): Used for evaluating bony lesions or fractures, and as an alternative when MRI is not feasible.

Fundus Examination

Dilated fundus examination is performed to check for optic disc edema.

Differential Diagnosis

When diagnosing GEA, it is important to differentiate it from the following diseases.

Disease	Key differentiating features
Compressive optic neuropathy (general)	Slowly progressive, unilateral visual dysfunction, afferent pupillary defect, central scotoma
NA-AION (non-arteritic anterior ischemic optic neuropathy)	Acute onset, middle-aged or elderly, noticed upon waking in the morning, altitudinal visual field defect (especially inferior)

In compressive optic neuropathy, the extraocular muscles may hypertrophy at the orbital apex and compress the optic nerve, causing papilledema and redness. The mode of onset and visual field pattern are clues for differentiating from NA-AION.

5. Standard Treatment

The principle of treating GEA is to address the underlying disease. After treatment of the underlying disease, GEA and other signs (RAPD, decreased visual acuity, decreased color saturation, etc.) resolve in most patients.

Treatment strategies by causative disease are as follows:

• Optic nerve compression due to thyroid eye disease: First-line treatment is steroid pulse or half-pulse therapy. After 1–3 courses, switch to oral administration. If steroid-resistant, consider orbital decompression surgery.
• Orbital tumors (cavernous hemangioma, schwannoma, etc.): Surgical removal based on tumor type, location, and size is standard. For optic nerve sheath meningioma, radiation therapy may be selected in some cases.
• Idiopathic orbital inflammation/sarcoidosis: Steroid therapy is effective.
• IIH (idiopathic intracranial hypertension): Treatment to lower intracranial pressure (medical therapy or optic nerve sheath decompression) is indicated.

Precautions in treatment

When administering steroids for thyroid eye disease, the cumulative dose exceeding 8 g in prednisolone equivalent increases the risk of acute liver injury. Dose management and liver function monitoring are necessary.

Q Will vision recover after treatment?

A

After treatment of the underlying disease, GEA and related signs such as RAPD, visual acuity loss, and desaturation resolve in most patients. However, if optic nerve compression has been prolonged, complete recovery of visual function may not be achieved.

6. Pathophysiology and Detailed Mechanism

Two hypotheses have been proposed for the mechanism of GEA.

Axonal Conduction Block Hypothesis

Gaze-dependent optic nerve compression: When the eye is deviated, a tumor or enlarged extraocular muscle in the orbit compresses the optic nerve.

Inhibition of axonal impulse conduction: Mechanical compression disrupts impulse conduction within the axon, leading to transient vision loss.

Reversibility: Returning the eye to the primary position relieves compression, restoring impulse conduction and vision.

Ischemia Theory

Blood flow reduction due to compression: Mechanical compression by a tumor or hypertrophic muscle reduces blood flow to the optic nerve or retina.

Transient ischemia: Local ischemia causes temporary vision loss.

Special mechanism (IIH): In an eccentric eye position, the tense optic nerve sheath is compressed, increasing intrasheath pressure and impairing retinal blood flow.

In cases of cavernous sinus meningioma, a mechanism has been reported where the tumor compresses the carotid artery, and during abduction, stretching of adjacent tissues reduces ophthalmic artery perfusion.

As a common mechanism of compressive optic neuropathy, hypertrophy of the extraocular muscles at the orbital apex (funnel region) compresses the optic nerve, potentially presenting with papilledema and redness. If this persists, it may lead to findings resembling retrobulbar optic neuritis.

References

1. Orcutt JC, Tucker WM, Mills RP, Smith CH. Gaze-evoked amaurosis. Ophthalmology. 1987;94(3):213-218. doi:10.1016/s0161-6420(87)33471-2. PMID: 3587895
2. Otto CS, Coppit GL, Mazzoli RA, et al. Gaze-evoked amaurosis: a report of five cases. Ophthalmology. 2003;110(2):322-326. doi:10.1016/S0161-6420(02)01642-1. PMID: 12578775
3. Tsai RK, Chen JY, Wang HZ. Gaze-evoked amaurosis caused by intraconal cavernous hemangioma: a case report. Kaohsiung J Med Sci. 1997;13(5):324-327. PMID: 9226975
4. Orlans HO, Bremner FD. Dysthyroid Orbitopathy Presenting with Gaze-Evoked Amaurosis: Case Report and Review of the Literature. Orbit. 2015;34(6):324-326. doi:10.3109/01676830.2015.1078374. PMID: 26505217
5. Garg A, DeAngelis D, Hojilla CV, Micieli JA. Gaze-evoked amaurosis from idiopathic orbital inflammation. Orbit. 2022;41(5):620-623. doi:10.1080/01676830.2021.1904423. PMID: 33781156