Transient Loss of Vision

Transient vision loss (TVL) is an ophthalmological symptom that instills apprehension in the minds of patients and clinicians. The patient is usually concerned that the loss is permanent, while the clinician focuses on ruling out severe underlying pathology. Causes vary and include life-threatening conditions such as carotid artery disease or cardiac emboli. Alternatively, a benign migraine can also cause transient vision loss. Appropriate assessment of patients presenting with this symptom is necessary to address the underlying cause adequately.

TVL is a temporary and sudden loss of visual acuity in 1 or both eyes. When multiple vision fields are affected, they may be called transient visual obscurations (TVOs). This condition can be alarming for patients and presents a diagnostic challenge for clinicians. Understanding the potential etiologies, associated anatomy, natural history, and spread patterns is crucial for effective diagnosis and management. Transient vision loss can occur in various clinical scenarios and is often a symptom of underlying systemic or ocular conditions. The duration of vision loss typically ranges from a few seconds to minutes and may occur intermittently. TVOs are often described as a gray or black curtain descending over the visual image and are sometimes accompanied by flashes of light (photopsia) or geometric shapes (scintillating scotomas). Transient vision loss can result from any disruption along the visual pathway.

The following structures may be disrupted:

1. Eye: The retina receives and processes light, converting it into neural signals. The macula of the retina plays a critical role in central vision. The central retinal artery, vein, and optic nerve head are essential for maintaining retinal function.

2. Optic nerve: This cranial nerve (CN II) transmits visual information from the retina to the brain and is susceptible to ischemia, inflammation, and compression.

3. Optic chiasm and tracts: The optic nerves partially cross here, forming optic tracts that convey information to the thalamus's lateral geniculate nucleus (LGN).

4. Lateral geniculate nucleus: Located in the thalamus, the LGN processes and relays visual information to the visual cortex.

5. Visual cortex: The primary visual cortex (V1) interprets the visual information received in the occipital lobe.

Common causes of transient vision loss may be grouped based on system or mechanism:

1. Vascular: Transient ischemic attacks (TIAs) affecting the ocular circulation, such as amaurosis fugax. These events are often harbingers of more severe cerebrovascular accidents (strokes).

2. Ocular: Conditions like giant cell arteritis (GCA), papilledema, and optic neuritis can lead to transient vision loss. GCA, an inflammatory condition affecting medium and large arteries, can cause severe visual impairment if untreated. Papilledema, caused by increased intracranial pressure, leads to transient obscuration due to optic nerve head swelling.

3. Neurological: Migraine with aura, characterized by visual disturbances preceding headache, is often accompanied by transient vision loss. Seizures and other cortical events can also produce transient visual symptoms.

4. Mechanical: Transient vision loss can occur due to mechanical pressure on the optic nerve or globe, as seen in certain head positions or during Valsalva maneuvers.

Transient vision loss can have various presentations based on multiple features:

1. Monocular vs binocular: Monocular vision loss suggests disruption anterior to the optic chiasm (ie, retina or optic nerve), while binocular loss typically results from post-chiasmal pathology (ie, optic tracts, LGN, or visual cortex).

2. Duration and frequency: Short, repetitive episodes typically indicate a vascular or mechanical cause, while longer durations are associated with inflammatory or demyelinating diseases.

3. Associated symptoms: The presence of pain (eg, optic neuritis), headache (eg, migraines), or systemic symptoms (eg, jaw claudication in GCA) can guide the differential diagnosis. Early identification and treatment of the underlying causes are essential to prevent permanent visual loss and associated morbidity. Transient vision loss is a concerning symptom requiring a thorough evaluation to rule out potentially life-threatening conditions.