Sudden blindness, or acute vision loss, is a rapid reduction in the ability to see, occurring over seconds to a few days. This abrupt change can affect one or both eyes, manifesting as a complete blackout, significant blurring, or the loss of a specific part of the visual field. Sudden vision loss is always a medical emergency requiring immediate professional evaluation, regardless of whether it is painful or painless. Causes range from structural issues within the eyeball to problems affecting the blood supply or the neurological pathways leading to the brain. Recognizing the distinct symptoms associated with these origins is important for understanding the necessary medical response.
Causes Originating in the Eye
Structural or pressure-related problems within the eye can cause rapid vision deterioration.
Retinal Detachment
Retinal detachment occurs when the light-sensitive retina pulls away from the underlying blood vessels that supply it. Patients often report a sudden increase in flashes of light or numerous small specks (floaters). This can progress to a shadow or a curtain moving across the field of vision. Prompt surgical intervention is needed to reattach the retina and prevent permanent vision loss.
Acute Angle-Closure Glaucoma
This condition involves the rapid increase of fluid pressure inside the eye. The iris blocks the drainage angle, preventing aqueous humor fluid from exiting. The sudden rise in intraocular pressure damages the optic nerve quickly, causing severe eye pain, headache, nausea, and the perception of colored halos around lights.
Vitreous Hemorrhage
A vitreous hemorrhage is bleeding into the clear, jelly-like substance filling the eyeball. This causes sudden vision loss that often presents as a dense cloud or a shower of new, dark floaters. This bleeding frequently occurs in people with diabetic retinopathy or those who have suffered eye trauma.
Causes Related to Blood Flow Blockages
Vascular events that obstruct blood flow to the visual system are serious and time-critical causes of sudden vision loss.
Central Retinal Artery Occlusion (CRAO)
CRAO, often called an “eye stroke,” happens when the main artery supplying the retina becomes blocked, typically by an embolus from the carotid arteries or the heart. This blockage results in a nearly instantaneous, profound, and usually painless loss of vision in one eye. Because the retina’s delicate tissue can only survive for a very short time without oxygenated blood, the therapeutic window for intervention is narrow.
Central Retinal Vein Occlusion (CRVO)
CRVO involves a blockage in the main vein that drains blood from the retina. The onset of vision loss is usually less sudden and less severe than with CRAO, presenting more as a gradual blurring or dimming of sight.
Giant Cell Arteritis (GCA)
Giant Cell Arteritis (GCA) is a systemic inflammatory condition affecting arteries throughout the body, including those supplying the optic nerve. If the inflammation restricts blood flow, it can cause vision loss often preceded by symptoms like a new, persistent headache, jaw pain when chewing, and scalp tenderness. Without immediate treatment, GCA carries a high risk of rapidly progressing to blindness in the second eye.
Causes Stemming from the Optic Nerve and Brain
Sudden vision loss can result from problems affecting the optic nerve or the visual processing centers in the brain.
Optic Neuritis
Optic neuritis involves inflammation and damage to the optic nerve, the bundle of fibers transmitting visual information from the eye to the brain. This condition typically causes vision to deteriorate over several days and is associated with pain upon moving the affected eye, along with a dulling of color perception. Optic neuritis is often an early sign of demyelinating diseases like Multiple Sclerosis.
Stroke and Visual Field Loss
A stroke that affects the visual cortex in the occipital lobe can cause sudden vision loss in specific parts of the visual field, known as a homonymous hemianopia. Because the brain’s visual pathways are crossed, a stroke on one side of the brain will affect the corresponding visual field in both eyes. Although central visual acuity may remain normal, the loss of peripheral vision can be profound.
Transient Ischemic Attack (TIA)
A TIA, or amaurosis fugax, involves a brief, painless episode of monocular vision loss described as a shade or curtain coming down over the eye. While the vision returns completely, amaurosis fugax is a critical indicator of potential future stroke risk, usually due to an embolus from the carotid artery.
Migraine Aura
Temporary disturbances can originate from neurological events such as a migraine aura. Visual symptoms can include temporary blindness or a scintillating scotoma, which is an expanding area of flickering, zigzag lines or shimmering light. Unlike ischemic events, migraine auras are characterized by these “positive” visual disturbances. The vision loss associated with a migraine is temporary and resolves completely.
Immediate Steps to Take When Vision is Lost
Sudden vision loss demands immediate medical attention, regardless of whether pain is present. The most important action is to call emergency services or proceed immediately to the nearest emergency room. Do not attempt to drive yourself, as impaired vision poses a significant danger.
When communicating with medical staff, provide specific details about the onset of symptoms. Note the exact time the vision loss began and describe any associated symptoms, such as headache, jaw pain, or pain with eye movement. Providing an accurate list of current medications and pre-existing conditions, like diabetes or high blood pressure, helps physicians narrow down the potential cause. Timely presentation allows for rapid triage and the initiation of sight-saving treatments.