A sudden change in vision in one eye, such as blurring, partial or complete loss of sight, flashes of light, new floaters, or blind spots, requires immediate medical evaluation. This abrupt alteration in visual acuity signals a potential underlying issue.
Disruptions to Ocular Blood Flow
Conditions affecting the blood supply to the eye can lead to rapid vision changes. A retinal artery occlusion, often described as a “stroke” of the eye, occurs when a blockage in the retinal artery causes sudden, painless vision loss. This blockage can be complete, affecting the entire central retinal artery, or partial, affecting a branch of it.
A retinal vein occlusion occurs when a vein draining blood from the retina becomes blocked. This can cause blood and fluid to leak into the retina, resulting in blurred or partial vision loss, which may develop suddenly. The accumulation of fluid can lead to swelling in the macula, impacting central vision.
Amaurosis fugax involves a temporary loss of vision in one eye, often described as a curtain descending over the field of vision, which typically lasts for minutes. This transient episode is a warning sign of a temporary blockage in a blood vessel supplying the eye, often associated with transient ischemic attacks (TIAs) or mini-strokes. A vitreous hemorrhage, which is bleeding into the vitreous humor, the jelly-like substance filling the eye, can cause sudden floaters, cobweb-like visual disturbances, or a general blurring of vision.
Retinal and Optic Nerve Damage
Direct damage or dysfunction of the retina or the optic nerve can also cause sudden vision changes. Retinal detachment occurs when the light-sensitive retina pulls away from its supporting tissue at the back of the eye. This separation can cause symptoms such as flashes of light, a sudden increase in floaters, and the sensation of a shadow or curtain obscuring part of the vision. If left untreated, retinal detachment can lead to permanent vision loss due to the retina losing its blood supply.
Optic neuritis involves inflammation and swelling of the optic nerve, the bundle of nerve fibers that transmits visual information from the eye to the brain. This condition typically causes pain with eye movement and can lead to blurred, dimmed, or even sudden loss of vision in the affected eye, with colors often appearing “washed out.” Optic neuritis is frequently linked to autoimmune conditions like multiple sclerosis.
Wet macular degeneration, a form of age-related macular degeneration (AMD), involves the abnormal growth of fragile blood vessels under the macula, the central part of the retina responsible for sharp, detailed vision. These new vessels can leak blood or fluid, causing sudden distortion or a blind spot in central vision, and can lead to rapid and severe vision loss. This condition can progress very suddenly, sometimes within a single day.
Other Acute Visual Impairments
Other distinct conditions can also lead to sudden visual changes in one eye. Acute angle-closure glaucoma is characterized by a rapid and significant increase in pressure inside the eye. This sudden pressure spike can cause severe eye pain, redness, blurred vision, and the perception of halos around lights, and it constitutes a medical emergency.
Migraine aura can cause temporary visual disturbances that may precede a migraine headache, although they can sometimes occur without a headache. These visual phenomena can include flashing lights, zigzag lines, brightly colored spots, or blind spots, and typically last less than an hour. While often associated with a headache, these visual symptoms can appear independently.
An eye injury or trauma, such as from blunt force or a penetrating object, can directly cause sudden vision loss. Internal damage from such injuries, including bleeding within the eye or damage to the retina or optic nerve, can result in immediate and sometimes permanent visual impairment.
Giant cell arteritis (GCA), also known as temporal arteritis, is an inflammatory condition affecting blood vessels, particularly those in the head and neck. If the blood supply to the optic nerve is disrupted due to this inflammation, it can lead to sudden, often permanent, vision loss in one eye. Associated symptoms can include a new persistent headache, jaw pain when chewing, and scalp tenderness.
When to Seek Immediate Medical Attention
Any sudden change in vision in one eye requires immediate medical attention. Prompt evaluation helps identify the cause and initiate treatment, which can prevent permanent vision loss. Delaying medical attention can worsen the outcome for many eye conditions.
Contact an eye doctor or proceed to an emergency room immediately if experiencing symptoms such as sudden blurred vision, partial or complete vision loss, new flashes of light, an increase in floaters, or a shadow appearing in the visual field. Additional concerning symptoms include eye pain, headache, nausea, weakness, or speech changes accompanying the vision alteration. Swift action is essential to preserving vision.