A sudden blind spot, medically termed a scotoma, refers to an area within your field of vision where your sight is reduced or entirely absent. Unlike a general blurriness, it is a distinct patch where information is missing. This visual phenomenon can be quite alarming due to its abrupt onset.
What a Sudden Blind Spot Is
A sudden blind spot is a new and noticeable visual field defect, distinct from the normal physiological blind spot that the brain typically compensates for. Unlike the normal blind spot, a sudden blind spot was not previously present and warrants attention.
Common Temporary Causes
Temporary blind spots can arise from conditions that do not cause permanent damage to the eye or brain. Ocular migraines, also known as retinal migraines, are a rare condition that can lead to temporary blind spots, flashes of light, or vision loss in one eye. These symptoms usually resolve within an hour and are characterized by a temporary reduction in blood flow to the retina or behind the eye.
Another common cause is a migraine with aura. Many migraine sufferers experience visual aura symptoms, which can include shimmering, zigzag lines, flickering lights, or blind spots in both eyes. These visual disturbances typically last between 5 minutes and an hour and may occur with or without a subsequent headache. The visual aura often starts as an area of impaired vision surrounded by shimmering zigzag lines that gradually enlarge before dissipating.
Serious Underlying Causes
Sudden blind spots can also indicate more serious underlying medical conditions affecting the eye or brain.
Retinal detachment is a condition where the retina, the light-sensitive tissue at the back of the eye, pulls away from its supporting layers. This can cause a sudden blind spot, often described as a shadow or curtain falling across the vision, and may be accompanied by new flashes of light or numerous floaters. Prompt treatment is necessary to prevent permanent vision loss.
Wet age-related macular degeneration (ARMD) involves the growth of abnormal blood vessels under the macula, the central part of the retina responsible for sharp, detailed vision. These vessels can leak fluid or blood, leading to rapid vision distortion and a sudden blind spot in central vision. This condition progresses quickly and requires immediate medical intervention to preserve sight.
Central retinal artery occlusion or central retinal vein occlusion are conditions where blood flow to or from the retina is blocked. An artery occlusion, often described as an “eye stroke,” causes sudden, painless, and severe vision loss or a large blind spot in one eye. A vein occlusion can also lead to sudden blurry vision or blind spots due to blood and fluid leakage into the retina.
Glaucoma can cause a sudden blind spot, especially acute angle-closure glaucoma, along with severe eye pain, headache, nausea, and blurred vision. This occurs when the eye’s drainage system becomes blocked, leading to a rapid increase in intraocular pressure. In advanced stages of open-angle glaucoma, gradual vision loss can also manifest as blind spots, though these are typically not sudden.
Optic neuritis, an inflammation of the optic nerve, can lead to sudden vision loss or a blind spot, often accompanied by pain with eye movement. This condition can be associated with autoimmune diseases like multiple sclerosis. The inflammation disrupts the transmission of visual information from the eye to the brain.
Neurological causes include transient ischemic attack (TIA) or stroke, which affect blood flow to the brain, including areas responsible for processing vision. A TIA, often called a “mini-stroke,” can cause temporary blind spots, tunnel vision, or loss of vision in one eye. A full stroke affecting the visual cortex or optic pathways can result in permanent blind spots or total vision loss in specific areas of the visual field.
When to Seek Urgent Medical Care
Any new, sudden, persistent, or worsening blind spot in your vision warrants immediate evaluation by a healthcare professional. Prompt diagnosis is important to prevent permanent vision loss or address a potentially life-threatening condition.
Specific red flags include the blind spot appearing with associated eye pain, new flashes of light, or a sudden increase in floaters, which are small specks or strands that drift across your vision. Other concerning symptoms that require immediate medical evaluation include a sudden headache, weakness or numbness on one side of the body, or changes in speech.