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Symptoms
Blind Spots
Blind spots in the vision are a serious symptom that needs to be urgently addressed by an eye care specialist. The medical term for a blind spot is a scotoma. The visual system is complicated but blind spots are most often due to an abnormality in the retina, the optic nerve tract or the visual centers of the brain. It is important to discover the cause of the blind spot since it may be progressive and permanent if not treated, and can sometimes be a warning sign of serious diseases that can affect other parts of the body. Blind spots can be distinguished from floaters by the fact that floaters continue to drift around in the vision after eye movement stops, but a blind spot will stop with eye movement. Also, floaters, which can look like a blurred screen in the peripheral vison, can be seen through, whereas a scotoma completely blocks out vision in the area.
Blind spots can be transient in some cases, lasting for minutes to hours or they can be permanent and progressive, worsening over time. Here are some of the most common causes of a blind spot or scotoma.
Causes
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Age related macular degeneration (AMD). Blind spots in this condition only involve the center of vision, never the peripheral vision. This is the reason that patients with AMD will never go totally blind as a result of this condition. With “dry” AMD, a central blind spot can develop, but this is slow. It usually takes a long time to develop a central blind spot that impedes the visual function (see Age related macular degeneration under “Diagnosis”). “Wet” AMD tends to develop much more quickly, sometimes in days or weeks. This is a more serious problem which requires a more urgent evaluation. Timely treatment can actually stop or reverse some of the vision loss in many cases.
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Retina detachment. The blind spot in a retinal detachment starts in the peripheral, or side vision first and gradually enlarges. This area often looks like a half moon or crescent. This can be distinguished from multiple floaters by the fact that nothing can be seen in the area affected, rather than it being just a blurred area. Once the blind area reaches the central vision the eye is no longer able to read or see any detail. It is important to try to stop the blind spot from progressing into the central vision, so an urgent evaluation is needed.
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Diabetic retinopathy. This condition can cause blind spots in the vision due to bleeding in the eye, a retinal detachment, or loss of circulation to areas of the retina. These blind spots can come on slowly or rapidly, and can involve any area in the vision.
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Macular hole. This is a condition involving the central area of the retina (the macula) caused by shrinkage of the vitreous gel which pulls on the macula resulting in a central hole. Often this starts with distortion of the central vision with central blurring, leading gradually to a central blind spot. This spot can gradually enlarge, but eventually stops and never involves the peripheral vision. The condition requires surgery in most cases.
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Migraine prodromes. This occurs in classic migraine headaches and sometimes, especially in older people, without headaches. This is a transient blind spot, most often in the peripheral vision, which starts small and gradually enlarges over a period of minutes. It can be associate with zig-zag flashing lights and can last for minutes or up to an hour. In classic migraines this is usually followed by a migraine headache. In older individuals, this is frequently the only symptom with no headache. This can occur in people who have never had a migraine headache when they were young. But many patients have a personal or family history of migraine headaches.
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Blockage of circulation to the retina. Conditions that cause a blockage of the arteries or veins in the retina (see “Retinal artery occlusions” and “Retinal vein occlusion” under “Diagnosis”) frequently present with the sudden onset of a blind area. This can be outside the center of vision but it can involve the center. It can also extend into the peripheral vision, but it usually doesn’t start in the far peripheral vision first. It usually comes on relatively quickly, within days or weeks. These conditions require a comprehensive eye evaluation, often with imaging tests, to determine the cause and whether they can be treated.
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Transient vision loss “like a shade” being pulled over the vision. When this comes on suddenly, lasts for minutes to an hour and goes away, leaving the vision almost normal, it is a very concerning sign for a possible TIA or “pre-stroke” symptom in the eye. The medical term is “Amauosis fugax”. This is an urgent condition because it can lead to a stroke only involving the eye, as described in the previous section, or to a full blown stroke involving other parts of the body.
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Other diseases that do not involve the retina can also cause blind spots in the vision, such as glaucoma, a stroke to the optic nerve or to the visual centers of the brain. These conditions can only be distinguished from retina problems with a thorough eye evaluation.
Since urgent treatment can improve the prognosis for preserving or restoring vision in some of these conditions, and it is not possible to diagnose these conditions without a thorough dilated eye examination, we recommend that people developing a new blind spot in their vision call an ophthalmologist as soon as possible to schedule an examination.