A scotoma is a strange name for a common problem. A scotoma, pleural is scotomata, is an area of diminished or absent vision that is surrounded by an area of normal or near normal vision. It comes from the Greek work for darkness. Patients with scotomata usually comment that there is a part of the vision in one eye that is blind or abnormal.
When patients present to the office with these complaints, it’s not difficult to recognize that they have a scotoma. The trick is to figure out what’s causing them, and what can be done. Causes can range from simple transient problems to really serious vision threatening diseases. A scotoma can be an early sign of major problems like MS, or can be symptom so retinal diseases.
By far the most common cause of scotomata is migraine. In migraine patients many times neurologic symptoms precede the headache. One of the most common symptoms is scintillating scotomata. These are described as flashing yellowish lights in the vision. Usually they resolve about the time the migraine headache begins. This is called migraine with aura, or classic migraine. When this history is given by the patient it’s pretty simple to understand and explain the scotomata, and treatment is simply treatment for the migraine. If the migraines are frequent patients may benefit from preventative therapy, and if infrequent abortive treatment to use early in the course of migraine is usually indicated. The scotomata can actually be somewhat helpful in making it clear to the patient that they are starting a migraine, and lead them to early treatment to prevent the severe migraine.
Here is an simulated You Tube of a Scintillating Scotoma as an aura to a migraine headache:
Other scotomata can be causes by more serious problems. Anything that causes a part of the retina to not function can cause a loss of part of the visual field. Examples are macular degeneration, blockage of a blood vessel in the retina, and demyelinating diseases like multiple sclerosis. Tunnel vision is a type of scotomata where the central vision is preserved and the peripheral vision is lost. Reinitis pigmentosa, a congenital cause of vision loss can present with a peripheral ring scotoma. Patients with diabetes who have laser treatment of abnormal blood vessel growth can have scotomata in the areas where the retinal vessels have been coagulated.
If you suspect a scotoma you can close the unaffected eye, and fix your vision on something to hold the eye still. Then move an object like the eraser on a pencil, or your thumb around the field of vision. You should notice the loss of vision when the object enters the scotoma.
If you suspect a scotoma you should definitely seek medical attention to find out what’s wrong and to see how to manage the problem. Most of the time unless the problem is scintillating scotomata with migraine, an ophthalmology consultation is going to be needed. Your opthalmologist is likely to do formal visual field testing, a dilated fundoscopic exam, and possibly brain and optic nerve imaging with MRI to try to determine the cause. Sometimes more sophisticated ways to look at the circulation of the eye is needed.
If nothing else today you’ve learned a cool new word that is also used in by psychologists to describe a mental blind spot as in the the inability to see something that is obvious because of a psychological block.