A scotoma is a blind spot, an area of partial or complete vision loss within your field of vision. This visual abnormality can occur in one or both eyes, affecting your ability to see clearly in a specific location. The word “scotoma” originates from the Greek word for darkness. While everyone has a natural blind spot where the optic nerve connects to the retina, a scotoma refers to an abnormal blind spot that may indicate an underlying health issue.
Understanding Scotoma
A scotoma can manifest in various ways, with individuals experiencing it as a blurry spot, a dark patch, a flickering area, or an empty space in their vision. The characteristics of a scotoma, such as its size, shape, and location, can vary significantly. Some scotomas are temporary, resolving on their own, while others can be permanent. The location of a scotoma profoundly impacts its effect on daily activities; for instance, a central scotoma, which affects the middle of your vision, can make tasks like reading or recognizing faces challenging. In contrast, peripheral scotomas, located at the edges of your visual field, may be less disruptive unless they are particularly large.
Scotomas are further categorized into “positive” and “negative” types based on how they are perceived. A positive scotoma is a blind spot that an individual actively sees, appearing as a dark, colored, or flickering spot. This type often suggests a problem with the retina. Conversely, a negative scotoma is an area of vision loss that the brain tends to “fill in,” making it unnoticeable to the individual. Negative scotomas may suggest issues with the optic nerve.
Common Causes
Scotomas can arise from various underlying conditions or factors that affect the visual system, including the retina, optic nerve, or parts of the brain responsible for vision. One common cause is migraine with aura, where temporary visual disturbances precede or accompany a headache. These scintillating scotomas usually last less than an hour.
Glaucoma, an eye disease characterized by increased pressure inside the eyeball, can damage the optic nerve and lead to gradual vision loss, often presenting as arc-shaped or ring-shaped scotomas. Macular degeneration, particularly age-related macular degeneration (AMD), frequently causes central scotomas due to the deterioration of light-sensing cells in the macula, the central part of the retina. Optic neuritis, an inflammation of the optic nerve, often results in acute, unilateral vision loss and can cause central scotomas.
Scotomas can also be a consequence of neurological events like a stroke, which can damage areas of the brain that process visual information, leading to blind spots in the visual field. Brain tumors, depending on their location and size, can exert pressure on the optic nerve or other visual pathways in the brain, causing scotomas or other visual field loss. Retinal detachment, where the retina pulls away from its normal position, can result in a growing blind spot, and if the macula detaches, central vision can be severely impacted. Certain medications can also list scotoma as a side effect, affecting vision.
When to Consult a Doctor
It is advisable to seek professional medical advice if you experience a scotoma or any new, sudden, or persistent changes in your vision. While some scotomas, such as those associated with migraines, may be temporary and benign, others can signal serious underlying conditions that require prompt diagnosis and management. For instance, a growing blind spot, especially if accompanied by flashes of light and floaters, could indicate a retinal detachment, which is a medical emergency requiring urgent attention. Do not attempt to self-diagnose any visual changes. Consulting an eye care professional, such as an optometrist or ophthalmologist, is recommended for evaluation to determine the cause and discuss next steps.