Scotomas (Blind Spots): Causes & Treatment
Vision is one of the most essential senses we rely on to interact with the world. The eyes
and the brain work together to create a picture of our surroundings, but the system is not
flawless. Almost everyone has a natural blind spot in each eye where the optic nerve exits the
retina. This blind spot is where the optic nerve leaves the eye because in that area there are no
photoreceptors. Most people never notice their blind spot because the brain fills in the missing
information. However, some people develop additional blind spots that are more disruptive to
a patient’s life.
What is a Scotoma?
A scotoma is an area of alteration in a person’s field of vision. It is essentially a
blind spot where vision is reduced or totally absent. If the vision is reduced it is called a relative
scotoma, and if vision if totally absent it is referred to as an absolute scotoma.
In medicine, a scotoma refers to an area of partial alteration or complete loss of vision
within an otherwise normal visual field. Patients may describe them as gray patches, blurry
zones, or missing pieces in their sight. There are several different types of scotomas including
central, paracentral, peripheral, positive and negative.
Central scotomas are located at the center of vision. This can make reading, recognizing
faces and detailed work very difficult. These are commonly caused by age related macular
degeneration or optic neuritis. Paracentral scotomas are blind spots near the center of vision.
They interfere with tasks that require focusing slightly off-center, such as reading across a line
of text. Peripheral scotomas are in the outer field of vision. These may go unnoticed for a long
time but can cause problems with mobility, navigation, or driving.
A positive scotoma is when a person sees a dark, blurry, or shimmering spot in their
vision. A negative scotoma is when the spot is not consciously seen, but testing reveals missing
vision.
What Causes Blind Spots?
Scotomas can arise from a wide variety of causes, ranging from eye diseases to
neurological conditions. The underlying issue is usually damage to the retina, optic nerve, or the
visual processing centers in the brain. Some common retinal causes include age related macular
degeneration, diabetic retinopathy, retinal vein or artery occlusion or retinal detachments or
tears. Some common optic nerve disorders include optic neuritis, glaucoma or ischemic optic
neuropathy. Some common neurological causes include stroke, brain tumors or brain injury.
Treatment Options for Scotomas
Treatment options for scotomas depend heavily on their cause, size, and impact on daily
functioning. While some scotomas are permanent due to irreversible tissue damage, others can
improve with treatment or be adapted to with rehabilitation strategies. If the scotoma is
caused by a treatable retinal, optic nerve or neurological disease, then treating the underlying
cause can make the scotoma resolve or improve.
If a scotoma is permanent, patients can adapt with rehabilitation strategies such as low
vision aids, eccentric viewing training or orientation and mobility training. Assistive technology
such as screen-reading software and text-to-speech programs, contrast-enhancement tools and
even augmented reality (AR) glasses can all be implemented to help a patient function better in
their day-to-day life.
