The total area that your eye sees when focused on a fixed point is known as your visual field. Whenever you look at an image or object, the area of focus in the center part of your visual field comprises your central vision. The remainder of what you see and that is not in focus along the edge of your visual field is your peripheral vision. Think of it as what you can see out of the “corner of your eye” without turning your head.
Both diseases of the eye as well as problems in the brain can cause peripheral vision loss. This blog will examine peripheral vision loss, discuss ways to test for it, and explore how to treat it.
What Is Peripheral Vision?
The retina (the thin layer of tissue at the back of the eye) serves an important function in how we see the world. The retina senses light and sends a signal to the optic nerve, which carries this visual information to your brain where it is processed as vision. More specifically, cells in the retina called rods and cones respond to light in different ways to create your central and peripheral vision.
The macula, the central part of the retina, is made up of cones, which require high light levels, are sensitive to color, and provide clear central vision and focus on fine details. By contrast, the outer portion of the retina that makes up peripheral vision consists of rods, which provide vision in low light but do not provide color or much detail.
Peripheral Vision Loss
The loss of peripheral vision means you cannot see to the side without turning your head. A loss of side vision can affect your ability to safely navigate through your environment or detect motion around you. As peripheral vision loss progresses, it can create a condition called “tunnel vision” in which it is difficult, or impossible, to see the outer edges of your visual field.
To give you a sense of what this is like, look through a toilet paper roll while covering one eye. You will only be able to see what is directly in front of you, not what is on either side of you or above and below eye level.
Why Is My Peripheral Vision Blurry?
Oftentimes, blurry peripheral vision can be a sign of a serious condition and should not be ignored.
The following are common causes of blurry peripheral vision or peripheral vision loss:
Glaucoma: A buildup of intraocular pressure (IOP) causes damage to your optic nerve, which gradually deteriorates your vision. This vision loss begins on the periphery of your vision, more specifically toward the nasal portion of your visual field. If left untreated, the vision loss spreads to encompass more of your visual field and can lead to blindness.
Retinitis pigmentosa: There is no cure for this genetic disorder, which causes cells in the retina to break down, including the rods and cones, leading to blindness. Damage to the rods leads to loss of peripheral vision and difficulty seeing at night, which are early signs of retinitis pigmentosa.
Optic Neuritis: Inflammation of the optic nerve that can cause pain and result in temporary vision loss, including peripheral vision.
Optic nerve atrophy: In certain cases, the cells of the optic nerve can die due to a number of reasons including poor blood flow, lack of oxygen, glaucoma, trauma, or a congenital disease. This damage causes the loss of vision, including peripheral vision.
Compressive Optic Neuropathy: The optic nerve can also become damaged when it is compressed by a tumor or inflammation caused by conditions such as thyroid eye disease. Symptoms of compressive optic neuropathy include blurred vision and partial or complete vision loss.
Retinal detachment: Age, injury, diabetic scarring, or other conditions can cause the retina to detach from the back of the eye, which can cause severe vision loss or blindness. One common symptom of a detached retina is the darkening of your peripheral vision.
Papilledema: Also known as optic disc swelling, this condition occurs when raised intracranial pressure presses on the optic nerve from behind and causes it to swell. Peripheral vision loss can be one of the symptoms.
Head trauma/stroke: An accident, such as a traumatic brain injury, or a stroke, can damage your eye’s optic nerve and lead to peripheral vision loss.
How to Test Peripheral Vision
If you experience any difficulties with your peripheral vision, your eye doctor will perform testing to determine the extent of your visual field and/or visual clarity within your field of view. Such tests include:
Confrontation Visual Field Test
This simple test involves you covering one eye and looking at your eye doctor or eye care technician as they hold up fingers in your side vision and ask you to tell them how many fingers you see. They will then ask you to repeat this process with the other eye. The exam gives them a basic understanding of what you can see on the side when looking straight ahead at a fixed object. While the exam is easy to conduct and does not involve any instruments, it may not be as accurate in diagnosing small visual field defects.
Automated Static Perimetry Test
This test involves looking into a perimeter (a device used to test visual field) with one eye covered and pressing a button whenever you see lights appear. The lights will be present at varying spots, both in your central vision and peripheral vision. Failing to note when light appears to the side of the visual field will signal to your eye doctor that you may have an issue with your peripheral vision. Static perimetry tests are commonly used to monitor glaucoma and diseases of the macula.
Kinetic Visual Field Test
This test uses the same process as the perimetry test, but the kinetic test involves moving light in and out of your peripheral vision to map the edge of your visual field. Kinetic visual field tests are better suited for neuro-ophthalmological conditions and peripheral retinal diseases.
Peripheral Vision Loss Treatment
Depending on the cause of peripheral vision loss it can be either temporary or permanent. For example, reattaching a detached retina or reducing inflammation associated with optic neuritis can bring back lost peripheral vision. However, peripheral vision lost to glaucoma or retinitis pigmentosa cannot be regained.
The permanent loss of vision will require you to adjust how you interact with the world visually and there are low vision aids available to assist you. A few examples include prism eyeglasses that can redirect images to the center of your visual field or special lenses that reduce image sizes to compress more visual information into your available field of view.
Tell your eye doctor right away if you are experiencing changes to your peripheral vision. Early diagnosis and treatment of the underlying condition causing your peripheral vision loss is the best way to limit the damage. Even if you are note experiencing any symptoms, it is still a good idea to have regular, comprehensive eye exams so your eye doctor can detect issues before they become problems and keep your eyes healthy.