When you first learn to drive, you are taught to use your peripheral vision to check your mirrors and blind spots, but what exactly is peripheral vision?
What are the limits to a human’s peripheral vision? If you notice changes in your peripheral vision, is your eye or your brain affected? Most importantly, what types of eye disease or brain conditions result in a loss of peripheral vision?
What’s peripheral vision?
Peripheral vision refers to the area of sight outside of one’s central vision. It is the ability to see things outside of where you are directly looking. If you were to lose parts of your peripheral vision, you would be unable to see to the side without moving your head.
Normal visual fields are 100 degrees towards the ear, 60 degrees towards the nose and up, and 75 degrees down. A loss of vision in one quadrant is called a visual field defect.
As peripheral field loss progresses, a condition called “tunnel vision” may occur. If you ever looked through a paper towel roll as a kid, the experience is comparable to tunnel vision. Losing your peripheral vision can make it difficult to navigate the world and to perform tasks like driving and moving about safely.
What conditions affect your peripheral vision?
Any trauma, disease, or eye pathology that affects either the brain, retina, or optic nerve can affect your peripheral vision. Glaucoma and strokes are the most common conditions that affect your peripheral vision.
Conditions of the eye
Glaucoma, optic neuritis, retinitis pigmentosa, proliferative diabetic retinopathy, and retinal detachments are conditions of the eye that result in either permeant or temporary peripheral vision loss.
Glaucoma
Worldwide, glaucoma is the leading cause of irreversible vision loss. Patients are asymptomatic until the disease progresses to an advanced stage. Glaucoma is a progressive optic neuropathy characterized by the loss of the retinal ganglion cells and results in damage to the optic nerve.
There are several risk factors for developing glaucoma including high intraocular pressure. Reducing the pressure within the eye is the only way to slow damage to the optic nerve and preserve a patient’s visual field. In glaucoma, damage typically occurs to the inferior aspect of the nerve first, resulting in peripheral visual field loss in the upper part of the eye. Patients with glaucoma have visual field testing every six months to monitor changes in their peripheral vision.
Optic neuritis
Optic neuritis is an eye presentation of systemic inflammation which typically presents as sudden, unilateral loss of vision and pain when moving your eyes. Optic neuritis is most frequently associated with multiple sclerosis (MS).
Improvements in vision depend on the reason for the optic neuritis, the duration and severity of vision loss, and treatment. Visual field defects and the degree of peripheral vision loss can vary considerably with optic neuritis. IV and oral steroid treatment can speed vision recovery.
Retinitis pigmentosa
Retinitis pigmentosa (RP) is an inherited retinal disease without a known treatment. RP is a progressive condition that results in the breakdown of the retina over time resulting in vision loss. Patients with RP have difficulty with night and peripheral vision. The condition is identified by a doctor when patients present with the classic triad of artery attenuation, pigmentary changes in the retina, and waxy, whitening of the disc.
Proliferative diabetic retinopathy
Proliferative diabetic retinopathy (PDR) is an advanced stage of diabetic retinopathy, a common complication of diabetes that affects the blood vessels in the retina. The disease is characterized by:
- Neovascularization—The growth of new, abnormal blood vessels in the retina, which can lead to bleeding and scarring
- Vitreous hemorrhage—Leaking blood from the new vessels may fill the vitreous cavity, the clear gel-like substance that fills the eye
- Tractional retinal detachment—The abnormal blood vessels can cause scar tissue to form, which may pull the retina away from the back of the eye, leading to retinal detachment and severe vision loss.
Neovascularization must be treated with called pan-retinal photocoagulation (PRP). A laser is used to reduce the oxygen demand in the outer layers of the retina in order to divert adequate oxygen and nutrients to the usable areas of the retina. Unfortunately, the laser is used 360 degrees around the retina resulting in a permanent loss of the patient’s peripheral visual field.
Retinal detachment
Rhegmatogenous retinal detachment (RRD) is the most common type of retinal detachment. With this condition, fluid from the vitreous cavity leaks into the subretinal space, resulting in a separation of the retinal layers. Retinal detachments often result in a temporary field defect that appears like a bubble or curtain in the patient’s vision. A retinal detachment is considered an emergency. Once the surgery is performed, and the retina is tacked down, peripheral vision will be regained.
Conditions of the brain
A stroke, brain damage, or migraine may cause a temporary or permanent loss of one’s peripheral vision.
Stroke
After a stroke, patients often lose portions of their visual field. It is common to lose half of the visual field (right or left) in both eyes because the stroke affects the brain, located past the optic chiasm.
It is estimated that 20% to 57% of people who have had a stroke have visual field defects, However, it remains unknown whether interventions like treatment to improve scanning or prisms improve the patient’s daily living ability. Visual field defects vary depending on the portion of the brain affected by the stroke.
Brain damage
Traumatic brain injury (TBI) is a major cause of mortality and affects more than 1.7 million Americans each year. Depending on the location and the severity of the injury, parts of both the brain and eye can be affected.
Studies suggest TBI patients suffer from various vision-related issues including photophobia, double vision, blurred vision, loss of vision, palsy, optic nerve abnormalities, and visual processing problems. Optic nerve injury is the most common result after a TBI.
Migraine
A migraine headache may cause a temporary type of peripheral vision loss called a visual aura. The experience typically lasts for 20-30 minutes. Patients may experience blind spots, zig-zag lines, shimmering spots, or flashes of light. Migraines with visual aura are estimated to affect 8% of the general population and are a risk factor for several cardiovascular conditions including stroke, myocardial infarction, and atrial fibrillation.
How is peripheral field loss diagnosed?
A piece of equipment called a visual field machine or perimeter is used to test for peripheral vision loss in many of the above conditions and monitor for progression in patients with glaucoma. Patients asked to complete a visual field test will look into the center of a bowl-shaped instrument called a perimeter. The eye not being tested will be covered with a patch and the other eye will focus on a central target throughout testing.
Small, dim lights will be shown in different places in your peripheral vision and the machine tracks which lights you do not see. This test is “static” because the lights do not move but blink at each location with differing amounts of brightness. The machine finds the dimmest light you can see at each location in your peripheral vision.
You will be shown some lights that are too dim for you to see. This is done to determine your visual threshold or the brightness that you have trouble seeing half the time.
Can you regain a loss of peripheral vision?
Peripheral field loss can be temporary or permanent depending on the cause, Unfortunately, most cases are permanent.
Field loss from a retinal detachment can be restored when the retina is repaired and reattached, and if the loss is due to optic neuritis, once the inflammation is treated, the defect should resolve. However, glaucoma and retinitis pigmentosa result in permanent field loss. Lastly, some stroke survivors may see minor improvements in their vision in the months afterward.
Loss of one’s peripheral vision can be devastating. Performing everyday tasks, driving, or navigating the world becomes extraordinarily difficult. Fortunately, with proper identification and treatment, peripheral vision loss is often restored. Early diagnosis and treatment are key to regaining peripheral vision.
