Loss of vision is a general term used to describe losing your ability to see well, whether quickly (acute) or gradually (chronic). All ages can suffer from vision loss.
Some children are even born with a congenital disease that causes them to have no vision or to threaten them to lose sight over time. It is well-known that vision loss increases with age.
Over 37 million Americans are older than 50 years, and 25% of those older than 80 have a visual impairment. One of the major problems with vision loss is the related disability.
It was estimated that the indirect and direct costs of treating adults with visual impairment are $54 billion every year.
It is also associated with increased risk of falls, loss of independence, depression, and increased mortality.
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What are the causes of vision loss?
By far, the most common cause of loss of vision is refractive errors. These are the errors caused by inherited changes in the shape or strength of our cornea and lens. This causes people to have:
- short-sightedness (also known as myopia)
- farsightedness (hyperopia, or hypermetropia)
- astigmatism, or presbyopia (aging sight that requires reading glasses for people above the age of 40).
These errors are easily correctable with eyeglasses, contact lenses, or refractive surgeries such as LASEK.
The normal eye creates a clear image by bending or reflecting light in order to focus it onto the retina.
Refractive errors occur when a component of the eyes optical system fails to focus the optical image. Presbyopia occurs when the lens loses its normal accommodating power and can no longer focus on objects viewed at arm’s length or closer. Aside from errors of refraction, when someone complains of loss of vision, several factors have to be considered
First, the patient’s age is very important. Some vision changes are regarded as a normal part of aging. In people older than 40 years of age, it is prevalent to experience a gradual loss of vision with trouble focusing on close objects.
These experiences can be caused by diseases such as cataracts, glaucoma, macular degeneration, or diabetic retinopathy. Of course, there are multiple other possible causes, but these are less common.
For younger patients, common causes of visual loss may include dry eyes, infections, injuries, or vision changes as part of systemic diseases.
We should also consider patients’ history. Certain systemic diseases are highly associated with loss of vision, such as diabetes, hypertension, high cholesterol, and heart diseases.
As a general rule, anything that blocks the passage of light to the back of the eye, or disrupts the transmission of nerve impulses from the back of the eye to the brain will cause loss of vision
For example, in diseases affecting the cornea such as herpes, Vitamin-A deficiency, persistent contact lens use can cause the light not to reach the retina
Also, retinal detachment, diabetes, inadequate blood supply to the retina, or macular degeneration prevent the retina from sensing the light normally, causing loss of vision
Disorders affecting the optic nerve such as brain tumors, strokes, infections, multiple sclerosis, glaucoma, or optic neuritis can all affect the passage of impulses from the retina to the brain. Strokes and tumors specifically can also affect the brain, making it unable to interpret information sent by the eye.
What are the main types of vision loss?
There are multiple ways to classify types of vision loss. It can be even classified as correctable by refraction versus uncorrectable by refraction.
Vision loss can also be classified as acute versus chronic.
Acute loss of vision is when someone experiences blurriness that happened quickly over minutes, hours, or days.
Chronic loss of vision usually happens over weeks, months, or years.
Actute vision loss
In the first scenario causes may include:
- eye trauma
- blockage of the blood flow to or from the retina
- pulling the retina away from its usual position at the back of the eye.
In these situations, vision may become cloudy or blurry, completely absent or disturbed by seeing flashes of lights or floaters.
Its most often painless but could be associated with pain, redness, headache, and sensitivity to light. Sudden blockage of the blood flow to the occipital lobe of the brain frequently happens when someone gets a stroke
Some types of stroke do not hit the brain, but they affect the eye’s small vessels, causing blockage of the blood flow, conditions known as retinal artery occlusion, or retinal vein occlusion.
One of these strokes’ most common presentations is called “Amaurosis fugax.” This is a type of vision loss due to lack of blood flow and perfusion to the optic nerve and retina. It is painless, and patients describe a dark curtain or shade coming over their vision.
- carotid artery disease
- other atherosclerotic diseases
- embolic disease from the heart or aorta
- hypercoagulable/hyperviscosity state
- illicit drugs such as cocaine
- rarely inflammation of the arteries.
Inflammation of the blood vessels that supply the eye and the optic nerve, or inflammation of the optic nerve can also cause acute vision loss. This is known as optic neuritis.
Bilateral vision loss
It is also common to see bilateral optic disc swelling, in a condition called “papilledema.” It typically causes transient bilateral vision loss lasting a few seconds. Patients typically note the vision changes when changing positions, such as from supine to standing.
- primary or metastatic intracranial tumor
- intracranial hemorrhage
- obstructive hydrocephalus (decreases cerebrospinal fluid [CSF] drainage)
- brain abscess
Chronic vision loss
In the second scenario, where vision loss is primarily chronic, vision is usually lost in phases. It is also usually on both eyes, unlike acute loss, which mainly happens in one eye. In cataracts, for example, patients may initially experience glare, especially in the dark. That causes difficulty in driving at night. They may also complain that colors appear duller than they used to.
In AMD, the patient will complain of distortion of vision, where straight lines appear crooked or wavy. They may also describe a black or gray patch affecting their central field of vision.
In glaucoma, patients mostly do not notice anything, as the changes are so subtle and affect peripheral vision primarily. Optic nerve diseases are usually presented with headaches and sometimes additional neurological or endocrinological abnormalities
Central vision loss
Depending on the area of vision loss, it is also classified as central versus peripheral loss of vision.
Central vision loss usually occurs from damage to the macula area.
This is the centermost area of the retina, and the area with the highest number of light receptors (photoreceptors)
When people lose central vision, they usually are seen by a doctor much faster than people presenting with peripheral loss of vision.
This is because losing central vision will feel like missing major details or seeing blurry spots exactly in front of your visual field.
Even someone with a poor vision at baseline will observe this loss of vision very quickly, especially when these blurry spots turned into dark or black spots. Diseases affecting the central vision include:
- age-related macular degeneration
- diabetic retinopathy
- vitreous hemorrhage
- optic neuritis.
On the other hand, Peripheral vision is what you see on the sides without turning your head.
Patient’s usually notice the loss in the peripheral vision when they realize they can no longer see the cars coming from their side when they attempt to cross the street. They often say that now they need to turn their head all the way before they cross the street in order to see the traffic.
When you lose peripheral vision, you will see things in the center clearer and brighter as compared to things on the side. With progression, this causes people to have what is famously known as (tunnel vision).
Diseases affecting the peripheral vision include glaucoma, retinitis pigmentosa, retinal detachment, and eye strokes.
It is essential to realize that other vision problems come in a combination of both central and peripheral vision loss, and with one eye being affected far more than the other.
Some diseases also manifest by problems with night vision only or just difficulty to distinguish different colors
When to see a doctor?
It is always advisable to receive a comprehensive eye examination with an optometrist for everyone below the age of 40 if there are no symptoms or history of eye diseases in the family.
For people above the age of 40, or in case of systemic diseases including diabetes or hypertension, an annual or semiannual eye examination is required. In case you developed any symptom of visual loss, you should always be seen by a doctor to investigate the cause. One of the significant problems with the loss of vision is that patients will not notice until it is too late. Also, be aware that reduced peripheral vision may affect your ability to drive safely.
Suppose the cause was just a refractive error that is correctable by glasses or contacts.
In that case, this is a very benign problem, except in children where it is important to correct refractive errors as soon as possible, so they do not develop lazy eyes, or “amblyopia.”
Sudden loss of vision, on the other hand, is considered a medical emergency.
Anyone with sudden vision loss over minutes, hours, or days should immediately seek medical attention. An ophthalmologist’s examination and investigations are a must to save vision before irreversible neurological damage can occur. If you, or someone you know experiences sudden blurriness of vision, they have to immediately go to the nearest emergency room to be evaluated by an ophthalmologist.
To put this into context, watch out for these symptoms. If you experience any of them, see an eye doctor right away:
1. Flashes of light, floaters, or gray shadow
2. Sudden loss of vision in one eye
3. Eye pain, discharge, or persistent redness
4. Discomfort, tearing, or scratchiness with contact lenses
5. Redness, pain, blurriness after an eye surgery
Investigating causes of loss of vision will include a thorough history.
You will be asked questions about your symptoms, medical history, family history, and current medications.
You will also be asked to describe when the loss of vision occurred, whether it affected one or both eyes, and about any accompanying manifestations including hallows, floaters, pain, or redness. A comprehensive eye examination, a dilated fundus examination, and a neurological examination will take place to test functionality of different parts of the eye and its connection to the brain.
These include optical coherence tomography (OCT), ultrasonography of the eye, and color fundus photography. Depending on the case, there will also be several blood tests, imaging tests, and visual function assessment tests
Workup must evaluate for sources of emboli and ischemia, including imaging with bilateral carotid Doppler ultrasonography and/or magnetic resonance angiography (MRA)/computed tomography (CT) angiography of the neck and/or head.
An echocardiogram may be indicated to evaluate for embolic heart disease.
Basic laboratory tests assessing risk factors for hematologic and atherosclerotic disease, such as complete blood count (CBC), fasting blood glucose or hemoglobin A1C levels, and cholesterol levels, should be done to rule out other causes of ischemia and to optimize health maintenance.
These help identify the cause and other criteria that judge the best treatment course suitable for each patient.
If you have had eye surgery and experience any redness, eye pain, or blurring of vision, call your doctor right away for an evaluation.
Even if a symptom appears to go away, you are better off checking with your eye specialist if you encounter any warning signs.
If you were found to have a gradual loss of vision caused by a refractive error, your optometrist will be able to help to prescribe suitable glasses or contact lenses.
Depending on your age and corneal health, you may also be eligible for refractive surgery, such as LASEK. Suppose the cause of your visual changes was a cataract, which means the cloudiness of your lens inside the eye. In that case, you will be provided the option of undergoing cataract surgery to remove the cataract and implant a new intraocular lens.
If you were found to have high ocular pressure (glaucoma), you may be given the option to manage it using eyedrops. You may also be advised to undergo surgery with or without using eye drops.
If eye drops are prescribed, you absolutely must take your glaucoma medication regularly to control high eye pressure, or you risk permanent optic nerve damage and development of blind spots in your visual field. Left untreated, glaucoma can lead to permanent loss of peripheral vision and even blindness.
Some visual impairment causes, including retinitis pigmentosa, Stargardt disease, or choroideremia, may benefit from enrolling in clinical trials.
Other, such as diabetic retinopathy, retinal vein occlusion, or retinal detachment, may benefit from laser therapy or surgical intervention to prevent or treat acute bleeding inside the eye
It is also possible that patients with transient ischemic attacks or strokes who present very early to benefit from the use of blood thinners, but this is given only under strict medical conditions
Vision loss can be a severe and risky condition. Visit the nearest emergency room if you experience acute loss of vision, especially in one eye.
Obtain annual screening visits to get a comprehensive eye exam by an ophthalmologist to rule out silent vision loss causes. While there are multiple treatment options available, early detection is the key for your vision to be preserved.