What Causes Blurred Vision?

While cataracts are one of the most common causes of blurry vision, especially in people over 55, there are many causes of blurry vision. Let’s review a list of some of the most common causes of blurry vision.

We’ll start in the front part of the eye, the cornea, and work our way back, to disorders that impact the retina, optic nerve, and even the brain.

Refractive error is one of the most common causes of blurry vision

Refractive error refers to how nearsighted or farsighted the eye is. If your prescription changes, your vision will be blurry unless you address it with new glasses, contacts, LASIK, or other vision correction procedures.

Causes of Blurry Vision in the Cornea

The cornea is the clear window on the outside of the eyes that we look through. It needs to be crystal clear and have an appropriate curvature to focus light on the back of the eye. There are conditions that can cause the cornea to be cloudy or have an irregular shape. Let’s review them.

Dry Eyes

Starting in the front part of the eye, we have the tear film. The cornea is the clear window on the outside of the eye. It’s like a natural glasses lens or contact lens that we look through all day.

On top of the cornea is the tear film. Our natural tears coat the cornea and ensure that its surface is smooth.

If the surface of the eye becomes dry, then the cornea takes on a lumpy and bumpy appearance microscopically. When the surface of the eye isn’t smooth, it’s like a rough or blurry glasses lens. This bumpy surface scatters light, which results in blurry vision.

Corneal Scars

The cornea can become scarred from trauma, chemical injury, or infections. These scars result in permanent opacities in the clear cornea. These opacities will block and scatter light resulting in blurry vision.

Corneal Astigmatism

Corneal astigmatism refers to the cornea having a shape that differs from that of a sphere. Ideally, a perfect lens is spherical. If our natural lens has irregular peaks or valleys, then light will be scattered resulting in blurry vision.

Regular astigmatism is easily fixable with LASIK, lens replacement, or cataract surgery. Irregular types of astigmatism can be more challenging to treat.

Fuchs Dystrophy

Fuchs dystrophy is a condition in which the endothelial “pump” cells in the back of the cornea become dysfunctional. This can result in swelling accumulating in the cornea, which results in blurry vision. Fuchs dystrophy can become somewhat common with age. Often patients can treat it with eye drops, but if more severe, there are surgical options.

Causes of Blurry Vision in the Lens

Nearly everyone is born with a natural lens inside the eye. The function of the lens is to be clear and have a shape that focuses light on the back of the eye. When we’re younger this lens is flexible, and allows us to have a range of vision.

Cataract

One of the most common causes of blurry vision is cataract. A cataract is when the natural lens inside the eye becomes cloudy. This is a normal part of aging, and happens to everyone if they live long enough. We’ve got lots of resources on our site about the different types of cataracts, and information on lens implants and virtually every aspect of modern cataract surgery.

Causes of Blurry Vision in the Retina

The retina is like the film in the back of a camera. It has photoreceptors that sense light, and there are small blood vessels that provide them nutrients and oxygen. Let’s discuss some of the common retinal causes of blurry vision.

Macular Degeneration

The macula is the center part of the retina which is responsible for our highest resolution vision. There are cells in the macula called “photoreceptors” that are responsible for sensing light, and transmitting this information to the optic nerve, and the brain, where it is processed into the images of the world we perceive.

Over time, these photoreceptors can degenerate and lose their ability to function. Because these photoreceptors are in the center of the macula, the pattern of vision loss tends to be in the center, and peripheral vision tends to be spared.

The most common cause of macular degeneration is aging. There are genetic and environmental factors that contribute as well. There are vitamins which have been shown to slow down the progression of macular degeneration.

Macular Pucker or Epiretinal Membrane

The photoreceptors in the macula need to be flat, like the film in a camera, to sense light properly and transmit a clear image. Imagine how pictures would turn out if the film had wrinkles in it. This is what happens to vision in patients who have a macular pucker, also known as an epiretinal membrane.

The eye is filled with a clear jelly called the “vitreous”. The vitreous is glued to the back part of the eye, the retina. Over time, the vitreous pulls away from the retina. If it pulls on the macula, it can result in the macula wrinkling, which causes a distortion of vision.

Surgery can be done to fix this, called a vitrectomy. Like any surgery, the risks and benefits of this procedure should be discussed with your doctor.

Retinal Detachment

The retina has a blood supply underneath it which delivers oxygen and nutrients. If a tear or hole develops in the retina, then the liquid from inside the eye can get under the retina, and cause a separation between the retina and its blood supply. When the retina is separated from its blood supply, it’s called a “retinal detachment”.

Retinal detachment is an emergency. Initial symptoms may be the sudden onset of flashes, floaters, or a dark curtain over part of the vision. If you are having these symptoms, you should contact an eye doctor immediately.

Vascular Diseases

There are many diseases of the blood vessels in the retina. There are arteries, veins, and smaller microscopic branches of these blood vessels.

When blood vessels develop blockages, the cells that rely on those blood vessels to deliver oxygen and nutrients are deprived and become damaged.

When arteries develop blockages, this is similar to a stroke, and can cause loss of vision in one eye. An example of a very serious type of arterial blockage in the eye is called a “central retinal artery occlusion”. The central retinal artery is a branch from the internal carotid artery, which supplies the brain. In addition to the loss of vision caused by a central retinal artery occlusion, patients should be evaluated for their risk of having a stroke. This is a medical emergency.

Veins can also develop blockages. While the mechanism is different from a retinal artery occlusion or stroke, the consequences can be just as serious. When a vein in the retina is blocked, it’s called a “retinal vein occlusion” or “RVO”.

Diabetic Retinopathy

Diabetes causes microvascular injury to blood vessels. When the concentration of glucose is too high inside a blood vessel, damage occurs to the blood vessel walls. This damage can result in blood vessels leaking. Eye doctors can see bleeding or leakage from these tiny blood vessels under the microscope.

Damage to blood vessels also results in poor delivery of oxygen and nutrients to the retina. When retinal cells don’t get their nutrients, they release signals to grow more blood vessels. These resulting new blood vessels are abnormal, and are called “neovascularization”. This process of neovascularization can lead to vision threatening complications of diabetic retinopathy.

Managing your diabetes and having routine eye exams are the best thing you can do to prevent complications of diabetes in the eye.

Causes of Blurry Vision in the Optic Nerve

The optic nerve transmits information from the retina to the brain where it can be processed. It’s like an electrical cable that carries information. If this cable becomes damaged, it can result in vision loss.

Glaucoma

Glaucoma is a progressive optic neuropathy, most commonly related to high pressure inside the eye. If the pressure inside the eye is too high, it can squeeze the delicate fibers of the optic nerve, resulting in their damage. The pattern of glaucoma vision loss first impacts peripheral vision. This can occur so slowly that patients may not notice this loss of vision until it’s too late. Having routine eye exams is important to catch it early, and slow it’s progression.

Optic Atrophy

There are many causes of optic nerve damage, or atrophy. These include infections, inflammation, other medical disorders, tumors, blood vessel problems, metabolic causes, and more. These can happen in one eye or both.

Causes of Blurry Vision Related to the Brain

After light is focused by the front part of the eye, and sensed by the back part of the eye, it is transmitted via the optic nerve to the brain where it is processed. If there are problems in the brain, it can result in vision loss.

Stroke

A stroke is when the blood flow to the brain is blocked. When the cells of the brain can’t get oxygen and nutrients they are unable to function.

The back part of the brain, known as the occipital cortex, is responsible for visual processing. If a stroke impacts this region of the brain, vision will be lost.

Tumors

Tumors can occur in the occipital cortex, damaging this important processing region for vision. They can also occur along the pathways the visual information travels from the space behind the eye, called the orbit, through the front and middle of the brain, as the information makes its way to the occipital cortex.

Summary

There are many causes of blurry vision. It is possible that you might have suffered blurred vision suddenly without the knowledge of what might be going on In your eye or body. You may get blurred vision for so many reasons, and you mustn’t start panicking when this happens. It may also be a simple issue as much as it may indicate that you have an eye problem or disease.

You may need to get an eye exam to establish what is causing your blurry vision. This should be an essential step, especially if the blurred vision has not gone away by itself after a while. The following are some ways to get rid of blurred vision, especially when it is sudden