Blurry vision can be caused by a number of different issues. It's important for an eye doctor to determine if the cause of blurry vision is due to the need for glasses, or if blurry vision is due to something more concerning. Blurry vision is general description patients use for a decline in clarity of vision. Images or letters may appear hazy and out of focus. As you can imagine, blurred vision is the most common reason for eye examination requests.
An eye doctor will ask the patient about what their blurred vision is like. Is the blurring happening occasionally or all the time? One or both eyes? What distance? When did the blurring start? Are there any other symptoms associated with the blurring (such had headache, eye strain, double vision, new floating spots in vision, etc.)?
Blurred vision makes it especially difficult to perform in the classroom, read a book, or use the computer for long periods of time. Blurry vision can even be caused by or contribute to trouble focusing eyes together and a variety of binocular vision dysfunctions . When blurred vision in one eye or both eyes occur, it is time to see an eye care provider. Treatment for blurred vision is based on the cause or diagnosis.
The first three (and most common!) causes of blurry vision are glasses-related issues. This is called "refractive error", which is a fancy term for needing eyeglasses. Myopia, hyperopia, astigmatism, and presbyopia are the fancy medical terms for these specific conditions.
Myopia is also referred to as nearsightedness or sometimes short-sightedness. Nearsightedness can cause blurry vision, most likely when looking at things that are far away, as the eye is unable to focus a clear image on the retina. Close-up objects will look clear. The use of contact lenses or eyeglasses can help correct myopia. Some patients may choose to have refractive surgery, such as LASIK, to correct their myopia. Severe myopia can sometimes cause thin spots to develop in the retina, which can lead to a retina tear or detachment. This is a good reason to also have dilated health exams if you suffer from nearsightedness, as well as glasses checks.
Hyperopia is also called hypermetropia, farsightedness, or long-sightedness. When a person is far-sighted, objects are often clear far away, and the eye must flex and focus using the process called accommodation to make images up close appear clear. If a patient is unable to accommodate enough to make the images clear, images that are close may appear blurry. High amounts of hyperopia require the eye to exert considerable effort to make things clear—this extra focusing can sometimes cause an eye to turn inward, a condition called accommodative esotropia. Glasses, contact lenses, and, for some patients, eye surgery can be used to correct hyperopia.
Astigmatism can cause blurry vision at any distance. Astigmatism is an optical term with means the eye needs a lens with two powers to place a clear image on the retina. This may be due to an irregularly shaped cornea or lens which doesn’t allow the light rays to come to a single focus point on the retina. The result is a blurry image regardless of distance. Frequently astigmatism is present with hyperopia or myopia. Just like the prior two, glasses, contact lenses, and refractive surgery can help alleviate blurry vision due to astigmatism.
Presbyopia is the fancy term for "aging eyes". This is a naturally occurring age-related condition that unfortunately occurs after having too many birthdays. You may have seen someone around age 40 or 50 that struggles to see up close, holds a book or newspaper as far away as possible or uses a cheap pair of magnification glasses from the local store to read. Although frustrating, this is a normal aging change to the eye. The focusing (accommodating) system of the eyes loses its ability to make objects up close clear by about the 4th decade of life. In addition, the focal mechanism, the lens of the eye, becomes thicker and less flexible as the eye ages. Eventually, a cataract will even develop as the lens ages. Presbyopia will affect everyone at some point, whether the patient uses glasses for myopia, hyperopia, astigmatism...or even never needed glasses at all! The fix for presbyopia is the use of a lined bifocal or trifocal, a progressive lens (no-line bifocal), or contact lenses that have a near power added into them. Surgery isn't a great option for presbyopia, unfortunately.
Although contact lenses can be a fix for the conditions above, contact lenses that are worn for a longer period than prescribed may become dirtied by proteins and other debris building up on the lenses. This can not only cause blurry vision but also increases the risk of eye infections that can cause permanent damage to the cornea and other structures of the eye. Be sure to ask your eye specialist about proper contact lens cleaning and wear to best protect your eyes!
Many disorders of binocular vision can cause blurry vision and are often associated with a need for glasses. Eye disorders such as the lazy eye (amblyopia), eye turn (strabismus), and convergence insufficiency are first treated with glasses or contact lenses followed by vision therapy. The goal of vision therapy is to help a patient achieve clear, comfortable binocular vision. Your eye specialist will likely check your binocular vision abilities with a cover test, suppression tests, Worth 4 Dot, and tests of stereopsis. Each test tells how your eyes team together, and what skills may need to be improved through vision therapy.
Cataracts can cause a number of vision changes, such as blurry vision, halos or glare at night or with bright light, and sometimes single-eye (monocular) double vision. Cataracts are a normal part of the eyes aging and are actually the number one cause of preventable blindness worldwide. The lens of each eye starts to become yellow and brown and develops some interesting opacifications to it. Some cataracts develop very slowly; other types may come on quickly, over the period of just a few years. In general, most patients have some degree of a cataract around age 60. However, children and even babies can develop a cataract! If pediatric cataracts are not removed, they can inhibit the normal development of a child's visual system. In most cases, however, your eye care provider will correct blurry vision due to cataracts with glasses and will help you decide when you are able to have your cataracts removed. Cataract surgery is often quite simple. The cataract in an eye is removed by an eye surgeon and replaced with an artificial lens. Cataract surgery solves many of the issues caused by cataracts; however, patients often need to use a pair of glasses after surgery to fine-tune clarity of vision.
Dry eye syndrome can affect your eyes in numerous ways. Common complaints are blurry and fluctuating vision, eye irritation, and (occasionally) eye pain. The use of artificial tears or gels helps re-wet the surface. Sometimes an eye doctor will use prescription medications or plug the tear ducts to keep more tears on the eyes.
Floaters are actually clumps of the jelly-like fluid, the vitreous humor, casting a shadow on the retina. Floaters may cause blurry vision if the floater casts a shadow over central vision, and once the floater moves away vision will clear. New floaters in one or both eyes are cause for concern. Floaters can be associated with a torn or detached retina, which needs immediate treatment so that a patient does not permanently lose vision. If you notice new large floaters, lots of new, small floaters, or floaters associated with flashing lights (like lightning strikes in your vision), go see an eye doctor right away.
Glaucoma damages the optic nerve resulting in loss of vision. Early glaucoma is often not noticeable by a patient, which is why glaucoma is referred to as the "silent theft of sight". Glaucoma is often due to elevated eye pressure that causes damage to the delicate fibers of the optic nerve (cranial nerve II). Glaucoma often affects peripheral vision first and central vision in later stages; thus, glaucoma can be a direct cause of blurred vision and vision loss. The best way to catch glaucoma is to undergo an eye examination periodically. If a patient is diagnosed with glaucoma, your eye doctor may prescribe medicated eye drops, or recommend laser or glaucoma surgery depending on the severity of your condition.
The macular is the area of the retina responsible for our high-definition (20/20 and better) vision. With age, the retina at and around the macula may develop aging changes known as macular degeneration. The actual process is a buildup of damaged light-sensitive cells (cones) and deposits along with the basement layer of the retina. Cells become damaged due to lack of nutrients, and occasionally the eye tries to grow new blood vessels that are very leaky, leading to bleeding under the retina. Chronically blurry vision, especially in elderly patients should be evaluated, as macular degeneration, specifically the bleeding form, can cause permanent vision loss.
Diabetes can affect multiple organs, the eye included. Poor blood glucose (sugar) control can cause the lens of the eye to swell, leading to temporary vision changes and changes in glasses prescription. Diabetes can also cause cataracts as well as bleeding and swelling in the retina. Sometimes blurry vision associated with a large glasses prescription change is the first sign of poor blood sugar management. If you are diabetic, ask your eye specialist how often you have an eye health check. Diabetics are often dilated for eye health checks at least annually to screen for diabetic eye disease.
Besides morning sickness, swollen feet, constipation, backache, and fatigue, hormonal fluctuations can also cause blurry vision. Vision may return to its normal state following the end of pregnancy, but it's a good idea to have an eye health check to make sure the eyes are healthy if you notice blurry vision during pregnancy.
Migraines are often thought of as a painful headache; however, migraines can cause a myriad of symptoms, including blurry vision, light sensitivity (photophobia), vision distortions (migraine aura), and even temporary vision loss. Any headache that is new or with signs such as those listed should be evaluated—first by your medical doctor and then by an eye specialist.
As you can see, many different issues can cause blurry vision. Some problems are easily solved with a new pair of eyeglasses, while other problems are more concerning. Your eye doctor will check you for glasses, test your binocular vision, and perform an eye health check to correctly diagnosis the cause of blurry vision.
Keep in mind, if you have sudden changes to your vision, you should always contact your eye doctor immediately.