Most people have some type of vision disorder. Some of the most common problems affecting a person's vision are refractive errors. These occur when the shape of a person's eye doesn't make it possible for light to focus directly on their retina. Many common types of vision disorders are caused by refractive errors. Most adults over the age of 35 will have some type of refractive vision disorder.
Definition & Facts
Refraction occurs when rays of light are bent as they pass through a person's cornea and then go to their eye's lens. The retina then focuses the light and provides images to the brain. Common types of errors involving this process include the following:
- Presbyopia is a vision condition related to aging. When a person's eye ages, their lens is not able to change shape sufficiently to permit their eyes to focus on objects close to them.
- When a person has nearsightedness, light focuses in the front of a person's retina instead of on their retina. This is also known as myopia.
- Farsightedness is also known as hyperopia and results in the inability to see objects up close clearly
- With astigmatism, a person's eyes do not focus light evenly on their retina and the tissue in the back of their eye. It is usually congenital, that is, present at birth.
Many vision disorders are genetic disorders. When a parent has a vision disorder, there is an increased chance that their children will have the same vision disorder.
Symptoms & Complaints
When a person has myopia or nearsightedness, they can clearly see objects that are up close. Objects far away appear blurry to them.
With astigmatism, a person may see images that seem to be stretched out or blurry.
Hyperopia causes objects in the distance to be seen more clearly than when objects are close. Individuals will experience hyperopia in different ways. It's possible for a person with farsightedness to not notice any problems when they are young. When individuals has a severe case of this condition, their vision may be blurry with objects at any distance.
In addition to family history and genetic factors, there are a number of different factors that can result in a person experiencing a vision disorder. When a person has dry eye syndrome (DES) or dry eyes, it can impact their vision in a number of ways. It could cause blurred as well as fluctuating vision.
It is also common for females to develop blurry vision when they are pregnant. In some cases, diplopia or double vision could occur. This is a result of the hormonal changes a woman is experiencing. This can cause the shape and thickness of their cornea to change.
Eye strain may be another cause of vision disorders. Many people read for hours at a time. They may also spend a lot of time on a computer as well as drive for long distances. Doing this can cause overuse of a person's eyes.
Diagnosis & Tests
When a person visits an ophthalmologist, they will be asked to describe the location and length of time they have been experiencing symptoms. An eye examination will be performed which involves a variety of tests.
A refraction test is designed to determine focusing abilities. This is done with a Snellen chart or eye chart. This is a lighted box that shows rows of letters of different sizes. A person will be asked to read the letters on the chart.
An automated refraction test is done with a device that can measure the refractive errors in an eye. An individual sits in front of an autorefractor. It emits a beam of light, and the response of a person's eyes are measured.
A visual field test involves an ophthalmologist facing a person and moving a small object toward the center of a person's vision. This will be done from the left, right, above and below. The person tells the ophthalmologist when they first see the object. This is a test of a person's peripheral vision.
Ophthalmoscopy involves the use of an ophthalmoscope which is a device that appears to be a small flashlight connected to a magnifying lens. When this is used, it shines directed light into a person's eye. This enables their lens, cornea, retina, optic nerve, arteries, retinal veins, and more to be carefully examined.
Treatment & Therapy
There are a variety of treatments available for vision disorders. Most cases can be treated with corrective lenses such as glasses or contact lenses. Types of lenses used to treat presbyopia include single-vision reading glasses, bifocals as well as trifocals. In some cases, monovision therapy may be used to treat presbyopia.
Photorefractive keratectomy (PRK), which is a type of refractive surgery may be used to treat hyperopia and myopia. Patients with these conditions may also be treated with a refractive surgery known as radial keratotomy. A person with nearsightedness can be treated with acrylic corneal implants.
Prevention & Prophylaxis
Individuals with dry eyes, which can lead to vision disorders, may attempt to correct their situation with lubricating eye drops. Should their DES be in the more advanced stages, tear duct plugs (also known as a punctal plug) or prescription medication may be necessary to keep their eyes adequately lubricated.
Eating a healthy diet has been shown to help decrease vision problems. Eating dark, leafy vegetables as well as foods rich in omega 3 fatty acids promote eye health.
It is important to rest one's eyes regularly when reading. Proper care and cleaning of contact lenses is also important for maintaining the health of one's eyes. Finally, one should wear protective eyewear when engaging in work or activities that may pose a danger to the eyes.