There are many different parts of the eye that help to create vision. Light passes through the cornea, the clear, dome-shaped surface that covers the front of the eye. The cornea bends - or refracts - this incoming light. The iris, the colored part of the eye, regulates the size of the pupil, the opening that controls the amount of light that enters the eye. Behind the pupil is the lens, a clear part of the eye that further focuses light, or an image, onto the retina. The retina is a thin, delicate, photosensitive tissue that contains the special "photoreceptor" cells that convert light into electrical signals. These electrical signals are processed further, and then travel from the retina of the eye to the brain through the optic nerve, a bundle of about one million nerve fibers. We "see" with our brains; our eyes collect visual information and begin this complex process.
The most common vision problems are refractive errors, more commonly known as nearsightedness, farsightedness, astigmatism and presbyopia. Refractive errors occur when the shape of the eye prevents light from focusing directly on the retina. The length of the eyeball (either longer or shorter), changes in the shape of the cornea, or aging of the lens can cause refractive errors. Most people have one or more of these conditions.
The cornea and lens bend (refract) incoming light rays so they focus precisely on the retina at the back of the eye.
What is refraction?
Refraction is the bending of light as it passes through one object to another. Vision occurs when light rays are bent (refracted) as they pass through the cornea and the lens. The light is then focused on the retina. The retina converts the light-rays into messages that are sent through the optic nerve to the brain. The brain interprets these messages into the images we see.
What are the different types of refractive errors?
The most common types of refractive errors are nearsightedness, farsightedness, astigmatism and presbyopia.
Nearsightedness (also called myopia) is a condition where objects up close appear clearly, while objects far away appear blurry. With nearsightedness, light comes to focus in front of the retina instead of on the retina.
Farsightedness (also called hyperopia) is a common type of refractive error where distant objects may be seen more clearly than objects that are near. However, people experience farsightedness differently. Some people may not notice any problems with their vision, especially when they are young. For people with significant farsightedness, vision can be blurry for objects at any distance, near or far.
Astigmatism is a condition in which the eye does not focus light evenly onto the retina, the light-sensitive tissue at the back of the eye. This can cause images to appear blurry and stretched out.
Presbyopia is an age-related condition in which the ability to focus up close becomes more difficult. As the eye ages, the lens can no longer change shape enough to allow the eye to focus close objects clearly.
Who is at risk for refractive errors?
Presbyopia affects most adults over age 35. Other refractive errors can affect both children and adults. Individuals that have parents with certain refractive errors may be more likely to get one or more refractive errors.
What are the signs and symptoms of refractive errors?
Blurred vision is the most common symptom of refractive errors. Other symptoms may include:
- 1. Double vision
- 3. Glare or halos around bright lights
- 5. Headaches
6. Eye strain
How are refractive errors diagnosed?
An eye care professional can diagnose refractive errors during a comprehensive dilated eye examination. People with a refractive error often visit their eye care professional with complaints of visual discomfort or blurred vision. However, some people don't know they aren't seeing as clearly as they could.
How are refractive errors corrected?
Refractive errors can be corrected with eyeglasses, contact lenses, or surgery.
Age-related eye diseases and conditions
Since your 40s, you probably noticed that your vision is changing. Perhaps you need glasses to see up close or you have more trouble adjusting to glare or distinguishing some colors. These changes are a normal part of aging. These changes alone cannot stop you from enjoying an active lifestyle or stop you from maintaining your independence. In fact, you can live an active life well into your golden years without ever experiencing severe vision loss. But as you age, you are at higher risk of developing age-related eye diseases and conditions. These include: age-related macular degeneration, cataract, diabetic eye disease, glaucoma, low vision and dry eye.
Get a comprehensive dilated eye exam.
Everyone age 50 or older should visit an eye care professional for a comprehensive dilated eye exam. Many eye diseases have no early warning signs or symptoms, but a dilated exam can detect eye diseases in their early stages before vision loss occurs. Early detection and treatment can help you save your sight. Even if you aren't experiencing any vision problems, visit your eye care professional for a dilated eye exam. He or she will tell you how often you need to have one depending on your specific risk factors.
Common Age-related Eye Diseases and Conditions:
Age-related Macular Degeneration (AMD)
AMD is a disease associated with aging that gradually destroys sharp, central vision. Central vision is needed for seeing objects clearly and for common daily tasks such as reading and driving.
A cataract is a clouding of the lens in the eye. Vision with cataract can appear cloudy or blurry, colors may seem faded and you may notice a lot of glare.
Diabetic Eye Disease
Diabetic eye disease is a complication of diabetes and a leading cause of blindness. The most common form is diabetic retinopathy which occurs when diabetes damages the tiny blood vessels inside the retina.
Glaucoma is a group of diseases that can damage the eye's optic nerve and result in vision loss and blindness. It is usually associated with high pressure in the eye and affects side or peripheral vision.
Dry eye occurs when the eye does not produce tears properly, or when the tears are not of the correct consistency and evaporate too quickly. Dry eye can make it more difficult to perform some activities, such as using a computer or reading for an extended period of time.
Low vision is a loss of eyesight that makes everyday tasks difficult. A person with low vision may find it difficult or impossible to accomplish activities such as reading, writing, shopping, watching television, driving a car or recognizing faces. Low vision means that even with regular glasses, contact lenses, medicine, or surgery, people find everyday tasks difficult to do. Reading the mail, shopping, cooking, seeing the TV, and writing can seem challenging. But, many people with low vision are taking charge.
Simple Tips for Healthy Eyes
Your eyes are an important part of your health. There are many things you can do to keep them healthy and make sure you are seeing your best. Follow these simple steps for maintaining healthy eyes well into your golden years.
Have a comprehensive dilated eye exam. You might think your vision is fine or that your eyes are healthy, but visiting your eye care professional for a comprehensive dilated eye exam is the only way to really be sure. When it comes to common vision problems, some people don’t realize they could see better with glasses or contact lenses. In addition, many common eye diseases such as glaucoma, diabetic eye disease and age-related macular degeneration often have no warning signs. A dilated eye exam is the only way to detect these diseases in their early stages.
During a comprehensive dilated eye exam, your eye care professional places drops in your eyes to dilate, or widen, the pupil to allow more light to enter the eye the same way an open door lets more light into a dark room. This enables your eye care professional to get a good look at the back of the eyes and examine them for any signs of damage or disease. Your eye care professional is the only one who can determine if your eyes are healthy and if you’re seeing your best.
Know your family’s eye health history. Talk to your family members about their eye health history. It’s important to know if anyone has been diagnosed with a disease or condition since many are hereditary. This will help to determine if you are at higher risk for developing an eye disease or condition.
Eat right to protect your sight. You’ve heard carrots are good for your eyes. But eating a diet rich in fruits and vegetables, particularly dark leafy greens such as spinach, kale, or collard greens is important for keeping your eyes healthy, too. Research has also shown there are eye health benefits from eating fish high in omega-3 fatty acids, such as salmon, tuna, and halibut.
Maintain a healthy weight. Being overweight or obese increases your risk of developing diabetes and other systemic conditions, which can lead to vision loss, such as diabetic eye disease or glaucoma. If you are having trouble maintaining a healthy weight, talk to your doctor.
Wear protective eyewear. Wear protective eyewear when playing sports or doing activities around the home. Protective eyewear includes safety glasses and goggles, safety shields, and eye guards specially designed to provide the correct protection for a certain activity. Most protective eyewear lenses are made of polycarbonate, which is 10 times stronger than other plastics. Many eye care providers sell protective eyewear, as do some sporting goods stores.
Quit smoking or never start. Smoking is as bad for your eyes as it is for the rest of your body. Research has linked smoking to an increased risk of developing age-related macular degeneration, cataract, and optic nerve damage, all of which can lead to blindness.
Be cool and wear your shades. Sunglasses are a great fashion accessory, but their most important job is to protect your eyes from the sun’s ultraviolet rays. When purchasing sunglasses, look for ones that block out 99 to 100 percent of both UV-A and UV-B radiation.
Give your eyes a rest. If you spend a lot of time at the computer or focusing on any one thing, you sometimes forget to blink and your eyes can get fatigued. Try the 20-20-20 rule: Every 20 minutes, look away about 20 feet in front of you for 20 seconds. This can help reduce eyestrain.
Clean your hands and your contact lenses—properly. To avoid the risk of infection, always wash your hands thoroughly before putting in or taking out your contact lenses. Make sure to disinfect contact lenses as instructed and replace them as appropriate.
Practice workplace eye safety. Employers are required to provide a safe work environment. When protective eyewear is required as a part of your job, make a habit of wearing the appropriate type at all times and encourage your coworkers to do the same.