What are Refractive Errors?
In refractive errors, the shape of the eye prevents light from focusing on the retina. The length of the eyeball (longer or shorter), changes in the shape of the cornea, or aging of the lens can cause refractive errors. There are different types of refractive errors, but the most common are Myopia, Hyperopia, and Astigmatism and Presbyopia.
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.
Myopia, also known as nearsightedness, is a common type of refractive error where close objects appear clearly, but distant objects appear blurry. Some of the signs and symptoms of myopia include:
● Difficulty seeing distant objects, such as highway signs
Hyperopia, also known as farsightedness, is a common type of refractive error where distant objects may be seen more clearly than objects that are near. Hyperopia develops in eyes that focus images behind the retina instead of on the retina, which can result in blurred vision. This occurs when the eyeball is too short, which prevents incoming light from focusing directly on the retina. Hyperopia can affect both children and adults. It affects about 5 to 10 percent of Americans. Common signs and symptoms of hyperopia include:
● Blurry vision, especially for close objects
Astigmatism occurs when light is bent differently depending on where it strikes the cornea and passes through the eyeball. The cornea of a normal eye is curved like a basketball, with the same degree of roundness in all areas. An eye with astigmatism has a cornea that is curved more like a football, with some areas that are steeper or more rounded than others. This can cause images to appear blurry and stretched out. Common signs and symptoms of Astigmatism include:
● Difficulty driving at night
● Distorted or blurred vision at all distances
Presbyopia is a common type of vision disorder that occurs as you age. It is often referred to as the aging eye condition. Presbyopia results in the inability to focus up close, a problem associated with refraction in the eye.
Presbyopia happens naturally in people as they age. The eye is not able to focus light directly on to the retina due to the hardening of the natural lens. Aging also affects muscle fibers around the lens making it harder for the eye to focus on up close objects. The ineffective lens causes light to focus behind the retina, causing poor vision for objects that are up close.
When you are younger, the lens of the eye is soft and flexible, allowing the tiny muscles inside the eye to easily reshape the lens to focus on close and distant objects. Anyone over the age of 35 can develop presbyopia. Everyone experiences some loss of focusing power for near objects as they age, but some will notice this more than others. Common signs and symptoms of presbyopia are:
● Having to hold reading material farther than arm’s distance
● Problems seeing objects that are close to you
Myopia, presbyopia and astigmatism can be corrected with eyeglasses, contact lenses, or surgery. The simplest means of correcting presbyopia is eyeglasses. Eyeglasses for presbyopia have higher focusing power in the lower portion of the lens. This allows you to read through the lower portion of the lens and see properly at distant through the upper portion of the lens. It is also possible to purchase reading eyeglasses. These types of glasses do not require a prescription and can help with reading vision.