How Do Your Eyes Work?

How Do Your Eyes Work?

Your eyes are one of the most complex organs in the body, second only to the brain. They perform much like a camera, allowing light to enter and processing it into data that our brains use to form images. When one part of the eye is not functioning correctly, the entire visual system can be affected. In this blog, we’ll discuss the anatomy and basic functions of the eyes, and explain how common eye diseases affect them. 

Anatomy of the Eye

Anatomy of an Eye

Image: National Institute of Health National Eye Institute (NIH.NEI)

The eyes are often called the windows to the soul, but they are truly the windows to the brain. The visual process begins when light enters the eye through the cornea, the clear dome at the front of the eye. The cornea bends the light so that it will be focused on the correct part of the eye as it passes through. Next, the light travels through the opening, called the pupil, in the colored portion of the eye, called the iris. The iris acts like the shutter on a camera, allowing a portion of light to enter. The light continues, passing through the crystalline lens. The lens again focuses the light, allowing it to reach all the way to the back of the eye, ending at the retina. The retina is a light sensitive layer of brain tissue containing cells which turn the light into electrical impulses. These impulses travel through the optic nerve to the brain, where they are used to form the images we see. 

Sometimes light doesn’t land in the correct part of the eye. If the eye is too long, the light ray will not be able to reach the back, and vision will be blurry. This condition is called myopia, or nearsightedness. If the eye is too short, light will not be focused when it reaches the back of the eye. This condition is called hyperopia, or farsightedness. Light passing through the eye may be bent at the wrong angle due to an imperfectly shaped cornea, called astigmatism. Astigmatism may cause images to appear off axis. These conditions, called refractive errors, are usually corrected with glasses, contact lenses, or refractive surgery like Lasik or PRK. 

In addition to refractive errors, there are many diseases that affect our eyes. Some of the most common diseases are:

Glaucoma: 

Glaucoma is a group of diseases that cause damage to the optic nerve due to an increase in pressure inside the eye. This damage can lead to blindness if not detected and treated early. Glaucoma is often present without symptoms and is diagnosed by an eye doctor during a dilated eye exam. Vision loss occurs in the periphery, especially the portion closest to your nose. Glaucoma can be treated with medication, lasers, surgery, or a combination of the three. According to the National Institute of Health (NIH) anyone can get glaucoma, but some people are at higher risk. Those at additional risk include:: 

  • People over age 60 
  • People who are African American or Hispanic/Latino and over age 40 
  • People who have a family history of glaucoma 

Diabetic Retinopathy:

Diabetic retinopathy is a complication of diabetes which causes new blood vessels to grow in the back of the eye. These blood vessels eventually leak blood into the vitreous humor, causing “floaters” which can impair vision. As the disease progresses, it can lead to Diabetic Macular Edema, which is swelling of the macula caused by leaking fluid in the retina. Other complications include neovascular glaucoma, and retinal detachments. Diabetic retinopathy can occur with type 1, type 2, and gestational diabetes, and women who are pregnant are at increased risk. Treatments for this disease include injections and laser treatment. Controlling your diabetes is crucial to decreasing your risk of developing diabetic retinopathy. 

Macular Degeneration:

AMD is a common eye condition among people aged 50 and older. It is a leading cause of vision loss in older adults. It gradually destroys the macula, the part of the eye that provides sharp, central vision needed for seeing objects clearly. If the macula is damaged, fine points in the vision become distorted. Symptoms may include blurry or wavy spots in the central vision. Overtime, this may progress to total loss of central vision. The disease can take one of two forms: dry or wet. If you have the wet form of AMD, the treatment is an intraocular injection performed by an ophthalmologist. There is no treatment for the dry form. In addition to regular eye exams, the doctors at Mountain View Eye Center recommend eye supplements, such as AREDS-2, and a healthy diet rich in leafy green vegetables and Omega 3 Fatty Acids. To learn more about Macular Degeneration, visit our website.

Cataracts:

Cataract is a condition in which proteins in the lens of the eye clump together, causing the lens to become cloudy or opaque. When this occurs, light can’t pass through the lens correctly, so it does not reach all the way to the retina. This causes the vision to become blurry or dim. Most cataracts are related to the aging process, but they can also be secondary to other diseases such as glaucoma or diabetes. Additional causes include trauma to the eye, steroid use, or radiation. Some people are born with congenital cataracts. Symptoms of cataracts include: cloudy or blurry vision, dim color vision, glare or halos appearing around lights, poor night vision, double vision, and frequent prescription changes in your eyeglasses or contact lenses.

These symptoms can also be a sign of other eye problems. If you have any of these symptoms, talk with your eye care professional. When cataract symptoms become severe, the only treatment is surgery. For more information about cataracts and cataract surgery, read our blog Cataract Awareness.

The visual system is complex, but learning more about the anatomy of the eyes can help us understand how they function. We hope that you found the information in this blog helpful. Stay tuned for weekly updates, and for more information about your eyes, please visit the patient education portion of our website at: https://mountainvieweyes.com/patient-education-fairbanks-ak/

Written by:

Gina Stafford, COA, LDO, ABOC

Sources:

National Institute of Health National Eye Institute How the Eyes Work https://www.nei.nih.gov/learn-about-eye-health/healthy-vision/how-eyes-work

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