Eye health

The eyes are complex organs. There are many parts that must work together to produce clear vision. Read on to get a basic overview of eye anatomy and learn about common eye conditions.

The major parts of the eye are listed below. Problems or malfunctions in any part of the eye cause many common eye conditions.


The cornea is a layer of clear tissue at the front of the eye that helps focus light.

Tear ducts

The openings to the tear ducts are located in the upper and lower eyelids at the inner corner of each eye. Tears are secreted by the lacrimal gland from the outer, upper eyelid to the surface of the eye. Tears keep the cornea lubricated and clear of debris. The tear ducts drain the tears away.

Iris and pupil

The colored part of the eye is the iris. It is a set of muscles that control the pupil, which is the opening in the middle of the eye. The iris controls the amount of light coming in through the pupil.

Lens and retina

The lens is behind the pupil. It focuses light onto the retina, the light-sensitive cells on the back of the eyeball. The retina converts images into electrical signals that are sent to the optic nerve.

Optic nerve

The optic nerve is a thick bundle of nerve fibers attached to the back of the eye. It transmits visual information from the retina to the brain.

When light isn’t focused properly, it causes blurry vision. Glasses, contacts, or surgery can usually correct refractive errors, which include:

  • myopia (nearsightedness), which is when faraway objects look blurry
  • hyperopia (farsightedness), which is when close-up objects look blurry
  • astigmatism, which can result in blurry vision because the cornea is not perfectly shaped to direct light into the eye
  • presbyopia, which is farsightedness that’s caused by the loss of elasticity of the eye’s lens due to aging

Glaucoma is increased pressure of the fluid inside the eye. This can cause optic nerve damage. Glaucoma is a common cause of blindness. Age, race, and family history are important risk factors.

A cataract is a clouding of the lens, causing blurry or color-tinted vision. People with cataracts often report “haloes” surrounding objects they’re looking at, particularly at night. This condition is most common in older adults.

Cataracts can be removed by surgery that replaces the damaged lens with an artificial lens.

Age-related macular degeneration (AMD) is gradual damage to the cells of the macula. This condition is most common in people over 60 years of age.

AMD causes blurry vision, especially in the center of the field of view. According to the Centers for Disease Control and Prevention, AMD is the most prevalent cause of blindness and vision loss in people over age 65 in the United States.

Amblyopia is commonly referred to as a “lazy eye.” It occurs when vision has not properly developed in the eyes, and the brain begins to favor the eye with better vision.

This happens if one of the eyes is blocked from producing clear images during the critical years from ages birth to 6. One eye may be inhibited by problems such as a lid droop, tumor, or misaligned eyes (strabismus) that are not corrected when a child is young.

It is crucial to have an eye doctor evaluate a young child whose eyes do not align or who has vision problems to ensure that the condition is properly diagnosed and treated.

Diabetic retinopathy is damage to the blood vessels of the retina caused by diabetes. It causes blurred or dark spots in the field of vision and can eventually lead to blindness.

The best way to avoid these vision problems is to keep your blood sugars under control, and see your eye doctor every year for a dilated eye exam. Proper care can lessen complications.

When the retina separates from the back of the eye, it’s called a detached retina. It causes blurry vision and partial or complete loss of vision and should be treated as a medical emergency.

Dry eye is a lack of tears. It’s usually due to a problem with the tear formation, tear ducts, or eyelids, or it’s a side effect of certain medications. This condition can cause pain and blurry vision.

The eyes are complex, and it’s important to know the different parts and how they function.

Knowing how each part works can help you recognize vision problems and symptoms of common eye conditions so you can get early treatment and maintain your eye health.