We are approaching the end of another year – 2021. Throughout the year we provided critical information about eye health and diseases. We will end this year by providing insights into how our eyes work. Make a New Year’s resolution that is specific to your eye health.
Every morning, we open our eyes and become immersed in a wealth of visual information. The eyes and related brain structures are complex systems that allow us to experience visual information from the surrounding world. It is easy to take clear vision for granted, but even subtle changes in the structure or functioning of the eyes can disrupt our sight. An eye care provider conducts a thorough eye exam to ensure that these components are functioning well together.
Our eyes sit in a bony protective socket, the orbit, which has six extraocular muscles to each eye. These muscles allow movement of the eye up and down, side to side, and eye rotation. The eyeball is not a single, spherical structure as is commonly thought. It consists of a smaller, curved portion called the cornea that attaches to a larger, roughly spherical structure called the sclera (the white of the eye). The eyeball contains a jelly-like substance called the vitreous fluid.
Toward the front of the eye are three essential structures: the iris, pupil, and lens. The iris is the colored part of your eye – it can expand and contract to determine how much light to let in through the pupil, the black hole in the center of your eye. Finally, the lens is a flexible, convex structure that changes shape to direct light rays in different directions within the eye.
At the back of the eyeball is a layer of tissue called the retina. The retina consists of millions of photosensitive cells that react to certain types of light. Cone cells are clustered toward the center of the retina and react to colors and details in bright light. Rod cells, which are spread toward the periphery of the retina, react to dim lighting conditions (See Eye Anatomy below_Source: All About Vision).
- The Uvea Of The Eye
- Pupil: Aperture Of The Eye
- The Retina: Where Vision Begins
- Macula Lutea Of The Eye
- Choroid Of The Eye
- Lens Of The Eye
- Ciliary Body
- Eye Muscles
- Aqueous Humor
- Optic Nerve
- Fovea Centralis
Eyes Facilitating Vision
- Surface of the eyes and the eyelids inner surface contain the clear membrane conjunctiva.
- Tear film contains three layers and they lubricate the eyes.
- Lacrimal gland makes the watery part of the tears and sits under the outside edge of the eyebrow (away from the nose) in the orbit.
- Meibomian gland produces oil that becomes part of the tear film, and tears drain from the eye through the tear duct (See illustration below for “Eye Surface”).
- As light enters the eye through the pupil it passes through the lens, which changes shape to ensure that the light rays hit the retina. When the light rays reach the back of the eye, it stimulates the rod and cone cells to fire. Cone cells detect fine details and colors in the center of your visual field. Rod cells detect edges in peripheral vision and allow us to perceive shapes in dim light.
- In the retina there are rods and cones that convert light energy, functioning as a digital camera, into electrical signals that exit the eye through the optic nerve below the center of the retina.
- And finally, the optic nerve carries visual information to the occipital cortex in the very back of your brain, where it is processed to result in a vibrant visual experience (Back of eye illustration below).
Front of The Eye
Back Of The Eye
If any part of this complex arrangement functions improperly there is vision impairment. Thus, it is essential to receive regular optometry exams to have your eye structures and visual abilities checked. Start out the year right by visiting with us so that we can determine your eye health. Marcus Tullius Cicero stated, “The face is a picture of the mind with the eyes as its interpreter.” Cherish your eyes.
Merry Christmas, Happy Holidays, and Happy New Year to you and your family.