A Look at the Human Eye

Human eye

How the Human Eye Works

Seeing is possible thanks to a complicated series of events that start in the eyes and end in the brain. The entire process happens almost instantaneously and is only successful if every part of your visual system works properly.

It All Starts with the Cornea

Your cornea, a clear, rounded layer of tissue that covers your pupil and iris, helps light reach your eyes by bending the rays as they enter your pupils.

The iris and pupil work together to let light into the eye. Have you noticed that your pupils look bigger when the light is dim? Tiny muscles in the iris make the pupil bigger when it's harder to see, allowing more light to enter your eyes. The muscles shrink the size of your pupils when it's bright outside or inside.

The Lens Is Essential for a Clear Picture

Light rays pass through the lens and the vitreous humor after entering the eye. The lens is a transparent disc located inside the eye under the iris and pupil, while the vitreous is the clear gel that gives the eye its shape.

The muscles that control the shape of the lens relax, causing the lens to flatten when you look at an object in the distance. The opposite happens when you look at something nearby. The muscles contract, thickening the lens. The ability of the lens to change shape allows you to shift your focus from near to far objects and back again.

The lens focuses light rays on the retina in the back of the eye. If your eyeball is too long, the rays will focus in front of the retina, causing myopia, or nearsightedness. If you're nearsighted, close objects are easy to see, while everything in the distance looks blurry.

Hyperopia, or farsightedness, occurs when your eyeball is too short. Light rays focus beyond your retina and make your near vision blurry.

As you get older, the lenses of your eyes become less flexible. The loss of flexibility affects your ability to see near objects clearly. This condition, called presbyopia, usually begins in your early- to mid-forties, according to the American Optometric Association. Fortunately, a pair of reading glasses will make it much easier to read a book or thread a needle.

The Retina Transforms Light Rays

The retina covers the back of the eye and contains two types of photoreceptor cells. The rods, found in the outer part of the retina, are essential for side vision and help you see in dim light. Cones, the other type of photoreceptor cells, are located in the macula, the center part of the retina. Cones are needed for color vision and also help you see fine details easily.

The retina turns light rays into electrical impulses, then sends the impulses to the occipital lobe of the brain through the optic nerve. Problems with your retinas or optic nerve can affect your vision.

If you have macular degeneration, a common age-related eye condition, your central vision may be blurry or you may notice blank spots in the middle part of your vision. Increased eye pressure due to glaucoma can damage your optic nerve, causing partial or total loss of vision.

How Your Brain Helps You See

The visual cortex in the brain's occipital lobe serves as the vision command center. The cortex processes and stores images and helps you make sense of what you see. Thanks to your brain, you can recognize faces, colors, letters, and shapes. You can also see fine details, avoid obstacles, keep your balance, predict the speed of moving objects, remember the things you've seen in the past, and easily recall information after reading it.

Your brain also controls the muscles that move your eyes and turns the slightly different information received from each of your eyes into one clear image.

If a stroke, tumor, infection, disease, or head trauma injures the brain, your vision and your ability to understand what you see can be temporarily or permanently affected.

Annual visits to the optometrist help you ensure that every part of your visual system is working properly. Contact our office if you're ready to schedule your next eye exam.

Sources:

American Optometric Association: Adult Vision: 41 - 60 Years of Age

National Eye Institute: How the Eyes Work

American Optometric Association: How Your Eyes Work

American Macular Degeneration Foundation: How the Eye Works as a Camera

American Academy of Ophthalmology: Eye Anatomy: Parts of the Eye and How We See, 3/9/21

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  • of the best, most thorough, articulate, accessible doctors I’ve ever seen. Her office is packed full of state of the art cool eye tools that provide incredible insight (oops... pun actually works) and she explains so that this non-medical patient can understand. This exam was most comprehensive. One of my eye doctors is a friend and even when visiting him in Santa Monica office, the time Dr Joyce spent with me was comparable. I only wish she had more specialties (e.g. dermatology, podiatry). I’m a patient now so I feel safe. You better call for an appointment now lest she stops taking new patients. Thank you, Dr Joyce!

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  • This was my first time at Eyecare For You. The facility was very clean and the office staff pleasant. The young man who I was with in the beginning to do the initial check in process was very efficient, professional and it was very evident that he took his job seriously. I especially liked that he cleaned off each piece of equipment prior to my resting my chin and forehead on them. Dr Joyce was also very professional and personable. Her work ethic was spot on, and she explained each process very clearly and made sure I understood before she moved on to the next section. The equipment seemed to be the most current and I was overall very impressed with the care I received here. I will be returning.

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  • Excellent experience with Dr Joyce and others on the staff. No need to get records transferred from previous eye care center. Eyecare For You appears to have the latest hi-tech testing equipment and will determine the best option(s) to improve your vision to its maximum capability. I expect my new prescription glasses with anti-glare coating will minimize glare at night and should allow me to see better than ever. Cost was very reasonable. I have already recommended two friends to call for an appointment ASAP.

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  • Dr. Kathleen Joyce is absolutely amazing! I haven't seen her in over 2 years but she still made me feel like I just saw her last week. She pays attention to details and makes you excited to see her in the office! She really goes the extra mile

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