Answers by Dr. Mitchell Gossman, an ophthalmologist at Eye Associates of Central Minnesota, located in St. Cloud
How does the eye work?
Of course, describing all the details of how the human eye works is far beyond the scope of a short article, but it helps to draw an analogy between the parts of the eye and the parts of a camera. In fact, the eye is not just a camera, it’s a living movie camera! Let’s review its parts.
All cameras have lenses that focus light and form an image of the outside world. In fact, all modern cameras have multiple lenses within them. The eye also has multiple “lenses.” The front of the eye, the clear dome-shaped structure (contact lenses ride on this) called the “cornea,” allows light to enter the eye. Not only does the cornea admit light into the eye, it contributes to focusing the image.
This partially-focused image then passes through the pupil. The pupil is, obviously, the opening in the colored part of the eye called the iris. The iris regulates how much light enters the eye, and even has the same name as the part in a camera that does the same thing, but is also called the “diaphragm.” The opening in a camera is called the “aperture,” and its size is usually adjustable.
In the eye, the “lens,” also known as the “crystalline lens” or “natural lens,” is behind the pupil and completes the focusing of the image. The corresponding part in a camera is another artificial lens (usually many lenses), and they perform the same purpose, further focusing light. The human lens has the amazing ability to change its power, which is why we can focus up close without glasses (until about age 45 as any reading glasses wearer knows).
The eye is spherical, and most of its space inside is occupied by a clear jelly called the “vitreous.” In the camera, the space behind the last lens is called the “image space” and is filled with air (unless it’s in space such as the Hubble Space Telescope where it’s empty vacuum). When the vitreous has defects like strings and specks, we see them as “floaters.”
The camera lens focuses the image onto a sensor which produces the image that’s sent to your computer later, and in years past was focused on film then sent to the photofinishing shop. In the eye, the image is focused, passes through the vitreous, and is projected on the “retina” where the actual image is formed.
To view the digital image, you can view it on the screen of the camera or cellphone, but if you want to save it permanently, you might connect your camera to a computer. In the human eye, the images formed are sent to the brain via the “optic nerve.” So, the optic nerve is like a USB cable connected to your brain.
There you have it, the eye is nothing more than a camera, but a remarkable living camera.
Find out more
Dr. Mitchell Gossman is a comprehensive ophthalmologist, along with Dr. Melanie Thares, an optometrist, at Eye Associates of Central Minnesota. The office is located at 628 Roosevelt Road, Suite 101, in St. Cloud. To make an appointment or to learn more, call 320-774-3789 or email info@eaofcm.com.
“Ask the Expert” is sponsored content (paid advertising) provided by Eye Associates of Central Minnesota. To learn how your business can promote its products and services like this, contact Sr. Perspective at 320-334-3344.
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