Structure of the eye

The eye is one of the most vital organs for humans, responsible for our sense of vision, one of the five primary senses. Despite its small size, just about 23 mm in diameter, smaller than a one-dollar coin—the eye serves essential functions. It can distinguish up to a million different colors and is capable of detecting and measuring obstacles and distances in our surroundings.

Humans rely heavily on their vision, with approximately 80% of the information we gather about the world coming from our eyes. In modern society, it is no exaggeration to say that this tiny organ plays a central role in our daily lives.

A transparent, 5-layered membrane about 0.5 mm thick that covers the colored part of the eye. Light entering the eye first passes through the cornea. 

The lens adjusts its thickness depending on the distance of the object being viewed. It becomes thicker when focusing on nearby objects and thinner for distant ones, much like a camera lens.

The colored part of the eye, which controls the amount of light entering by adjusting the size of the pupil. It functions similarly to the aperture of a camera.

A thin membrane, approximately 0.2 mm thick, located at the back of the eye. It senses light and converts it into images, similar to how film works in a camera.

The depth of the eye, measured from the cornea to the retina. The average length is around 23 mm.

How we see things

The structure of the human eye is similar to that of a camera. The cornea and lens at the front of our eye act like the camera lens, while the retina at the back of the eye functions like the film in a camera.

When we look at an object, light carrying the color and shape of the object enters the eye. This light is refracted by the cornea and lens (similar to a camera lens), and then focuses on the retina (like the film of a camera), creating a clear image. This image is sent to the brain, allowing us to perceive a clear view of the object.

In a camera, the lens moves back and forth to adjust focus, while in the human eye, small muscles attached to the lens alter its thickness to adjust focus. When the lens properly focuses light on the retina, we perceive a clear image.

If the focus is off, either in front of or behind the retina, the image becomes blurred, similar to a camera being out of focus.

This results in unclear vision.
When the focus is correctly maintained on the retina without any adjustments, it is referred to as “normal vision.” However, if the focus is in front of the retina, it is called “myopia,” and if the focus is behind the retina, it is known as “hyperopia.” “Astigmatism” occurs when the focus position changes depending on the direction from which light enters the eye.