Your Eye is like a Camera

The eye can be thought of as the camera of the natural world. Like a camera, your eye has:

• A variable opening – the pupil;
• A lens system – this includes a transparent layer called the cornea (this is responsible for focusing) and a spherical lens inside the eye behind the iris;
• A ‘film’-like layer called the retina – a layer of photosensitive cells at the back of the eye;

The eye also has various sets of muscles that control the size of the pupil, the shape of the lens system (essentially controlling the ‘zoom’ function of the eye), and the general movement of the eyeball.

When the eye is directed at an area, light bounces off objects and passes through the cornea and pupil.

The lens, located between the pupil and the inside of the eye, refracts (bends) this light, focusing it onto the retina at the back of the eye. This light-sensitive layer is packed with sensory cells called ‘rods’ and ‘cones’ that change photons of light into electrical signals.

These signals can then be transmitted to the brain through the optic nerves and be reinterpreted as a clear image.

For you to process this image effectively, four things must happen:

• The image must be reduced to fit onto the retina;
• The scattered light must be focused accurately at the surface of the retina;
• The image must be curved to match the curve of the retina;
• The brain must be able to interpret the image.

Many of these necessities are achieved with the help of muscles attached to the lens. These muscles contract and relax to change the shape of the lens system and keep the light from the object focused on the retina, even when your eyes move.

The nervous system is responsible for controlling this complex set of muscle movements.

Most vision problems occur when the eye cannot effectively focus images onto the retina. This can be due to several reasons.

The most common vision problems have to do either with the shape of the cornea, the length of the eye, or the elasticity of the lens.

These common issues are known as refractive errors and most commonly manifest as short-sightedness (myopia), long-sightedness (hyperopia), astigmatism, and presbyopia. These errors can usually be corrected with external visual aids such as glasses, contact lenses, or Laser Eye Surgery.