Understanding the anatomy of the eye

If we compare vision to a video recording device, the eye is the camera or camcorder. To be viewed, the image filmed by the camcorder must be transmitted to a computer and a screen. This camcorder – computer – screen assembly is the visual system.

The cord connecting the camcorder to the computer is comparable to the optic nerve.

The lens system of the visual system is equipped with two lenses <: the cornea and the crystalline lens. The cornea is the most powerful lens of the eye and focuses the image onto the sensitive "photographic" film that is the retina.

But the crystalline lens must also act on the light ray so that the image forms precisely on the retina. This image is then seen clearly by the brain.

The crystalline lens acts as a zoom and enables image focusing, or "accommodation".

Accommodation is the means by which the eye can automatically adjust to see near or far as needed. This can be compared to the autofocus system of a camera. Accommodation is achieved through the crystalline lens.

The crystalline lens is a lens located inside the eye. The power of the crystalline lens can vary. When observing a distant object, the crystalline lens is at rest; when the object comes closer, the crystalline lens curves and increases its power, enabling near vision.

Examples of minimum reading distances by age, showing the evolution of the crystalline lens (for an emmetropic eye):

• Child aged 2: 5 cm
• Child aged 6: 7 cm
• Adult aged 20: 10 cm
• Adult aged 40: 25 cm
• Adult aged 70: 2 m

When all the "lenses" of the eye are perfectly clear, well adjusted, and functioning perfectly, we see clearly. It only takes one of them to be out of adjustment for vision to become blurry at distance, up close, or both.

But be careful, you may have blurry vision for another reason, and glasses do not always allow you to see clearly, just as changing the lenses of a camera does not produce beautiful photos if you forget to put good film in the camera!