How the Eyes Work
Everything about our eyes is designed to focus light and interpret and transmit it as information to the brain:
- The cornea, iris, ciliary body, and lens all work on focusing light onto the retina.
- The choroid, aqueous and vitreous humours, and the lacrimal system provide balance, maintain pressure, and nourish the ocular tissues.
- Light that enters the eye is refracted through the cornea, aqueous humour, lens, and vitreous humour before it reaches the retina. How well these parts work together account for visual acuity.
- The visual information received by the retina is then transmitted to the brain through the optic nerve.
Rods & Cones
The retina contains 2 types of photoreceptor cells: rods and cones.
- Rods help us see in low-light. The human eye has about 120 million rods.
- Cones allow us to see colour. The human eye has about 6 to 7 million cones.
The eye has 3 different types of cones that contain several types of pigment, each reacting to different light wavelengths. The 3 types of cones are called either blue, green, or red, or short (S), medium (M), or long (L), based on the wavelength of light they react to.
When the eye is missing some of these pigments, this is called colour deficiency.