The eye and eye conditions

• The cornea refracts light - bends it as it enters the eye
• The iris controls how much light enters the pupil
• The lens further refracts light to focus it onto the retina
• The retina contains the light receptors
• The optic nerve carries impulses between the eyes and the brain
• The sclera is the tough white outer layer of the eye. It helps protect the eye from injury
• The suspensory ligament changes the shape of the lens. it loosens the lens to make the lens thicker.
• The ciliary muscle changes the shape of the lens. It contracts to make the lens thicker
• When you focus on a nearby object the ciliary muscles contract and the suspensory ligaments loosen, making the lens thicker and more curved.
• When you focus on a distant object the ciliary muscles relax and the suspensory ligaments are pulled tight, making the lens thinner and more flat
• Hyperopia (Long-sightedness) is when you can only see things from a far distance away. It requires Convex lenses to fix the light to the focal point.
• The hypothalamus (located in the brain, also known as the thermoregulatory centre) is responsible for regulating body temperature, hunger, and thirst.
• In bright light, the eye's circular muscles contract, the radial muscles relax and the pupil constricts in order to make the pupil shrink and reduce the amount of light going into the eye.

  
• In dim light, the circular muscles relax, the radial muscles contract and the pupil dilates so the pupil grows larger and lets as much light into the eye as possible