Eyes 👁️

• What is the retina and its function?


  Retina: Light-sensitive layer at the back of the eye.

  Function: Converts light into neural signals for the brain to process vision.
• What are the two types of light receptor cells and what do they do?

  Rods: sensitive to low light intensity, no colour detection responsible for night vision, impulse sent when connection to optic nerve

  Cones: sensitive to high light intensity, responsible for colour vision, located in fovea, impulse sent when connection to optic nerve
• What is the optic nerve and its function?

  Optic nerve: bundle of sensory neurones at back of eye

  Function: carries impulses from retina to brain.
• What is the pupil and its function?

  Pupil: Dark area in the centre of iris/gap or hole surrounded by muscles

  Function: allows light to pass through the eye
• What is the iris and its function?

  Iris: coloured part of the eye

  Function: control the size of the pupil, regulating the amount of light that enters the eye. Muscles constrict/dilate.
• What is the cornea and its function?

  Cornea: Transparent outer layer of the eye and convex (curved)

  Function: refracts to allow light to enter and focuses light for a clearer image
• What is the lens and its function?

  Lens: transparent, bi-convex, flexible disk behind iris, attached to ciliary muscles by suspensory ligaments.

  Function: refracts light further, finetunes focus on retina
• What are suspensory ligaments and their function?

  Suspensory ligaments: connect lens to ciliary muscles

  Function: holds lens in place
• What is the choroid layer and its function?

  Choroid layer: pigmented layer between retina and sclera ,filled with blood vessels

  Function: absorbs light, stops refraction, bring oxygen and nutrients to the eye
• What is the fovea and its function?

  Fovea: most sensitive part of the eye and right at back

  Function: cone cells in fovea responsible for colour vision
• What is the ciliary and its function?

  Ciliary: ring of smooth muscle, connected to lens by suspensory ligaments.

  Function: adjusts shape of lens
• What is the sclera and its function?

  Sclera: tough, white outer layer

  Function: protective layer around eye
• What is the conjunctiva and its function?

  Conjunctiva: mucus membrane that lubricates eye by producing tears and mucus.

  Function: helps prevent entry of microbes in eye.
• What is the blind spot?

  Blind spot: small circular area in retina,insensitive to light,no rods or cones
• Draw and label a diagram of the eye.


  This is an image:

  
• What is pupil reflex?

  It is automatic and part of natural reflex.
• What are the two types of muscle that control pupil size and what are they known as?

  They are called circular and radial muscles and are named antagonistic pairs as they work together but do opposite things.
• When dim light reaches the eye what happens?

  The radial contracts as the circular relaxes. Pupils dilate and more light enters eye.
• What happens when bright light reaches the eye?

  The radial relaxes and circular contracts as the pupils constrict and get smaller letting less light into the eye.
• What is accommodation?

  It brings out fine focusing which is done by the lens as it changes shape to focus on near or distant objects. Suspensory ligaments tighten or loosen as ciliary muscles contract or relax.
• What happens with near objects during accommodation?

  ciliary muscles contract, suspensory ligaments loosen/relax. Lens becomes shorter, curved and thicker as light is refracted more.
• What happens with distant objects during accommodation?

  ciliary muscles relax, suspensory ligaments tighten and contract, lens becomes longer, less curved and thinner. Light is refracted less.
• What is short sightedness?

  Short sightedness (myopia) is when far objects are blurry and light is focused on the front of the retina as they are refracted more than needed. The eyeball is too long or cornea too curved.
• What is long sightedness?

  Long sightedness (hyperopia) is when near objects are blurry and light is focused behind the retina as they aren't refracted enough. Eyeball is too short, cornea losing curvature, lens too thin/low.
• What is the treatment for short sightedness?

  Laser eye surgery or glasses and contact lenses with a concave lens

  
• What is the treatment for long sightedness?

  Laser eye surgery or glasses and contact lenses with a convex lens

  
• What are cataracts and their treatment?

  A protein build up inside the lens making it cloudy, can lead to blindness and causes misty/blurry vision.

  Treatment: Replace lens with a plastic lens.
• What is colour blindness and its treatment?

  It is when cone cells do not work properly. Unable to tell difference between red, green and brown.

  Treatment: None