The Eye Flashcards
What is the Sclera
Tough, supporting wall of eye
What is the cornea
Transparent outer layer found at front of eye - refracts light into the eye
What is the iris
Contains muscles that allow it to control the diameter of the pupil that controls amount of light allowed in eye
What is the lens
Focuses light on to the retina - contains receptor cells sensitive to light intensity and colour
How is shaped of eye controlled
Ciliary muscles and Suspensory ligaments
What does optic nerve do
Carries impulses from receptors on retina to brain
What is the iris reflex
When lots of light shine into eye the light receptors in eye detect the light and reflex triggered so circular muscles in iris contract and radial muscles relax-reduce amount of light in eye
Opposite happens in dim light
What does the eye do when looking at near objects
Ciliary muscles contract which slackens the suspensory ligaments and lens becomes fat (curved) and increases the amount by which it refracts light
What does eye do to look at distant object
Ciliary muscles relax that allows the suspensory ligaments to pull light that makes lens go thin and refracts light by smaller amount
How does the eye focus light
By changing the shape of the lens - known as accommodation
Why are people Long sighted
-Long-sighted people are unable to focus on near objects
-occurs when lens is wrong shape and doesn’t refract light enough or eyeball is too short
-images are brought to focus behind the retina
Why are people short sighted
-Unable to focus on distant objects
-occurs when lens is wrong shape and refracts light too much or eyeball to long
-images of objects brought to focus in front of retina
How to help long sighted and short sighted
-Use glasses of with a convex lens which refracts light rays so focus on retina - long sighted
-use glasses with concave lens so light rays focus on retina- short sighted
What is the medical term for long sighted
Hyperopia
What is medical term for short sighted
Myopia
What are treatments for vision defects
-contact lenses
-laser eye surgery
-replacement lens surgery
How do contact lenses work
-Thin lenses that sit on surface of eye and shaped to compensate fault in focusing.
-popular as lightweight and invisible
-more convenient for sport and activities
-2 types of contact lenses - hard and soft. Soft more comfortable but risk higher infections
How does laser eye surgery
-Bad eyesight corrected
-laser used to vaporise tissue which changes shape of cornea - slimming it down and making less powerful for short sight
-change shape to make more powerful for long sight
- risk of complications such as infection or eye reacting to make things worse
How does replacement lens surgery work
-long sight treated by replacing lens of eye
-natural lens removed and artificial lens is inserted
-carries risk of damage to retina
