The Human Eye Flashcards
What is myopia
(near-sightedness)
Have difficulty seeing distant objects
Light rays converge before the retina
When they hit the retina, the light rays are diverging
Causes:
Shape: the distance between the lens and retina is too large
Strength: the cornea-lens combination is too strong
The solution is a diverging lens (negative meniscus)
Diverge the rays before they go through the lens of the eye
They can cross later to have an image on the retina
What is hyperopia
far-sighedness)
Can see far away, but have difficulty seeing nearer objects
The image is made past the retina
Causes:
Shape: the distance between the lens and retina is too small
Thinner eyeballs
The cornea-lens combination is too weak
When the objects are far away, the refracted light rays can meet at the cornea because of the weak cornea-lens
The solution is a converging lens (positive meniscus)
To converge the rays before they go through the lens of the eye
The rays can cross sooner to have an image form on the retina
What is a cataract
A cataract is a cloudy part on the lens
Very common as you get older
Proteins and fibers in the lens begin to break down, causing vision to become hazy or cloudy
What is the lens on the eye
A lens refracts light so it hits the retina
What is the retina
The retina is located at the back of the eye
Converts the light signal into electrical signal that is transmitted to the brain through the optic nerve
Filled with photoreceptive cells are referred to rods or cones
What is the cornea
The cornea allows light to enter the eye and refracts light on the lens
The lens and cornea create a converging lens together
The lens refracts to the retina
They produce a smaller, real, and inverted image on the retina
The brain (optic nerve) makes corrections on the image, to make it a same and upright image
What is the pupil
A pupil is a hole of the eye that allows light to pass through
The pupil adjusts to light by enlarging or reducing the size of the pupil
Shrinks when there is too much light
Enlarges when there is less light
What is the iris
The iris is a ring that controls the size of the pupil
The pupil is a hole which is created by the iris
Controls how much light enters your pupil
What are ciliary muscles
Ciliary Muscles control the shape of the lens
Allow to accommodate and refocus on an object
Changes the focal point
Ciliary muscles relaxed = thin lens = less refraction = to see objects farther away
Ciliary muscles contracted = thick lens = more refraction = to see objects closer
