Log 2 - Optics Flashcards
Definition of how we see
Comprised of light reflecting off an object and entering our eye. The eye focuses the light and forms an image by turning the image into an electrical impulse that is sent along the optic nerve to the brain
The cornea provides what percentage of the eyes refractive ability
about 2/3
The crystalline lens provides what percentage of the eyes refractive ability
about 1/3
How often do the eyelids close and open on average
12-15 times per minute
What does a smaller pupil aperture mean to the quality of image
Larger depth of field
True or False
Our eyes don’t send images to the brain
True
Definition of Emmetropia
when rays of light fall directly on the retina, causes no refractive error
Definition of Ametropia
defect which prevents light rays from being brought to a single focus on the retina, involves hyperopia, myopia and astigmatism
Hyperopia Definition
is farsighted. it is shorter than an emmetropic eye and light rays fall behind the retina. Everyone is born hyperopic and tends to loosen as the eye grows.
Myopia Definition
Nearsighted eye. Can’t see distance, and rays of light fall in front of the retina, because the eye is longer than normal
-minus (concave) lens
Astigmatism Definition
When rays of light do not come to a point of focus on the retina
-vertical lines of letters appear sharper than horizontal lines or vise versa
Presbyopia Definition
When the vision for reading or other close up work declines due to the loss of elasticity of the crystalline lens and weakness of the ciliary muscle.
Anisometropia Definition
a difference in refractive errors of the eyes exist, more than 3.00D
What does 20/20 represent
A patient can read at 20 feet what a person with normal acuity can read at 20 feet
Far Point of Accommodation is at what distance?
the most distant point from the eye at which an object can be clearly seen (infinity)
Hyperopic eye - behind the cornea
Myopic eye - some finite distance in front of the cornea
