Refractive Errors

Front 1

Refractive errors are normal.
They are NOT a form of visual impairment.

Back 1

Refractive Errors

Front 2

(Near-sightedness) Eye ball is too large.
Point of focus of light rays is in front of the retina

Back 2

Myopia

Front 3

(Far-sightedness) Eyeball is too small.
Point of focus of light rays is behind the retina.

Back 3

Hyperopia

Front 4

(Regular and irregular)
Regular is caused by bulge in cornea. (can correct)
Irregular is caused by "bumpy" cornea(can't correct)

Back 4

Astigmatism

Front 5

(lens hardens with age)
Lens cannot change shape to focus light rays on retina.
Found in individuals usually older than 40.
Convergence and accommodation

Back 5

Presbyopia

Front 6

The process of the lens of the eye changing shape to focus light rays on the retina.
Ciliary muscle relaxes causing suspensory ligaments to tighten streching the lens and making it thinner resulting in less focusing.
Ciliary muscle contracts, lessening tautness of the suspensory ligaments causing the lens to become thicker resulting in more focusing power.

Back 6

Accommodation

Front 7

The process of the two eyes coming together to view objects at a close distance. The closer the object, the more convergence is needed.
Convergence and accommodation work together. The closer the object of regard, the more the eye must accommodate and the more the eyes must converge. **

Back 7

Convergence

Front 8

Light rays emanating from objects 20 feet away or further reach the eye in parallel form.
Light rays emanating from objects closer than 20 feet reach the eye as they spread apart.
The closer the object, the more spreading apart they are

Back 8

Other about Accommodation and convergence

Front 9

Refract or bend light rays
Triangular shaped glass. Light rays passing through bend TOWARD THE BASE(thicker part)

Back 9

Prisms

Front 10

Comprised of two prisms which are put together base to base.
These lenses bend light rays together

Back 10

Convex lens

Front 11

Composed of two prisms put together at their points, These lenses spread light rays apart.

Back 11

Concave

Front 12

MYOPIA
CONCAVE
DIVERGE

Back 12

HYPEROPIA
CONVEX
CONVERGE

Front 13

A measure of the power of a prism or lens to bend light rays.
(1 Diopter lens will bring parallel light rays to a focus 1 meter behind the lens)

Back 13

Diopter

Front 14

the point of focus is in front of the retina so concave lenses are used to spread the light rays apart sufficiently to bring the point of focus on the retina.
-Concave lenses correct myopia

Back 14

Myopia

Front 15

The point of focus is behind the retina, convex lenses bring the light rays together sufficiently to bring the point of focus on the retina
-Convex lenses correct hyperopia

Back 15

Hyperopia