Perception

This is the normal condition where the light refracts properly onto the retina.

Myopia occurs when light that enters the eye focuses in front of the retina. This results in nearsightedness (difficulty seeing objects farther away from you).

Hyperopia occurs when light that enters the eye focuses behind the retina. This results in farsightedness (difficulty seeing objects close to you).

Items that are close together are often seen as part of a group.

Example: The image on the left shows two groups of 2 by 4 dots & the image on the right shows six groups of 2 by 2 dots.

Items that look alike tend to be grouped together based on various formal properties such as color, size, shape, position, etc.

Example: The image on the left shows how you would group by shape and the image on the right by color.

Items that are missing parts or sections can still viewed as whole.

Example: These images do not have a complete contour, but are still viewed as a circle, rectangle, and triangle respectively.

Items that are symmetrical share the same form and are thought to belong to the same object so they are grouped together.

Example: The left shows three groups of symmetrical lines and the right shows three groups of lines depicting parallelism.

Items that are perceived to be in the same group are expected to move in the same direction.

Example: The left image shows a pattern and the right image shows a disruption in the motion of the lines (by the diagonal line).

Items where intersection occurs imply that there are at least two separate items.

Example: Image 1 shows the most likely objects that are causing the intersection, image 2 is also probable, but less likely.

Retinitis pigmentosa is a degenerative disease that results in the death of photoreceptors (rods and cones) and the pigment epithelium (which prevents too much light from entering the eye).

Causes
This disease can occur at any age (later onset usually results in more rapid degeneration of cells). It is an inherited disease that is the result of a gene mutation that produce incorrect amounts of protein necessary for proper functioning.

Treatment
Currently there is no treatment for this disease and researchers are still looking for ways to treat this disease which is responsible for causing individuals to go blind. Sunglasses do provide some protection UV light rays.

Age-related macular degeneration occurs when the macula and retina degrade and no longer allow individuals to see fine detail.

Causes
This disease is associated with age-related vision loss as well as color perception and gets progressively worse over the years.

Treatment
Currently there is no treatment for this disease, however, effects can be lessed or slowed down by taking various vitamins, receiving laser therapy, or wearing specialized glasses.

Cataracts occurs when the eye's lens becomes cloudy which makes it more difficult for light to pass through and get to the retina.

Causes
This disease can occur at any age, although typically are more likely to develop at an older age and can become more severe as a result of other disesases such as high blood pressure or diabetes.

Treatment
This disease can be treated by removing the lens and replacing it with a synthetic lens.

Strabusmus occurs when the coordination between the two eyes are weak which results in either esotropia (eyes cross inward) or extropia (eyes turn outward).

Causes
This disease can occur in both children and adults. It is does not allow individuals to focus on specific points, and it results in double vision and lack of depth perception.

Treatment
This disease can be treated through the use of glasses, eye patches, eye drops, or surgery. Without treatment, you can run the risk of permanent loss of vision in the weaker eye.

Anisometropia occurs when there is light is refracted differently in each eye and will often result in amblyopia (lazy eye) in the eye that has the blurrier vision.

Causes
This disease typically occurs around the age of six to late adolescence. Light in one eye is refracted in front of the retina (myopia) and light in the other eye is refracted behind the retina (hyperopia) which results in both nearsightedness and farsightedness respectively.

Treatment
This disease can be easily treated by getting prescription glasses or contact lens that adjust the for the incorrect light refraction.

Glaucoma occurs when there is an increased pressure within the eye.

Causes
This disease typically occurs in middle age individuals. And it is casused by elavated levels of fluid presseure that occur in the aqueous humor region.

Treatment
This disease can be controlled through the use of eye drops or surgery. The damage that has already occurred as a result of glaucoma cannot be reversed, so early treatment is important.