psychology 4051 the eye/optics. light the stimulus for vision is light energy-a small part of the...

Psychology 4051

The Eye/Optics

Light

• The stimulus for vision is light energy-a small part of the spectrum of electromagnetic radiation.

• Other organisms are sensitive to other parts of the electromagnetic spectrum.

Light

• The wavelength of light determines the hue or color that we perceive.

The Eye

• The eye possess a circular shape– Eyeball is often referred to as a globe.

• The eye is held in position and moved by a series of six extraocular muscles.

The Eye

• Strabismus: Misalignment in the position of the eyes.

• Esotropia: One or both eyes are misaligned in the inward position.

• Exotropia: One or both eye are misaligned in the outward direction.

The Eye

• Strabismus can be treated by adjusting the extraocular muscles.

• E.g., in esotropia, the medial rectus muscle can be recessed.

The Eye• The eye is divided into two chambers• Anterior chamber: the region of the eye between the cornea and the lens that

contains aqueous humor.

The Eye

• Aqueous Humor: a clear watery fluid that occupies the front chamber of the eye and nourishes the lens and the cornea.

The Eye

• Posterior Chamber: Rear section of the eye from the back of the lens to the retina.

• Filled with vitreous humor.

The Eye/Optics

• The stimulus for vision is light.• For us to perceive objects and patterns, the

eye must take light reflected of the surface of the object or pattern, and project it onto the retina.

• The light must be refracted and focused on the retina

The Eye/Optics

The Eye/Optics

• Cornea: Carries out the initial bending of light.

• The primary refractive surface.

• Pupil: An opening in the front of the eye through which light passes.

The Eye/Optics

• Iris: A series of muscles that control the size of the pupil, and in turn, controls the amount of light entering the eye.

The Eye/Optics

The Eye/Optics

• Coloboma: an abnormality in the iris that leads to an irregularly shape pupil.

The Eye/Optics

• Lens: a transparent biconvex structure that refracts light.

• Changes its thickness (accommodates) to focus objects at different distances.

The Eye/Optics

• Suspended by the zonule fibers which are attached to the ciliary body/muscles.

The Eye/Optics

• Distant Objects: Ciliary muscles contract, lens is relatively flat

• Near Objects: Ciliary muscles relax, lens is spherical

The Eye/Optics

• Cataract: Opacities on the lens which disrupt the passage of light and prevent the formation of a sharp image on the retina.

The Eye/Optics

• The eye is approximately 24 mm long.• If the eye is substantially shorter or longer,

optical problems will occur.• Myopia: the eye is too long to match its focal

power. The image is focused in front of the retina.

The Eye/Optics

• Corrected with a concave lens that reduces overall refractive power

The Eye/Optics

• Hyperopia: The eye is too short to match its focal power. The image is formed in behind the retina.

• Also referred to as hypermetropia.

The Eye/Optics

• Corrected with a convex lens that increases the overall refractive power of the eye.

The Eye/Optics

• Astigmatism: a distortion in the shape of the cornea.

• The cornea is curved more sharply along one axis than along the other.

• As a result, the image is distorted.• Can be corrected by using a lens that

counteracts the distortion

The Eye/Optics

• If one or more of these lines appears faint, or fuzzy, you have astigmatism along that meridian.