Sensory

How many types of photoreceptors? What are they called

2 rods and cones

_____ lies between the cornea and the iris.

Anterior chamber

either the cornea or the lens has an irregular curvature. As a result, parts of the image are out of focus, and thus vision is blurred or distorted.

Astigmatism

is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera.

Choroid

Bright light: Pupil constrict as ____ ____ of iris constricts (parasympathetic)

Cicular muscles

farsightedness, the eyeball length is short relative to the focusing power of the cornea and lens, or the lens is thinner than normal, so an image converges behind the retina. Individuals can see distant objects clearly, but not close ones.

Hypermetropia

nearsightedness, which occurs when the eyeball is too long relative to the focusing power of the cornea and lens, or when the lens is thicker than normal, so an image converges in front of the retina. individuals can see close objects clearly, but not distant objects. I this is due to the shape of the eyeball. it is posterior from a normal person would have their retina.

Myopia

The third and inner layer of the eyeball, lines the posterior three-quaters of the eyeball and is the beginning of the visual pathway.

Retina

___ allows us to see in dim light, such as moonlight because rods do not provide color vision, in dim light we can see only black, white, and all shades of gray in between.

Rods

the space anterior to the lens—consists of two chambers

anterior cavity

a transparent watery fluid that nourishes the lens and cornea. ___ ____ continually filters out of blood capillaries in the ciliary processes of the ciliary body and enters the posterior chamber. It then flows forward between the iris and the lens, through the pupil, and into the anterior chamber. From the anterior chamber, ___ ____ drains into the scleral venous sinus (canal of Schlemm) and then into the blood. Normally, ____ ____ is completely replaced about every 90 minutes.

aqueous humor

The optic disc is also called, ___ because it contains no rods or cones, we cannot see images that strike the blind spot.

blind spot

Three types of cone are present in the retina

blue cones green cones red cones

Part of the eye, the ______ is a circular structure just behind the iris composed of the ciliary muscle and ciliary processes which attach to the lens.

ciliary body

Brighter lights stimulate ____, which produce color vision.

cones

____ refers to this medial movement of the two eyeballs so that both are directed to- ward the object being viewed, for example, tracking a pencil mov- ing toward your eyes. The nearer the object, the greater the degree of convergence needed to maintain binocular vision.

convergence

A surface that curves outward, like the surface of a ball, is said to be ____. When the surface of a lens is ____ that lens will refract incoming light rays toward each other, so that they eventually intersect.

convex

The lens of the eye is ___ on both its anterior and posterior surfaces, and its focusing power increases as its curvature becomes greater.

convex

is a transparent coat that covers the colored iris. Because it is curved, the ____ helps focus light onto the retina

cornea

When the eye is focus- ing on a close object, the lens becomes more ____, causing greater refraction of the light rays.

curved

The ___ ____ is the area of thee highest visual acuity.

fovea centralis

a flat, colored, ring-shaped membrane behind the cornea of the eye, with an adjustable circular opening (pupil) in the center helps the light enter the eye

iris

behind the pupil and isis with the cavity of the eyeball, is the ___. It helps focus images on the retina to facilitate clear vision. It separates the posterior chamber of the anterior cavity from the virteous chamber.

lens

is the minimum distance from the eye that an object can be clearly focused with maximum accommodation.

near point of vision

The site where the optic (II) nerve exists the eyeball.

optic disc

____ are specialized cells that begin the process by which light rays are ultimately converted to nerve impulses.

photoreceptors

detect light that strikes the retina of the eye

photoreceptors

-With aging, the lens loses elasticity and thus its ability to curve to focus on objects that are close. Therefore, older people cannot read print at the same close range as can younger people. -By age 40 the near point of vision may have increased to 20 cm (8 in.), and at age 60 it may be as much as 80 cm (31 in.) -usually begins in the mid-forties. At about that age, people who have not previously worn glasses begin to need them for reading. Those who already wear glasses typically start to need bifocals, lenses that can focus for both distant and close vision.

presbyopia

The opening of the iris. The ____ may appear to open (dilate) and close (constrict), but it is really the iris that is the prime mover; the____ is merely the absence of iris. The pupil determines how much light is let into the eye. Both ____ are usually of equal size.

pupil

a layer at the back of the eyeball containing cells that are sensitive to light and that trigger nerve impulses that pass via the optic nerve to the brain, where a visual image is formed.

retina

the "white" of the eye, is a layer of dense connective tissue made up mostly of collagen fibers and fibroblasts. The ____ covers the entire eyeball except the cornea; it gives shape to the eyeball, makes it more rigid, protects its inner parts, and serves as a site of attachment for the extrinsic eye muscles.

sclera

the clear colorless transparent jelly that fills the eyeball posterior to the lens a transparent jellylike substance that holds the retina flush against the choroid, giving the retina an even surface for the reception of clear images

vitreous body

The larger posterior cavity of the eyeball is the ____ ____, which lies between the lens and the retina.

vitreous chamber

If the surface of a lens curves inward, like the inside of a hollow ball, the lens is said to be _____ and causes light rays to refract away from each other.

Concave

About 75% of the total refraction of light occurs at the ____. The ____ provides the remaining 25% of focusing power and also changes the focus to view near or distant objects.

Cornea lens

lies behind the iris and in front of the zonular fibers and lens

Posterior chamber

Dim light: Pupil dilates as ___ ___ of iris contract (sympathetic)

Radial muscles

When light rays traveling through a transparent substance (such as air) pass into a second transparent substance with a different density (such as water), they bend at the junction between the two substances. As light rays enter the eye, they are refracted at the anterior and posterior surfaces of the cornea. Both surfaces of the lens of the eye further ____ the light rays so they come into exact focus on the retina.

Refraction