- PIGMENTED LAYER - NEURAL LAYER

1. Blue cones, which are sensitive to blue light. 2. Green cones, which are sensitive to green light. 3. Red cones, which are sensitive to red light.

VISION part III Flashcards by Kimberly Cambia

innermost layer of the eyeball

NERVOUS TUNIC/RETINA

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the inner coat of the eyeball, lines the posterior three-quarters of
the eyeball and is the beginning of the visual pathway

RETINA

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is the site where the optic (II) nerve exits the eyeball. Bundled together with the optic nerve are the two blood supply: central retinal artery,
a branch of the ophthalmic artery, and the central retinal vein

OPTIC DISC

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2 LAYERS OF RETINA

PIGMENTED LAYER
NEURAL LAYER

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non-visual portion of retina
-It is a sheet of melanin-containing epithelial cells located between the choroid
and the neural part of the retina

PIGMENTED LAYER

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multilayered outgrowth of the brain
that processes visual data extensively before sending nerve impulses into axons that form the optic nerve

NEURAL LAYER

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3 distinct layers of retinal neurons:

PHOTORECEPTOR LAYER
BIPOLAR CELL LAYER (horizontal and amacrine cells)
GANGLION CELL LAYER

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are specialized cells in the photoreceptor layer that begin the process by which light rays are ultimately converted to nerve impulses

PHOTORECEPTORS

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2 TYPES OF PHOTORECEPTORS

RODS AND CONES

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HOW MANY RODS ARE IN THE RETINA

120 MILLION

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HOW MANY CONES ARE IN THE RETINA

6 MILLION

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very sensitive to light (have low light threshold)
dim light (black and white vision)
PERIPHERAL VISION

RODS

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RHODOPSIN IS MADE UP OF CHON

SCOTOPSIN

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responsible for color vision

CONES

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CONE ARE MADE UP OF CHON -

PROTOPSIN

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derivative of vit. A

RETINAL

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3 types of CONES

Blue cones, which are sensitive to blue light.
Green cones, which are sensitive to green light.
Red cones, which are sensitive to red light.

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inability to distinguish between certain colors because of the absence or deficiency of 1 or 3 photopigment

COLOR BLINDNESS

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inability to see well at dim light

NIGHT BLINDNESS/NYCTALOPIA

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Good vision depends on adequate intake of

CAROTENOID

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a small yellow spot near the center of the posterior portion of the retina

MACULA LUTEA

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A small pit/depression at the center of the
macula lutea. It contains only CONES, thus, the area of highest visual acuity or resolution

CENTRAL FOVEA

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ABILITY TO SEE IMAGES MOST CLEARLY

VISUAL ACUITY

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SHARPNESS OF VISION

RESOLUTION

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BLIND SPOT is a white spot just medial to the macula lutea. Where blood vessels, optic nerve enter the eyes. It contains no photoreceptors, thus objects focused on this area cannot be seen.

OPTIC DISC

FUNCTIONS OF THE COMPLETE EYE:

1. REFRACTION 2. ACCOMMODATION

- is the bending of light as it passes from one medium to another.

REFRACTION

is a process by which the lens of the eye changes in shape/curvature to adjust for vision at various distances; the lens either increase/decrease in its curvature

ACCOMMODATION

4 MEDIA OF REFRACTION

1. cornea 2. aqueous humor 3. lens 4. vitreous humor

is the crossing point of light rays

FOCAL POINT

is the process of causing light to converge (bend toward each other

FOCUSING

CHARACTERISTICS OF IMAGES FOCUSED ON THE RETINA:

1. INVERTED/UPSIDE-DOWN 2. RIGHT TO LEFT REVERSAL

what is the image seen on the retina when there is a convergence of light rays

INVERTED/UPSIDE-DOWN

what is the image seen on the retina when the light from right side strikes the left side of the object and vice versa

UNDERGO RIGHT TO LEFT REVERSAL

The light rays reflected from the object are nearly PARALLEL to one another

VIEWING AN OBJECT @ 20 ft. DISTANCE

Light rays that are reflected from the object are DIVERGENT ( they move away from each other

VIEWING AN OBJECT - NEAR OBJECT (NEAR VISION)/CLOSER THAN 20 ft.

Thus, when viewing at closer objects, light rays must be refracted more to allow the image to be focused on the retina called

accommodation

What makes the lens increase in its curvature?

 The CONTRACTION of the ciliary muscle, allowing the ciliary process & choroid to be pulled forward toward the lens -- this action releases tension on the lens & on the suspensory ligaments  Because the lens is elastic, it changes its shape: shortens, thickens, bulges (increase in convexity)

 In order to accommodate light rays, the ciliary muscles should RELAX, causing the suspensory ligaments to exert greater tension on the lens, thus the lens becomes more flat: stretched in all direction by the suspensory ligaments decreased convexity of the lens

DISTANT OBJECT (FAR VISION)

3 REQUIREMENTS FOR ACCOMMODATION (1)

1. CHANGE IN THE SHAPE near vision: increased in curvature far vision: decreased in curvature

3 REQUIREMENTS FOR ACCOMMODATION (2)

2. CONSTRICTION/DILATION OF THE PUPILS bright light: constriction dim light: dilation

3 REQUIREMENTS FOR ACCOMMODATION (3)

3. CONVERGENCE OF THE EYES - medial movement of eyeballs (*The nearer the object, the greater is the degree of convergence needed to maintain binocular vision)

convergence is not complete, it produces double vision

DIPLOPIA

minimum distance for near point vision

4 inches in young adult

Image is focused in front of the retina, thus the person has to move closer to the object to allow clearer vision

MYOPIA – Nearsightedness

causes of myopia

a. Elongated eyeball b. Thickened lens

correction for myopia

CONCAVE LENS

FARSIGHTEDNESS

HYPEROPIA/HYPERMETROPIA

CAUSES OF HYPEROPIA

a. Shortened eyeball b. Thin lens

CORRECTION FOR HYPEROPIA

CONVEX LENS

The cornea’s curvature is asymmetrical, so light rays are focused at 2 points on the retina, rather than at one point resulting to: o blurred vision, shadows on the letters, squinting o double vision

ASTIGMATISM

CORRECTION FOR ASTIGMATISM

Eyeglasses wherein its anterior outer surface corrects visual defects & the posterior surface. Matches the curvature of the cornea.

–inflam of the conjunctiva, from bacterial infxn

CONJUNCTIVITIS

*Contagious Conjunctivitis:

pink eye

– a cyst caused by infection of the sebaceous glands along the edge of the eyelids

CHALAZION

infection of an eyelash/hair follicle

STYE

NEARSIGHTEDNESS

MYOPIA

FARSIGHTEDNESS

HYPEROPIA

decrease in the ability of the eye to accommodate for near vision; comes with aging

PRESBYOPIA

a defect in which the cornea or lens is not uniformly curved & the image is not sharply focused

ASTIGMATISM

absence of perception of 1 or more colors; most of which have genetic origin

COLOR BLINDNESS

most common cause of blindness -clouding of the lens as a result of aging, infection or trauma; also excessive exposure to UV rays

CATARACT

- excessive pressure build up; results from an interference with normal circulation of AH or from overproduction - tunnel vision/increase of IOP - lost of peripheral vision

GLAUCOMA

*increase pressure w/in the eye can interfere with circulation & may lead to malfunction/destruction of the optic nerve

BLINDNESS