The Eye VISION Alyssa Jimenez & Cristina Santiago.
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Transcript of The Eye VISION Alyssa Jimenez & Cristina Santiago.
The EyeVISION
Alyssa Jimenez&
Cristina Santiago
Components Of the eye❖Eyelid (palebra)❖ Lacrimal apparatus❖Extrinsic Muscles❖Cranial Nerves
Components cont.
Eyelid● Also known as the
palebra● Protective shield for
the eyeball● Conjunctiva
Lacrimal Apparatus
● Tear secretion and distribution
● Lacrimal gland● Nasolacrimal gland
Extrinsic Muscles● Hold eyeball in orbital cavity
and allow for eye movement
● Superior Rectus Muscle
● Inferior Rectus Muscle
● Lateral Rectus Muscle
● Medial Rectus Muscle
● Superior Oblique Muscle
● Inferior Oblique Muscle
Structure of the eye● three tunics
■ fibrous■ vascular■ interna
The outermost tunicafunction: protection●Consists of:
Cornea: helps focus incoming light rays Sclera: protection, attachment of eye
muscles aqueous humor
The middle tunica● tunica vascular
o supplies eye tissue with oxygen and nutrients
● Consists of: choroid coat: contains
many blood vessels Pupil lens iris: colored ring around pupil
ciliary body: o ciliary muscles: control
shape of lenso ciliary processes: hold lens
in place.o accommodation: lens
changes shape to focus on close objects
o Aqueous Humor: thin, watery fluid that fills the space between the cornea and the iris
the innermost tunica● Tunica Interna
the retina● inner lining of
eyeball● site of
photoreceptors● vitreous humor
Cranial Nerves● Occipital Lobe● Oculomotor Nerve*ex: maintaining the opening of an
eyelid/pupil constriction● Optic Nerve
*ex: brightness,perception,contrast
Structure cont.● Blind spot: no photoreceptors present● posterior cavity: filled with vitreous
humor● jelly-like fluid,which maintains the spherical shape of
the eyeball
Visual Receptors● Two types of visual receptors
Cones:o color visiono produce sharp imageso absorb lighto less sensitive in low light levels
Rods:o night visiono produce silhouettes of imageso do not differentiate coloro sensitive to low light levelso peripheral areas of retina
Rhodopsin & Iodopsin light● Rhodopsin light:
o absorbing pigmento embedded in membranous discs
● Iodopsin light: o a photosensitive violet pigment that occurs in
the cones of the retina and is transformed by light into retinal and an opsin protein.
Dark Currents in photoreceptors
*Sodium channels stay open in photoreceptor when no light is being absorbed*Constant current of sodium into cell keeps photoreceptor the most active in darkness
Refraction ● The refraction process is similar to the way a camera’s lenses tale in light
● The bending of a wave when a light passes a fast medium to a slow medium bends the light ray toward the normal to the boundary between the two media, this is how the eye interprets refraction
● 80% of refraction occurs in the cornea is the most drastic change in the index of refraction which the light experiences
● 20% of refraction occurs in the inner crystalline lens● Light is refracted, or bent, when it passes from one medium to a medium with
different density ● Ex: air to glass to air
Convergent vs. Divergent ● Convergent waves are rays of light that converge light that is traveling parallel to
their principal axis - Convex lenses refract light in a towards each other
● Divergent waves are rays of light that diverges light that is traveling parallel to their principal axis; travels through the center of either lens,straight through and is not refracted
- Concave lenses refract parallel light rays away from each other
Dark vs. Light Vision ● Dark light is dim vision, when an individual’s eye adapts to a loss of illumination- The pigmentation of the eye in dark vision ,is very minimal, consists of rod cells,
but since neither rods or cone can survive in the dark for long, blindness is a definite possibility
The photoreceptors found in dark light are rods A. Factors that affect Dark Light - Intensity and duration of the pre- adapting light
- Size and position of the retinal
- Wavelength distribution
- Rhodopsin regeneration (deficiency of vitamin A)
Dark vs. Light Vision Cont● During Light vision, the eye quickly adapts to background illumination and is
then able to distinguish and identify objects The photoreceptors found in light vision are cones 1. S- cones, short- wavelength sensitive cones 2. M- cones, middle- wavelength sensitive cones3. L- cones, long wavelength sensitive cones
Stereoscopic Vision ● The single perception of a slightly different image from each eye
● Gives us the ability to see objects with height, width, and depth ( a sort of 3-D experience)