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)