Physiology Of Vision Flashcards
What are the accessory structures of the eye?
Palpebrae -continuation of skin
Superficial epithelium of eye -lacrimal caruncle and conjuctiva
Lacrimal apparatus -produces and removes tears
What are the chambers of the eye?
Cillary body and lens divides into the vitreous humor and aqueous humor
The anterior and posterior chamber
What are the 3 layers of the eye?
Outer fibrous layer
Intermediate vascular layer
Deep inner layer
What is the vascular layers function?
Provides a route for blood vessels and lymphatic that supply tissues of the eye
Regulates amount of light into eye
Secretes and reabsorbs aqueous humor
Controls shape of lens which is essential for focusing
What does the vascular layer contain?
Iris
Cilallary body
Choroid
What is the aqueous humor?
Fluid that circulates within the eye and diffuses through walls of anterior chamber into clearly Venus sinus
What is intraocular pressure?
Fluid pressure in the aqueous humor and helps retain eye shape
What is the function of the Fibrous layer?
It consists of the sclerosis,cornea,corneal limbus
And it supports and protects the eye
And serves as an attachment site for extrinsic eye muscles and contains structure that assist with focusing
Where do tears pass through?
Lacrimal Puncta
Lacrimal conaliculi
Lacrimal sac
Nasolacrimal duct
What is the inner layer called?
Retina (neural part).contains rods and cones as photo receptors
What us the outer layer called?
The pigmented part
What are rods?
They are highly sensitive to light and don’t discriminate against colours
What are cones?
They provide colour vision and densely clustered in fovea at the sender of macula
What does the nunnery neural part contain?
Bipolar cells that synapse with ganglion cells
Horizontal cells where photo receptors synapse with bipolar cells
Amancrine cells where bipolar cells synapse with ganglion cells
They facilitate or inhibit communication between photo receptors and ganglion cells and alter sensitivity of retina
What is the lens?
It lies at the back of the cornea and is held by suspension ligaments
It contains lens fibers which are cells inside of lens and filled with crystallins which are transparent proteins
What is a cataract?
When the balance of lens is disturbed and transparency is lost
When does the greatest amount of refraction occur?
When light passes from the air into corneal tissue and additional refraction occurs when light passes from aqueous humor into the relatively dense lens and lens provides extra refraction needed to focus the light rays from object towards a focal point on retina
What is focal point?
Specific point of intersection on retina
What is focal distance?
Distance between center of lens and its focal point
What is focal distance determined by?
Distance of object from lens
Closer the object the greater the focal distance
Shape of lens
The rounder the lens the more the refraction and shorter focal distance and flatter one
What is the accommodation for far objects?
Shape of lens changes to focus image on retina
Rounder to focus the image of nearby objects and flatter to focus on distant objects
Lens is held by suspensory ligaments originating at cillary body when cillary muscles relax the syspensory ligaments pull at the circumference of lens making it flatter
What is the accommodation for near objects?
Smooth muscle fibers on the cillary body act like sphincters when the cillary muscles contact cillary body moves towards the lens thereby reducing tension in suspensory ligaments the elastic capsule then pulls the lens into a more spherical shape that increases the refractive power of the lens this brings lights from nearby objects into focus on the retina
What is astigmatism?
When cornea is unequal think and light passes through cornea and lens is not refracted properly and visual image is distorted
What is myopia?
Eyeball being too deep or resting curve of lens is too great and can be corrected with diverging concave lens
