The Eye and Vision Flashcards
Constriction of the pupil is brought about by contraction of the?
Circular muscle of the iris
During accommodation for near vision what happens?
The lens increases in curvature
In humans, both eyes focus on only one set of objects. This is called
Binocular vision
Intraocular pressure is primarily due to the
Aqueous humor
Most of the refraction of light entering the eye occurs at the
Cornea
The anterior cavity contains
Aqueous humor
The blind spot is the area where
The optic nerve exits the eye
The fibrous tunic is composed of the?
Sclera and cornea
The point of greatest visual acuity is the?
Central fovea
The white of the eye, which gives shape to the eyeball, makes it more rigid, and protects its inner parts is the?
Sclera
When entering a dark room on a sunny day, it takes some time to be able to see because
It takes time for the retina to rebuild its rhodopsin
What are the three-layers the wall of the eye is made up of?
The fibrous tunic (outer layer), vascular tunic (middle layer) and the retina (inner layer)
What is the fibrous tunic made up of?
Cornea and sclera
What is the function of the eye lids?
Shield and protect the eyeball from mechanical injury and drying out
What is the function of the eyelashes?
Protect the eye from airborne dirt, dust and irritants to the eye
What is the function of the eyebrows?
Protects the eye from moisture to maintain sight
What is the function of the lacrimal apparatus?
Produce tears to protect the eyeball and cornea through moisture and antibodies against infection. Contains lysozyme to kill pathogens
What is the function of the extrinsic eye muscle?
Control movement of the eyeball and superior palpable
What are lysozyme?
A protective bactericidal enzyme, protects, cleans and lubricates the eyeball
What are the three layers of the tunics?
Fibrous tunic (outer-layer) Vascular layer (middle layer) Retina (inner layer)
Structures involved with the Fibrous?
Sclera and Cornea
Function of sclera?
Fibrous and tough and provides protection and form
Function of Cornea?
Refracts 75% of light for focus
Structures involved with the vascular?
Choroid, ciliary body and iris
Function of the choroid?
- Blood flow in the eye, provides nutrients, oxygen and removes waste
- Melanocytes which produce melanin to absorb scattered light within the eye ball and maintain sharp clear images
Function of the ciliary body?
Changes shape of the lens
Function of the iris?
The coloured part of the eye, which controls the amount of light entering the eye
Describe the retina of the eye?
Contains photoreceptors which change light to electrochemical signals that are transmitted to CNS
Describe rods?
- Only one type of rod (rhodopsin)
- Rhodopsin is responsible for black and white vision
- More numerous
- Rod shaped
Describe cones?
- 3 different types of rhodopsin
- Responsible for coloured vision
- Only found in the fovea centrails
- Coned shaped
What is accommodation?
Changing shape of the lens to allow sharp focusing of light onto the retina
What happens when you view a near object?
The Ciliary muscles contract and the Lens thickens
What is the visual pathway?
Optic nerve - hypothalamus - midbrain - primary visual area and association area
Age related changes to the eye?
- Lens lossens
- Sclera thickens and changes colour
- Iris fades and develops irregular pigment, muscle weaken
As they extend from the retina to the brain, nerve fibers?
From the nasal half of each retina cross to reach the opposite visual cortex
Which cranial nerve carries visual impulses to the brain?
II
What is refraction?
Involves bending of light rays by cornea and lens to focus an image on the retina
What is pupil constriction?
Constriction of smooth muscles in the iris changes the pupil diameter to control light entering the eye and prevent light scattering around the retina
Describe the pupil?
Opening in the eye which allows light to travel into the eye
Describe ways in which an image can be formed
Refraction - bending of light rays by the cornea and retina to focus an image on central fovea
Accommodation - lens increases/decreases curvature to focus the image on the retina
Convergence - medial movement of the eyeballs to keep both eyes focused on object
Pupil constriction - prevents light rays entering the eye from the periphery of the lens