The Eye Flashcards
How does the retina generate impulses
Through a series of chemical reactions which are then conducted along the optic nerve
How are the impulses from the retina carried on
By fibres of the optic tract to synapse with cells in the lateral geniculate nucleus of the thalamus
Axons then reach the primary visual cortex in the occipital lobe through optic radiation
What are the 6 extra ocular muscles of the eye
Medical and lateral recti
Superior and inferior recti
Superior and inferior obliques
What are the 3 nerve supplies for the extra ocular muscles
Oculomotor
Trochlear
Abducens
What is the laevator palpebrae superioris innervated by
The oculomotor nerve
What are the 3 main functions of the eyelids
Provide mechanical protection
Blinking facilitates replenishing of the protective tear film
Contains glands which secrete outermost lipid layer of tear film
What is the function of the iris
Regulate the amount of light that can enter the retina
What is the function of the cornea
Protecting the eye from outside infiltrates and ultraviolet radiation
What is the function of the pupil
Allow light to enter the eye so it can be focused on the retina to being the process of sight
What is the function of the lens
Transmit and focus the light onto the retina in order to create clear images of objects at various distances
What is the function of the sclera
Helps maintain eye shape and protects from injury
What is the function of the eyes ciliary body
Produces the fluid in the eye called aqueous humor
What is the function of the choroid in the eye
Supplies oxygen and nutrients to outer retina, light absorption, thermoregulation and modulation of intraocular pressure
What is the function of the macula
Translates light that enters your eye into the images you see
What is the function of the retina
Converts light that enters the eye into electrical signals which the optic nerve sends to the brain the create the image
What is the function of the vitreous
Maintain the round shape of the eye
How does the parts of the eye work together
Light passes through the cornea which can bend the light to help focus the eye - some light enters the eye at the opening called the pupil - iris controls how much light the pupil lets in - light passes through the lens which works together with the cornea to focus light correctly on the retina - photoreceptors turn the light into electrical signals
What are rod cells for
More abundant
Cylindrical shaped
High sensitivity to light
Function in night vision
Low visual acuity
Absent at the fovea
What are cone cells for
Fewer in number
Conical shaped
Low sensitivity to light
Responsible for colour vision
Localised at fovea
What is the fovea
A small depression within the neurosensory retina where visual acuity is the highest
What is the extra cranial pathway of the optic nerve
Formed by the convergence of axons from the retinal ganglion cells - leave the bony orbit via optic canal (passage through sphenoid bone) and enters cranial cavity running along the surface of the middle cranial fossa
What is the optic chiasm
Within the middle cranial fossa the optic nerves from each eye unite to form this
What happens at the optic chiasm
Fibres form the nasal (medial) half of each retina cross over to the contralateral optic tract while fibres from the temporal (lateral) halves remain ipsilateral
What does the left optic tract contain
Fibres from the left temporal (lateral) retina and the right nasal (medial) retina
What does the right optic tract contain
Fibres from the right temporal retina and the left nasal retina
What is conjunctiva
Formed of a mucus membrane that covers the inner surface of both eyelids covers the anterior portion of the sclera and ends at the corneo scleral junction
What is the appearance of viral conjunctivitis
Clear, watery discharge
What is the appearance of bacteria conjunctivitis
Mucopurulent discharge
What is keratoconus
A non inflammatory usually bilateral protrusion of the cornea
What is glaucoma
Occurs due to faulty drainage of aqueous humor leading to build up of pressure manifests as loss of peripheral vision
What is cataract
Caused by opacification clouding of the crystalline lens
