Visual System Flashcards
What is the space between the lateral and medial canthus of the eye?
The palpebral fissure
What term refers to the lateral confluence of the upper and lower eyelid regions?
Lateral canthus
What term refers to the medial confluence of the upper and lower eyelid regions?
Medial canthus
What is the opening within the iris?
The pupil
Which globular nodule structure resides besides the medial canthus of the eye?
Caruncle
Which structure is the border between the cornea and sclera?
Limbus
Where is the lacrimal gland located?
Located within the orbit, latero-superior to the globe
What are the three types of tears?
Basal
Reflex
Emotional (crying)
What is the function performed by the lacrimal gland?
It continually releases fluid which cleanses and protects the eye’s surface as it lubricates and moistens it. These lacrimal secretions are commonly known as tears.
What are basal tears?
Basal tears are your basic functional tear. They are released continuously in tiny quantities to lubricate the cornea and keep it clear of dust. This is vital to ensure good visual acuity and comfort. Basal tears also fight against bacterial infection as a part of the immune system.
Which tears are referred to the increased tear production in response to ocular irritation?
A reflex tear
What does the tear pathway comprise of?
Afferent pathway
CNS
Efferent pathway
Lacrimal gland
Which afferent nerve innervates the cornea?
Sensory nerve fibres via the ophthalmic branch of trigeminal nerve.
How is the efferent pathway mediated?
Mediated by the parasympathetic nerve, innervating the lacrimal gland.
How are tears drained by the lacrimal system?
The tear film drains through the two puncta, tiny openings on the upper and lower medial lid margins
Flows through the superior and inferior canaliculi converging into a single common canaliculus, draining into a tear sac –> Into the nasal cavity through the tear duct.
Which two superior and inferior eyelid structures are responsible for tear film drainage?
The puncta
How are tears drained from the puncta to the tear sac?
Tears flow through the superior and inferior canaliculi to the tear sac
What is the fate of tears within the tear sac?
Exit the tear sac through the tear duct into the nasal cavity.
What are the four primary functions of the tear film?
1) Maintains smooth cornea-air surface (Clear vision)
2) Oxygen supply to cornea
3) Removal of debris
4) Bactericide
How many layers comprise the tear film?
Composed of three layers:
1) Lipid layer (Superficial)
2) Water layer
3) Mucin layer
Which glands along the lid margins produce the superficial lipid layer of the tear film?
Meibomian glands
What is the purpose of the mucinous layer corneal surface?
Maintains surface wetting.
What provides oxygen supply to the anterior segment of the eye (cornea)?
The tear film considering there are no blood vessels supplying the cornea
What is the function of the lipid layer of the tear film?
Responsible for protecting the tear film from rapid evaporation.