Eyelids, eye abnormalities and conjunctiva Flashcards
What are the functions of the eyelids?
Protect eyeball
Spread tear film into lacrimal punctuae to remove foreign material and exclude late
What is the space between the eyelids called?
Palpebral fissure
What are the corners of the eye called?
Medial and lateral canthus
How are the canthus of the eye attached to the bone? Which species is the exception?
Canthal ligaments
Dog - poorly developed, replaced by retractor anguli oculi
Lid margins are hairless, however which lid has cilia and which way are they directed?
Upper
Directed away from the eyeball
What supports the eyelids? What does this contain?
Tarsal plate
Contains tarsal glands
Which species has a poorly developed tarsal plate?
Dog (compared to cat)
What is the term that describes the abnormal growth of hairs from the tarsal glands?
Distichiae
Do cats have dogs have more sclera visible? What about horses?
Dogs have more visible than cats
Horses have lots visible but often pigmented
Horses have a loose lid at the medial canthus. What do they have at the medial canthus?
Lacrimal caruncle
What is a sty an infection of?
Sebaceous and sweat glands at the base of eyelashes
What provides sensory innervation to the eyelids?
Trigeminal
Upper lid = ophthalmic
Lower lid = maxillary
Brachiocephalic breeds have protuberant eyes. What does this mean and what does it cause?
Eyeballs too large for orbit
Can’t close eyes when sleeping –> dry eye (keratoconjunctivitis) and keratitis
Why may fluroscein dye not appear in the nares of brachycephalic breeds?
Lacrimal duct drains into caudal nasal cavity then nasopharynx
What is entropion and what does it cause? (ectropion not as problematic)
Inwards turning of the eyelids
Hairs rub on eye and cause ulceration
What is diamond eye?
Ectropion in the middle of the eye, with entropion either side
What is found within the conjunctiva?
Lots of blood vessels
Lymphoid tissue
Mucus membrane and goblet cells
Where does the conjunctiva fuse with the orbital fascia?
Behind the limbus
Why isn’t conjunctiva present over the cornea?
Wouldn’t be able to see
What are the 3 types of conjunctiva?
Bulbar
Palpebral
Nicitating
What does the bulbar conjunctiva do?
Lines the sclera
What does the palpebral conjunctiva do?
Lines the inside of the eyelids
How is nicitating conjunctiva/membrane formed from palpebral conjunctiva?
Palpebral conjunctiva reflects back at ventral fornix
To become nicitating membrane
The nicitating conjunctiva/membrane/3rd eyelid is a reflection of palpebral conjunctiva. What does it contain?
T shaped support cartilage
When does the nicitating conjunctiva protrude?
When blinking due to retractor bulbi
What is different about the nicitating membrane of the cat?
Has some skeletal muscle - can actively protrude
What is the gland of the 3rd eyelid called? What does it do?
Nicititans gland
Produces part of tear film
What is the protrusion of the 3rd eyelid?
Cherry eye
What is the function of the tarsal/Meibomian glands?
Secrete lipid rich Meibum
Prevent evaporation of tear film
