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Year 2 Semester 2 > Eye > Flashcards

Flashcards in Eye Deck (63)
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In the horse, a portion of the orbit is contributed to by the zygomatic process of which bone?



In the dog, which vessels pass through foramina to gain access to the orbit?

Ophthalmic artery and vein
Orbital vein
Cranial nerves 2, 3, 4, 6 (optic, oculomotor, trochlear, abducens)
Ophthalmic branch of cranial nerve 5


What are the three layers of the orbital fascia?

Fascia bulbi
Fascial sheaths of the extra-ocular muscles


Which species do not possess a retractor bulbi muscle?

Birds and snakes


What are the functions of the eyelids?

Close to exclude light
Protect the eyeball
Spread the tear film across the eye and into the lacrimal punctae
Help to remove foreign material from the eye


At what age do cats and dogs open their eyes?
What is the eyelid opening called?

10-14 days
Palpebral fissure


The cilia on the upper eyelid (eyelashes) are associated with which glands?

Modified sweat glands (glands of Moll)
Sebaceous glands (glands of Zeis)


What causes a stye to form?

Infection of sebaceous or sweat glands in the upper eye lid


In the dog, the lateral palpebral ligament is absent, but what is its function replaced by?

Retractor anguli oculi muscle


Closure of the eyelids is due to what?

Contraction of the orbicularis oculi muscle, which is innervated by the facial nerve (CN VII)


Sensory innervation to the eyelids is via which nerve?
This branches into what?

Trigeminal (CN V)
Branches into ophthalmic branch (innervates most of upper lid and medial part of lower lid) and maxillary branch (innervates lower lid and joins with ophthalmic branch to supply lateral portion of upper lid)


What is the nictitating membrane?
Where does it sit?

Third eyelid
A reflection of conjunctiva containing a T-shaped cartilage support.
Sits ventromedially in the conjunctival sac, and the free edge is snug against the eyeball


What are the three portions of the tear film?

Lipid layer
Mucin layer
Aqueous layer


The lacrimal nerve is a branch of which nerve?

Ophthalmic branch of CNV
Provides parasympathetic and sympathetic innervation


What are the three layers of the globe and what do they do?

Fibrous layer- supports the eyeball shape
Uvea- provides nutrition to the structures of the eye and acts to alter light transmission
Neural layer- retina


What is the cornea?
How thick is it in dogs and cats?

The clear, curved rostral surface of the eyeball which transmits and refracts light.
0.7mm thick


Which 2 factors give the cornea its clarity?

Lack of corneal blood vessels
Arrangement of lamellae


What makes up the anterior and posterior uvea?

Anterior uvea= iris and ciliary body
Posterior uvea= choroid


Describe the pathway of aqueous humour

It is produced in the posterior chamber, flows through the pupil into the anterior chamber and drains at the iridocorneal angle


What are the 4 layers of the choroid?

Suprachoroidea-transition between sclera and choroid
Large vessel layer-cools the eye
Medium vessel layer-contains tapetum lucidum
Choriocapillaris-consists of fenestrated capillaries which supply the retina


What is aqueous humour produced by?

Ciliary processes of the ciliary body


What is the normal range for intra-ocular pressure in a dog?



How is a glaucoma formed?

When production of aqueous humour exceeds drainage and intra-ocular pressure rises


What are 'floaters'?

Clumps of hyaluronic acid, occurs in old age when the lamellar arrangement of fibrils in the vitreous humour breaks down and the vitreous becomes more liquid.


How does a cataract form?

Changes inside the lens disrupt normal metabolism and lead to deposition of lens protein or accumulation of vacuoles and disruption of lens fibres.
This affects transparency and size of lens.


What are the 3 inner layers of the retina?

Nerve fibre layer
Ganglion cell layer
Inner plexiform layer


Where are cones most numerous?

Area centralis of the retina


Which area of the retina has the most ganglion cells?

Visual streak


Give 3 functions of the retinal pigment epithelium

Phagocytoses spent photoreceptor segments
Vitamin A metabolism
Moves metabolites into and out of the retina


How are cats able to actively protrude their third eyelids?

They possess some striated muscle in their third eyelids