Unit 1 - Eyelids Flashcards
What are the three main layers of the eyelid?
Outer layer, middle layer, and innermost layer
What are the components of the outer layer of the eyelid?
Skin, hair follicles, and sebacious glands
T/F: Dogs and cats have both upper and lower lid cilia.
False - they only have upper lid cilia
What are the components of the middle layer of the eyelid?
Muscle, tarsal plate, and meibomian glands
What are the components of the innermost layer of the eyelid?
Palpebral conjunctiva
What are the functions of the eyelid?
Corneal protection
Production, distribution, and drainage of tear film
What does the orbicularis oculi muscle do and what innervates it?
It closes the eye lids and is innervated with the facial nerve (CN VII)
What does the levator palpebra superioris muscle do and what innervates it?
It opens the eyelid and is innervated by the oculomotor (CN III)
What does the Muller’s muscle do and what innervates it?
It elevates the upper lid and is innervated by the sympathetic nervous system
What provides sensation to the eyelid?
The ophthalmic and maxillary branches of the trigeminal nerve (CN V)
In what direction should eyelids close?
From lateral to medial
What is ankyloblepharon?
Adhesion of the eyelid margins
When is ankyloblepharon normal?
Until 10-14 days postpartum in dogs and cats
When is ankyloblepharon abnormal?
If it persists past 15 days of age
Can occur with ophthalmia neonatorum
How should ankloblepharon be medically managed if it has been 15+ days post partum?
They should be opened with gentle traction on the eyelids or by blunt dissection
What is eyelid agenesis?
When there is absence of a portion of the eyelid
What lesion can eyelid agenesis result in?
Secondary trichiasis and exposure keratitis due to the cornea being exposed
What species is eyelid agenesis most common in?
Cats, especially feral, and horses
If the eyelid agenesis defect is small, how should it be treated?
Frequent use of ocular lubricants, cryosurgery for trichiasis hairs, and a simple wedge resection
If the eyelid agenesis defect is large, how should it be treated?
Reconstructive procedure to form a functional eyelid - refer to a specialist
What is a micropalpebral fissure?
A congenital small eye opening that may accompany other congenital defects (microphthalmos)
What breeds typically get micropalpebral fissures?
Miniature breeds, sheltie, collie, chow chow, Kerry Blue terrier, and others
How is micropalpebral fissure treated?
It rarely requires surgical intervention, but lateral augmentation canthoplasty if entropion is present and problematic
What is macropalpebral fissure?
Overly large eyelid openings
Macropalpebral fissure in combination with a shallow orbit results in what?
Conformational exophthalmos
What breeds is macropalpebral fissure common in?
Brachycephalic breeds
What other ocular manifestions can result from macropalpebral fissure?
Increased proptosis risk, possible lagophthalmos, exposure keratitis, and concurrent trichiasis
How is macropalpebral fissure treated and when is it indicated?
Surgical shortening of the eyelids is indicated if pigmentation, exposure keratits, or recurrent corneal ulcers
What surgical treatment for marcopalpebral fissures addresses multiple issues that brahcycephalics have with their eyes?
medial canthoplasty
What is entropion?
Inversion of the eyelid margin
What is ectropion?
Eversion of the eyelid margin
What is diamond eye?
A combination of entropion and ectropion
Common in Bloodhounds, Clumber Spaniel, St. Bernard, and Great Dane
What are the clinical signs associated with entropion?
Pain and squinting (blepharospasm) and excessive lacrimation (epiphora)
What corneal sequelae result from entropion?
Ulceration, vascularization, pigmentation, and corneal scarring
What is anatomic entropion?
Entropion in young dogs that is breed-related
What is spastic entropion?
Lid spasm associated with pain
What is cicatrical entropion?
Entropion resulting from previous surgery, trauma, or chronic eyelid inflammation
How is entropion temporarily corrected?
Eyelid tacking
When is temporary entropion treatment indicated?
In cases of anatomic entropion and spastic entropion