Ophthalmology - Lacrimal System Flashcards
What are the layers of the tear film?
- lipid (outermost)
- aqueous (middle)
- mucinous (innermost)
What is the source of the aqueous layer?
lacrimal gland and gland of the third eyelid
What are the possible causes of quantitative KCS?
- immune mediated destruction of lacrimal tissue
- excision of third eyelid gland
- PSNS lesions
- canine distemper
- drugs
What are the clinical signs associated with quantitative KCS?
- blepharitis
- mucoid/mucopurulent discharge
- keratoconjunctivitis
- corneal pigmentation
- can be blinding if severe
How is quantitative KCS treated?
- topical cyclosporine
- if no response: Tacrolimus
What is neurogenic KCS?
loss of parasympathetic innervation to the lacrimal gland and ipsilateral nostril
What are the possible causes of neurogenic KCS?
trauma
severe otitis interna
neoplasia
idiopathic
How is neurogenic KCS treated?
Pilocarpine
- stimulates PSNS
Which virus causes KCS in dogs?
Canine Distemper virus
What is the surgical option for treating KCS?
parotid duct transposition
- moves parotid salivary duct to the lower conjunctival fornix
- saliva replaces tears
What are the disadvantages/complications of parotid duct transposition?
- reaction to higher pH of saliva
- moist pyoderma from overproduction
- mineral deposition in cornea and eyelids
What is the source of the lipid layer?
meibomian glands
What is the function of the lipid layer?
stabilize the aqueous layer and prevent evaporation
What test results indicate quantitative KCS?
- superficial corneal and conjunctival inflammation (keratoconjunctivitis)
- shirmer tear test < 15 mm/min (sicca)
What test results indicate qualitative KCS?
superficial keratoconjunctivitis with a normal shirmer tear test
What is the source of the mucin layer?
conjunctival goblet cells
What is the function of the mucin layer?
creates surface tension that anchors the aqueous and lipid layer to the cornea
What test/result indicated mucin deficiency?
Tear Film Breakup Time
- time it takes for fluroecein stain to beak up on the ocular surface
- abnormal < 20 seconds
What is the underlying cause of qualitative KCS?
lipid or mucin deficiency
What are the clinical signs associated with qualitative KCS?
- blepharospasm, epiphora, hyperemia, superficial conjunctivitis and keratitis, and corneal fibrosis
- corneal fibrosis: whitish hazy appearance
How is qualitative KCS treated?
- replace the tears (lubrication)
- immunomodulation: cyclosporine
Describe the anatomy of the nasolacrimal drainage system
- lacrimal gland on lateral upper lid
- two lacrimal puncta on the medial canthus
- puncta come together at lacrimal sac
- continue to the nasal punctum
What is epiphora?
overflow of tears on the face
What are possible causes of epiphora?
- poor drainage (hypoplastic puncta, entropion)
- blockage (FB, neoplasia, inflammation)
What is the Jones test?
- looking at patency of the nasolacrimal drainage system
- fluorescein in the eye, hold nose down, look for stains in the nares
What are the clinical signs associated with Dacryocystitis?
- mucopurulent discharge
- epiphora
- swelling in the medial canthal region
What is Dacryocystitis?
inflammation of the nasolacrimal drainage system
What are the possible causes of Dacryocystitis?
foreign bodies
infection
trauma
