Flashcards in 3: Nictitans / Nasolacrimal - giuliano Deck (64):
what is epiphora?
tear production - serous exudate
what is physis bulbi?
end stage, shrunken eye
what is the Nictitias?
what is the topographical distribution of the Nictitans?
origin, shape, important features of it
origin: anterior ventro medial orbit
shape: triangular, covered w conjunctiva
contains "T-shaped" hyaline cartilage runs through the center
at the base, has bland of the 3rd eyelid
what is the function of the Nictitians?
- to protect the globe
- sec and distribution of tears
- aid in removal of particulate matter from the eye
- "windshield wiper"
the movement of the 3rd eyelid is an active process
what does the movement of the 3rd eyelid depend on?
- orbital tone
- orbital fat
- hydration status
an animal with little fat or who is dehydrated will become enopthalmic and will display an elevated 3rd eyelid as a result
where is the gland of the 3rd eyelid loc?
encompasses the base of the cartilage
what type of secretion is produced by the gland of the 3rd eyelid?
from what aspect and structures is the material secreted?
- seromucous secretions
- exit thru ducts that open into the posterior aspect of the 3rd eyelid btwn lymphoid
- on bulbar aspect of 3rd eyelid, it is normal to have a complement of lymphoid follicles, that look like cobble stones
how much basal tear production can be attributed to the gland of the 3rd eyelid?
30% - 70%
a common and appropriate treatment to a consistently prolapsing 3rd eyelid gland is removal
why or why not?
FALSE - THE 3RD EYELID SHOULD BE REMOVED ONLY IF IT IS CANCEROUS
risk: predisposes animal to dry eye - keratoconjunctivitis secca => BAD
2 classifications of 3rd eyelid dz?
- dz of the conjunctiva that affects the 3rd eyelid
- 1* dz of the 3rd eyelid
what are 1* dzz of the 3rd eyelid?
- gland prolapse
- elevated 3rd eyelids
- malformed or scrolled cartilage
when does 3rd eyelid gland typically prolapse? and in what species?
less than 1 yo
what is the common term for 3rd eyelid gland prolapse?
what are proposed causes of 3rd eyelid gland prolapse?
- weak fascial attachments to the ventromedial orbit
- immune stimulation [often dogs have been vaccinated a few weeks before this occurs]
what are the clinical implications of a prolapsed 3rd eyelid gland?
- conjunctivitis / chronic irritation
- cosmetic concerns
tx of prolapsed 3rd eyelid gland?
- manual replacement [usually temporary]
- surgical - complicated!
post op care for prolapsed gland of the 3rd eyelid?
topical abx [broad spectrum]
systemic anti inflammatory
cone of shame
common causes of prolapsing 3rd gland of the eyelid:
- conformation [breed enophthalmos]
- non pigmented leading edge [can be deceiving and look uneven; common in merle often]
- dec in orbital contents [deh, emaciation, phthisis bulbi, microphthalmos]
- inc in orbital contents [neoplasia, abscess, hematoma]
- sympathetic denervation [horner's syndrome]
- ocular pain w retractor bulbi contraction
- rare: tetanus, dysautonomia
the signs of Horner's syndrome, due to loss of sympathetic tone, occur b/c the 3rd eyelid has lost its sympathetic innervataion
there is not sympathetic tone in extra orbital Mm
the sympathetic tone is in the peri orbita [orbital cone] so this loses its tone, causing the globe to sink back and the eyelid comes up
what signs are seen in Horner's syndrome?
elevated 3rd eyelid
what is "haws" syndrome?
concurrent GI signs
what is cause of scrolled cartilage malformation of nictitans?
- 3rd eyelid cartilage is bend or malformed
the tail of the "T" bends backwards
- breed predispositions [large breed dogs]
c/s of scrolled cart of 3rd eyelid?
tx for scrolled cartilage?
surgical excision of the cartilage
an alternative tx for scrolled cartilage is excision of the gland of the 3rd eyelid
do NOT remove gland of the 3rd eyelid
tx for laceration of nictitans?
address exposed sharp cartilage
common cause of corneal ulcer, related to the 3rd eyelid?
foreign body behind the 3rd eyelid - anesthetize animal and look behind the eyelid
lymphoid tissue on the palpabral surface of the 3rd eyelid is normal
what is the significance of this?
lymphoid tissue is normally on the bulbar aspect of the eyelid
lymphoid tissue on the palpebral surface indicated lymphoid conjunctivitis and follicular hyperplasia
what is the MC neoplasia found on 3rd eyelid?
remove the 3rd eyelid
what is the significance of SCC of the 3rd eyelid in cattle?
it is the MC reason for condemnation of carcass at slaughter
what is the anatomy of the nasolacrimal system?
superior and inferior puncta lead to canaliculi -> leads to lacrimal sac -> leads to naso lacrimal duct -> leads to nares and out the nasal punctum
what are the 3 components to the tear film? list them from superficial to deep
what is the function of the lipid component of the tear film?
where is it produced?
- stabilize and prevent evaporation of aqueous layer
- produced by the Meibomian glands in the eyelid
what is the function of the aqueous component of the tear film?
where is it produced?
- provides corneal nutrition and removes waste products
- produced by the orbital gland and the gland of the 3rd eyelid
what is the function of the mucus component of the tear film?
where is it produced?
- interface of tear film with hydrophobic cornea
- secretory IgA
- prod by conjunctival goblet cells
if comparing the aqueous layer fluid dynamics within the nasolacrimal [NL] anatomy to a sink, which parts are the faucet and drain?
faucet = orbital lacrimal gland, gland of the 3rd eyelid, accessory gland
drain = naso lacrimal outflow tract [puncta, canaliculi, NL sac, NL duct, nasal punctum]
how does fluid flow across the eye?
- tears produced and secreted into "cul-de-sacs"
- spread by eyelids and 3rd eyelid
- pool and mix along lower eyelid
- flow thru NL duct sys
what 2 basic categories do dzz of tear film dynamics fit into?
too much production
too little production
what dz is too little tear film production called?
KCS is the dec in prod of which component of the tear film?
common and uncommon in what species?
- dec in aqueous component
what is the etiology of KCS?
#1: immune mediated
congenital [breed - pug, yorkie]
drug induced [anesthesia, atropine]
drug toxicity [sulfas, Etogesic, comfortis]
sx - removal of 3rd eyelid gland
systemic dz - distemper
how to dx KCS?
Schirmer Tear Test (STT)
what are normal values for dogs and cats for STT?
normal dogs: over 15mm/60s
10-15 mm/60s = marginal
5-10 mm/60s = KCS
less than 5mm/60s = severe KCS
cats: tend to be lightly lower values; interpret test in context of c/s
- lackluster cornea
- mucopurlent discharge
- keratitis: pigment, vessles, ulceration
- conjunctivitis: hyperemia, thickening
why does mucopurulent discharge occur during KCS?
not enough aqueous component to tear film
often 2* bacT infection
goblet cells in over drive to prod more mucus b/c innervation detects dry eye
- tear stimulation and immunomodulation, BID for 6 weeks
- topical cyclosporine A [ointment]
- topical tacrolimus [compounded for cyclosporine non responders]
- tear substitutes: additional lubrication, frequent application, lack nutritional aspects of normal tears, give frequently
a more simplified and effective treatment for KCS is tear substitutes alone
tear substitutes need to be used as an adjunctive therapy
what function is topical cyclosporine or tacroliums in the Tx of KCS?
potent T cells suppressors
to target the immune mediated aspect of KCS, which is the MC cause in dogs
how is the Tx of neurogenic KCS different than typical KCS treatment?
- stimulate tear production with Tx: pilocarpine = parasympathomimetic
usually used for glaucoma - put in food and titrate dose until animal gets SLUDD or vomits then bring dose down
**note: not for standard KCS cases
abx - for 2* bacT infections; short term
mucinolytics - remove exudates w saline before applying medication: 5-10% acetylcysteine
if using corticosteroids to Tx KCS, what is the best way?
- give orally
caution: can suppress immune system too much and essentially "melt" the cornea
what aspects of client education are KEY?
- remove mucopurulent debris w sterile saline rinses prior to administering medications
- wait at least 5 mins btwn drops
- lift up head and bring bottle around back of eye or use lavage tube
- warm up tube of ointment
pilocarpine and other drugs used to Tx KCS may be irritating long term and cause uveitis. what surgical options are there to help the condition?
- parotid duct transposition: after Sx, salivation will help lubricate eyes BUT may lead to corneal pigmentation and mineralization b/c saliva is not equivalent to tears
- permanent partial tarsorrhaphy / canthoplasty: narrow eyes to conserve existing tears
if patient has epiphora, or is producing too much tear film, what are differentials?
- excessive lacrimation due to irritation: distichia, ectopic cilia, foreign body, tumor, entropion, uveitis, trichiasis
- drainage abnormality: obstruction of NL sys, importorante punctum, dacryocystitis
what test is used to determine patency of NL duct system?
Jones test - fluorescent stain in eye and 5 mins later, it should be coming out the nose
how to Dx epiphora?
- complete ophthalmic exam
- Jones test
- NL flush
- culture and sensitivity
- x ray, CT/MRI, contrast dacryocystorhinography
how to evaluate patency of NL duct system using a NL flush?
5-10 mL syringe
fill w eyewash and fluorescent stain
24 gauge IV catheter w stylette removed
insert catheter tip in upper lacrimal puncta
flush around caniliculi
occlude lower puncta w finger and flush down NL duct
- Tx 1* cause - often refer for more invasive examination
- Tx 2* infection - common w obstruction of NL sys
- anti inflammatories maybe
what are common locations for obstruction of NL system?
etiologies of NL drainage abnormalities?
malformation [imperforante puncta, displaced puncta]
what is dacryocystitis?
inflammation of NL duct sytsem
mucopurulent discharge, possible swelling at the medial canthus