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961.e2 Tear Film Abnormalities (Excluding KCS)

Tear Film Abnormalities (Excluding KCS) Client Education
Sheet
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• Swollen eyelids
BASIC INFORMATION
• Previous bout(s) of conjunctivitis respon- (eosinophilic, cats), and corneal exposure/
incomplete blinking (e.g., lagophthalmos)
Definition sive to standard topical medication(s) but • Blepharitis
The relatively common ophthalmic condition recurrent
is characterized by abnormal mucin (produced • Squinting Initial Database
by goblet cells of the conjunctiva) and/or lipid • Corneal cloudiness • History ± bouts of conjunctivitis that were
(produced by meibomian [tarsal] glands) temporarily responsive to routine topical
components of tears. Keratoconjunctivitis sicca PHYSICAL EXAM FINDINGS medications
(KCS) is discussed on p. 568. • Systemic: generally unremarkable except in • Complete ophthalmic exam:
those cases where systemic disease is present ○ STT: normal or elevated STT values
Synonyms (e.g., diabetes mellitus; generalized cornifica- expected; normal STT value ≥ 15 mm/
Qualitative tear deficiencies or abnormalities tion defect/seborrhea) min for dogs; varies in cats because stressed
• Ophthalmic cats often have decreased STT values.
Epidemiology ○ Serous or mucoid to mucopurulent ocular ○ Fluorescein dye application: secondary
SPECIES, AGE, SEX discharge corneal ulceration is possible.
Dogs and cats, any age, either sex ○ Conjunctival hyperemia ± chemosis ○ Intraocular pressures (IOPs): normal
○ Signs of keratitis with chronicity: corneal IOP values expected; normal IOPs of
GENETICS, BREED PREDISPOSITION vascularization, pigmentation, and/or 10-20 mm Hg (dogs and cats)
• Cats predisposed to corneal sequestration ulceration
(e.g., brachycephalic breeds) may be pre- ○ ± Blepharospasm Advanced or Confirmatory Testing
disposed to tear film abnormalities (TFAs). ○ ± Protrusion of the third eyelid • Meibomian gland exam using magnification
• Dog breeds with inherited entropion, ○ ± Blepharitis, usually marginal with associ- (lipid tear abnormalities): slight protrusions
ectropion, or allergies may be predisposed ated meibomianitis with or without overt of meibomian gland ductal openings; swollen,
to developing qualitative tear deficiencies lipogranulomas/chalazia rounded, hyperemic eyelid margins; yellowish
if conditions are untreated and chronic subconjunctival masses (lipogranulomas/
conjunctivitis results. Etiology and Pathophysiology chalazia) possible
Mucin tear deficiency: • Evaluation of TFBUT: mean normal TFBUT
RISK FACTORS • Primary/spontaneous of unknown cause = 20 seconds in dogs and 16 seconds in cats;
• Disorders affecting the meibomian glands • Secondary to chronic conjunctivitis; loss TFBUT is rapid/accelerated with mucin tear
(e.g., alkali burns of the eye) of the conjunctival goblet cells, diminished deficiency (i.e., TFBUT < 5-10 seconds):
• Patients with diseases resulting in primary mucin production with unstable tear film ○ TFBUT is performed before instillation
(e.g., feline herpesvirus type 1 infection) Lipid tear deficiency: of topical solutions on the surface of the
or secondary chronic keratoconjunctival • Inflammation of the meibomian glands eye or a few hours after ophthalmic exam.
disorders (e.g., entropion/ectropion, KCS; (which produce the lipid component of ○ Evaluates stability of the tear film
allergies with associated conjunctivitis) the tear film) directly or by extension from ○ Performed by instilling one drop of
• Dogs with diabetes mellitus are more likely margins of the eyelids (marginal blepharitis) fluorescein stain onto the eye, closing the
to have shorter tear film break-up times (see ○ Diseased meibomian glands produce eyelids to distribute the stain, and when
Advanced Testing below) than nondiabetic highly polar lipids that destabilize the opening them, immediately begin timing.
dogs. nonpolar lipid layer of the tear film, Using a cobalt blue filter, time until the
• Repeated cryotherapy for treatment of allowing rapid evaporation of the aqueous appearance of the first black/dark spot in
numerous distichia component of tears. the green fluorescein-stained corneal tear
○ Dried lipid plugs meibomian gland ducts. film.
ASSOCIATED DISORDERS ○ Chronic meibomianitis can cause rupture • Palpebral conjunctival biopsy and staining
• Conjunctivitis and TFAs commonly coexist and lipid release into palpebral tissue. with periodic acid–Schiff (PAS) for quanti-
(unclear which is causative). ○ With eyelid agenesis: lack of meibomian fication of epithelial goblet cells (diminished
• Superficial keratitis (nonulcerative or ulcerative) glands to absent with mucin tear deficiency)
• Eyelid disorders: entropion, ectropion, eyelid
agenesis (rare), autoimmune disorders (rare), DIAGNOSIS TREATMENT
infectious marginal blepharitis (occasional)
• Chemical ocular burns (rare) Diagnostic Overview Treatment Overview
• Primary or secondary skin disease involving Diagnosis is suspected on presenting com- The treatment goals are to stabilize the tear
eyelid mucocutaneous junctions (occasional) plaint and physical exam (e.g., recurrent film and eliminate ocular pain. Identifying
• KCS (common) conjunctivitis, red eye, ocular discharge) and and treating the underlying cause of the TFA
• Diabetes mellitus in dogs (common) confirmed with identification of abnormal is essential.
meibomian glands (lipid tear deficiency) and/
Clinical Presentation or abnormal tear film break-up time (TFBUT). Acute General Treatment
DISEASE FORMS/SUBTYPES Generally have normal Schirmer tear test (STT) • Varies, depending on the underlying cause
Mucin tear deficiency, lipid tear deficiency results • Lacrimomimetics (tear substitutes and stabi-
lizers) q 4-8h (e.g., viscous mucinomimetic
HISTORY, CHIEF COMPLAINT Differential Diagnosis such as hyaluronic acid 0.4%) for mucin tear
Common chief complaints from clients: • Other keratoconjunctival disorders: KCS, deficiency. Emollient/oil-based tear supple-
• Red eye conjunctivitis, pannus (chronic super- ment (e.g., Lacri-Lube ointment) for lipid
• Serous or mucoid to mucopurulent ocular ficial keratitis, dogs), feline herpesviral tear deficiency may be used for initial 3-4
discharge keratitis, proliferative keratoconjunctivitis weeks without concurrent lacrimostimulant if
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