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-Mucin, a hydrated glycoprotein, makes up the deepest tear layer (1 - 2 um thick). --> fills in any irregularities of the corneal surface, thereby providing a smooth ocular surface.
1. Orbital gland (main source in dogs)
2. Gland of third eyelid (nictitating membrane)
3. Harderian gland
-secrete the AQUEOUS component of tears: intermediate layer < 7 um thick, accounts for most of total tear volume & consists of water, electrolytes, glucose, urea, surface-active polymers, glycoproteins, & tear proteins (lactoferrin & some serum proteins - IgA, albumin, & lysozyme)
1. Meibomian (Tarsal) glands - most important
2. Glands of Zeis
-thin (0.1 um) superficial lipid layer provides a thin, oily covering over the aqueous tear layer --> prevents evaporation & promotes a stable, even spread of tears over the cornea.
Is this Conjunctival hyperemia or Episcleral injection?
EPISCLERAL Injection (hyperemia)
Conjunctival hyperemia = general response of conjunctiva to disease
Episcleral injection, which occurs w/ glaucoma & anterior uveitis.
PHENYLEPHRINE drop on eye --> Conjunctiva vessels blanch right away. Episcleral vessels require ~10 min. to blanch.
deficiency in aqueous tears --> desiccation (extreme dryness) & inflammation of conjunctiva & cornea, ocular pain, progressive corneal dz., & reduced vision.
(in image, note the horrible film of mucin that is just sticking to the cornea)
-Primary conjunctivitis (i.e., bacterial or viral infection NOT associated w/ some other dz.) is relatively rare in dogs (more common in cats). Conjunctival fornices contain a considerable microbial flora. --> Primary conjunctivitis is a Dx. made by excluding secondary causes of conjunctivitis.
Clinical signs of Conjunctivitis
ACUTE: (shown in image)
-Hyperemia, Chemosis (edema of conjunctiva), Cellular exudate
-Hyperemia, Pigmentation or depigmentation, Folliculitis, Exudation, Keratinization
-Allergies in dogs
-Foreign bodies (--> examine fornices & behind NM)
-Ophthalmic drug preservatives (Thimerosal, Neomycin, Benzalkonium chloride)
(2 types, Tx. for each)
May be a component of ATOPY in dogs.
Environmental allergens & irritants
(NOTE: there is also a PCR test available for Chlamydophila & Mycoplasma.)
CHV-1 (canine herpes virus 1)
-FHV-1 (Feline Herpes virus 1) --> conjunctivitis & keratitis
-*Chronic conjunctivitis could indicate FeLV or FIV
On the affected side:
-PTOSIS - drooping of the eyelid
-MIOSIS - pupil constriction
-ENOPHTHALMOS - eye sunken back in orbit
-Protrusion of Nictitating Membrane (3rd eyelid)
---> HORNER'S SYNDROME
loss of sympathetic innervation to the eye
-Decreased orbital mass
-Retro- or Epibulbar mass effect
-Pain / Enophthalmos
Prolapsed Gland of NM/3rd eyelid ("Cherry eye")
*Need to surgically CORRECT these, can NOT just resect them! - NM contributes significantly to tear production. - surgical POCKET TECHNIQUE
-what is this condition?
-which dog breeds are most commonly affected?
= Atypical Pannus; Chronic Superficial Keratitis
- Pannus = vascularization. In ophtho, referring to vascularization of the cornea. ATYPICAL PANNUS is vascularization affecting the 3rd eyelid. It is associated w/ PLASMOMA, plasma cell infiltration of the NM --> thickening, depigmentation, & follicle formation
- German Shepherd, Belgian Sheepdog, Belgian Tervuren, Greyhound, Borzoi, Doberman, English Springer Spaniel
Lacrimal Secretory System:
Nasolacrimal Outflow System:
1. Congenital/Inherited - pugs, yorkies, miniature schnauzers, Cockers, English bulldogs, beagles
2. *Immune-mediated (40% of cases)
3. Drug-Induced - Atropine, Sulfonamides, Phenazopyridine, Etodolac NSAID, anesthetics
4. Systemic dz. - Distemper, DM, hypothyroidism, etc.
5. Chronic Blepharoconjunctivitis (conjunctival dz.) --> scarring of lacrimal ducts
Others: Neurogenic, Trauma to orbit & lacrimal gland, Irradiation, Infectious, Drug toxicity, Iatrogenic.
-Dry, lusterless cornea
-English Bulldog -Pug
-Lhasa Apso -Shih Tzu
-Pekingese -Boston Terrier
-American Cocker Spaniel
-Cavalier King Charles Spaniel
-West Highland White Terrier (WHWT)
-Canine Distemper virus
-FHV-1 (Feline Herpesvirus 1) --> shorter tear film break-up time (TFBUT) - 7-10 sec. vs. normal 12-21 sec.
-Hypothyroidism, Hyperadrenocorticism, SLE, RA
-Diabetes mellitus --> 28% lower Shirmer tear test (STT), 37% lower corneal sensation, 58% shorter TFBUT
- (may be related to lacrimal gland aplasia or hypoplasia)
- Yorkies, Chinese Crested, Pugs, Min. Schnauzers
1. Transitory decreased Schirmer tear test (STT):
- General anesthesia (GA) --> can reduce tear production for 24 hrs. (>2 hrs. GA can have prolonged effect).
2. Drug toxicity:
- Sulfas: Sulfasalazine, Sulfadiazene, Tribrissin (can be permanent), Phenazopyridine (can be permanent)
- EtoGesic (Etodolac NSAID) - can be permanent
Parasympathetic innervation travels with CN 7 (facial n.) - disruption may result from the following:
-Fracture of mandible & stylohyoid bone
-Iatrogenic following surgery: Stylohyoid ostectomy, Orbital or craniofacial surgery
Amputation of gland of NM can --> Iatrogenic KCS.
-Individual variation in contribution of NM gland to aqueous tears.
-Greater risk in breeds predisposed to KCS
-*Greater risk if STT (Schirmer tear test) low prior to amputation.
-Must monitor tear production (STT) so can identify if develop KCS before end up with complications such as corneal ulceration.
0.2-2.0% CYCLOSPORINE A (Optimune) - Topical Tx.
- Immunomodulating agent, Lacrimostimulant
- 1% recommended (0.2% not that effective for dry eye)
- increases tear production 80% of cases
- has T cell inhibitory activity
- reduces pigmentary keratitis & fibrosis
- dose: BID - TID
- may take 3-4 wks. before increasing tear production
0.2-2.0% CYCLOSPORINE A (CsA) - Optimune or compounding pharmacy.
0.03% TACROLIMUS - has same effect as CsA & may work in CsA nonresponders
1% PIMECROLIMUS - new drug from Novartis, very effective for canine KCS, may work in place of CsA
2% PILOCARPINE (Cholinergic agent) - used in Neurogenic KCS & CsA nonresponders (*NOT a primary Tx.! - used in very small # of cases)
Goal: to resolve pain & inflammation & to maintain vision.
-Replace tears using LacrimMIMETICS ("artificial tears"): Hypotears, Tears Naturale, Lacrilube, SERUM
-Mucolytics: ACETYLCYSTEINE 5% - to break up the mucus layer that has accumulated & is coating the cornea.
-Topical antibiotics & anti-inflammatories as needed - can use steroids, *BUT must be careful! b/c risk of developing secondary corneal ulcers w/ those.
- CONJUNCTIVAL FLAP: for deep corneal ulcers, to provide supportive tissue & blood vessels
- PAROTID DUCT TRANSPOSITION: saliva does NOT equal tears! --> calcium deposits, requires continued topical medication (EDTA 1%, topical antibiotics, anti-inflammatories, artificial tears) - was more common before discovered Cyclosporine could increase tear production.
- KCS = QUANTITATIVE, aqueous tear component
- Qualitative Tear Film Deficiency = disturbances of the tarsal or meibomian glands (lipid layer) & the conjunctival goblet cells (mucin layer)
ROSE BENGAL stain
-Tx. underlying issues such as Blepharitis & Meibomianitis
-Artificial tears gel or ointment
-Cyclosporine A (immunomodulating agent, lacrimostimulant)
-Antibiotics & anti-inflammatories as needed
inflammation +/- infection of the lacrimal sac
- can be very painful
- usually d/t obstruction of tear sac & attached nasal tear duct by inflammatory debris, foreign objects, or masses pressing on the duct --> Epiphora (watering eyes), conjunctivitis resistant to Tx., & occasionally a draining fistula in medial lower lid.
- skull rad.s w/ contrast (dacryocystorhinography) may be necessary to establish the site, cause, & prognosis of chronic obstructions.
-EPIPHORA (tears running down face rather than through normal outflow system) & Staining
-Normal lacrimation w/ abnormal outflow
-Mucoid punctal discharge
-Pain on palpation of lacrimal bone
-Swelling of medial canthal region
-Alopecia & dermatitis
-NEGATIVE JONE'S TEST (fluorescein doesn't drain)
-Complete eye exam & STT (Schirmer's tear test)
-Cytology & Culture
-Jones Test - fluorescein dye through lacrimal duct, should drain out the nose if patent NL duct (sometimes in cats & brachycephalic dogs, may drain into mouth instead of nose d/t accessory ducts)
-Nasolacrimal duct irrigation
-Imaging: U/S, Dacryocystorhinography (contrast study of NL outflow tract), CT or MRI, Endoscopy (used more in humans, a few cases in dogs)
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