Conjunctivitis and KCS

• The anatomy of the conjunctival surfaces

  Thin transparent/ pink mucous membrane.

  Starts at limbus, forms continuous sheet over eyelids, third eyelid and globe.
• What is the Pathophysiology of the conjunctiva?

  Freely mobile apart from attachments at limbus and eyelid margin - allows free movement of ocular structures.

  • Conjunctival oedema (chemosis) or subconjunctival haemorrhage can be marked due to this.

  Contributes to tear film (goblet cells produce mucin), and the conjunctival is lubricated by the tear film:

  • KCS (dry eye) affects conjunctival health as well as the cornea.

  Provides the only lymphatic drainage of the eye
• What is the anatomy and physiology of the conjunctiva?

  Sparse sensory innervation (ophthalmic branch of trigemianl) - easy to anaesthetise with topical anaesthetic for minor procedures.

  Rich vascular supply - rapid healing.

  Bulbar conjunctiva overlies sclera - two layers of blood vessels
• Normal variations - mucinosis

  Mucinosis common in Shar Pei dogs.

  Mimics chemosis (conjunctival oedema) but normal for breed.

  
• Normal variations - medial canthal pocket syndrome

  Dolicephalic breeds with naturally deep-set eyes (enophthalmos) - e.g. Dobermann, Standard poodle.

  Mucus accumulates at medial canthus, allows discharge to build up.

  No treatment indicated, other than the owner being aware they may need to clean there eyes more often.
• What are the clinical signs of acute conjunctivitis?

  Unilateral or bilateral.

  Hyperaemia (redness)

  Chemosis (oedema)

  Swelling/thickening.

  Discharge - lacrimation vs mucoid, prurulent, mucopurulent or haemorrhagic (very occasionally).

  Mild irritation/blepharospasm.

  Occasionally pruritus (e.g. allergic conjunctivitis).
• What are the clinical signs of chronic conjunctivitis?

  Thickening d/t squamous metaplasma of epithelium.

  Hyperpigmentation.

  Follicular hyperplasia - especially posterior third eyelid and in conjunctival fornices.

  NB follicular conjunctivitis is common in young dogs; may need treatment but often resolves spontaneously.

  
• What are the differential diagnoses for prurulent discharge from the eye?

  Infection like bacterial conjunctivitis.

  Grass seed foreign body in conjunctiva.

  KCS (dry eye).
• What are the differential diagnoses for thick/tenacious discharge from the eye?

  Dry eye (KCS) - very classic signs.
• What are the differential diagnoses for serous(watery) discharge from the eye?

  Increased lacrimation d/t Ocular pain.

  tear overflow (epiphora) d/t reduced nasolacrimal drainage.
• What are the differential diagnoses for haemorrhagic discharge from the eye?

  Ocular trauma

  Neoplasia

  Coagulopathy (unusual)
• What is the aetiology of canine conjunctivitis?

  Infectious - primary or secondary.

  Non-infectious - irritants, FBs, allergies.

  Secondary to:

  • Adnexal disease (eyelids, tear film, nasolacrimal duct)
  • Other ocular disease:
  • Local disease - ulcers, blepharitis, orbital disease.
  • Intraocular disease - uveitis, glaucoma, episcleritis/scleritis.
• Primary infectious conjunctivitis

  Uncommon in dog, more important in imported dogs:

  • Viral infection e.g. canine herpesvirus-1.
  • Bacterial infection.
  • Parasitic infection e.g. Thelazia or Leishmania spp - imported dogs.
  • Fungal infection rare in UK.

  Secondary bacterial infection is very common:

  • Commensal Gram +ve organisms e.g. Staphylococcus spp
• What is Entropion and what is the treatment for it?

  Entropion is the inversion (inward turning) of the eyelid margin.

  Treatment: Hotz-celsus surgery, removal of the elliptical piece of skin.

  
• Distichiasis

  Extra eyelashes emerge from meibomian gland orifices.

  Often multiple lashes.

  May cause irritation/conjunctivitis, but can be incidental - don’t always need treating.

  Several treatment methods, most common are cryotherapy and electrolysis. Can be quite challenging to treat.
• Ectopic cilia

  Arise from follicle inside/near meibomian gland - emerge through conjunctiva at right angles to cornea.

  Normally single eyelash.

  Always causes irritation +/- corneal ulcer - need treatment.

  Treatment is local surgical excision. Challenge is finding it in the first place as they are very small.

  
• Keratoconjunctivitis sicca (KCS)

  Local immune-mediated destruction of lacrimal tissue: lacrimal gland and third eyelid (nictitans) gland.

  Common cause of canine conjunctivitis especially WHW terriers, Pug Shih Tzu, Bull dog, CKCS, English cocker spaniel.

  Usually young - middle aged dogs.

  Usually bilateral.
• What are cause of KCS in the dog?

  Immune mediated is the most common cause.

  Congenital - lacrimal gland aplasia/hypoplasia.

  Neurogenic - problem with the nerve supply to lateral gland - unilateral dry eye/dry nose.

  Toxic - Sulphonamide drugs - check history.

  Endocrine disease - diabetes mellitus, hypothyroidism.

  Iatrogenic - removal of third eyelid gland.
• What are the clinical signs of KCS?

  Recurrent conjunctivitis that improves with any topical therapy as anything lubricates eye!

  Tacky mucoid-mucopurulent discharge, will often have a distortion to the reflection of the surface (distorted purkinje image)

  Blepharospasm

  +/- Corneal ulceration.

  
• You are presented with a dog with recurrent conjunctivitis in both eyes. The right eye is shown below. Schirmer tear test reading are 13mm/min in the right eye and 9mm/min in the left eye, what is the most likely diagnosis?

  1 Bacterial conjunctivitis

  2 KCS in the right eye only.

  3 KCS in the left eye only.

  4 KCS in both eyes.

  5 Lower lid Entropion.

  4
• What is the treatment for immune mediated KCS?

  Progressive disease: early treatment best (before lacrimal tissue is destroyed).

  Lifelong therapy - control not cure.

  Tear substitutes form part of the treatment protocol.

  • Various false tear preparation in the eye drop, gel or ointment formulation.

  Tear stimulants (lacrimongenic)

  • Cyclosporine 0.2% (Optimmune)

  Broad spectrum topical antibiotic to treat secondary infection, generally if you can get the animal to produce there own tears then they won’t need the antibiotics.
• What is epiphora?

  Tear overflow due to poor tear drainage.

  Congenital atresia/agenesis of part of nasolacrimal system or mail positioned tear punctum - common, usually non-painful.

  Obstruction by foreign or inflammatory material - may cause dacryocystitis.
• Dacryocystitis in rabbits

  Cause of most conjunctivitis in rabbits, due there overlong molar tooth roots pressing on the duct.

  Treatment must include nasolacrimal duct flushing (NB single lower nasolacrimal puncta).

  Underlying cause: overlong molar roots pressing on nasolacrimal duct.

  Often recurrent, aiming to manage rather than cure.
• What is the conjunctival involvement is systemic disease?

  Anaemia

  Jaundice

  Coagulopathy

  Neoplasia e.g. lymphoma

  Auto-immune disease.
• Subconjunctival haemorrhage

  Most commonly due to blunt trauma:

  • Check carefully for intraocular damage.

  Other differential diagnoses include coagulopathies, systemic hypertension and vasculitis.
• How do you treat canine conjunctivitis?

  Treat/remove the underlying cause.

  Topical antibiotic therapy:

  • Fusidic acid (Isathal)
  • Licensed products in UK - first choice.
  • Treats Gram +ve organisms most commonly found in canine conjunctivitis.
  • Chloramphenicol drops/ointment - bit more broad spectrum, not licensed.
  • Other antibiotics based on culture and sensitivity.
• Feline infectious conjunctivitis

  Primary infectious conjunctivitis is common (unlike in dogs):

  • Chlamydophila felis (bacterium)
  • Feline herpesvirus-1 (FHV-1)(virus)
  • Feline calicivirus (FCV)
  • Mycoplasma felis (bacterium)
  • Bordetella bronchiseptica (bacterium)
• What are the clinical signs of Chlamydophila felis?

  Unilateral conjunctivitis, becomes bilateral within a few days.

  Chemosis often marked, hyperaemia.

  No corneal signs - just the conjunctivitis.

  Absent or mild upper respiratory disease.
• How do you diagnose Chlamydophila felis?

  Clinical signs +/- conjunctival for PCR test:

  • Sterile swab rolled in conjunctival sac, placed in sterile, dry tube.
• What is the treatment for Chlamydophila felis?

  Initially respond well to a topical antibiotic but will not clear the infection from the system with this.

  Systemic treatment indicated as organism affects respiratory tract, GIT and reproductive tract as well as eye.

  Doxycycline is the antibiotic of choice.

  • 10mg/kg daily for 3-4 weeks to eradicate organism
  • NB may cause teeth discolouration in young animals.
  • NB can cause oesophagitis - give with food/syringe water afterwards.
  • Treat all the animals in the house otherwise it tends to cycle back between them.
• Feline herpesvirus-1

  Important ocular pathogen.

  Clinical signs vary according to age:

  • Bilateral conjunctivitis in conjugation upper respiratory signs (cat flu).
  • +/- corneal ulceration.

  Adult cats (had cat flu when young)

  • Unilateral ocular discharge with mild conjunctivitis.
  • History of previous upper respiratory infection.
  • Wide range of other conditions e.g. corneal ulceration, sequestrum, entropion, eosinophillic keratitis.
• Diagnosing feline herpes virus-1

  Based on history and clinical signs.

  Conjunctival swan for PCR test:— Same technique as for C.felis.

  Swab site of interest i.e. swab cornea, conjunctiva and/or oropharynx.

  PCR has superseded culture (like C felis).

  Care with interpretation:

  • False negatives common d/t/ intermittent shedding.
  • False positives common - many cats have been exposed FHV-1, so positive result could reflect FHV-1 reactivation that is coincidental secondary to the ocular disease.
• What is the treatment for FHV-1?

  Nursing:

  • Cleaning eyes, nutrition, rehydration.

  Broad-spectrum antibiotic to prevent/treat secondary bacterial infection:

  • Topical for eyes (e.g. fusidic acid, chloramphenicol)
  • Systemic for respiratory involvement e.g. amoxycillin-clavulanate.

  Anti-viral:

  • Topical e.g. ganociclovir 4x daily (can be tricky in cats)
  • Systemic e.g. famcyclovir (expensive) 90mg/kg BID recommended dose.