Small animal ophthalmology Flashcards
Conjunctivitis and keratoconjunctivitis sicca, feline ophthalmology
Describe the anatomy of the conjunctiva
- Thin transparent pink mucous membrane
- Starts at limbus and covers globe (bulbar conjunctiva) and lines inner aspects of upper/lower eyelids (palpebral conjunctiva)
- Space formed called conjunctival sac
- Lines both sides of third eyelid
- Fornix is the “u-turn” of conjunctiva
- Freely mobile apart from attachments at the limbus and eyelid margin
Describe the physiology of the conjunctiva
- Rich vascular supply to allow rapid healing
- Sparse nerve supply
- Provides the only lymphatic drainage of the eye
Describe the appearance of the CALT
- Conjunctival associated lymphoid tissue
- Appears as little follicles, roughened areas of conjunctiva
Describe the nervous supply of the conjunctiva
- Supplied by CNV ophthalmic brnach
- Easy to anaesthetise with topical anaesthetic
- Facilitates minor surgery e.g. conjunctival biopsy
Describe the common clinical signs of acute conjunctivitis
- Uni or bilateral
- Hyperaemia (conjunctival redness)
- Chemosis
- Swelling or thickening
- Mild irritation e.g. mild blepharospasm
- Discharge (lacrimation)
- Pruritus may be seen in allergic conjunctivitis and may lead to self trauma
Describe the potential appearance of discharge in conjunctivitis
- Mucoid
- Purulent
- Mucopurulent
- Haemorrhagic
Describe mucinosis in Shar Pei dogs
- Mimics chemosis but is normal for breed
- Muzzle also looks swollen
Describe medial canthal pocket syndrome
- Normal variation in dolicephalic breeds
- Have naturally deep set eyes
- Mucus accumulates at medial canthus, should be flushed away naturally but does not occur properly in these breeds
- No treatment indicated, can flush with contact lens solution every few days
Describe the clinical signs of chronic conjunctivitis
- Hyperaemia, discharge etc. as for acute
- Thickening (squamous metaplasia of epithelium)
- Hyperpigmentation
- Follicular hyperplasia
Describe what is meant by follicular hyperplasia
- Nodule like structure representing lymphoid tissue
- Most obvious on posterior third eyelid and in conjunctival fornices
- Follicular conjunctivitis common in young dogs, may need treatment but often resolves spontaneously
List the potential aetiological agents of canine conjunctivitis
- Infectious
- Non-infectious
- Extension from local disease
- Secondary to another ocular disease
- Secondary to systemic disease
Describe infectious conjunctivitis in dogs
- Primary infectious uncommon
- Secondary bacterial very common e.g. dry eye, abnormal eyelid conformation, often by commensal G+ve e/g/ Staph, Strep.
- Viral infection v. uncommon e.g. canine herpesvirus-1
- Parasitic uncommon e.g. Thelazia more common in dogs imported from eastern Europe
- Fungal rare in UK
Describe the common sign of bacterial conjunctivitis
Purulent discharge
List the common underlying causes for conjunctivitis in dogs
- Eyelid problem e.g. entropion, ectropion
- Eyelash problem e.g. distichia, ectopic cilia
- Tear film problem e.g. dry eye
- Tear duct infection (dacryocystitis)
- Trauma e.g FB, laceration
- Allergic e.g. atopic dermatitis
- Irritants e.g. smoke sand, neomycin
- Ligneuous conjunctivitis in Doberman
- Radiation induced
What is entropion and how is it treated?
- Inturned eyelid
- Surgical treatment
- Removal of elliptical piece of skin
Describe ectropion as a cause of conjunctivitis
- Everted eyelid margin
- Common in St Bernards, eyelids too big
- “Normal” in many breeds
- If marked, can accumulate debris in sac which predisposes to infection and conjunctivitis
Describe distichiasis as a cause of conjunctivitis
- Extra eyelashes
- Often incidental finding but can cause conjunctivitis
- Unlikely to be causing conjunctivitis if found at 5yo, more likely to be the cause if found at 1yo
Give examples of how conjunctivitis may be an extension from local ocular disease
- Blepharitis eyelid inflammation)
- Lacrimal disease e.g. cherry eye
- Orbital disease e.g. retrobulbar abscess
Give examples of diseases that may have conjunctival involvement
- Anaemia
- Jaundice
- Coagulopathy
- Neoplasia e.g. lymphoma
- Auto-immune disease
- Systemic hypertension
List the breeds that are predisposed to cherry eye
- Bulldog
- Lhasa Apso
- Shih Tzu
- Mastiff breeds
Explain why excision is not recommended as the treatment for cherry eye
- Third eyelid gland produces 1/3rd of tear volume
- Breeds predisposed to cherry eye also predisposed to dry eye
List the potential causes of keratoconjunctivitis sicca
- Most common: immune mediated destruction of lacrimal tissue, stopping fluid production
- Congenital: lacrimal gland aplasia/hypoplasia
- Neurogenic: uniateral, dry eye/dry nose
- Toxic: sulphonamide drugs
- Endocrine disease: diabetes mellitus, hypothyroidism
- Iatrogenic: removal of TEG, some drugs
List the breeds that are predisposed to KCS
- WHWT
- Pug
- Shih Tzu
- Bulldog
Describe the typical presentation of KCS
- Young dog
- Bilateral
- Progressive
- Recurrent conjunctivitis that improves with any topical therapy as anything lubricates eye
- Conjunctivitis
- Sticky discharge
How is KCS diagnosed?
- Shirmer tear test
- Clinical signs
Describe the treatment of KCS
- Lifelong therapy
- Tear substitutes
- Tear stimulations (lacrimogenic) e.g. ciclosporin 0.2% (Optimmune)
- Broad spectrum topical antibiotic to treat secondary Staph infection
What is the main difference between feline and canine conjunctivitis?
Canine usually not infectious, feline usually infectious
List the potential aetiologies of feline conjunctivitis
- Infectious
- Non-infectious
- Extension from local disease
- Secondary to another ocular disease
- Secondary to systemic disease
List the 5 primary agents of feline infectious conjunctivitis
- Chlamydophila felis (bacterium)
- Feline herpesvirus 1
- Feline calicivirus
- Mycoplasma felis
- Bordatella bronchiseptica
Describe the presentation and treatment of feline calicivirus
- TYpically upper respiratory disease, oral ulceration, polyarthritis
- Generally do not test and treat for it as a cause of conjunctivitis
- Anti-viral treatment ineffective
Describe Mycoplasma spp. as a cause of conjunctivitis in cats
- Also found in normal cats
- Diagnosis by PCR
- Topical antibiotic e.g. tetracyclines (Doxycycline)
Describe Bordetella bronchiseptica as a cause of conjunctivitis in cats
- G-ve bacterium
- Affects respiratory tract of cats (and dogs) and rare zoonosis
- Diagnosis: culture and/or PCR
- Treatment: doxycycline
What 3 causes of conjunctivitis are treated by doxycycline in the cat
- Chlamydophila
- Mycoplasma
- Bordetella
Describe the clinical signs of chlamydial conjunctivitis in cats
- Unilateral conjunctivitis, becomes bilateral within a few days
- Chemosis often marked, hyperaemia
- No corneal signs, no corneal ulcer
- Absent or mild upper respiratory disease
Describe the diagnosis of chlamydial conjunctivitis in cats
- Clinical signs
- Conjunctival swab for PCR
- Culture superseded by PCR, lots of false negatives
Describe the treatment of chlamydial conjunctivitis in cats
- Systemic treatment indicated as organism affects resp, GI and repro tract
- Doxycyline antibiotic (5mg/kg BID or 10mg/kg SID for 3 weeks)
- Treat all in contacts with doxy as well
- Amoxyclav good for pregnant queens or kittens
What is the main side effect of doxycycline in cats?
Discolouration of teeth and oesophagitis
Describe the clinical signs of FHV-1 in kittens and youung cats
- Bilateral conjunctivitis in conjunction with upper resp signs (cat flu)
- +/- corneal ulceration
Describe the clinical signs of FHV-1 in adult cats
- Unilateral ocular discharge with mild conjunctivitis
- History of previous upper resp infection
- Wide range of other conditions e.g. sequestrum entropion, eosinophilic keratitis
- Dendritic corneal ulcer (linear ulcer) pathognomic if seen
How can chlamydial and herpes conjunctivitis be distinguished from one another in cats?
Herpes causes coneal diseas, non in chlamydial