Conjunctivitis & KCS

Question 1

Anatomy: conjunctival surfaces

Answer 1

• thin transparent/pink mm
• starts at limbus, forms continuous sheet over eyelids, 3rd eyelid and globe
• palpebral conjunctiva = lining the inner surface of eyelids
• bulbar conjunctiva = over the globe, appears white with little vessels over it (i.e. white of eye)
• conjunctival fornix = where palpebral conjunctiva is reflected round and becomes the bulbar conjunctiva
• limbus = where it meets the cornea

Question 2

Pathophysiology of the conjunctiva

Answer 2

Freely mobile apart from attachment at limbus and eyelid margin - allows free movement of ocular structures
- conjunctival oedema (chemosis) or subconjunctival haemorrhage can be marked

Contributes to tear film (goblet cells product mucin) and lubricated by tear film
- KCS affects conjunctival health

Provides the only lymphatic drainage of the eye - CALT (conjunctival-associated lymphoid tissue
- chronic antigenic stimulation -> lymphocytes form active follicles (follicular hypertrophy)

Question 3

Anatomy & physiology of the conjunctiva

Answer 3

Spare sensory innervation (ophthalmic branch of trigeminal)
- easy to anaesthetise with topical anaesthetic

Rich vascular supply
- rapid healing

Bulbar conjunctiva overlies sclera
- 2 layers of blood vessels
- episcleral & conjunctival vessels

Question 4

Conjunctiva - normal variation: mucinosis

Answer 4

• common in Shar Pei dogs
• mimics chemosis (conjunctival oedema) but normal for breed

Question 5

Conjunctiva - normal variation: ‘medial canthal pocket syndrome’

Answer 5

• dolichocephalic breed with naturally deep-set eyes (enophthalmos) e.g. Doberman, Standard Poodle
• mucus accumulates at medial canthus
• no tx indicated
• O may need to just clean eyes more often

Question 6

Acute conjunctivitis - CS

Answer 6

• uni or bilateral
• hyperaemia (redness)
• chemosis (oedema)
• swelling/discharge
• discharge: lacrimation vs mucoid, purulent, mucopurulent or haemorrhagic
• mild irritation/blepharospasm
• occasionally pruritus e.g. allergic conjunctivitis

Question 7

Chronic conjunctivitis - CS

Answer 7

• thickening d/t squamous metaplasia of epithelium
• hyperpigmentation
• follicular hyperplasia, esp posterior 3rd eyelid and in conjunctival fornices
• NB follicular conjunctivitis is common in young dogs, may need tx but often resolves spontaneously

Question 8

Ddx for a discharging eye

Answer 8

Purulent discharge
- bacterial conjunctivitis
- grass seed FB in conjunctiva
- KCS with secondary bacterial infection

Thick/tenacious discharge
- KCS

Serous (watery) discharge
- increased lacrimation d/t ocular pain
- epiphora d/t reduced nasolacrimal drainage

Haemorrhagic discharge
- ocular trauma
- coagulation problem

Question 9

Aetiology of canine conjunctivitis

Answer 9

Infectious
- primary or secondary

Non-infectious
- irritants
- FBs
- allergies

Secondary to
- adnexal dz (eyelids, tear film, nasolacrimal duct
- other ocular dz
– local dz e.g. ulcers, blepharitis, orbital dz
– intraocular dz e.g. uveitis, glaucoma, episcleritis/scleritis

Question 10

Canine infectious conjunctivitis - causes

Answer 10

Primary infectious conjunctivitis
- uncommon in dog
- 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 bacteria infection
- very common
- commensal gram+ve organisms e.g. Staphs & Streps
- less commonly: E.coli, Bacillus spp, Proteus spp, Pseudomonas spp

Question 11

Underlying causes for conjunctivitis

Answer 11

FBs
- check under 3rd eyelid as can hide here
- important in small furries e.g. GPs

Irritations
- e.g. smoke, sand, neomycin

Allergic
- e.g. atopic dermatitis

Adnexal dz
- eyelid and eyelash problems
- tear film problems e.g. KCS
- tear duct infection (dacryocystitis)

Question 12

Causes of conjunctivitis: entropion - what is it? tx?

Answer 12

= inversion (inward turning) of the eyelid margin
- tx: Hotz-celsus sx: removal of elliptical piece of skin OR combined Hotz-celsus and wedge resection
– combined good as Hotz-celsus turns the eyelid out and resection shortens the eyelid
– bc a lot of dogs with entropion the eyelids are too long, so just turning it out is not enough

Question 13

Causes of conjunctivitis: ectropion - what is it?

Answer 13

= eversion / outward turning of eyelid marking
- some never have CS, but often end up with chronic conjunctivits due to the exposure of it

Question 14

Causes of conjunctivitis: eyelid mass - tx

Answer 14

• wedge resection
• mostly adenomas and therefore benign

Question 15

Causes of conjunctivitis: eyelash (cilia) disorders

Answer 15

• distichia
• ectopic cilia

Question 16

Causes of conjunctivitis: distichiasis - what is it? what can is cause? tx options?

Answer 16

= extra eyelashes emerge from meibomian gland orifices
- often multiple lashes
- may cause irritation/conjunctivitis but can be incidental
- don’t always need treating (i.e. if incidental finding)
- tx: cryotherapy & electrolysis
– not the best as have side effects and can have a certain number of hairs that regrow

Question 17

Causes of conjunctivitis: ectopic cilia - what is it? what can is cause? tx options?

Answer 17

• arise from follicle inside/near meibomian gland -> emerge through conjunctiva at right angles to cornea
• normally single eyelash
• always causes irritation ± corneal ulcer -> needs tx
• tx: surgical excision

Question 18

Causes of conjunctivitis: keratoconjunctivitis sicca (KCS) - what is it? signalment?

Answer 18

• local immune-mediated destruction of lacrimal tissue: lacrimal gland and 3rd eyelid (nictitans) gland
• common cause of canine conjunctivitis esp WHWT, pug, Shih Tzu, bulldog, CKCS, English cocker spaniel
• usually young-middle aged dogs
• usually bilateral

Question 19

Other causes of KCS in the dog

Answer 19

Immune-mediated
- most common cause

Congenital
- lacrimal gland aplasia/hypoplasia

Neurogenic
- unilateral, dry eye/dry nose
- problem with the nerve supply to the lacrimal gland

Toxic
- sulphonamide drugs -> check history

Endocrine dz
- DM, hypothyroidism

Iatrogenic
- removal of 3rd eyelid gland

Question 20

CS of KCS

Answer 20

• recurrent conjunctivitis that improves with any topical therapy as anything lubricates the eye
• tacky mucoid-mucopurulent discharge stuck to ocular surface
• distorted purkinje image
• blepharospasm
• ± corneal ulceration

Aqueous component of the tears is affected, therefore the conjunctiva tries to overcompensate and produces more mucus which is tacky/sticky, hence the thick discharge. Secondary bacterial infection is common as well - no tear film hence bacteria not washed away.

Question 21

Corneal changes with chronic KCS

Answer 21

• corneal vascularisation, fibrosis and pigmentation
• reduced vision

The cornea relies on the tear film for a lot of its nutrition, therefore without the tear film the blood vessels grow in to try and provide that nutrition.

Question 22

Diagnosis of KCS

Answer 22

STT
- quantitative measure of aqueous production
- measures basal and reflex tear production
- position in middle-lateral 3rd of eye, eyelids open or closed
- 15-25mm/min = normal
- 10-15mm/min = borderline (diagnostic of KCS if CS support)
- <10mm/min = underproduction = KCS
- >25mm/min = suggests overproduction i.e. ocular irritation

Question 23

Tx of (immune-mediated) KCS

Answer 23

• progressive dz: early tx best (before lacrimal tissue is destroyed)
• lifelong therapy: control not cure
• tear substitutes: various false tear preparations in eye drop, gel or ointment formulation
• tear stimulants (lacrimogenic): cyclosporine 0.2% (Optimmune)
• broad spec topical antibiotic to treat secondary infection

Question 24

Causes of conjunctivitis: nasolacrimal dz - cause, signs

Answer 24

• epiphora: tear overflow due to poor tear drainage
• congenital atresia/agenesis of part of nasolacrimal system or malpositioned tear punctum: common, usually non-painful
• obstruction by foreign or inflammatory material: may cause dacryocystitis

Question 25

Causes of conjunctivitis: dacryocystitis in rabbits - tx, underlying cause

Answer 25

- cause of most conjunctivitis in rabbits - tx 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

Question 26

Conjunctivitis: extension from local ocular dz - conjunctiva may be affected by...

Answer 26

Orbital dz - e.g. retrobulbar abscess Corneal dz - e.g. ulceration Lacrimal dz - e.g. 'cherry eye' Blepharitis - eyelid inflammation

Question 27

What important ocular conditions is a red eye seen with?

Answer 27

- uveitis - glaucoma - scleritis/episcleritis

Question 28

Conjunctival involvement in systemic dz - examples

Answer 28

- anaemia - jaundice - coagulopathy - neoplasia e.g. lymphoma - autoimmune dz

Question 29

Subconjunctival haemorrhage - differential diagnosis

Answer 29

Most commonly due to blunt trauma - check carefully for intraocular damage Other ddx: - coagulopathies, systemic hypertension and vasculitis

Question 30

What parts of the ophthalmic exam are most relevant in an animal presenting with conjunctivitis?

Answer 30

Hands off exam - blepharospasm? - nature of discharge? - eyelid conformation? STT Examine anterior segment with focal light source ± magnification - examine cornea and conjunctiva (including under TEL for FB) - examine eyelids - conformation and margins Fluorescein dye application - check for corneal ulcer - Jones test to assess teat duct Check for intraocular dz - e.g. PLR, menace response, direct direct (compare pupil sizes) ± IOP -> should all be normal if just conjunctivitis

Question 31

Treating canine conjunctivitis - treating/removing underlying cause

Answer 31

Topical antibiotic therapy - fusidic acid (Isathal) -- licenced product in UK (1st choice) -- treat gram+ve organisms most commonly found in canine conjunctivitis (Staph, Strep) - chloramphenicol drops/ointment - other antibiotics based on C&ST

Question 32

Aetiology of feline conjunctivitis

Answer 32

Infectious - common Non-infectious - as for dogs but less common - e.g. entropion: less common, may be acquired in older cats - KCS much less common, hard to diagnose (normal STT values highly variable), can see qualitative tear film problem Extension from other ocular dz - as for dogs Conjunctival involvement in systemic dz - as for dogs

Question 33

Feline infectious conjunctivitis - causes

Answer 33

Primary infectious conjunctivitis is common (unlike in dogs) - chlamydophila felis (bacterium) - feline herpesvirus-1 (FHV-1) (virus) - feline calicivirus (FCV) - mycoplasma feels (bacterium) - bordetella bronchiseptica (bacterium) Secondary bacterial infections common - usually secondary to primary infection (cf dogs - secondary infections also common but usually secondary to underlying problem e.g. adnexa/tear film)

Question 34

Chlamydophila felis - what is it?

Answer 34

- obligate intracellular bacterium - common cause of feline conjunctivitis

Question 35

Chlamydophila felis - CS

Answer 35

- unilateral conjunctivitis, becomes bilateral within a few days - chemosis often marked, hyperaemia - no corneal signs - absent or mild URT dz

Question 36

Chlamydophila felis - diagnosis

Answer 36

- CS ± conjunctival swab for PCR test -- sterile swab rolled in conjunctival sac, placed in sterile, dry tube

Question 37

Chlamydophila felis - ddx

Answer 37

- cf herpesvirus, this doesn't cause corneal signs and absent/mild URT dz

Question 38

Chlamydophila felis - treatment

Answer 38

Systemic tx indicated as organism affects resp tract, GIT and repro tract as well as eye Doxycycline antibiotic of choice - 10mg/kg daily for 3-4w to eradicate organism treat in contacts too) - NB may cause teeth discolouration in young animals - NB can cause oesophagitis: give with food/syringe water afterwards Amoxycillin-clavulanate in pregnant queen or kittens

Question 39

Feline herpesvirus-1 - CS

Answer 39

CS vary according to age Kittens & young cats - bilateral conjunctivitis in conjunction with URT signs (cat flu) - ± corneal ulceration Adults cats - unilateral ocular discharge with mild conjunctivitis - history of previous URT infection - wide range of other conditions e.g. corneal ulceration, sequestrum, entropion, eosinophilic keratitis - symblepharon: conjunctiva get sticky and start sticking together inappropriately (weird condition associated with FHV-1) - dendritic corneal ulcer: pathognomic for FHV-1 (lesion looks like cracks in the cornea)

Question 40

FHV-1 diagnosis

Answer 40

Hx & CS Conjunctival swab 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 for C felis Care with interpretation - false -ve's common due to intermittent shedding - false +ve's common: many cats have been exposed to FHV-1, so positive result could reflect FHV-1 reactivation that is coincidental or secondary to the ocular dz

Question 41

FHV-1 tx

Answer 41

Nursing - cleaning eyes, nutrition, rehydration Broad-spec antibiotic to prevent/tx secondary bacterial infection - topical for eyes (e.g. fusidic acid, chloramphenicol) - systemic for resp involvement e.g. amoxy-clav Anti-virals - topical e.g. ganciclovir 4x daily - systemic eg. famcyclovir (expensive) 90mg/kg BID recommended dose

Question 42

Other infectious causes of feline conjunctivitis - signs, diagnosis, tx

Answer 42

Feline calicivirus (FCV) - URT dz, oral ulceration, polyarthritis, conjunctivitis - anti-viral tx ineffective Mycoplasma spp - found in normal cats - diagnosed by PCR - sensitive to most topical antibiotics (e.g. chloramphenicol or tetracyclines) Bordetella bronchiseptica - affects resp tract of cats and dogs (dogs can infect cats) - potential zoonosis (rare) - diagnose by culture and/or PCR - tx: doxycycline

Question 43

Approach to feline conjunctivitis

Answer 43

Careful ocular exam to rule out adnexal or intraocular dz Usually primary infectious cause: hx and CS may help direct tx (e.g. corneal involvement -> suspect FHV-1) - topical chloramphenicol or tetracycline good 1st line choices - tx concurrent resp signs as appropriate If recurrent, consider swab for PCR to inform diagnosis/tx - chlamydophila infections need systemic antibiotics - FHV-1 infection may need anti-virals