Common eye conditions in dogs – clinical tips (Part 1)

12 January 2024

Confused about conjunctivitis or unsure about uveitis? 

Brush up on some of the more common ophthalmic conditions seen in dogs, with this overview and clinical tips from Mike Rhodes from Focus Referrals. 

Keep an eye out for part 2 to follow, which focuses on common eye conditions in cats. 

1) Entropion  

This is inversion of the eyelid(s), resulting in contact of eyelid hairs with the ocular surface leading to irritation and corneal disease. Clinical signs include blepharospasm, corneal ulceration and keratitis (where the eyelid hairs contact the ocular surface), increased tear production, epiphora and periocular wetting, increased blink rate and self trauma. Treatment options include temporary eyelid tacking sutures and permanent surgical correction. 

CLINICAL TIP – Always assess the dog with the head carriage lowered when checking the eyelid-to-globe conformation. Some forms of entropion only become apparent when the head is lowered. 

2) Distichiasis 

This is a condition where extra eyelashes originate along the eyelid margin within or adjacent to the meibomian gland openings. Clinical signs (normally seen in younger dogs <12 months of age) are increased tear production and epiphora, increased blink rate and ulcerative keratitis (position of the ulcer corresponds with the location of the distichia). 

There is no one treatment that is 100% effective at resolving distichiasis, but options are eyelid wedge excision, transconjunctival thermal electrocautery, cryotherapy, electrolysis and sharp knife surgery. 

CLINICAL TIP – The application of topical fluorescein (I-DEW FLO, Fluorescein Sodium Ophthalmic Strip) can help delineate the presence of the distichia. 

3) Ectopic cilia  

These cilia emerge through the palpebral conjunctival close to the eyelid margin and are directed perpendicularly to the corneal surface. Clinical signs (once erupted, ectopic cilia nearly always cause clinical signs) are blepharospasm, increased tear production and epiphora, increased blink rate and ulcerative keratitis (position of the ulcer corresponds with the location of the ectopic cilium, usually in the middle of the upper eyelid). Treatment is by surgical excision. 

CLINICAL TIP – If you have an indolent-type corneal ulcer in a young dog (<6 months of age) it is very likely that the underlying cause is an ectopic cilium. 

4) Conjunctivitis  

This is a relatively common condition and is usually secondary to other ocular or systemic disease processes in dogs. Clinical signs are conjunctival hyperaemia, chemosis, conjunctival swelling/thickening, conjunctival follicle formation (chronic cases) and ocular discharge (mucoid, mucopurulent, haemorrhagic). Treatment involves addressing and treating the underlying cause. In cases of entropion, ectropion, trichiasis and eyelid agenesis, surgical intervention is warranted; if due to an underlying tear film deficiency, topical lacrimogenic and/or lacrimomimetic therapy should be considered; follicular conjunctivitis can respond well to topical mast-cell stabilizers, e.g. olopatadine (Opatanol). 

CLINICAL TIP – Topical phenylephrine solution (Minims Phenylephrine hydrochloride 2.5%) can be applied to the eye to differentiate conjunctival hyperaemia i.e. conjunctivitis from deeper/intraocular inflammation e.g. episcleritis/uveitis. With the former, the hyperaemia blanches white very quickly (<10 seconds). Do not apply in cases of suspected glaucoma. 

5) Keratoconjunctivitis sicca 

This common clinical disease arises as a result of a deficiency of the aqueous component of the tear film being characterised by desiccation of conjunctiva and the cornea. Clinical signs are blepharospasm, conjunctival hyperaemia, tenacious mucopurulent ocular discharge, lack-lustre appearance to the corneal surface, corneal neovascularisation, corneal pigmentation and progressive corneal ulceration. Treatment options are lacrimostimulants, lacrimomimetics, antibiotics and surgical intervention. 

CLINICAL TIP – In a severe/absolute case of unilateral KCS in a dog with or without an ipsilateral dry nose, consider a neurogenic cause. 

6) Corneal ulceration – indolent superficial ulcers (superficial chronic corneal epithelial defects (SCCED) 

These types of ulcer typically persist for more than 2 weeks and are characterised by loose, non-adherent epithelial edges. Certain breeds are more likely to suffer from a SCCED and these lesions can only occur in dogs older than 5 years. Clinical signs are superficial corneal ulcer with loose, non-adherent epithelial edges, blepharospasm, conjunctival hyperaemia, ocular discharge (serous, mucoid, mucopurulent) and corneal neovascularisation. Medical treatment alone is unlikely to be successful. Instead, treatment is aimed at disrupting the abnormal layer within the anterior stroma to allow epithelial attachment to the stroma, including debridement alone, debridement and keratotomy (grid or punctate), diamond burr debridement (Algerbrush II), superficial keratectomy.  

CLINICAL TIP – These types of ulcer can only occur in middle-aged to older dogs (>5 years of age), therefore if you have younger dog with a non-healing ulcer, there has to be another cause e.g. adnexal abnormality (ectopic cilium). 

7) Corneal ulceration – a progressive corneal ulcer  

These types of ulcer progress from being superficial to involve the deeper corneal stromal layers. Further progression can result in exposure of the Descemet’s membrane leading to a Descemetocele and subsequent corneal rupture. Clinical signs are deeper corneal ulcer, ‘halo’ or ‘intensive’ staining pattern of fluorescein, blepharospasm (becoming less severe), conjunctival hyperaemia, ocular discharge (mucopurulent), corneal neovascularisation and a reflex anterior uveitis. Treatment options are anti-collagenases, antibiotics and surgical intervention.  

CLINICAL TIP – As the ulcer becomes deeper the eye often appears more comfortable to the owner because of the sparsity of corneal nerves within the deeper stroma. Therefore, the clinician should re-check such cases regularly, even if the owner feels the eye is getting better. 

8) Uveitis  

This refers to inflammation of the uveal tissue. Anterior uveitis is inflammation of the iris (iritis) and ciliary body (cyclitis); posterior uveitis is inflammation of the choroid. Panuveitis is inflammation of all three portions of the uvea. Clinical signs specific to uveitis are photophobia, aqueous flare, anterior chamber fibrin, keratic precipitates, hyphaema, hypopyon, iris swelling, rubeosis iridis, iris nodules, miosis and reduced intraocular pressure. Treatment options are topical corticosteroid, topical non-steroidal anti-inflammatory drugs, systemic corticosteroids, systemic NSAIDs and systemic immunomodulatory drugs.  

CLINICAL TIP – Always perform a thorough general physical examination in cases of suspected uveitis as some systemic disease processes actually present to the clinician with ocular signs e.g. lymphoma. 

 9) Glaucoma 

 This is a complex of pathological events arising as a result of the elevation of intraocular pressure above normal limits. The earliest effect is on the optic nerve head and retina, leading to vision loss, which may rapidly become irreversible. Clinical signs (acute) are raised intraocular pressure, pain, episcleral/conjunctival congestion/hyperaemia, vision loss in the affected eye, corneal oedema, mydriasis and reduced direct pupillary light reflex. Treatment includes topical prostaglandin analogues (first line treatment, such as Travoprost and Latanoprost), topical carbonic anhydrase inhibitors (such as Brinzolamide), topical combination treatments and surgical intervention.  

CLINICAL TIP – If the eyeball is obviously enlarged, this means the glaucoma is chronic (weeks to months) and whilst this condition can be uncomfortable, it is not an emergency. However, acute cases of glaucoma require urgent attention and/or referral, in order to lower the intraocular pressure and preserve vision. 

10) Cataracts 

A cataract is any opacity of the lens or lens capsule. Cataracts are described as incipient (<10% of lens involved), immature (>10% of lens but tapetal reflex present), mature (tapetal reflex not present) or hypermature (a ‘wrinkled’ and irregular lens capsule), as well as by their position within the lens (capsular, subcapsular, nuclear, cortical, anterior/posterior or polar). Treatment is by surgical intervention or medical management of lens induced uveitis through topical NSAIDs e.g. bromfenac. 

 CLINICAL TIPS – 1) Dogs with diabetic cataracts can have very good post-operative outcomes with cataract surgery via phacoemulsification. However, early referral is very important (even if the diabetes mellitus is not fully stabilised) to prevent complications associated with lens induced uveitis.  

2) To differentiate between a true cataract and nuclear sclerosis (age-related increased density of the lens) perform distant direct ophthalmoscopy with the dial set to zero. A cataract will appear as a black opacity within the tapetal reflex. 

Further information 

Due to the low number of topical medications licensed for ocular use in animals, appropriate treatment can be prescribed via the prescribing cascade (https://new.bsava.com/Resources/Veterinary-resources/Medicines-Guide/Prescribing-cascade) 

BSAVA Manual of Canine and Feline Ophthalmology https://www.bsavalibrary.com/content/book/10.22233/9781910443170  

Acknowledgements 

This article was produced by Mike Rhodes, Focus Referrals and Chair for the British Association of Veterinary Ophthalmologists