Eye Diseases in Cats and Dogs: Key Insights and Practical Tips for Veterinarians

Introduction 

The eyes are highly sensitive organs, and subtle signs such as discharge, redness, or squinting can indicate serious underlying conditions. Corneal transparency is maintained by avascularity, deturgescence, and the uniform arrangement of stromal collagen fibrils. Disruption of these mechanisms due to dystrophy, degeneration, inflammation, or abnormal intracellular/extracellular inclusions can lead to corneal opacification. Traditionally, diagnosis relied on signalment, history, and slit-lamp examination, but lesions may remain undetected until severe. Most corneal stromal opacities do not affect vision unless advanced, and histopathology is rarely required in client-owned animals^1,2,3. Understanding the eye’s anatomy and its susceptibility to disease is essential for timely diagnosis and effective management. 

Conjunctival and Superficial Ocular Disorders¹ 
Foreign bodies in the eye can cause corneal penetration, pain, mucopurulent discharge, and eyelid closure. Prompt removal and topical therapy are crucial to prevent secondary infection. 

Conjunctivitis, particularly when associated with systemic viral infections, may include fever, lethargy, and ocular chemosis.  

Vet Tip: Assess systemic signs to guide supportive or antiviral therapy. 

Keratoconjunctivitis sicca (KCS) presents with seromucous discharge, corneal pigmentation, and vascularization, often with reduced Schirmer tear test values.  

Vet Tip: Early intervention with tear substitutes or stimulants prevents chronic corneal damage. 

Neonatal conjunctivitis may show eyelid adhesions, swelling, and mucopurulent discharge.  

Vet Tip: Gentle cleaning with topical antibiotics is usually sufficient; systemic antibiotics are only needed if secondary infection is suspected. 

Eyelid disorders such as entropion, meibomitis, and trichiasis cause photophobia, blepharospasm, and localized corneal trauma.  

Vet Tip: Corrective surgery or eyelid hygiene can prevent chronic damage. 

 Keratitis and Corneal Ulcers^1,3 
Keratitis may present as corneal opacity without gloss, while corneal ulcers are painful, with tissue loss and serous, seromucous, or purulent discharge.  

Vet Tip: Fluorescein staining is essential; early topical antibiotic therapy or surgical intervention can prevent vision loss. 

Herpesvirus infections in cats may result in symblepharon, forming adhesions between the conjunctiva and the cornea. Stray cats are commonly affected, often resulting in blindness.  

Vet Tip: Surgical release may be attempted, but recurrence is frequent; early antiviral therapy is recommended. 

 Other Ocular Conditions¹ 
Dermoid cysts present with pain and tear discharge; complete surgical excision is recommended to prevent recurrence. 

Thelazia infections manifest with serous discharge, vascularization, and pruritus. Vet Tip: Treat with topical or systemic antiparasitic therapy and monitor for secondary keratitis. 

Cherry eye, or prolapse of the third eyelid gland, appears as redness, dryness, and vascularization. Vet Tip: Morgan’s pocket technique preserves gland function; post-operative lubrication and anti-inflammatories are important. 

Breed Predispositions 
Certain breeds are more prone to specific ocular diseases. KCS is common in Terriers, French Bulldogs, Cocker Spaniels, and Pomeranians. Cherry eye frequently affects Bulldogs, Cocker Spaniels, and select Terriers. Entropion occurs more often in brachycephalic cats, such as British Shorthair and Scottish Fold. Symblepharon is more frequent in stray cats and dogs and can result in permanent vision loss¹.  

Vet Tip: Awareness of breed predispositions supports early screening and targeted intervention. 

Advanced Corneal Imaging 
Modern imaging modalities, including Fourier-domain optical coherence tomography (FD-OCT) and in vivo confocal microscopy (IVCM), provide high-resolution, cellular-level views of corneal structures. Dense lipid or calcium deposits can create posterior shadowing on OCT, but high-frequency ultrasound can overcome this limitation. IVCM allows visualization of intracellular and extracellular deposits, aiding early detection of lipid keratopathy, calcium deposition, or dystrophies². 

In Mucopolysaccharidosis (MPS) type 1, diffuse stromal hyperreflectivity and keratocyte depletion are characteristic findings, though definitive diagnosis still relies on enzyme assays, genetic testing, or GAG metabolite detection. Imaging can also identify features similar to human pre-Descemet corneal dystrophy (PDCD), with hyperreflective deposits in middle-posterior stroma and enlarged keratocytes. While imaging cannot replace gold-standard diagnostics, it provides valuable in vivo insights and facilitates early recognition of subtle or under-recognized corneal disorders.² 

 Conclusion 
The eye’s delicate anatomy and exposure make it susceptible to trauma, infection, and congenital or systemic conditions. For veterinarians, careful history-taking, detailed ocular examination, and knowledge of breed predispositions are essential for accurate diagnosis. Advanced imaging modalities such as FD-OCT and IVCM complement clinical evaluation, providing microstructural insights that can guide early detection and monitoring. Timely recognition, appropriate intervention, and breed-specific awareness remain key to preserving vision and improving outcomes in cats and dogs . 

 References 

1. ÇAKI S, DURMUŞ AS. Evaluation of Eye Diseases in Cats and Dogs. Firat Universitesi Saglik Bilimleri Veteriner Dergisi. 2025 Jun 1;39(2). 

2. Park S, Sebbag L, Moore BA, Casanova MI, Leonard BC, Daley NL, Steele KA, Li JY, Murphy CJ, Thomasy SM. Multimodal ocular imaging of known and novel corneal stromal disorders in dogs. BMC Veterinary Research. 2022 Mar 26;18(1):117. 

3. Mishra A, Shahi A, Das B, Dwivedi PK, Jawre S, Singh R, Virendra A. Incidence of ocular affections in dogs with special reference to corneal ulceration. Bull Mastiff. 2021;1:3-3.