Clinical Insights into Canine Cataracts: From Pathogenesis to Postoperative Care

Cataracts continue to be one of the most frequent and often most frustrating causes of vision loss in dogs. What may start as a subtle lens opacity can rapidly evolve into a condition that alters a patient’s behaviour, mobility, and overall quality of life. For veterinarians, the challenge lies not just in identifying cataracts, but in understanding why they form, which ones will progress, and when intervention truly makes a difference. 

What Is a Cataract and Why It Matters 

A cataract is defined as any opacity of the crystalline lens that disrupts normal light transmission to the retina, leading to decreased visual function. In dogs, cataracts may arise from hereditary predisposition, metabolic disease such as diabetes mellitus, chronic ocular inflammation, trauma, or age-related degeneration. These lens changes are more than cosmetic; they can lead to secondary complications, including inflammation of intraocular structures and glaucoma, when left untreated¹. 

Vet Pearl: Look Beyond the Lens 

A cataract does not always equate to visual impairment. Early opacities may not interfere with vision, but progressive opacification and associated inflammation or lens instability can significantly compromise visual function. 

Diagnosis: Putting the Evidence into Practice 

Accurate diagnosis begins with a complete ophthalmic examination using slit-lamp biomicroscopy to evaluate the lens structure and degree of opacity. Assessment of the fundus through indirect ophthalmoscopy, when feasible, helps determine retinal integrity and rule out comorbid conditions. When the cataract precludes a direct view of the posterior segment, B-mode ultrasonography becomes invaluable. This imaging technique not only confirms the presence of cataract but also assesses the retina, vitreous, and other posterior structures. 

Emerging research indicates that deep learning and artificial intelligence may soon enhance cataract classification using imaging data, improving consistency and diagnostic confidence across practitioners². These technological advances may streamline decision-making and staging in the near future. 

Vet Pearl: Assess the Posterior Segment 

Before recommending surgery, confirm that the retina and optic nerve are functional. A cataractous lens can block visualization and delay recognition of retinal detachment or degeneration unless imaging such as ocular ultrasound is used. 

Surgical Management: Phacoemulsification Still the Gold Standard 

Surgical removal of the cataractous lens remains the only reliable method to restore functional vision in canine patients with visually significant cataracts. Phacoemulsification with intraocular lens (IOL) implantation is the established technique, with a growing body of evidence supporting its efficacy and safety. 

Recent comparative studies demonstrate that both monomanual and bimanual phacoemulsification techniques yield successful outcomes in experienced surgical hands. The choice of technique may depend on surgeon preference, equipment availability, and specific case factors, but both pathways have shown high rates of visual restoration in selected patients³. 

Because canine cataract maturity and concurrent ocular pathology influence prognosis, early surgical referral and intervention, before advanced lens changes or chronic inflammation develop, are associated with better visual outcomes. This evidence underscores the importance of not delaying surgical consideration when appropriate. 

Vet Pearl: Early Referral Improves Outcomes 

Dogs with immature or early mature cataracts tend to have fewer postoperative complications and better long-term visual results than those with long-standing, hypermature cataracts. 

Medical Management: Supportive but Not Curative 

While cataract surgery can restore vision, medical therapy does not reverse lens opacity. At this time, no pharmacologic agent has been validated to cure or reliably slow progression of canine cataracts. Medical management focuses instead on controlling secondary inflammation and maintaining comfort, particularly in patients awaiting surgery or when surgery is contraindicated. This distinction helps clinicians counsel owners realistically, avoiding false promises about nonsurgical “cure” treatments¹. 

Postoperative Ocular Hypertension: What the Evidence Shows 

One important postoperative consideration is ocular hypertension, a condition in which intraocular pressure rises after cataract surgery. A 2025 study found that postoperative ocular hypertension frequently develops in the early postoperative period and, if not promptly managed, increases the risk of secondary glaucoma and vision loss⁴. Vigilant monitoring within the first 24 to 48 hours after phacoemulsification is critical, with early intervention helping to preserve long-term visual outcomes. 

Vet Pearl: Monitor IOP Post-Op 

Persistent elevation in intraocular pressure soon after surgery is not uncommon and requires prompt medical control. Early postoperative pressure checks can make the difference between a successful outcome and long-term glaucomatous damage. 

Comparing Surgical and Non-Surgical Outcomes 

A widely referenced clinical study comparing dogs that underwent phacoemulsification with those that did not found that eyes suitable for surgical intervention yet managed nonsurgically developed more chronic complications over time, including persistent uveitis and glaucomatous changes⁵. Conversely, eyes deemed poor surgical candidates experienced similar outcomes regardless of whether surgery was attempted. These findings reinforce the value of early surgical evaluation and case selection based on comprehensive ophthalmic assessment. 

Practical Clinical Integration 

Integrating current evidence into practice involves several steps. First, ensure comprehensive diagnostic evaluation, including ocular ultrasonography when indicated. Second, communicate candidly with owners about the goals of surgery, associated costs, and postoperative care responsibilities. Third, anticipate and monitor complications such as postoperative ocular hypertension and persistent inflammation. Finally, use emerging diagnostic tools, including AI-assisted imaging classification when available, to enhance accuracy and consistency in cataract staging and treatment planning. 

 References 

1. Rani M, Singh K, Choudhary OP. Cataract in dogs: A comprehensive review. Int J Adv Biochem Res. 2024;8(7):966–970. 

2. Park S, Go S, Kim S, Shim J. Deep Learning-Based Classification of Canine Cataracts from Ocular B-Mode Ultrasound Images. Animals. 2025 May 4;15(9):1327. 

3. Bonea E, Roman M, Puiu I, et al. Comparative study on phacoemulsification techniques and intraocular lens implantation in dogs. Appl Sci. 2025;15(22):12250. 

4. Kang MG, Yi NY, Kim S. Development of postoperative ocular hypertension after phacoemulsification in dogs. Animals. 2025;15(3):301. 

5. Krishnan S, Hollingsworth SR, Smith PJ, et al. Comparison of outcomes in cataractous eyes of dogs undergoing phacoemulsification versus eyes not undergoing surgery. Vet Ophthalmol. 2019;23(2):286–291.