November 2021

In this VETgirl online veterinary continuing education blog, Dr. Shelby Reinstein, DVM, DACVO reviews what you need to know about diabetic cataract in your canine veterinary patients.

Sugar Rush! Diabetic Cataract Formation Pearls

Dr. Shelby Reinstein, DACVO

Diabetic cataract formation is very common and often develops quickly after diagnosis:

  • 50% of dogs develops cataracts within 5 months of diagnosis
  • 75% within 1 year
  • 80% within 16 months.
GSD dog cataract Shelby Reinstein VETgirl

Photo courtesy and copyright of Dr. Shelby Reinstein, DACVO

Rapidly forming cataracts are associated with significant lens-induced uveitis

  • The lens physically swells as it imbibes fluid, referred to as an “intumescent” cataract. The Y-sutures often spread apart due to large clefts of fluid.
  • Lens proteins leak out of the capsule, or the lens capsule may even rupture open due to rapid lens swelling
  • Diabetic lens-induced uveitis must be treated with aggressive medications and early referral for surgery will reduce the risk of complications.
  • Diabetic dogs have an increased risk of lens luxation, secondary glaucoma, retinal detachment, and blindness.

Clinical Signs of Lens-Induced Uveitis

  • Pain (squinting, tearing, rubbing)
  • Conjunctival hyperemia & episcleral injection
  • Diffuse corneal edema
  • Low intraocular pressure (IOP)
  • Aqueous flare
  • Anterior chamber may appear shallow / iris shifted forward
  • Miosis
  • Cataract

Diabetic cataracts begin at the far periphery of the lens equator with large fluid vacuoles, but tend to progress to maturity quickly:

  • A miotic pupil may preclude good evaluation of the lens, however any diabetic dog with uveitis should be considered to have significant cataract until proven otherwise.
  • Pupil dilation should be attempted with 1% tropicamide drops for lens examination
  • Lens capsule rupture
  • Appears as an opaque, irregular region of cataract, often associated with posterior synechia / iris adhesions. Usually located at the lens equator.
  • Lens capsule rupture causes intense uveitis with severe corneal edema, keratic precipitates, rapid secondary glaucoma, and often progressing to retinal detachment.
  • While some lens capsule ruptures can be managed surgically, this must be accomplished quickly, and post-operative complication rates are higher.

Diagnostic Testing

  • Menace response
  • Dazzle reflex
  • Pupillary light reflex
  • Schirmer tear test
  • Fluorescein stain
  • Tonometry

You can also read more about some of these essential eye examination tips HERE.

Medical Management of Diabetic Cataracts

Topical NSAID therapy should be initiated as soon as cataract formation is noted and given long term to prevent lens-induced uveitis.

  • Diclofenac 0.1% or Ketorolac 0.5% q12-24
  • Topical steroids should be avoided as maintenance therapy as they can be systemically absorbed and dysregulate the diabetes in some patients.
  • Active lens-induced uveitis should be treated aggressively:
  • Topical NSAIDs are used 2 to 4 times daily depending on severity
  • Topical steroids (prednisolone acetate 1%, dexamethasone 0.1%, NPDex) should be used q4-12, depending on the severity.
  • A fluorescein stain should be negative before administration of topical steroids:
  • Topical steroids can be used in conjunction with topical NSAIDS for the treatment of uveitis – this often allows lower frequencies of each medication. The client should be aware that frequent topical steroid administration may dysregulate their pet’s diabetes.
  • Topical atropine 1% solution or ointment q12-24 is necessary to maintain pupillary dilation – this reduces the risk of synechia and pain from ciliary muscle spasm.
  • Atropine should not be used in dogs with IOP over 25mmHg.
  • Oral NSAIDs are extremely helpful in treating diabetic lens-induced uveitis
  • Oral NSAIDs can be in conjunction with topical anti-inflammatories (steroids or NSAIDs).
  • Topical anti-glaucoma medications should be considered in dogs with IOP over 20 mmHg in the face of severe uveitis.
  • IOP will increase with treatment of the uveitis and may manifest into true glaucoma.
  • Dorzolamide 2% or Timolol 0.5%/Dorzolamide 2% q8-12 are appropriate first-line choices for most diabetic dogs.


  • Dogs with cataracts but no uveitis are rechecked every 3-4 months to assess for uveitis or glaucoma. These patients should be maintained on topical NSAIDs.
  • Dogs with active lens-induced uveitis should be rechecked within 3-5 days to ensure they are responding to medications and the IOP remains below 25 mmHg.
  • Medications are weaned over the course of weeks – months down to a maintenance regimen, ideally with a topical NSAID.
  • Early referral to an ophthalmologist for surgical consultation is paramount.

Surgical Management of Diabetic Cataracts

  • Removal of the lens via cataract surgery is the only way to restore vision and should be considered for most dogs with diabetic cataracts.
  • Cataract surgery has a reported success rate around 90-95% in most dogs.
  • Certain breeds or clinical conditions are associated with lower success rates (i.e. Boston terriers, diabetic Pugs, severe pre-operative uveitis).
  • Phacoemulsification with artificial intraocular lens (IOL) implantation is the surgical standard of care to remove cataracts in dogs. The ACVO YouTube video is helpful for clients considering surgery:
  • Dogs who undergo cataract surgery are monitored long-term and are generally maintained on topical NSAIDs.
Diabetic cataract with water clefting along Y-sutures dog cataract Shelby Reinstein

Photo courtesy and copyright of Dr. Shelby Reinstein, DACVO

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