Glaucoma and cataracts are the two most significant causes of vision loss in dogs, with glaucoma also causing severe pain that requires emergency treatment to prevent permanent damage.
Glaucoma causes severe pain that is often missed because dogs do not vocalise consistently even in extreme discomfort. Elevated intraocular pressure causes headache-equivalent pain, eye rubbing, reluctance to be touched near the face, and behavioural changes including lethargy and reduced appetite. Dogs with untreated glaucoma suffer continuously. Emergency reduction of intraocular pressure using medications or surgery is required within hours of diagnosis to have any chance of preserving vision. Even with rapid treatment, permanent vision loss often occurs in the affected eye. Cataracts, while not painful, progressively reduce visual acuity, affecting quality of life by limiting activities that depend on vision. Dogs that were previously ball-focused or visually oriented gradually disengage from these activities. Cataract surgery has high success rates and dramatically improves visual quality of life when performed before cataracts become hypermature.