Cataracts is generally inherited and is described as cloudiness of the crystalline lens of the eye, which varies from partial to complete opacity.
Cloudiness of the crystalline lens prevents light from passing through the retina, which will often cause some loss of vision.
Symptoms generally relate to the degree of vision impairment. For example, those with only a small level of cloudiness may not show any symptoms, however those with high opacity will suffer from loss of vision.
Cataracts is a progressive disorder that may lead to your dog becoming completely blind if not treated quickly. One method of treatment is surgery, but that is only usually recommended for hereditary forms.
Other forms of treatment are phacoemulsification which involves emulsification of the eye's lens with an ultrasonic handpiece. Once the lens is emulsified and aspirated, aspired fluids are replaced with a balanced salt solution.
Most cases are inherited, however it can be caused by a few other things including electric shock, diabetes mellitus, old age, inflammation of the eye or abnormal levels of calcium in the blood.