References
Canine cataracts
Abstract
The intraocular lens is uniquely designed to aid focused vision, and diseases of the lens such as cataracts are a common cause of blindness in dogs. The causes of cataracts are discussed including the main aetiologies such as hereditary cataract, senile and diabetic cataracts. The article focuses on dogs, as cataracts are less common in cats, although traumatic cataracts and rarely, inherited, congenital and developmental cataracts do occur in felines. The article discusses ways to examine and classify a cataract; the best way to diagnose an early cataract is examination with a veterinary ophthalmologist. Early detection is important, as it is not advised to breed from dogs affected with hereditary cataracts. Surgical extraction is currently the only method to remove a cataract and restore vision, and the common complications of cataract surgery are also explored.
The ocular lens continues to grow throughout life, with new lens fibres forming around the equator like the rings of a tree (Ofri, 2018). The lens nucleus is at the centre of the lens, surrounded by the cortex and the acellular lens capsule. The new lens fibres (cortical fibres) are laid down on top of older lens fibres, gradually condensing them towards the centre of the lens (Figures 1 and 2). Nuclear sclerosis is a change in the lens consistently found in older dogs (over 7 years old) (Leiva and Pena, 2021), where the centre of the lens becomes compressed and hardened. The owners will sometimes have noticed a cloudy appearance to the lens, but this is not a cataract. In humans, nuclear sclerosis becomes evident in middle age, when suddenly reading glasses are suddenly required to read small print.
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