In order to see, light rays from the outside world in front of the eyes are focussed on the retinas at the back of the eyes, generating nerve impulses which are transmitted to the brain for higher processing and vision. Anything interfering with the light rays as they pass through the eye will therefore affect the information generated.
The lens lies within the eyeball, between front and back chambers. All light rays have to pass through it in order to reach the retina. It is a collection of fibres contained within an elastic capsule. It is transparent and does not have a blood supply because blood vessels running within it would interfere with the passage of light through it. Instead, it is nourished by the fluids within the eyeball.
New fibres are being formed throughout life. In order for the lens not to grow inordinately and outgrow the eyeball, the old fibres move towards the centre of the lens and are compressed, resulting in an inner dense nucleus. This is called sclerosis and is a natural ageing process - there have as yet been no ways identified, of which I am aware, for preventing or slowing it down.
This feature of lens growth underlies the different approaches to cataracts. In the young dog, the lens can be needled and any lens debris left in the eyeball will be naturally absorbed. The nucleus in an older dog’s lens, however, must be totally removed as it would not be absorbed.
Sometimes, it may be said that sutures can be seen. They are to do with the material holding the lens fibres together and are characteristically seen as an upright ‘Y’ on one side of the lens and an upside-down ‘Y’ on the other side.
If an area of the lens or capsule loses its ability to transmit light and becomes opaque, it is said to be an opacity or cataract. There are essentially two main types of cataract:
1. Developmental – e.g. congenital (born with opacity), juvenile
2. Degenerative, e.g. diabetic, traumatic, secondary to a condition such as progressive retinal atrophy
The Staffie is prone to progressive, early onset juvenile cataract formation, said to start at five to eight months of age but often detected as early as three to four weeks of age. An affected dog will be blind by one to three years old. Hereditary Cataract (HC) is inherited as an autosomal recessive and can be identified with a DNA test.
Your Staffie, however, has been found to have cataracts forming at a much older age, suggesting degenerative cataracts. There may be an underlying problem such as diabetes, or it may simply be the start of old age sclerosis. Your vet will be in a better position to advise you since he can do a full health check, perhaps including blood tests.
I do hope this has helped.
