Index

Introduction
Homeostasis
Life Span
Systems
Regulatory Functions
Nervous System
Eyes
Ears
Nose
Tongue
Brain
Endocrine System
Hypothalmus
Pituitary
Thyroid
Adrenal
Nutritional Functions
Excretary Functions
Urinary System
Kidney
Bladder
Colon
Distributive Functions
Cardiovascular System
Blood
Respiratory System
Protective Functions
Reproductive Functions
Musculo-Skeletal System
Cancer
Arthritis
Obesity
Diabetes
Cushing's Disease
Heart Disease
Teeth
Skin and Coat
Conclusion
References


Systems - Eyes

With aging comes a loss of elasticity in the lens of the eye causing an inability to focus on nearby objects. The pupil is unable to expand and contract to the same degree as in youth, with the result that old dogs do not see as well in the dark and have a similar problem with very bright light. Ultraviolet light is damaging to lenses and, over time, may result in cloudiness. Additionally, chemical/genetic disease may also result in cataracts. Older dogs tend to have "hazy-looking" eyes, a condition known as, lenticular or nuclear sclerosis that does not seem to effect vision.

With age, drainage of the eye's aqueous humor may become reduced resulting in increased internal pressures and eventually glaucoma and blindness. Old age degeneration of the retina may result in Central Progressive Retinal Atrophy if it affects only the central vision. This is the area of the dog's vision that is the sharpest and generally the most important.

If overall degeneration of the retina occurs, it is known as Progressive Retinal Atrophy. Corneal disease may occur with calcium deposits forming in the cornea. This condition often results in extreme photophobia (fear of light), and has been associated with dementia and blindness in the dog.

Next Page - Ears