Vision changes are most commonly associated with normal lens thickening/dehydration (lenticular sclerosis), but may involve other lens and retinal changes. Visually challenged animals may not adapt well to change as they have depended on memory and routine to navigate around furniture, in and out of rooms, and up and down stairs. Household changes or rearrangements may be associated with an increase in anxiety, confusion and withdrawal. Visual recognition abilities may be decreased, as well, leading to subtle interaction changes.
Hearing loss is most often due to changes in external hearing mechanisms in geriatric patients. This deficit may lead to a decrease in owner responsiveness and apparent startle at the sudden appearance of visual or tactile stimuli. Owners may complain that their pet no longer greets them at the door – likely because the auditory cues of arrival are not received. Dogs and cats that are startled easily are susceptible to showing fear related aggression, both to human family members and other pets in the household.
The senses of taste and smell may also decline with increasing age. This change might manifest as alterations in appetite and food preferences. Olfactory loss is of special concern with cats as their ability to find and their willingness to consume food is closely associated with an intact sense of smell. Subsequent problems, such as undernourishment and fatty liver may result.