Final answer:
Two common diseases that impair vision in older adults are age-related macular degeneration (AMD), which affects central vision, and presbyopia, which results in difficulties focusing on close objects. Cataracts, caused by a clouding of the lens, are another major contributor to vision impairment and potentially blindness in older adults.
Step-by-step explanation:
There are several conditions that can impair vision as adults age, but two common diseases are age-related macular degeneration (AMD) and presbyopia. AMD is the leading cause of blindness in older adults and occurs with the death of cells in the macula, leading to a loss of central vision. Presbyopia, on the other hand, is an age-related condition where the eye loses the ability to focus on close objects, often noticed by the need for reading glasses as early as the age of 40.
Cataracts are another common issue that cause vision impairment, characterized by a clouding of the eye's lens. This leads to a reduction in the amount of light reaching the retina, which can result in blindness if untreated. Both vitamin A and C have been noted to help protect against cataract formation.