Beginning about age 40, when reading at closer distances begins to become a struggle, or having an elderly parent lose vision, people become concerned about eye health. But the truth is that vision and eye health are a lifelong concern. For those lucky enough to have two sighted eyes, the vision in each eye is precious. And many of the common diseases and injuries involving the eye can cause permanent and irreversible vision loss. Those who have only one functioning eye have to be even more cautious.