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As a squadron flight surgeon in the '80s, I remember the day my XO failed his vision test during his annual flight physical. While I was away on leave, he called me in a panic concerned that he was "going blind." He said he'd been referred to the optometry department for evaluation because of his 20/50 near-vision. No one had explained to him about the "birthday diseases," those normal processes everyone experiences if they celebrate enough birthdays.
The eye has a lens that sharply focuses light on the retina in the back of the eye (Figure 1). An elastic, pliable lens is required to change your focus from your wingman to your kneeboard. As we age, the lens of our eye becomes less elastic and less able to focus on items that are closer than arm's length (Figure 2). The ability to focus on near objects is known as accommodation and is greatest in childhood but diminishes as we age.
When the nearest point one can see clearly moves beyond a comfortable reading distance, the condition is termed "presbyopia," literally, "old eye." This process usually begins in a person's early 40s but may occur earlier in those who are farsighted, like many of our aviators. Many aviators aren't aware of this progressive condition until their annual physical, because their gauges and kneeboard are still far enough from their eyes to focus on without difficulty, and the near-vision test...