The near point of the eye |
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Text book writers often state that the near point of the eye is at 22 cm. The blurring of the image at shorter distances is implied to be rapid and obvious.  The editor was writing his first text when he was forty five. He decided to check the near point. Surprisingly, the figure, (22 cm), and the description were correct to within ±1 cm. Surprisingly, because he distinctly remembered finding the near point of his eyes to be poorly defined at ~5 cm at fifteen. Young eyes and middle aged eyes are not the same. Texts are written by middle aged persons. |
| As the eye ages the lens becomes less flexible and the near point becomes both better defined and more important. A sixty year old with a near point at 22 cm can read without glasses but requires negative lenses to see clearly at a distance. Graded focus lenses are the normal preferred solution. |