Eyesight age
How close you can focus on small text. It shrinks with age until about 60.
How to do it
- Keep glasses or contacts for distance on. Take reading glasses off.
- Hold the phone at arm's length with the small sentence in front of your eyes.
- Bring it slowly toward your face. The moment the words stop looking sharp, tap. Do it three times.
Your result
The small brown dog slept by the warm kitchen fire.
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What the research found
The eye focuses up close by changing the shape of its lens, and the lens stiffens steadily with age. That's why the near point, the closest distance at which small print stays sharp, moves out from about 10 cm in young adults to past arm's length by about 60, and why most people need reading glasses in their 40s. Your near point is read as an age with the standard average for that decline (Hofstetter's formula). In a study of 236 people aged 3 to 64, this way of measuring (moving text closer until it blurs) gave higher readings than lab instruments, so read the age as a rough guide. The camera works out the distance from the size of your iris, which is about 11.7 mm across in nearly all adults.
Studied in: 236 people aged 3 to 64 in Texas, and the standard age formula for focusing.
- Anderson HA, Stuebing KK. Subjective versus objective accommodative amplitude: preschool to presbyopia. Optom Vis Sci. 2014;91(11):1290-301. PubMed
- Rüfer F, Schröder A, Erb C. White-to-white corneal diameter: normal values in healthy humans obtained with the Orbscan II topography system. Cornea. 2005;24(3):259-61. PubMed