Accommodation Test (Presbyopia)

What it measures

This check estimates your near point of accommodation — the closest distance at which you can still bring small text into sharp focus — and converts it into an amplitude of accommodation in dioptres. It then compares that amplitude with the range expected for your age, which helps screen for presbyopia, the normal age-related loss of near focus.

How it works

After sizing a bank card to your screen and entering your age, you read a short, high-contrast line of text. Holding the screen at arm's length where the text is sharp, you slowly bring it toward one eye until the text first blurs and won't clear again, then record that distance. The near point in centimetres is converted to amplitude using D = 100 / distance (in cm), and that amplitude is checked against Hofstetter's age-expected minimum (15 − 0.25 × age). A reduced amplitude for your age is the hallmark of presbyopia.

Tips for an accurate result

• 1Move the screen in slowly — Bring the text toward your eye gradually. Moving too fast makes it hard to catch the exact distance where focus is first lost.
• 2Stop at the first sustained blur — The near point is where the text blurs and stays blurred — not where you can briefly force it clear with effort. Record that first point of lasting blur.
• 3Repeat and average — Take the measurement two or three times per eye and use a typical value. Accommodation fluctuates with fatigue, so a single reading can be off.