Lens Power in Diopters

P=1fP = \frac{1}{f}

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Opticians work in reciprocal meters because powers of thin lenses in contact simply add: a +2.0 dpt reading lens stacked on a +0.5 dpt correction acts as +2.5 dpt. A prescription of −4.0 dpt for nearsightedness is a diverging lens of focal length −25 cm. The relaxed human eye is a roughly +60 dpt system, most of it contributed by the cornea rather than the adjustable lens.

Lens Power in Diopters
P=1fP = \frac{1}{f}
Where
  • PP= Optical power
  • ff= Focal length
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