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Lens power is the focusing strength of an optical lens and is measured in diopters. It describes how much a lens converges or diverges light to help focus images on the retina. In prescriptions, lens power is used to correct nearsightedness, farsightedness, and astigmatism. Power can be measured and verified with instruments such as a lensometer.
read more about lens power ...Diopters describe optical power as the reciprocal of focal length in meters. Prescription lenses may include multiple power components.
Plus power converges light and is commonly used for farsightedness and near adds. Minus power diverges light and is commonly used for nearsightedness. A prescription of -2.00 diopters usually indicates distance correction for myopia, while +2.00 diopters often indicates hyperopia or a reading add depending on context. The sign and number must be interpreted with the full prescription format.
Eyeglass prescriptions list sphere, cylinder, and axis for each eye, and may include an add for near tasks. Contact lens prescriptions also include the brand, base curve, and diameter because fit matters in addition to power. Higher prescriptions may differ between glasses and contacts because contacts sit directly on the cornea and reduce vertex distance effects. Your eye care professional matches power to your visual needs and lens type.
Lens power is commonly checked with lensometry using a lensometer, which measures vertex power and other parameters such as cylinder axis and prism. This verification helps confirm that finished lenses match the intended prescription before dispensing. It is also used to identify an unknown pair of glasses and establish a reference prescription. Accurate measurement supports comfort and clear vision.
-2.00 indicates a minus two diopter spherical power, most commonly used to correct nearsightedness for distance vision. The exact meaning depends on whether it appears under sphere or another field. Your full prescription clarifies whether additional cylinder or add power is present.
No. In higher prescriptions, contact lens power may differ because contacts sit on the eye while glasses sit farther away. This difference is related to vertex distance and how power changes with position. Your eye doctor calculates the appropriate conversion when needed.
Cylinder power is the amount of lens power used to correct astigmatism. It works with an axis value that sets the orientation of the correction. Without the correct axis, vision may be blurred or distorted.
Yes. Refractive error can change with growth, aging, health conditions, and visual demands. Regular eye exams help detect changes so your prescription stays accurate for driving, work, and screen use.
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Refractive Errors. Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/8579-refractive-errors. Date Accessed February 6, 2026.
Refractive Errors. National Eye Institute, National Institutes of Health. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/refractive-errors. Date Accessed February 6, 2026.
Blindness and Visual Impairment (Fact Sheet). World Health Organization. https://www.who.int/news-room/fact-sheets/detail/blindness-and-visual-impairment. Date Accessed February 6, 2026.