“Eye power” is a casual term for your corrective lens prescription, which measures the exact amount of optical power needed to resolve a refractive error and focus light perfectly onto your retina. Measured in a unit called dioptres (D), the “perfect” or normal eye power is 0.00 D, meaning no external correction is needed to see clearly. When your eyeball, cornea, or lens has an irregular shape, light misaligns, requiring a customized plus, minus, or cylindrical lens to correct your vision. The Core Types of Eye Power
Refractive errors change how light behaves when entering your eye, requiring different lens shapes to fix.
Minus Power (Myopia / Nearsightedness): Light rays focus in front of the retina instead of on it. A minus sign (e.g., -2.50 D) means you see close objects clearly, but distant objects appear blurry.
Plus Power (Hyperopia / Farsightedness): Light rays focus behind the retina. A plus sign (e.g., +1.50 D) means your eyes must strain to focus on objects up close, while distance vision is generally clearer.
Cylindrical Power (Astigmatism): This occurs when your cornea is shaped more like a football than a basketball. It causes blurred or distorted vision at all distances and requires an added “Axis” degree number on your prescription to align the correction properly.
Add Power (Presbyopia): An additional plus power used for reading or close-up work. It typically affects individuals over the age of 40 due to the natural aging and hardening of the eye’s lens. How to Read Your Prescription
When you receive a prescription from an optometrist or ophthalmologist, it is broken down into specific categories using shorthand or Latin abbreviations: All Eye Powers Explained ( Cylinder , Spherical and more )
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