What is the meaning of Plus and Minus in optometry?

Your eyes are the natural camera. Inventors designed the cameras we carry around, following the design of the eyes. An important part of cameras is the lens. This lens was developed to mimic the behaviour of the lens in our human eyes. The case is the same for eyeglasses and contact lenses.

A lens is a piece of transparent material that is used to form an image of an object by focusing or dispersing rays of light from the object. Lenses are essential components of optical instruments, such as cameras, microscopes, telescopes, and eyeglasses.

The power of the lens

In optometry, plus and minus are terms used to describe the power of a lens. A plus lens is a convex lens that converges light rays and makes objects appear larger but pushes it farther away. A minus lens is a concave lens that diverges light rays and makes objects appear smaller but brings it closer. Plus and minus lenses are used to correct refractive errors in the eye, such as myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia.

How to measure the power

We measure the power of a lens in diopters. A plus lens has a positive (+) diopter value, while a minus lens has a negative (-) diopter value.

The + or – lens

The sign of the lens power shows whether the lens is converging or diverging, while the magnitude of the lens power shows how strong the lens is. A higher diopter value means a stronger lens that bends light more.

Are you a plus or minus user?

Here’s how to know what type of lens you are using.

A person who needs a plus lens to correct their vision has hyperopia or presbyopia, which means they have difficulty seeing near objects clearly.

A person who needs a minus lens to correct their vision has myopia which means they have difficulty seeing far objects clearly.

Whatever your lens challenge is, there is a lens for you. Your optometrist will need to conduct a series of tests to tell you the lens power you need and can get you fitted for eyeglasses or contacts that will help you see much better. Contact us today for more information on your lens requirements.