What does a "minus" sign in a prescription indicate?

• A. A lens for correcting farsightedness
• B. A lens for correcting nearsightedness
• C. A lens for reducing glare
• D. A lens with a higher refractive index

Answer: (B)

The presence of a "minus" sign in a prescription indicates that the lens is intended to correct nearsightedness, also known as myopia. In myopia, distant objects appear blurry because the light entering the eye is focused in front of the retina rather than on it. A lens with a "minus" power is concave, which means it is thicker at the edges and thinner in the center. This shape helps to diverge light rays before they enter the eye, allowing them to focus further back onto the retina, thereby improving vision for distant objects.

This concept is fundamental in optometry, as it allows eyecare professionals to prescribe the appropriate lenses for patients experiencing difficulty with distance vision. Understanding the meaning behind lens prescriptions is crucial for determining the correct treatment options.