When discussing contact lenses, the term “Plano” refers to a lens that carries no vision-correcting power. It is a specific designation used on a prescription to indicate zero refractive strength. For a person with perfect or near-perfect vision, a Plano lens allows them to wear a contact lens without altering their natural sight.
Defining Plano in Contact Lens Power
Plano is a term derived from the Latin word meaning “flat,” referring to a lens with a neutral power curve. This zero-power designation is formally represented as 0.00 diopters (D) on a prescription, sometimes abbreviated as “PL.” A diopter is the unit of measurement for the optical power of a lens, and positive or negative values indicate the degree of correction needed. A Plano lens is designed to rest on the cornea without converging or diverging light, meaning it will not correct refractive errors like myopia (nearsightedness) or hyperopia (farsightedness).
The purpose of a Plano lens is to maintain the wearer’s existing visual acuity, which is often 20/20, while benefiting from the physical presence of the lens. Unlike a corrective lens, which is shaped to bend light precisely onto the retina to improve focus, a Plano lens is uniformly shaped for comfort and fit alone. This design is for individuals who do not need vision correction but still want to wear contact lenses for other reasons. If only one eye requires no correction, that specific eye would be prescribed a Plano lens.
Common Uses for Plano Lenses
The most common application for Plano contact lenses is for cosmetic purposes, such as altering the eye’s natural color. These lenses, often called colored or costume contacts, change the appearance of the iris without affecting vision. Costume lenses are frequently used for holidays or theatrical events. The material and shape of the lens are the same as a traditional soft contact lens, but the surrounding area contains the desired color or pattern.
Even though they do not correct vision, Plano contact lenses are legally classified as medical devices by the Food and Drug Administration (FDA). This means a valid prescription from an eye care professional is required to purchase them, regardless of the absence of power. This requirement ensures the lens is properly fitted to the wearer’s eye curvature and diameter, which prevents discomfort, eye damage, and potential infections.
How Plano Fits Into a Full Prescription
On a contact lens prescription form, the term Plano is specifically assigned to the Sphere (SPH) field, which is the primary measure of lens power for correcting nearsightedness or farsightedness. Seeing “PL” or “0.00” in this box confirms that no spherical correction is needed. A prescription also contains other parameters, such as the Base Curve (BC) and Diameter (DIA), which define the physical fit of the lens on the eye. The Base Curve measures the curvature of the back surface of the lens to match the cornea, and the Diameter indicates the width of the lens. Even for a zero-power Plano lens, these measurements are mandatory to ensure the lens rests comfortably and allows sufficient oxygen flow to the eye.