Silmiväliä

Silmiväliä is a Finnish term that translates to "interpupillary distance" in English. It refers to the distance between the centers of the pupils of the eyes. This measurement is crucial in optometry and ophthalmology for several reasons.

Accurate silmiväliä measurements are essential for fitting eyeglasses and contact lenses correctly. When lenses are manufactured, their optical centers are aligned with the wearer's pupils. If the silmiväliä is not properly accounted for, the optical centers of the lenses will not be aligned with the eyes, which can lead to visual distortion, eye strain, headaches, and even double vision. This misalignment is known as pupillary distance error or incorrect optical center placement.

The silmiväliä can vary significantly from person to person. Factors such as age, sex, and ethnicity can influence this measurement, although individual variation is the most significant factor. Generally, the average silmiväliä for adults falls between 58 and 68 millimeters, with men tending to have a slightly larger average than women.

Optometrists and opticians use specialized tools like a ruler, a pupillometer, or a phoropter to measure the silmiväliä. This measurement is typically taken while the patient is looking straight ahead. For individuals who wear bifocal or progressive lenses, measuring the silmiväliä accurately is even more critical due to the multiple focal points within the lens. In some cases, especially with online glasses purchases, customers are asked to provide their own silmiväliä measurement.