Pupillietäisyys

Pupillietäisyys, often abbreviated as PD, refers to the distance between the centers of the pupils of an individual's eyes. This measurement is crucial in optometry and ophthalmology, particularly when fitting eyeglasses and contact lenses. The PD is typically measured in millimeters and can vary significantly between individuals. Factors such as age, ethnicity, and sex can influence the average PD. For instance, children generally have a smaller PD than adults, and certain ethnic groups tend to have different average measurements.

Accurate PD measurement is essential for several reasons. When glasses are made, the optical centers of the lenses must be aligned with the wearer's pupils. If the PD is incorrect, the wearer might experience symptoms like eye strain, headaches, blurred vision, or even double vision. This is because the eyes would be looking through the lenses at an angle, rather than through the precise optical center. Contact lenses also require a correct PD for proper fitting and comfort, although the margin for error is slightly larger compared to eyeglasses.

There are several methods for determining PD. Optometrists and ophthalmologists commonly use a ruler or a specialized device called a pupillometer. The pupillometer is a handheld instrument that uses light or a camera to precisely measure the distance. In some cases, a patient's PD can also be estimated based on facial measurements. While at-home measurement is possible, professional measurement is generally recommended to ensure accuracy, especially for prescription eyewear.