Final answer:
Lined style trifocals are glasses with three focal lengths for different distances, commonly featuring a 7mm segment for distance, a 28mm segment for intermediate vision, and a 7mm segment for reading.
Step-by-step explanation:
Common Numbers Associated with Lined Style Trifocals
Lined style trifocals are a type of corrective eyewear used to correct presbyopia and other focusing problems. These glasses have three different lens segments, each with its own focal length. The common numbers associated with lined style trifocals indicate the refractive power of these lens segments. The top section typically aids in seeing distant objects, the middle section is for intermediate vision, such as computer work, and the bottom section is for reading and other close tasks. The standard bifocal segment heights for these lenses are 7mm for the distance portion, about 28mm for the intermediate area, and the lower reading area usually measures about 7mm. However, these measurements can vary depending on the lens manufacturer, the frame size, and the individual needs of the wearer.
Opticians and eyewear professionals can customize these measurements for a more comfortable and effective visual experience. The process of determining the right trifocal lenses involves a thorough eye examination and consideration of the wearer's daily activities.