Trifocals eyeglasses are prescribed to those with advanced presbyopia. It is a condition of visual disability that onsets in some individuals after age 40. Trifocals are suggested to those who need three levels of prescriptions in their eyeglasses. Trifocal lenses have 3 separate regions for vision correction. First is for far sightedness, bottom part is for near sight and the intermediate vision segment in the middle is for arm's length correction that focuses on transitional position which is approximately an arm's length away.
Trifocal lenses are especially useful for those who spend a lot of time using the computer. The lenses are similar to bifocals, except for an addition of an intermediate vision segment just above the reading portion of the lens. Usually a semi circle towarsd the bottom of the lens accomodates both near and intermediate arm's length prescription. The midrange part is useful for activities that are an arm's length away such as reading on the computer.
Comparing Bifocals, Trifocals, and Progressive Lenses
Bifocal lenses serve a dual purpose effectively. However, there are few major disadvantages such as switching between near and far vision can be abrupt and there is no intermediate vision line available.
To a little extent, trifocal lenses help overcome the absence of intermediate region in bifocals. However, they are very difficult to get adjusted to because of the distinct lines that separate multiple levels of vision in each field.
Progressive lenses on the other hand offer superior vision and comfort when compared to bifocals and trifocals as they come closest to imitating natural vision of human eyes. As compared to bifocals and trifocals, progressive lenses offer multi focal vision correction that offer smooth and gradual focus from far to near vision. The biggest advantage of progressive lenses is that they eliminate the struggle of vision adjustment or abrupt jumps in images and offer all three fields of vision without any visible lines.
However, as said earlier, progressive lenses may take a while to get used to. Especially, if you are not used to the gradient lens. Also, typically progressive lenses work best in medium to large frames. If the frame length is smaller, then it may limit the reading portion of the lens.
Bifocal, Trifocal and Progressive lenses all have their own pros and cons. But, the biggest positive is that they provide an effective solution to those with multiple vision disabilities. They are the preffered choicce and have been prescribed worldwide to treat multi vision disorders by thousands of opticians.