Presbyopic patients with varifocal contact lenses

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If you need to read a menu, newspapers from an intentionally further distance, you have probably developed presbyopia. Bifocal contact lenses are one of the possible solutions to this vision problem. Bifocal contact lenses are available in soft and RGPs types, disposable type as well as silicone hydrogel extended type lasting up to 30 days.

Alternating and simultaneous multifocal contact lenses

varifocal contact lensesMultifocal contacts refer to lenses with more than one focal point or power. In this consideration, bifocal contacts are a sub-set of multifocal contacts. According to different lens designs, multifocal contacts are typically grouped into two categories: alternating vision lenses and simultaneous vision lenses. The latter one still has two sub-sets: concentric ring design and aspheric design. In general, alternating multifocal contact lenses are quite similar to bifocal and trifocal eyeglasses. And simultaneous-vision contact lenses function in a similar way to progressive eyeglasses.

How alternating bifocals work

With alternating bifocals or translating bifocals, your pupil looks through either the top section or the bottom section of the lenses with different powers in order to get respectively distance vision or close vision. In other words, these lenses allow your pupil to alternate between two power segments by looking either upward or downward. The switching process requires the movement of your eyes, rather than the automatic adjustment of the lenses. For instance, it is the lower power segment that functions while looking downward to read newspapers. This design is nearly the same as bifocal eyeglasses. Most alternating bifocals are RGPs, and their smaller size performs well during these shifts.

How concentric bifocals work

Concentric ring bifocals have a prescription in the center and one or more power rings around. These multiple rings alternate automatically for distance or close vision. The ring number is decided by your pupil size and light condition. Using two rings are the most common design. Different materials of bifocals bring different ring structures. GP bifocals always feature center-distance while soft bifocals feature center-near. Exceptions of soft bifocals include designs that are center-near on dominant eye but center-distance no non-dominant eye.

Aspheric multifocal contacts are true “progressive”

Aspheric multifocal contacts function similarly with progressive lenses which have multiple powers. They are the most popular multifocal contacts since they are also concentric and can simultaneously adjust to your vision needs at every moment. From another perspective, it is the eyes that gradually adapt to this simultaneous power change. Currently, bifocal contact lenses are available in a couple of types. But nearly all of them have noticeable power division. Only aspheric multifocal contact lenses have blended powers across the lens. Due to this unique design, only these lenses can be called progressive contact lenses.

Special bifocal variations

Thanks to technological advancements in bifocals such as monovision and modified monovision, a large number of bifocal contacts are available for your selection. These technologies have helped bifocal contacts gain much popularity. In detail, monovision allows your two eyes to take a near prescription and distance prescription respectively, both using single lenses. Modified monovision combines single-vision lenses and multifocal lenses on one person.

Take pupil size and near prescription into account

During bifocal contacts trials from your ECP, two elements are decisive: pupil size and near prescription. Bifocal contacts’ fitting is more complex and time-consuming, so you may be charged more. Some codes may be obeyed in choosing a proper type of multifocal contacts: aspheric contacts fit low near prescription but reject large pupils, and alternating contacts suit high near prescription.