Here are the lens designs that you will see when working with soft contact lenses. It's important to know the designs are based off of the prescription.
A spherical lens design presents as the same pattern at all meridians of the lens. Any prescriptions over one-and-a-half diopters (of astigmatism) will probably be fitted into a toric lens design, while some patients are able to tolerate a spherical lens with small amounts of astigmatism, masked by some lens materials, a toric lens will be able to better enhance the bottom line of vision.
For the toric lens design and how it compares to the sphere, it has different powers at different meridians. The contact lens itself usually has a weighted system and different thicknesses at variable meridians to prevent shifting of the lenses to maintain clear vision.
Multifocal contact lenses work similar to an ophthalmic progressive lens and the power just as you look through different parts of the lens. Contact lens prescriptions will include an add and indication of the dominant eye.
For monovision lenses, it's important to know this isn't a different lens design, however the lens utilization is a bit different. Typically, this is where the dominant eye is corrected for distance and the non-dominant eye is corrected for near. Each eye is fitted with a sphere and/or toric lens. You may occasionally hear monovision and multifocal patients comment on the adjustment period taking a little bit longer. Keep in mind that the goal is to best correct for how the patient utilizes their vision on a daily basis and this is accomplished through trial-and-error. Both types of these lenses are great options for presbyopic patients that may not always want to rely on their readers. Also important to note, certain occupations may hinder a patient from being a candidate for monovision and/or multifocal lenses.
Let's continue to ask questions on how we can help improve their vision and we can impact their life, especially in areas where they might benefit from optimal vision and freedom from glasses.