Addition lenses are often used to treat a range of eye conditions. Addition lenses are specifically used to help patients who do not have the ability to focus their eyes to see clearly up close. Eye focusing is called accommodation. Addition lenses are easy to prescribe in a pair of glasses and are often called the bifocal portion of the glasses. Addition lenses can be used for adults who have presbyopia (they cannot read up close without the aide of a bifocal) and for patients of all ages who have eye focusing problems (e.g. accommodative insufficiency, accommodative infacility, accommodative dysfunction).

Addition powers can also be put into contact lenses. Contact lenses that have addition powers in them are called multifocal contact lenses. These are often marketed for patients that are 40 and over who have presbyopia, and are prescribed to help patients see up close as well as far away in their contact lenses. Multifocal contact lenses are also used in children with nearsightedness because studies have shown that some multifocal designs can slow down the progression of nearsightedness. As stated before, addition lenses can be used to treat eye focusing problems in patients of all ages, before presbyopia. What is unclear is whether the addition power in contact lenses has the same treatment effect as an addition power in a pair of glasses when they are being used to treat eye focusing problems. This study will assess how different kinds of multifocal contact lenses (center distance or center near) will change eye focusing and eye teaming in young adult patients.

Soft multifocal contact lenses are used for a variety of reasons in patient care. In fact, studies have shown that soft multifocal contact lenses alter accommodation. While most often used to correct presbyopic vision, these lenses are also used in the management of accommodative and binocular vision disorders along with myopia management. Multifocal contact lenses correct vision at different distances by introducing a power gradient over the eye thus providing a range of clear vision at both distance and near.

For center near designs, the near addition is placed in the center of the lens, and the power becomes more negative in the periphery. Generally, it is thought that center near designs provide the most accommodative relief and superior near vision because the near addition is centered in the pupil. These lenses allow maximum near correction, even with miotic pupil size changes associated with accommodation. Conversely, for center distance designs, the distance prescription is placed in the center, and the power of the lens becomes more positive in the periphery to provide the near addition. To date, most studies have used center-distance lens designs to evaluate accommodative ability and function. Accommodative function while wearing center near lenses has likely not been studied often because these lens designs are used most in populations with no or waning accommodative ability (i.e. presbyopic patients). In this population lenses are used, specifically, to account for that accommodative inability.

Center near and distance designs have varying advantages and disadvantages for presbyopic vision correction. Selection of lens design can be based on a patient's individual visual needs. There is conflicting evidence on whether the add power in soft multifocal contact lenses can be used to manage accommodative and binocular vision disorders. These lenses do offer relief of accommodative demand associated with both accommodative and binocular vision disorders. It has been hypothesized that center near multifocal contact lenses provide a greater therapeutic effect as the central portion of the lens is the addition power. There have been case reports demonstrating benefits of multifocal contact lenses in accommodative insufficiency and convergence excess. Center distance lenses are used most often for myopia management. In these situations, the interest has been to determine if the child can maintain normal accommodative function while wearing the lenses. This study will aim to determine how accommodative function varies with center distance and center near multifocal contact lenses.

Inclusion Criteria:

• Ages 18 to ≤ 30 years old
• Acuity of 20/25 or better in both eyes with habitual contact lens prescription
• No history of ocular disease or active ocular inflammation
• No history of ocular or refractive surgery
• No current history of rigid contact lens wear
• Astigmatism ≤1.00 D
• Free of binocular vision disorder (strabismus, amblyopia, vergence dysfunction, accommodative dysfunction)

Exclusion Criteria:

• No prior or concurrent participation in myopia control or use of low dose atropine, multifocal contact lenses
• No use of any medications suspected to affect accommodation

If there is a benefit to sharing data, then data can be shared after publication of the primary outcome paper.

20 Participants were measured in all three treatments (single vision, center-distance, and center-near)

Enrollment to end of follow up. Each participant was seen for 2 visits, on two separate days. Each visit was no longer than 2 hours or 120 minutes each, so participants were seen for no more than 4 hours for the entire study. No participants' visits were separated by more than 2 weeks.

Adverse Events were described the same as Clinical Trials.gov has listed.

Adverse Events are typically reported "per intervention" but in order to ensure that there was no double counting of participants, the arms were listed (as advised by clinicaltrials.gov) to show the order of which treatment was received (because ALL participants received all the treatments and order was randomized). But all participants are accounted for in the reporting, as well as adverse events.

The participants were not allowed to adapt to the contact lenses outside of the office - all testing was done in office and participants were not allowed to take the contact lenses out of the office.

Participants will not know what lens they are in