Multifocal Lens Centration and Its Effect on Visual Performance in a Presbyopic Population

The purpose of this study is to use a corneal topographer, a device that is readily available in most optometric practices, in order to determine the position of the multifocal (MF) contact lens (CL) optics in relation to the optics of the eye. The specific purpose of this study is to evaluate if there is a relationship between the positioning of the optics of the study lenses and the objective and subjective visual performance as well as participant satisfaction. The MF CL lenses will be fitted to two groups of participants (previously unsuccessful vs. currently successful MF CL wearers).

HYPOTHESES

• The measurement of the power distribution acquired from the Medmont E300 corneal topographer is effective in determining MF CL lens centration and is a predictor of MF CL success.
• There is a difference in MF CL centration, determined by corneal topography, between successful and unsuccessful MF CL wearers.
• MF CL centration, determined by corneal topography, is correlated with visual performance, determined by ocular aberrometry, measures of visual acuity and subjective satisfaction.

Inclusion Criteria:

A person is eligible for inclusion in the study if he/she:

1. Is at least 42 years of age and has full legal capacity to volunteer;
2. Has read and signed an information consent letter;
3. Is willing and able to follow instructions and maintain the appointment schedule;
4. Has previous experience with wearing MF CLs;
5. Is able to be successfully fitted with all study lenses;
6. Has a vertex-corrected spherical distance prescription of +6.00 to 8.00D (inclusive) in both eyes;
7. Has a spectacle cylinder ≤0.75D in both eyes;
8. Requires a reading addition of ≥+1.00D;

Exclusion Criteria:

A person will be excluded from the study if he/she:

1. Is participating in any concurrent clinical or research study;

2. Has any known active* ocular disease and/or infection;

3. Has a systemic condition that in the opinion of the investigator may affect a study outcome variable;

4. Is using any systemic or topical medications that in the opinion of the investigator may affect a study outcome variable;

5. Has a known sensitivity to the diagnostic pharmaceuticals to be used in the study;

6. Is pregnant, lactating or planning a pregnancy at the time of enrolment;

7. Is aphakic;

8. Has undergone refractive error surgery;

9. Has monocular best-corrected VA of worse than 20/30 in each eye;

10. Has amblyopia or strabismus;

11. Has anisometropia >2D between both eyes

    • For the purposes of this study, active ocular disease is defined as infection or inflammation which requires therapeutic treatment. Mild (i.e. not considered clinically relevant) lid abnormalities (blepharitis, meibomian gland dysfunction, papillae), corneal and conjunctival staining and dry eye are not considered active ocular disease. Neovascularization and corneal scars are the result of previous hypoxia, infection or inflammation and are therefore not active.