Assessment of Progressive Lens Designs

Non-invasive double-blind randomised comparative study on presbyopic subjects wearing progressive lenses.

Background and rationale:

Nowadays many different types of progressive addition lenses are available for the correction of presbyopia. Progressive addition lenses provide a more natural correction for presbyopic people due to a gradual and progressive increase of lens power from far area through the intermediate portion to the near area. However, some patients still experience adaptation problems.

The primary purpose of the study is to evaluate the preference, adaptability and visual performance of progressive lens designs (up to three designs).

Study procedures:

Each participant is required to wear all pairs of spectacles one after another, each pair for one week.

Each participant will be required to visit the optometry clinic (at University of Milano Bicocca) three times:

Visit #1: Screening based on inclusion criteria, Informed Consent Form (ICF) form signing, Optometric exam and choice of the frame.

Subjects who will pass the inclusion/exclusion screening will be asked to sign the ICF and enrolled for the optometric exam. Subjects will choose the spectacle frame and all individual fitting parameters will be measured for lens' manufacturing.

Visit #2: Subjects will receive three marked pairs of progressive lenses. The three spectacle frames will be adjusted to fit properly on the subject' face. After 10-15 min of wearing of the first pair of lenses, each subject will be asked to answer to a questionnaire.

Visit #3 (last visit): questionnaires should be returned; the last comparison question will be answered during this visit, and subject will choose the best pair.

At the end of the study each participant will be entitled to get one pair of progressive lenses available in the market.

Subject population:

Presbyopic subjects have been already wearing any progressive additional lens (PAL) designs.

Number of Subjects:

40 +/- 2 subjects, the specified PAL design wearers and 40 +/- 2 the other PAL design wearers to be enrolled and signed the informed consent form.

Each subject will be wearing three different PAL designs. Subjects will be asked to choose one pair of spectacles (design) which they like the most.

Randomisation:

This study adopts a stratified permuted block randomisation to reduce an evaluation bias by the wearing sequence and prescriptions. The mean of both eyes' prescriptions is set as a single stratification factor.

Frames:

Each subject will choose a model of spectacle frame. Three identical frames will be taken for each subject.

Lenses:

1. Lenses will be produced in EU
2. Three different lens designs will be tested in the study.

Eligibility Criteria:
Inclusion Criteria:

1. Subjects should be experienced progressive lens designs wearers who have worn their current prescription for at least the last one month.
2. PAL wearers with 14 mm corridor
3. Age: 45 to 70 years old
4. Best Corrected Monocular visual Acuity (decimal) both at distance and near ≥ 1.0;
5. Normal binocular vision at distance \& near:

   * no strabismus on cover test,
   * no fixation disparity (Mallett aligning prism of less than 2Δ horizontally or vertically) at near
   * stereoacuity of 60" or better at near;
6. New prescription (found at visit #1) is in the range:

   * Spherical power: up to +/-6.00;
   * Cylindrical power: minus cylinder ≤ 2.5D;
   * Addition: 1.50-2.50D;
   * Difference in the power (spherical equivalent) between eyes: up to 2.0D
7. Understanding and speaking Italian or English to be able to answer questionnaires
8. Giving a written consent to participate in the study

Exclusion Criteria:

1. First prescription for progressive lenses.
2. Prescription found during visit#1 varies from current prescription more than 0.50D in any meridian
3. Wearing Single Vision lenses with accommodative support
4. Double vision or prismatic prescription in current glasses;
5. Known ocular disease including strabismus, any pathology, any eye surgeries that may affect visual acuity
6. Use of systemic or ocular medications that are likely to affect vision
7. Balance problem/vertigo problem
8. Concurrent participation in other vision-related research