An evaluation of contact lens and phase plate designs incorporating a novel surface shape to allow clear distance and near vision.

This trial will be a masked, randomised testing of up to 15 contact lens and/or phase plate prototypes with phase-step optics and a control lens. “Phase-step optics” is a type of surface shape that can be applied to a contact lens or phase plates to impart both far and near vision. The visual and functional assessment of participants wearing these lenses and phase plates will be compared with conventional control contact lenses. In addition, the study will investigate for associations between various baseline parameters like pupil size, corneal aberrations, ocular aberrations and visual functional performance. Participants will undergo a baseline examination in the initial visit. This visit will comprise auto-refraction, subjective refraction with visual acuity measurement and ocular assessment with a slit-lamp bio-microscope (a specialized microscope for viewing the eye). Contact lenses and/or phase plates will be trialled in each of the following two visits. The contact lenses will either be made of Polymethylmethacrylate (PMMA) or Hydroxyethylmethacrylate (HEMA or conventional hydrogel) material. Both of these materials are standard formulations of well-established contact lens materials. Their composition are defined by their chemical formulation as produced by the manufacturer of the materials. PMMA and hydrogel lenses behave differently on eye. One major difference is the presence of a ‘tear lens’. This is a microscopic volume of the wearer’s tears that resides between the back of a contact lens and the front of the cornea. In a PMMA lens, the tear lens has substantial optical power. In the hydrogel, the tear lens power is negligible. By testing both PMMA and hydrogel, we can determine the impact the tear lens optical power may have on the performance of phase-step contact lenses. The contact lenses and phase plates will have varied optical designs (surface shape). The optical design of the lenses will vary but not be limited to phase-step features such as varied groove numbers, varied spacing between grooves, varied groove heights in order to achieve different optical-visual outcomes. The maximum number of grooves on a lens shall be 24, and the maximum relative sag height (departure from the base surface geometry of the lens) shall be less than 5 microns. The criteria for this will be based on optical performance characteristics such as through-focus point-spread function and extended depth of focus range. Fitting visits will be performed by unmasked investigators and comprise contact lens fitting, assessment of contact lens visual acuity and assessment of contact lenses on eye with a slit-lamp biomicroscope. If the participant is a presbyope requiring reading spectacles of +1.50 dioptres (D) and above, no drops will be used. When this is not the case, to control the accommodation of the participant, the following will be administered: 1 drop benoxinate and 2 drops of 1% tropicamide (each of these drops separated by 5 min). This was the chosen regimen as it gives a good cycloplegic effect while being much shorter acting compared to cyclopentolate. Each of the contact lens visits will take a maximum of 2 hours in duration. All patients will trial all types of lenses in both eyes. The duration of each lens wear will be up to an hour. At the completion of each lens trial, the patient will fill out a subjective ratings of vision questionnaire utilising a 1-10 numeric rating scale. The second visit will occur at least 24 hours after the first visit. All contact lenses will be fitted and all assessments will be carried out by a registered optometrist.