Assessment of the Relationship of Soft Contact Lens Fit and Power (Fit & Lens pOwer Soft lenSes)

The purpose of this study is to assess whether changing the optical power (dioptres) of a contact lens has an impact on the vision and fit of the lens. As the modern contact lens users choose daily disposable soft contact lenses for their modality, the trial lenses used (provided by Coopervision) reflect this majority of the market -almost 80% of current UK market. The study will attempt to provide data supporting the use of contact lenses that do not meet a participant's visual needs (± 2.00 dioptres) as a satisfactory alternative when the lens power typically required is not in stock. Currently, there is no existing literature in modern contact lens design that compares the fitting assessment between 'fit-for-purpose' lenses and other lenses within the same design that would not be the final lens choice for the patient in respect to lens power.

This study aims to evaluate the vision and fit of commercially available prescription contact lenses of different strengths to determine if this changes the final lens and, if so, how it changes them. In addition, this study will compare subjective comfort, and key fitting criteria such as centration, movement, tightness, coverage and overall impression.

This data could help practitioners use lenses they already have in stock instead of ordering new ones and having patients return. By understanding if these lenses fit similarly, we can make it more convenient for both patients and eye care providers. Patients can get their lenses faster, and eye care providers can use their current stock effectively.

The two visits to take place at the Aston University Eye Clinic, data collection and assessments will include:

Participant's age, ethnicity, sex, ocular history to determine eligibility \[recorded electronically on a secure computer\]

Standardised OSDI questionnaire (paper copy only; which quantifies dry eye symptoms, severity, and frequency e.g. in the last week how often have your eyes felt gritty, watery, itchy, burning, in the last week how many times have you experienced these) will be administered at the first visit after written consent, will be scanned and upload ed to BOX.

Visit one and two will both include:

Application of contact lenses on participant's eyes. These will be randomised between the visits for each patient.

Comfort scale - a line from most comfortable to least comfortable where participant marks how comfortable they feel the lenses are when worn \[paper record\] as well as a '1-10' how comfortable do the lenses feel \[electronically recorded\].

The participant, after lenses have been applied, will have vision assessed objectively (autorefractor) and subjectively just as they would in normal practice conditions and recorded and then a video recorded ocular assessment of the contact lens fit which includes the horizontal movement of the lens, movement of lens while blinking, lens centration.

On completion of data collection, contact lenses are removed and after removal on visit two, participant is asked which lenses they preferred \[recorded electronically\].

The data collection relates to the structuring of the study by following standardised contact lens assessments within primary and secondary care optometry.

A participant's current eye care practitioner will not be informed regarding study participation and corresponding assessments/data unless findings warranting further management are discovered and participant consents to this information being shared. Participants are informed what lens make \& manufacture are being used so that, should they find these lenses more comfortable than their current contact lenses (if applicable) or considering contact lenses, they may inform their eye care practitioner.

Eligibility Criteria:
Inclusion Criteria:

* Between 18-60 years of age
* Vision correctable to at least 6/12 (20/40) or better in each eye
* with mental capacity to provide written consent in English (as per the Mental Capacity Act, 2005).
* happy to wear investigational contact lenses

Exclusion Criteria:

* Any active infection or inflammation, history of major systemic or ophthalmic conditions
* use of systemic or topical medications known to affect the eye in the previous 3 months
* history of ocular surgery, currently enrolled on another study/clinical trial that may impact outcome
* any other contraindications for typical contact lens wear
* As per the Mental Capacity Act, 2005, participants will be automatically excluded if not deemed to have Capacity for consent or under the age of 18.