None listed
Conditions
Brief summary
Conventional orthokeratology (OK) lenses are specialised rigid contact lenses that are worn overnight during sleep in order to reshape the front surface of the eye (the cornea) to temporarily correct mild to moderate degrees of refractive error, most commonly short-sightedness or myopia. OK lenses produce subtle changes in the curvature and power of the cornea, in the order of microns of change, when worn overnight. When the lens is removed on awakening, the reshaped cornea is now able to correct the vision of the patient during the day. The reshaping effect is temporary, and the cornea returns to its original shape and power if overnight lens wear is discontinued. Conventional OK lenses produce a single central zone of altered corneal power, and are usually used for refractive correction of simple myopia. Multifocal OK (MFOK) lenses differ from conventional OK lens designs in that the back surface design of the lens is modulated to produce a multifocal effect on corneal shape. In other words, the lens is designed to induce annular regions of alternating corneal flattening and steepening which result in concentric rings of varying corneal surface power. Contact lens designers claim that this produces a multifocal defocus effect on the neural layer of the back of the eye, or the retina, which is potentially useful for correcting presbyopia (poor reading vision), and for reducing myopic progression in children. There are no published data on the fitting performance of MFOK lenses of differing designs. For a MFOK lens to be effective for its optical purpose, in correcting or controlling refractive errors, the corneal reshaping effect must be centred over the pupil, and the corneal reshaping induced by overnight lens wear must produce the desired changes in corneal power. The research proposed here will investigate these aspects of MFOK lens performance, to determine the potential for various designs of MFOK lens to be useful for their refractive purpose in long term use.
Interventions
This study will investigate the short-term fitting performance and corneal reshaping efficacy of multifocal orthokeratology (MFOK) contact lenses. Participants who meet eligibility requirements will take part in one, two or all three parts of the study, which will be conducted by a research team of qualified optometrists. In Part 1 the static and dynamic fitting characteristics of MFOK contact lenses with different parameters will be evaluated in a series of 15-minute lens wearing trials, over a
This study will investigate the short-term fitting performance and corneal reshaping efficacy of multifocal orthokeratology (MFOK) contact lenses. Participants who meet eligibility requirements will take part in one, two or all three parts of the study, which will be conducted by a research team of qualified optometrists. In Part 1 the static and dynamic fitting characteristics of MFOK contact lenses with different parameters will be evaluated in a series of 15-minute lens wearing trials, over a maximum 1 hour period. Topical anaesthetic drops (0.4% oxybuprocaine) may be used to minimise discomfort after insertion and during fitting assessment of trial contact lenses. In Part 2, subjects will wear MFOK lenses in both eyes overnight only (7-8 hours per night) for up to 4 nights to evaluate lens fit in the closed eye. In Part 3, participants will wear MFOK lenses designed to correct their myopia, overnight only (7-8 hours per night) for up to 28 days, to evaluate lens fit and corneal reshaping efficacy. All contact lenses will be made of Boston XO material (Dk 100 ISO/Fatt units). The research team will initially insert lenses into the subjects' eyes at the School of Optometry and Vision Science at the University of New South Wales. For parts 2 and 3, subjects will receive face-to-face instructions on how to insert, remove, clean and maintain the MFOK lenses so that they can safely wear the study lenses during the required wearing period. Participant compliance with the study protocol in parts 2 and 3 will be monitored by text messages from the research team every second day during the lens wearing period.
Sponsors
CooperVision Inc
Study design
Allocation
Non-randomised trial
Intervention model
Single group
Primary purpose
Treatment
Masking
Open (masking not used)
Eligibility
Sex/Gender
All
Age
18 Years to 40 Years
Healthy volunteers
Yes
Inclusion criteria
Eligibility criteria include: - Aged 18 to 40 years - Refractive error between +2.50 and -6.00D (parts 1 and 2); between -2.00 and -5.00D (part 3); corneal toricity <1.50D (all parts) - No history of rigid contact lens wear - Soft contact lens wearers willing to discontinue lens wear for at least 24 hours before participation - Good ocular health with no history of ocular trauma or surgery - Good general health and no medications which may influence ocular health
Exclusion criteria
Potential participants will not be enrolled if they show: - Any contraindications for rigid contact lens wear - Anisometropia >0.75D - Ocular pathology or active ocular surface disease - Strabismus or amblyopia - History of adverse reactions to eye drops or topical anaesthetics - Not willing or able to comply with the treatment and followup schedule
Outcome results
None listed