Validation of topography derived RGP contact lenses in keratoconus
Research type
Research Study
Full title
Validation of Innovative Scheimpflug topography derived RGP contact lens designs In Optometry Network (VISION Initiative)
IRAS ID
299054
Contact name
Daniel P. Ehrlich
Contact email
Sponsor organisation
Moorfields Eye Hospital NHS Foundation Trust
Clinicaltrials.gov Identifier
NCT06312163
Duration of Study in the UK
1 years, 6 months, 0 days
Research summary
Research Summary -
Keratoconus is a eye condition in which the cornea adopts an irregular shape, this can lead to significant reductions in vision and quality-of-life. Rigid gas permeable contact lenses are commonly used to correct for corneal irregularity and improve vision in the disease. The fitting of such lenses is however a very time consuming and difficult process, with lens designs not being optimised for eye-shape measures captured using modern instruments and success being very much dependent upon clinician experience. This project aims to re-invent the fitting of complex contact lenses for keratoconus patients by (i) validating new contact lens designs that have been developed by linking data-rich corneal topography (shape) scans with historical records of what contact lens specifications worked in individual patients, (ii) evaluate the use of a virtual fitting module to allow clinicians to select these lenses based on patient eye shape measures, and (iii) determine if these lenses are more appropriate to use in a clinical setting. The use of a more appropriate lens design that may be selected virtually will reduce the risks of using trial contact lenses, improve the physical fit of lenses, reduce the need for clinical experience to achieve successful contact lens fits, and reduce costs.
Lay Summary of Results -
Background to the research:
• Why did the research need to be done?
Keratoconus (KC) is an eye condition in which the cornea adopts an irregular shape, which can lead to significant reductions in vision and quality-of-life. Rigid gas permeable (RGP) contact lenses are commonly used to correct for corneal irregularity and improve vision in the disease, but currently available lens designs and fitting processes are not optimised for modern clinical practice. For example, the lenses currently used were first introduced in the 1960’s, being adopted for KC management soon after. Despite advances in corneal imaging, the design and the fitting process for RGPs has also remained relatively unchanged, requiring much clinician experience and patient chair-time. On average 3-4 lenses need to be trialled but sometimes it can be many more than this.
• Why was it important to patients, public, services and society?
This project seeked to re-invent the fitting of complex contact lenses for KC patients by (i) validating a new contact lens design that have been developed by linking data-rich corneal topography (shape) scans with historical records of what contact lens specifications worked in individual patients, (ii) evaluating the use of a virtual fitting module on the corneal topography shape scans, to allow clinicians to select these lenses based on patient eye shape measures, and (iii) determine if these lenses are more appropriate to use in a clinical setting.The use of a more appropriate contact lens design that may be selected virtually will reduce the risks associated with using multiple trial contact lenses, improve the physical fit of lenses, reduce the need for clinical experience to achieve successful contact lens fits in complex cases, and reduce costs.
Aim of the research
The main questions the research aimed to answer are:
1. Does a “Scheimpflug” topography derived RGP contact lens design for KC have the equivalent overall contact lens fit as the patients' own lens?
2. Is the number of trial lenses required to fit a patient reduced compared to standard practice?
3. Is the time taken to fit a contact lens reduced compared to standard practice?
4. Is there user acceptance of the new lens?
5. Are the changes to the edge design of the contact lens clinically significant?
• what were your key aims and objectives?
The primary aim of this prospective, single-site, cohort study was to validate rigid gas permeable corneal contact lens (RGP) designs for KC derived from combining the data from corneal topography scans and contact lenses ordered in patients with KC attending a UK tertiary NHS Hospital contact lens clinic.
The secondary aims were to (i) determine if the new cl fitting system improves patient care in CL clinics, (ii) examine the usability of a virtual contact lens selection tool on a corneal topographer, and (iii) investigate the effect of axial edge lift (AEL) changes on virtual lens fit.Research plan
There were 3 work packagesWP1: For each participant data collection took place over two visits.
Visit 1: Pentacam topography scans and optimal 'virtual' lens selection.
Visit 2: Participants were fitted with 4 contact lenses (i) the optimal lens design as specified by the virtual fitting module, (ii) a contact lens with a clinically significant step flatter AEL (iii) a contact lens steeper in axial edge lift (AEL) (iv) the participant's own contact lens.Each CL fit was assessed with (i) slit lamp photography according to the standardised method proposed by Wolffsohn et al. (2013), and (ii) anterior segment OCT (MS39,CSO Hansom Instruments, UK). Best-corrected visual acuity was also measured for each lens design using high-contrast logMAR .
WP2. Participants attended one appointment where a traditional lens fit, and a lens fitted using the topography guided 'virtual' module (with the fitting method selected for each eye randomised). For each fitting method the total fitting time was measured and the total number of trial contact lenses used. Patients were invited to complete a questionnaire that evaluated their satisfaction of this process.
WP3. Clinicians not involved in the study were invited to examine a demonstration version of the virtual fitting module software interface that included anonymised patient data. After a 15-minute period of use they were asked to complete the validated system usability scale tool.
Describe your results, including:
Key Findings: Work Package 1
The Scheimpflug topography derived RGP contact lens design for KC have the equivalent overall contact lens fit as the patients’ own lens (selected using traditional empirical means). The changes to the edge curves of the virtually selected lens were significant and predicatable.Impact of WP1
The evaluated lens design has an equivalent fit to contact lens designs fitted using traditional methods (i.e., without virtual selection/decision support tools). The advantage of the new lens design is that it can be selected virtually thus potentially (i) reducing the risks associated with using multiple trial contact lenses to achieve a satisfactory fit, (ii) reducing chair time needed to fit a contact lens to a keratoconic eye, (iii) improving the physical fit of lenses, (iv) reducing the need for clinical experience to achieve successful contact lens fits in complex cases, and (v) reducing costs. Potential impact (ii) has been evaluated in component work-package two.Key Findings: Work Package 2
CLs fitted using the virtual method required on average fewer lenses and less time to achieve a satisfactory fit, compared to the conventional fitting technique.
The mean number of CLs trialled for each fitting episode was 2.08 (range 1 to 3) for the conventional fitting method and 1.35 (range 1 to 2) for the virtual fitting method. The Pentacam-HR assisted fitting method used on average 0.73 (p < 0.001) fewer CLs to achieve a satisfactory fit. The mean time taken to achieve a satisfactory fit was 11.45 mins (range 6.70 to 17.28 mins) for the conventional fitting method and 7.66 mins (range 3.62 to 15.97 mins) for the virtual fitting method (i.e. a reduction of 35%). The virtual fitting method was completed 3.79 mins faster (p < 0.001) (i.e. 33% faster).
No significant proportional bias was found to indicate any effect of KC severity on the fitting time using the conventional fitting method (r2 = 0.004, p = 0.767) or virtual fitting method (r2 = 0.102, p = 0.113) however, this needs further investigation with a larger cohort.Impact
This more efficient CL fitting technique could reduce chair time for the patient, thus improving their experience and journey time and in turn could allow an increase in clinic capacity.Key findings: Work Package 3
The median age of participants was 28.5 (min 23, max 78). The virtual lens selection software is well accepted by the hospital contact lens clinicians with all scores falling between the ‘good’ and ‘excellent’ range on the Systems Usability Scale. The mean usability score was 85.6, with a minimum of 70.0 and maximum of 90. All contribution scores from individual questions were 3 or above (higher score is more positive, maximum score 4). All participants were able to achieve a satisfactory fit on the virtual platform (using anonymised corneal topography scans with participants with a range of KC severity) within the 15-minute trial period.
Impact of Work package 3: This software is well accepted by this cohort of clinicians and should not pose a barrier to clinical implementation.Next Steps
To complete the regulatory requirements to introduce the lens into clinical practice and to then audit the clinical outcomes.Further work is needed to (i) determine if virtual lens selection provides health economic benefits over traditional lens fitting techniques. (ii) Investigate the software with practitioners with a range of CL fitting experience, a range of severities of KC and also for in other corneal diseases and indications for RGP CL fitting. (iii) Assess clinical of the software and impact to support clinical adoption. (iv) obtain feedback from clinicians who are not experienced in keratoconus CL fitting
REC name
London - Hampstead Research Ethics Committee
REC reference
22/LO/0279
Date of REC Opinion
6 May 2022
REC opinion
Further Information Favourable Opinion