Scleral contact lens thickness profiles: The relationship between average and centre lens thickness
File version
Accepted Manuscript (AM)
Author(s)
Vincent, Stephen J
Alonso-Caneiro, David
Kricancic, Henry
Collins, Michael J
Griffith University Author(s)
Year published
2019
Metadata
Show full item recordAbstract
Purpose:
To develop a methodology to reliably determine the thickness profile of scleral contact lenses and examine the relationship between the centre and average lens thickness for a range of lens designs and back vertex powers.
Methods:
High-resolution images of 37 scleral trial lenses (Epicon LC, Rose K2 XL and ICD 16.5) were captured using an optical coherence tomographer, and their thickness profiles were generated after correcting for known measurement artefacts. Centre lens thickness values were compared with manual lens gauge measurements, and repeatability was assessed by comparing average thickness values derived ...
View more >Purpose: To develop a methodology to reliably determine the thickness profile of scleral contact lenses and examine the relationship between the centre and average lens thickness for a range of lens designs and back vertex powers. Methods: High-resolution images of 37 scleral trial lenses (Epicon LC, Rose K2 XL and ICD 16.5) were captured using an optical coherence tomographer, and their thickness profiles were generated after correcting for known measurement artefacts. Centre lens thickness values were compared with manual lens gauge measurements, and repeatability was assessed by comparing average thickness values derived from orthogonal meridians of each lens. Results: The imaging technique displayed a high level of agreement with a manual lens gauge for centre thickness measurements; mean difference 5 ± 9 μm (95% LoA −14 to +23 μm), and a very high level of repeatability; mean difference between orthogonal meridians 1 ± 3 μm (95% LoA −6 to +8 μm). Lens thickness profiles varied between lens designs, with distance from the lens centre, and with back vertex power. Increasing back vertex powers resulted in a significant over or underestimation (up to 33% for high minus powers) of the average lens thickness based on the centre lens thickness. Conclusions: The thickness of scleral contact lenses varies with distance from the lens centre and the back vertex power. The average lens thickness value derived from the entire lens provides a more appropriate representation of the true lens thickness and should be used in the calculation of scleral lens oxygen transmissibility.
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View more >Purpose: To develop a methodology to reliably determine the thickness profile of scleral contact lenses and examine the relationship between the centre and average lens thickness for a range of lens designs and back vertex powers. Methods: High-resolution images of 37 scleral trial lenses (Epicon LC, Rose K2 XL and ICD 16.5) were captured using an optical coherence tomographer, and their thickness profiles were generated after correcting for known measurement artefacts. Centre lens thickness values were compared with manual lens gauge measurements, and repeatability was assessed by comparing average thickness values derived from orthogonal meridians of each lens. Results: The imaging technique displayed a high level of agreement with a manual lens gauge for centre thickness measurements; mean difference 5 ± 9 μm (95% LoA −14 to +23 μm), and a very high level of repeatability; mean difference between orthogonal meridians 1 ± 3 μm (95% LoA −6 to +8 μm). Lens thickness profiles varied between lens designs, with distance from the lens centre, and with back vertex power. Increasing back vertex powers resulted in a significant over or underestimation (up to 33% for high minus powers) of the average lens thickness based on the centre lens thickness. Conclusions: The thickness of scleral contact lenses varies with distance from the lens centre and the back vertex power. The average lens thickness value derived from the entire lens provides a more appropriate representation of the true lens thickness and should be used in the calculation of scleral lens oxygen transmissibility.
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Journal Title
Contact Lens and Anterior Eye
Volume
42
Issue
1
Copyright Statement
© 2019 British Contact Lens Association. Published by Elsevier Ltd. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence (http://creativecommons.org/licenses/by-nc-nd/4.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, providing that the work is properly cited.
Subject
Ophthalmology and optometry