Inter-relationship of soft contact lens diameter, base curve radius, and fit


PURPOSE: To evaluate the inter-relationship of soft contact lens base curve radius (BC), diameter, and lens fit using a mathematical model. METHODS: A spreadsheet mathematical model was used to evaluate theoretical fitting characteristics for various combinations of soft lens BC and diameter. The designs were evaluated using ocular topography data collected from 163 UK subjects. The model evaluated lens tightness (edge strain) and on-eye diameter (horizontal corneal overlap) and assumed that acceptable values fell within the range 0 to 6% and 0.2 to 1.2 mm, respectively. Analyses were undertaken of various trends relating to soft lens fit, including (1) the effect of BC and diameter on fitting success; (2) the effect of lens asphericity, BC, and sag on lens diameter on the eye; and (3) the effect of lens diameter on lens tightness. RESULTS: The highest overall success rate (90.2%) was achieved with an 8.60/14.2 mm (BC/diameter) design. Using this design on the sample population, the median edge strain value was 3.2% (IQR: 2.1%) whereas median corneal overlap was 0.62 mm (IQR: 0.35). There was a positive correlation (r = 0.37, P < .0001) between edge strain and corneal overlap. Edge strain showed significant correlations with each of the ocular topography variables, most notably corneal asphericity (−0.62, P < .0001). Corneal overlap showed significant correlations with corneal asphericity (r = −0.42, P < .0001) and corneal diameter (r = 0.92, P < .0001). For a 0.4 mm change in BC, it is necessary to change diameter by 0.2 mm to maintain similar on-eye diameter (arclength). When changing lens diameter, a change in BC of 0.2 mm is required to maintain similar tightness of fit. CONCLUSIONS: Mathematical modeling is a useful technique for large-scale evaluation of the interactions of soft contact lens design and fit. The study has given useful insights into the general performance of soft lens designs.

Publication DOI:
Divisions: College of Health & Life Sciences > School of Optometry > Optometry
College of Health & Life Sciences > School of Optometry > Optometry & Vision Science Research Group (OVSRG)
College of Health & Life Sciences
College of Health & Life Sciences > School of Optometry > Vision, Hearing and Language
Additional Information: This is a non-final version of an article published in final form in Young, G., Hall, L., Sulley, A., Osborn-Lorenz, K., & Wolffsohn, J. S. (2017). Inter-relationship of soft contact lens diameter, base curve radius, and fit. Optometry and Vision Science, In press. DOI: 10.1097/OPX.0000000000001048
Uncontrolled Keywords: Ophthalmology,Optometry
Publication ISSN: 1538-9235
Last Modified: 08 Jul 2024 07:29
Date Deposited: 22 Feb 2017 15:30
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Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
PURE Output Type: Article
Published Date: 2017-04-01
Accepted Date: 2016-10-27
Submitted Date: 2015-12-03
Authors: Young, Graeme
Hall, Lee
Sulley, Anna
Osborn-Lorenz, Kathrine
Wolffsohn, James S. (ORCID Profile 0000-0003-4673-8927)



Version: Accepted Version

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