How Corneal Shape Affects Soft Toric Contact Lenses More Than Their Design
Authors: Doll, T., Moore, J., Shihab, A.H., Lopes, B.T., Eliasy, A., Maklad, O., Wu, R., White, L., Jones, S., Elsheikh, A. and Abass, A.
Journal: PloS one
Publication Date: Nov 2020
Contact lens finite element model for a G1P lens design fitted to an average eye (IOP = 15 mmHg) on the ABAQUS finite element software: (a) before fitting, (b) after fitting. Colour scale is representing the magnitude of the displacement (U) in mm. Eye’s equatorial nodes were constrained in axial directions.
Summary:
If you wear contact lenses, you know the importance of a comfortable and effective fit. Our research focused on understanding how corneal shape and the design of soft toric contact lenses affect their performance on the eye. To do this, we generated computer models of different contact lens designs and simulated their behaviour on three different types of corneas: flat, average, and steep.
Our findings show that the shape of the cornea has a more dominant effect on the effective power change (EPC) - a measure of how the lens power changes when it's on the eye - compared to the lens design. In other words, the corneal shape influences the soft toric contact lens's on-eye power change more than the lens design.
We also found that the volume of the lens's peripheral zone, which is part of the lens connecting the optic zone to the edge profile, had a weak correlation with EPC when fitted to the flat eye, moderate correlation with the average eye, and strong correlation with the steep eye. This indicates that the relationship between the peripheral zone volume and EPC depends on the eye shape.
In conclusion, our research demonstrates that corneal shape has a more significant impact on soft toric contact lens performance than the lens design. This knowledge can help inform future contact lens design and fitting practices to ensure a better experience for wearers.