Fig 1.
Three designs of a soft contact lens with a base curve 8.2 mm, diameter 14.5 mm, spherical power -2.0 DS, cylindrical power +1.0 DC at axis 90° and central thickness 0.15 mm: (a) Gravity-based single-prisms stabilised lenses (G1P), (b) Blink-based two-prisms stabilised lenses (B2P), (c) Blink-based four-prisms stabilised lenses (B4P).
Fig 2.
Axial and tangential curvature (Ra, Rt) maps of the flat, average, and steep eyes used in the current study.
Fig 3.
Geometry parameters of a blink-based two-prisms stabilised lens (B2P) with base curve 8.2 mm, spherical power -2.0 DS, optical cylindrical power -1.0 DC, axis 90° and central thickness 0.2 mm.
In this figure, fillets radii r1 and r2 were set to 2.5 mm and = 2.0 mm respectively. See Appendix B for more details.
Fig 4.
Normalised eyelid pressure magnitude with time.
This distribution is based on the palpebral aperture measurement as reported in [34].
Fig 5.
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.
Table 1.
Finite element simulation parameters.
Fig 6.
Light raytracing according to Snell’s law in (a) a single meridian, (b) three-dimensional analysis (lens’s thickness has been increased in this figure for displaying purposes).
Fig 7.
Effective power change (EPC) for cylindrical lenses with axis 90° as a function of the peripheral zone volume (Vp) when fitted to the flat eye (1st column), average eye (2nd column), and steep eye (3rd column).
The three investigated designs are plotted in rows.
Fig 8.
Effective power change for lenses with axis 90°, 45°, and 0° as a function of the peripheral zone volume.
Fig 9.
Effective power change for lenses with axis 90°, 45°, and 0° as a function of the lens’s central thickness.
Fig 10.
Determination of corneal surface axial radius of curvature (r) at a certain meridian plane.
In this method, the centre of the curvature (c) is always restricted to the corneal visual axis.
Fig 11.
Determination of corneal surface tangential radius of curvature (r) at a certain meridian plane.
In this method, the centre of the curvature (c) is not restricted to the corneal visual axis.
Table 2.
Lens back-surface shape parameters.
Fig 12.
A typical FE model for the average eye used in this study where different colours represent different material models.
The eye’s equatorial nodes were constrained in axial directions.
Fig 13.
Stress-strain curves for the material models.
Contact lens’s material was modelled as a linear elastic material, however, the eye was modelled as a hyper-elastic material.