This poster demonstrates a software tool based on a Finite Element Model of the human eye, developed over a period of more than 15 years at both Dundee University and Liverpool University, that can demonstrate the fit of a known contact lens design on a particular subject’s eye through computer simulation.
Using this new technique, thickness maps for the tear layer under contact lenses can be created. These maps give important feedback to the contact lens fitting and design process and have the potential to enable the full customisation of contact lenses.
This work made extensive use of the Eye Surface Profiler (Eaglet Eye, Netherlands) in order to gain information on the ocular shape, including the sclera.
Topography maps play an important, increasing role in contact lenses design and fitting, particularly for large diameter lenses. Whenever an eye is measured using a topography machine, the fixation point is required to be in the machine head, around 2 to 10 cm in front of the eye. This practice induces rotation of the eye which can result in tilted maps affecting measurement accuracy. Additionally, it is not a simple matter to compensate for this induced error, as the eye itself has few, if any, identifiable characteristics to facilitate correct orientation.
This poster demonstrates methodologies to level the eye topography data around its geometrical axis, thus providing more accurate information regarding ocular shape
Three case Studies: Two subjects with keratoconus and one with amblyopia all experiencing significant VA improvement with non-orthogonal astigmatic spectacle correction in normal eyes, it is assumed that astigmatism is regular i.e. the power meridians are at a right angles (orthogonal). Cases where the power meridians are at angles less than 90° are termed irregular or non-orthogonal astigmatism.
All ophthalmic equipment, spectacle lenses and contact lenses assume astigmatism has orthogonal axes and this is the main reason complex contact lenses designs are developed to correct irregular corneas and keratoconus, as it cannot be corrected optically.
A means of creating spectacle trial lenses with non – orthogonal power axes has been developed and this poster demonstrates three case studies where subjects experienced significant visual acuity improvement from non-orthogonal astigmatism correction.