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An experimental study on the influence of low-contrast optotypes on the performance of multi-toric lenses for
Diana Gargallo1, Anabel Martinez-Espert2, Laura Remón3
1Applied Physics, University of Zaragoza, Zaragoza, Spain. dgargallo@unizar.es.
Purpose:
Achieving good visual quality with a conventional spherocylindrical (CSC) lens requires precise alignment with the principal meridians of the astigmatism to be corrected. Despite advancements in stabilisation, current contact lens and intraocular lens designs face limitations on this regard. This study introduces different trizonal multi-toric (TMT) lens designs endowed with three concentric zones to provide 3.50 D of astigmatic correction, with increased tolerance to rotational errors. Experimental results using low-contrast optotypes are also presented for the best purposed design.
Methods:
First, several variants of 3.50 D astigmatic TMT designs were created and evaluated by means of retinal image simulation. The optical TMT design was then selected based on its Visual Strehl Ratio (VSR) performance and simulated image quality. Subsequently, a double-blind clinical study was conducted using an adaptive optics visual simulator and low-contrast optotypes. The study compared the maximum low-contrast visual acuity (LCVA) achieved with the best TMT design to that of a conventional spherocylindrical (CSC) design under varying degrees of rotational error.
Results:
Numerical image simulations confirmed the superior rotational tolerance of the TMT designs, compared with CSC lenses, maintaining acceptable image quality up to ±7.50°, particularly with a 40% central zone. Clinical evaluation showed that the 3.50 D astigmatic CSC design provided better LCVA than the best TMT design when properly aligned; however, this advantage decreased quickly with increasing rotational error. At ±7.50°, the CSC suffered a nearly two-line loss (+0.19 logMAR) compared with a one-line loss (+0.07 logMAR) achieved for the best TMT design tested here.
Conclusions:
Retinal image simulations have shown that TMT designs with a 40% central zone exhibit superior tolerance to rotational errors than CSC lenses. Moreover, the LCVA of the TMT design used in this study remained more stable under rotational errors than that of a CSC lens.
