What question did this study set out to answer?

The aim is to evaluate the performance of different multi-toric lens designs in improving visual quality under low-contrast conditions.

February 28, 2026Open Access

An experimental study on the influence of low-contrast optotypes on the performance of multi-toric lenses for astigmatism compensation

Key Points

The aim is to evaluate the performance of different multi-toric lens designs in improving visual quality under low-contrast conditions.
Created various 3.50 D astigmatic multi-toric lens designs and performed retinal image simulation.
Selected best optical design based on Visual Strehl Ratio performance and simulated image quality.
Conducted a double-blind clinical study using an adaptive optics visual simulator and low-contrast optotypes.
Numerical simulations indicated that multi-toric lens designs have superior rotational error tolerance compared to conventional lenses.
In clinical evaluations, properly aligned conventional lenses outperformed multi-toric designs in low-contrast visual acuity; however, the advantage decreased with rotational error.
At ±7.50° of rotational error, the conventional design experienced a two-line loss in visual acuity compared to one-line loss for the multi-toric design.

Abstract

Abstract 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.

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