Combining Small Aperture Approach and Toric Correction for Irregular Astigmatism Management

$\textbf{Purpose:}$
Irregular astigmatism poses a challenge in cataract surgery due to its complex geometry and associated higher-order aberrations (HOAs), which limit the efficacy of conventional toric intraocular lenses (IOLs). IOLs featuring a small-aperture have shown promise in managing such cases through the “pinhole effect,” yet they do not correct the underlying astigmatic power. This study investigates the potential of a hybrid IOL design featuring both small-aperture and toric elements to address these limitations.

$\textbf{Setting:}$
David J. Apple Laboratory for Ocular Pathology.

$\textbf{Design:}$
Experimental study.

$\textbf{Methods:}$
A retrospective analysis of 22 eyes with irregular astigmatism was conducted using semi-personalized eye models derived from Pentacam (Oculus) tomography data. Simulations were performed in OpticStudio to evaluate three IOL systems: a toric IOL, a small-aperture, and a combined small-aperture+toric IOL. Image quality was assessed using Strehl Ratio (SR) and RMS error. Landolt C simulations and correlation analyses were also performed.

$\textbf{Results:}$
The hybrid IOL significantly outperformed the toric and small-aperture IOLs alone, achieving mean SR of 0.80±0.17 (vs. ... mehr0.10±0.07 and 0.20±0.19, respectively, p<0.001) and the lowest RMS error (0.07 µm, p<0.001). Simulations demonstrated superior visual quality and less sensitivity to corneal asymmetry. R$^2$ analyses confirmed a strong association between corneal astigmatism and improved optical quality in the combined model.

$\textbf{Conclusions:}$
Integrating a toric correction within a small-aperture optic yields superior optical performance in irregular astigmatism simulations. In clinical practice, combining sulcus-fixated pinhole implants with toric posterior-chamber IOLs or sulcus-fixated toric lenses with a small-aperture posterior-chamber IOL may achieve better outcomes in complex corneal profiles.