Impact Of Iol Tilt And Decentration On Astigmatism And Higher-Order Aberrations In Scleral-Fixated Intraocular Lenses

Scleral fixation of intraocular lenses (SFIOLs) in eyes without sufficient capsular support has gained increasing clinical relevance. Flanged fixation techniques in particular may be associated with an increased risk of IOL tilt and decentration. Deviations from the ideal optical axis are suspected to induce postoperative refractive changes, including astigmatism and higher-order aberrations (HOAs). This study aimed to evaluate the relationship between IOL tilt and decentration and the resulting optical aberrations.

Single-center prospective randomized comparative study, Medical University of Vienna

Patients lacking capsular support were consecutively enrolled and randomized to either the Yamane group (YG) or the 4-flanged group (4G). Twelve weeks postoperatively, subjective refraction was assessed. Anterior segment OCT (CASIA2, Tomey) was performed to quantify IOL tilt, decentration, and corneal astigmatism. Scheimpflug tomography and wavefront analysis (Sirius and Peramis, CSO) were used to measure internal astigmatism (IA) and internal higher-order aberrations.

Residual ocular astigmatism (ORA) was calculated using vector analysis based on subjective refraction and corneal astigmatism. Multivariable regression analysis was performed to identify independent predictors of ORA.

Fifty-one patients were evaluated (27 YG, 24 4G). Median ORA was 0.58D in the 4G and 0.75D in the YG(p=.41).

Mean IOL tilt and decentration were 5.2±2.5° & 0.48 ± 0.32 mm in the 4G and 7.8±4.7° and 0.57±0.27mm in the YG, respectively.

In multivariable regression analysis, both the magnitude of IOL tilt and its axis orientation were independent predictors of ORA. Each additional degree of tilt was associated with an increase in ORA of approximately 0.05D(p<.05). A physiological tilt axis located in the temporo-inferior quadrant (180–270°) was associated with a reduction in ORA of 0.3D(p < 0.05).

IOL decentration was not a significant predictor of ORA. No significant association was found between tilt or decentration and induced coma aberration.

Conclusions
Both the magnitude and orientation of IOL tilt significantly influence induced astigmatism in scleral-fixated intraocular lenses. In contrast, IOL decentration appears to play a minor role. These findings highlight the importance of precise three-dimensional lens positioning and suggest that not only the extent but also the direction of tilt is clinically relevant for postoperative refractive outcomes.