Clinical Tolerance to Experimentally Induced with-the-Rule and Against-the-Rule Astigmatism After Implantation of an Extended Depth-of-Focus Intraocular Lens: A Defocus-Curve Study.

Purpose: To quantify the clinical tolerance to induced with-the-rule (WTR, 90°) and against-the-rule (ATR, 0°/180°) astigmatism after implantation of an extended depth-of-focus (EDOF) intraocular lens (IOL), and to identify axis-specific trade-offs across the defocus curve. Methods: In this non-randomized, comparative, cross-sectional study, nine pseudophakic patients (nine dominant eyes) implanted with a Tecnis Symfony Results: Distance VA remained functionally preserved with +1.00 D, while +2.00 D produced clinically meaningful deterioration and +3.00 D caused broad loss of acuity across vergences. Axis orientation modulated performance: WTR preserved distance acuity around plano, whereas ATR relatively favored intermediate and very near vergences (approximately -2.00 D to -3.50 D). ANOVA confirmed significant effects of cylinder magnitude and vergence (both p<0.01) and a significant axis-by-vergence interaction near plano and +0.50 D (p<0.05). These findings support a practical tolerance envelope of about +1.00 D for EDOF recipients, beyond which functional penalties become evident. Conclusion: After EDOF implantation, regular astigmatism of ~+1.00 D is generally tolerated, while +2.00 D and +3.00 D compromise function across the defocus curve. Axis matters: WTR preferentially preserves distance VA and ATR relatively supports intermediate/near performance. These data provide actionable thresholds and axis-aware guidance for toric planning, residual-targeting, and patient counseling.