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® EDOF IOL underwent monocular photopic testing (85 cd/m2) at 4 m using Early Treatment Diabetic Retinopathy Study (ETDRS) charts. Defocus curves were acquired from -5.00 D to +2.50 D in 0.50-D steps over best subjective refraction. Regular myopic astigmatism was optically induced with +1.00 D, +2.00 D, and +3.00 D positive cylindrical lenses at canonical axes (0°, 45°, 90°, 135°); analyses focused on WTR (90°) and ATR (0°/180°). Visual acuity (VA) was converted to logMAR. Repeated-measures ANOVA with Tukey post hoc testing assessed effects of cylinder magnitude, axis, and vergence (α=0.05).

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.