Back-toric & bitoric corneal GP
Multiple labs
Manufacturer / labMultiple labs
Product / familyToric / bitoric corneal GP
DesignCorneal GP with a toric back surface (and toric front for bitoric) for high or lenticular astigmatism
Corrects / indicated for≥2.50 D corneal astigmatism where a spherical GP rocks or decentres, against-the-rule and oblique cyl, residual astigmatism management
MaterialBoston XO / Optimum Comfort / Paragon HDS 100
Dk100 ×10⁻¹¹ (material)
Overall diameter9.0-10.4 mm
Optic zone7.5-8.5 mm
Centre thickness~0.15 mm
Power rangesphere + cyl to lab limits
Cylinderback-surface toricity typically 1.5-5.0 D of corneal cyl
Axisaligned to flat K meridian
Wear scheduledaily wear
ReplacementEvery 1-2 years
Fitting approachUse a bitoric diagnostic set or empirical bitoric calculation (Mandell-Moore). Mark the lens to confirm rotational stability.
Spherical power effect (SPE) bitoric lenses rotate without inducing cylinder, the pragmatic default for corneal astigmatism.
Verify parameters against current manufacturer documentation before fitting.