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IOL Power Calculations

Cataract Surgery Arizona

Corneal Bypass Method.1

The Corneal Bypass Method of post-LASIK corneal power estimation is one that was recently described by Walter et al in the March, 2006 issue of the Journal of Cataract and Refractive Surgery. The advantage of this method is that it is done without having to calculate the post-LASIK corneal power.

Using this technique, the IOL power is calculated using the post-LASIK axial length and the pre-LASIK keratometry. The target refraction is set for the pre-LASIK spherical equivalent. This "bypasses" the post-LASIK corneal power.

The corneal bypass method for the right eye would be carried out as follows using the post-LASIK axial length:

 

If the pre-LASIK keratometry was 45.37 D / 46.00 D, and...

The spherical equivalent before LASIK was -5.62 D, and...

The post-LASIK IOLMaster axial length is 26.32 mm, then...

The IOL power for a -5.62 D refractive result would be +17.27 D

The corneal bypass method for the left eye would be carried out as follows using the post-LASIK axial length:

 

If the pre-LASIK keratometry was 45.25 D / 46.12 D, and...

The spherical equivalent before LASIK was -5.12 D, and...

The post-LASIK IOLMaster axial length is 25.95 mm, then...

The IOL power for a -5.12 D refractive result would be +17.86 D

References

1. Walter KA, Gagnon MR, Hoopes PC, Dickenson PJ. Accurate intraocular lens power calculation after myoic laser in sitiu keratomileusis bypassing corneal power. J Cataract Refract Surg 2006 32 (3) 425 - 429.