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Masket Method.10

The Masket Method of post-LASIK corneal power estimation is a postoperative regression method developed by Samuel Masket and recently published in the Journal of Cataract and Refractive Surgery. This technique takes advantage of the fact that there appears to be a linear relationship between the spherical equivalent of the total amount of the stable laser vision correction (LSE) and the over-estimation of central corneal power by simulated keratometry. This works following both myopic and hyperopic LASIK.

By this method, the IOL power is calculated using the Holladay 1 formula for axial lengths greater than 23.0 mm and the Hoffer Q formula for axial lengths less than 23.0 mm. The SRK/T formula is generally not recommended here as the artifact of very flat Ks may sometimes result in an under-correction. The IOL power is calculated without a double K method correction. Ks are provided by simulated keratometry. The calculated IOL power is then adjusted by the vertex distance corrected laser vision correction spherical equivalent determined at four to six months after the procedure, multiplied by -0.326 with 0.101 added to this product. Follow this link to an Excel spreadsheet for Correcting for Vertex Distance.

(LSE x -0.326) + 0.101 = Post-LASIK IOL power adjustment Cataract Surgery ArizonaWhere...

  LSE = The vertex distance corrected laser vision correction spherical Cataract Surgery Arizonaequivalent.

The Masket method for the right eye following LASIK would be carried out as follows:

 

If the calculated IOL power is +15.26 D for a -0.25 D result, and ...

The stable laser vision correction spherical equivalent is -5.38 D, then ...

(LSE x -0.326)  +  0.101  =  Post-LASIK IOL power adjustment
(-5.05 D x -0.326)  +  0.101  =  +1.75 D = IOL power adjustment
+1.75 D  +  15.26 D  =  17.01 D = Final adjusted IOL power

The Masket method for the left eye following LASIK would be carried out as follows:

If the calculated IOL power is +15.09 D for a -0.25 D result, and ...

The stable laser vision correction spherical equivalent is -4.00 D, then ...

(LSE x -0.326)  +  0.101  =  Post-LASIK IOL power adjustment
(-3.82 D x -0.326)  +  0.101  =  +1.35 D = IOL power adjustment
+1.35 D  +  15.09 D  =  16.44 D = Final adjusted IOL power

References

1. Masket S, Masket SE. Simple regression formula for intraocular lens power adjustment in eyes requiring cataract surgery after excimer laser photoablation. J Cataract Refract Surg 2006 32 (3) 430 - 434.

 


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