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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.
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(LSE x -0.326) + 0.101 = Post-LASIK IOL power adjustment
 Where...
LSE = The vertex distance corrected laser vision correction spherical equivalent.
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The Masket method for the right eye following LASIK would be carried out as follows:
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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 ...
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(LSE x -0.326) |
+ |
0.101 |
= |
Post-LASIK IOL power adjustment |
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(-5.05 D x -0.326) |
+ |
0.101 |
= |
+1.75 D = IOL power adjustment |
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+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:
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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 ...
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(LSE x -0.326) |
+ |
0.101 |
= |
Post-LASIK IOL power adjustment |
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(-3.82 D x -0.326) |
+ |
0.101 |
= |
+1.35 D = IOL power adjustment |
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+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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