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Post Keratorefractive Surgery
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Post Keratorefractive Surgery.

Determining Corneal Power after RK, ALK, PRK and LASIK.

The true corneal power following RK, ALK, PRK and LASIK is difficult to measure by any form of direct measurement, such as keratometry, or corneal topography.

Corneal Power Keratorefractive Surgery
 

Keratometry and topography assume a normal relationship between the anterior and posterior corneal curvatures, and measure the anterior corneal radius.

Incisional keratorefractive surgery for myopia flattens both the anterior corneal radius and the posterior corneal radius. Ablative keratorefractive surgery for myopia flattens the anterior corneal radius but leaves the posterior corneal radius mostly unchanged.

Standard keratometry measures an intermediate area and extrapolates the central power based on some very broad assumptions. For this reason, keratometry, autokeratometry and simulated keratometry by topography will typically over-estimate central corneal power, following keratorefractive surgery for myopia. Failure to keep this important fact in mind will often result in an unexpected and unpleasant post-operative hyperopic surprise.

IOL MasterASCRS POST KERATOREFRACTIVE ON-LINE CALCULATOR for myopic LASIK, hyperopeic LASIK, and prior radial keratotomy.
ASCRS POST KERATOREFRACTIVE ON-LINE CALCULATOR IOL POWER CALCULATION FORMULAS
"DOUBLE K" FORMULA CORRECTIONS: Learn how 2-variable IOL power calculation formulas may be another source of errors following keratorefractive surgery. Lacking the Holladay 2 formula, instead you can use the "Double K" correction method in conjunction with the SRK/T, Hoffer Q or Holladay 1 formulas.
MYOPIC LASIK IOL POWER CALCULATION FORMULAS
HYPEROPIC LASIK IOL CALCULATIONS: How to estimate the central corneal power following hyperopic LASIK.
RADIAL KERATOTOMY IOL POWER CALCULATION FORMULAS
MYOPIC LASIK IOL CALCULATIONS: How to estimate the central corneal power following myopic LASIK.
HYPEROPIC LASIK IOL POWER CALCULATION FORMULAS
RADIAL KERATOTOMY (RK) IOL CALCULATIONS: How to estimate the central corneal power following radial keratotomy (RK).

Keep in mind that the above methods will give an estimation of the true central corneal power and may not be exact. At present, these techniques represent the best clinical methods available. Hopefully, in the future we may have a more accurate, and less time-consuming, method for measuring these challenging eyes.

 

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