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Double-K method can improve outcomes in calculating IOL power for post-RK eyes
WAIKOLOA, Hawaii — Using the effective refractive power in a double-K method can improve outcomes when calculating IOL power for post-RK eyes, a surgeon said here.
“We do pretty well with post-RK eyes just using the effective refractive power, which is essentially the central corneal power, which is a number you can get from any state-of-the-art topographer,” Mark Packer, MD, FACS, said at Hawaiian Eye 2013.
Mark Packer
The central corneal power is essentially the front surface of the cornea, usually within the central 3 mm, and it usually has some gradient to accentuate the central K, he said.
The double-K formula is necessary because the keratometry is used for two purposes in these IOL formulas: to measure the power of the cornea and to estimate the effective lens position.
In post-RK cases, the power of the cornea has changed, but the contribution of the keratometry to a measurement of the effective lens position has not changed, Packer said.
“The size of the eye is basically not altered, just the curvature of the cornea. So you want to use a double-K method. Use the Ks separately, and that is what the Holladay 2 formula does. You plug in the effective refractive power,” Packer said.
Disclosure: Packer is a consultant for WaveTec Vision.