The Topographic Central Corneal Power Adjustment Method of post-LASIK corneal power estimation was originated by Doug Koch and Li Wang and is based on determining the central power of the cornea using either the Zeiss Humphrey Atlas topographer or the adjusted effective refractive power (EffRP_adj) of the Holladay Diagnostic Summary of the EyeSys Corneal Analysis System.

Using this technique, the 1, 2, 3 and 4 mm power values of the Numerical View of the Zeiss Humphrey Atlas topographer are averaged together and used as the central corneal power value (Ccp). As an alternative, the adjusted effective refractive power (EffRP_adj) of the Holladay Diagnostic Summary of the EyeSys Corneal Analysis System can be used.

This value is then reduced by 19% for every diopter of myopia corrected by LASIK.

C_CP	+	(ΔD x 0.19) = Post-LASIK adjusted corneal power Where...
C_CP	=	the EffRP_adj, or the averaged Zeiss Atlas central corneal power, and...
ΔD	=	the refractive change after LASIK at the spectacle plane.

The topographic central corneal power adjustment method for the right eye would be:

If the averaged topographic central corneal power is 41.97 D, and...

The change in refractive power at the spectacle plane is -5.38 D, then...

	C_CP	+	(ΔD x 0.19)	= Post-LASIK adjusted corneal power
	41.97 D	+	(-5.38 x 0.19)	= 40.95 D

The topographic central corneal power adjustment method for the left eye would be:

If the averaged topographic central corneal power is 42.61 D, and...

The change in refractive power at the spectacle plane is -4.00 D, then...

	C_CP	+	(ΔD x 0.19)	= Post-LASIK adjusted corneal power
	42.61 D	+	(-4.00 x 0.19)	= 41.85 D

References

1. Koch, D., Wang I. Calculating IOL power in eyes that have had refractive surgery. J Cataract Refract Surg 2003 29(11) 2039-2042.

2. Wang L, Booth MA, Koch DD. Comparison of intraocular lens power calculations methods in eyes that have undergone LASIK. Ophthalmology 2004 111(10) 1825-1831.

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