Oculus Pentacam Module: Holladay Report

The new Holladay Report – the big step forward in IOL calculation

The big step forward making IOL calculations much easier are the so called Equivalent Keratometer Readings, EKRs. These K-readings, calculated in the 4.5mm zone around the pupil center, can be used for IOL calculations for patients who have underwent refractive surgery like LASIK, PRK or RK in the past. The calculation of IOLs for those cataract patients was a challenge especially if no pre-operative data were available.

With a Placido based topographer or with manual keratometry it is not possible to calculate the posterior corneal curvature. Therefore the conversion from anterior curvature into refractive power is always done using a refractive index of 1.3375. This number has to be considered as an average value which assumes a constant radii ratio between posterior and anterior corneal surface of 82.3%.

But after corneal refractive surgery the radii ratio between the posterior and the anterior corneal surface changes. During the myopic treatment the anterior cornea is flattened which results in a lowering of the radii ratio. In contrary the cornea is steepened during the hyperopic treatment which results in a higher radii ratio. After RK treatment the radii ratio rises, too.

The EKRs in the Holladay Report consider all these effects because the Pentacam measures the posterior corneal surface. Therefore they can be used for patients who have underwent refractive surgery in the past. They can be directly plugged into your preferred IOL formula eg. Holladay II.

The Holladay Detail EKR Report offers more information for the pre-op planning. The refractive power distribution of the EKRs in the respective zone is shown in the lower left. In combination with the upper right diagram a pre-op prediction of the outcome can be done.