Purpose:

To evaluate the accuracy of the Hoffer Q, SRK/T, Holladay 1, Haigis and Barrett Universal II formulas using a "true axial length" measured by the Argos biometer using individual refractive indices v/s a "simulated axial length" that applies a regression relating the optical path length to the IOLMaster 500 measurements

Methods:

This is a retrospective study on 318 cataractous eyes measured by the Argos biometer. Two values for the axial length (AL) were evaluated, the "True AL" as given by the biometer to a "simulated AL" mimicking the IOLMater 500 measurements. The accuracy of the different formulas was evaluated with these two measurements, while keeping the K readings, ACD depth and all other measurements the same.

Results:

The "simulated AL" underestimated the AL in short eyes and overestimated the AL in longer eyes. The use of the "True AL" resulted in a lower mean and median absolute errors, especially in the long eyes, with a higher percentage of eyes within +/- 0.50 D,0.75 D and 1 D.

Conclusions:

Using individual indices to measure the optical path of the eye yields a more precise measurement that results in more accurate IOL power calculations