Comparison of two different optical biometry devices with consequences for IOL calculation accuracy

Poster Details

First Author: P.Hoffmann GERMANY

Co Author(s):                  

Abstract Details

Purpose:

To compare the measuring outputs of two optical biometry devices and to evaluate their consequences for IOL calculation accuracy utilizing real postoperative refraction data.

Setting:

Private eye clinic in Germany

Methods:

1156 routine cataract eyes were measured preoperatively with the IOLMaster V5 (Zeiss, Jena, Germany) and the Lenstar V2 (Haag-Streit, Bern, Switzerland) optical biometer. Axial length, exterior anterior chamber depth, corneal radii, corneal astigmatism and horizontal corneal diameter were compared statistically. Lens thickness data was proprietary to the Lenstar and could not be compared. To evaluate the clinical impact of the measurements, IOL powers were calculated with them using (1) the Haigis formula as built into the devices and (2) a modified version thereof that takes advantage of Lenstar’s crystalline lens position and thickness data. In the latter case, only two IOLs were considered, the spherical Alcon SA60AT (n=320) and the aspherical aberration-correcting AMO Tecnis 1piece (n=113).

Results:

Axial length measurements were virtually identical (IOLM 23.59±1.33 vs. LS 23.59±1.33 mm, Pearson’s r=0.99). Mean corneal radius was 7.75±1.10 vs. 7.75±1.14 mm, r=0.98. External anterior chamber depth was 3.05±0.39 vs. 3.16±0.45 mm, r=0.79. Horizontal corneal diameter was 11.83±0.41 vs. 12.07±0.50 mm, r=0.74. Corneal astigmatism (nC=1.332) was 1.03±0.90 vs. 0.98±0.89 D, r=0.89. Internal anterior chamber depth was 2.60±0.16 mm, lens thickness 4.56±0.44mm. Using the built in Haigis formula with the appropriate constants published on ULIB, prediction error was 0.05±0.43 D for the IOLMaster and 0.03±0.45 D for the Lenstar (t-Test p=0.13). The mean absolute prediction difference between IOLM and LS calculation was 0.11 D. When we applied our modified version of the formula, we achieved 0.00±0.40 vs. 0.00±0.48 D (p=0.91) for the spherical lens and 0.00±0.40 vs. 0.00±0.35 D for the aspherical lens (p=0.90).

Conclusions:

Several papers have compared measurement results of IOMaster and Lenstar. However, most of them presented a small patient series and none of them examined the clinical impact. We present a large case series with pre- as well as postoperative data. Preoperative measurement data can be assumed as virtually identical with a slight tendency for deeper anterior chambers and less corneal astigmatism with the Lenstar. Precision of IOL calculation is very similar with no systematic error. The IOLMaster holds a very slight advantage when the original Haigis formula is used. However, the difference is extremely small and not statistically significant. The reason is the axial length measurement. Lenstar is more prone to user error and cannot obtain valid data in some eyes where the IOLMaster still can, especially in posterior capsular cataract. FINANCIAL DISCLOSURE?: No