Posters

Comparison of intraocular lens power measurements obtained using optical and ultrasonic methods with an AL-Scan biometer

Poster Details

First Author: H. Imamoglu TURKEY

Co Author(s):    A. Turk   A. Kalkisim   M. Kola              

Abstract Details

Purpose:

With its auto tracking feature, the AL-Scan biometer is an optical biometer device capable of non-contact calculation of IOL power in a simple and repeatable manner. In addition to its ability to take optical biometric measurements, the AL-Scan biometer is also capable of performing measurements using an ultrasonic method thanks to its optional ultrasonic probe. This feature represents a particular advantage in cases in which optic measurements cannot be taken for various reasons. The purpose of this study was to compare IOL power results obtained from optic and ultrasonic biometric measurements using different generation IOL power calculation formulations.

Setting:

Karadeniz Technical University, Faculty of Medicine, Department of Ophthalmology, Trabzon, Turkey.

Methods:

Thirty-two eyes with cataracts of 18 patients, nine female, were included in the study. Optic biometric measurements and ultrasonic biometric measurements obtained by the using the same device (AL-Scan optical biometer, Nidek Co. Ltd., Japan) were performed in all eyes. IOL power calculations were subsequently performed for the same brand IOLs (Sensar AR40e IOL, AMO, Santa Ana, CA, USA) using two different calculation formulae. The results obtained using the two methods were then subjected to statistical comparison.

Results:

Mean age of the participants was 72.5±9.07. Mean anterior chamber depth (ACD) obtained with the optic method was 3.06±0.32 mm and mean axial length (AL) was 23.4±1.13 mm. The corresponding values with the ultrasonic method were 3.11±0.32 mm and 23.32±1.16 mm, respectively. Calculated IOL power values in the optic method were 20.91±2.61 D for the Haigis formula and 20.92±2.7 D for the SRK/T formula. The corresponding values using the ultrasonic method were 21.83±3.11 D for the Haigis formula and 20.81±2.76 D for the SRK/T formula. IOL power values obtained using the two methods differed significantly when the Haigis formulation was used, but were similar when the SRK/T formulation was employed.

Conclusions:

The Haigis formulation that uses true ACD measurement values in IOL power calculation give rise to incorrect results in IOL power calculation at ultrasonic biometry. The Haigis formulation should therefore only be used for optic biometry. However, when the SRK/T formulation is employed this results in similar IOL power calculations with optic and ultrasonic biometric measurements using an AL-Scan optical biometer.

Financial Disclosure:

NONE