Refractive outcomes more impacted by ACD than IOL position

This prospective study found that the IOLMaster and Pentacam HR devices can be used interchangeably for anterior chamber depth (ACD) measurements, and that the impact of IOL position on postoperative refraction is relatively small compared with the impact of minor corneal curvature or axial length measurement errors.

The authors used the partial coherence interferometry (PCI)-based IOLMaster and the Pentacam HR Scheimpflug device for pre- and postoperative biometry and anterior segment measurements in 36 consecutive cataract patients. They used the Haigis formula to calculate predicted refraction with ACD estimations and compared this with the actual postoperative refraction. Scheimpflug images were used to assess changes in ACD and the distance between the cornea and the iris and the distance between the iris and the lens/IOL.

The devices produced comparable ACD values in phakic eyes, and when used for IOL power calculations and postoperative refraction prediction, their prediction errors were similar. Furthermore, the mean predicted refractive outcome from a 1.0 mm difference in ACD was 0.32 D.

They also found that the increase in ACD after cataract surgery is an increase in both the distance between the cornea and the iris and the distance between the iris and the lens/IOL and that these distances are of the same magnitude.

They write that standard IOLMaster biometry is sufficiently accurate for routine cataract surgery planning, but the Pentacam is a useful tool for detailed imaging of the pseudophakic anterior chamber and IOL position.