Verification of biometry measurements is crucial in patients with existing ICLs

Investigators evaluated the effects of implantable collamer lens (ICL) implantation on IOL power calculation prior to cataract surgery and the effectiveness of simultaneous use of anterior segment optical coherence tomography (AS-OCT).

Study design

This was a prospective, randomized, consecutive case series of 100 Japanese patients in whom biometry was performed with an IOL Master 700 and AS-OCT before and after implantation of a posterior ICL for myopia or myopic astigmatism. Pre- and post-implantation IOL power calculations were performed utilizing the SRK/T, Haigis, and Barrett Universal II formulas.

Outcomes

The IOL Master 700 misidentified the anterior surface of the ICL as the anterior surface of the crystalline lens in 75 of 100 eyes. This led to a statistically significant difference in the calculated IOL power using formulas that make use of AC depth and/or lens thickness (Haigis and Barrett Universal II). After correction for AC depth and lens thickness as measured by AS-OCT, there was no statistically significant difference between the pre- and post-implantation IOL power calculations.

Limitations

The mean patient age was 31.1 years; therefore, cataractous changes were not present in this population. As the patients age and changes occur in the anterior crystalline lens, there may be improvements in the ability of the IOL Master 700 to distinguish the surface of the crystalline lens.

Clinical significance

As ICL implantation continues to increase in the United States, it is important for surgeons to understand the potential limitations of biometry in these patients’ eyes for cataract surgery. Verification of the correct identification of the anterior surface of the crystalline lens is key to successful IOL power calculations in these patients. When in doubt, surgeons should confirm the anterior chamber depth and lens thickness using another device such as AS-OCT.