Horizontal and anterior chamber diameter for phakic intraocular lens sizing

Clinical relevance Proper selection of phakic intraocular lens diameter is necessary to avoid complications related with excessive vaulting after its implantation. Background Horizontal corneal diameter, measured as white-to-white distance, is one of the parameters used for phakic intraocular lens diameter calculation. Agreement was assessed between three parameters: white-to-white distance obtained with swept source optical coherence tomography, and white-to-white distance obtained with Scheimpflug camera and angle-to-angle parameter obtained with anterior segment optical coherence tomography. Methods This study included 55 eyes of 43 patients. The white-to-white distance was measured with two biometry techniques: swept source optical coherence tomography and Scheimpflug camera. The angle-to-angle was measured with anterior segment optical coherence tomography. Analysis of agreement was performed by the Bland-Altman method. For every patient, simulation of Visian Implantable Collamer Lens (ICL) sizing was performed using the Online Calculation and Ordering System with different white-to-white distance or angle-to-angle. Results Statistically significant differences were found between swept source optical coherence tomography biometer and anterior segment optical coherence tomography (p = 0.001) and between swept source optical coherence tomography and Scheimpflug camera (p < 0.001). However, there was a good correlation between swept source optical coherence tomography and Scheimpflug camera (intraclass correlation co-efficient = 0.623), with a shift toward higher white-to-white distance values on swept source optical coherence tomography. A relatively high correlation intraclass correlation co-efficient (0.772) and lack of statistically significant differences (p = 0.068) between anterior segment optical coherence tomography and Scheimpflug camera results were observed. Simulation of phakic intraocular lens sizing showed that swept source optical coherence tomography white-to-white distance should not be used interchangeably with Scheimpflug camera white-to-white distance or angle-to-angle. Conclusion White-to-white distance measured with swept source optical coherence tomography was significantly different from values obtained with other methods. Angle-to-angle may support ICL sizing, helping in verification of white-to-white distance values obtained with other devices.