Preoperative Anatomy Parameters in Implantable Collamer Lenses

Purpose: To determine patient preoperative anatomical features and the parameters of implantable collamer lenses (ICLs) relevant in explaining vault variability. Setting: Ophthalmology Xi’an Aier Gucheng Eye hospital , Xi’an China. Design: Retrospective case series. Methods: : This study comprised 88 eyes of 45 patients implanted with myopic or toric ICLs between May 2021 and August 2021.Pentacam imaging was used for assessing white-to-white (WTW) diameter, central keratometry, anterior chamber depth(ACD), central corneal thickness and vault. Anterior-segment optical coherence tomography（AS-OCT） was used to measure the horizontal anterior chamber angle distance (ATA). Ultrasound biomicroscopy (UBM) was used to measure horizontal and vertical sulcus to sulcus(vSTS). According to different ACD,we divide ACD into shallow group(2.8 to 3.2 mm),medium group(3.2 to 3.5 mm),and deep group(＞3.5mm). Results: : Linear regression analysis found significant correlation between WTW diameters and ATA diameters( y= 0.9605x+0.1491,R² = 0.9148),with a coefficient of determinant of 0.9148 (P＜0.01). Linear regression analysis found significant correlation between hSTS and vSTS（y=0.9855x-0.0178,R²=0.1979）,with a coefficient of determinant of 0.1979 (P＜0.01). WTW diameters showed statistically significant difference in shallow and medium ACD (t=-3.28,P＜0.01 ), significant difference in shallow and deep ACD (t=-4.69,P＜0.01 ),there was no correlation in medium and deep ACD(t=-1.41,P＞0.05 ). There was a statistically significant correlation between WTW diameters and hSTS diameters when the ACD was less than 3.5 mm (t=-0.451, P=0.000) (t=1.406, P=0.026),but weak correlation when the ACD was bigger than 3.5 mm(t=1.594, P=0.051). ATA and WTW with a mean difference close to zero ( -0.66 mm). Despite the relatively high correlation (intraclass correlation co-efficient =0.689), the range of agreement is quite broad (1.33 mm). Conclusions: : ATA measured with AS-OCT can not be used interchangeably with WTW obtained with Pentacam. WTW diameters and hSTS diameters have a statistically significant correlation when the ACD was less than 3.5 mm. WTW, ATA, hSTS and vSTS all should be considered during design the size of lens and regulating the vault after surgery.