Arcscan Insight 100-Derived Measurements Of Ciliary Body Inner Diameter In Myopic Chinese Adults: Distribution, Determinants, And Implications For Icl Sizing

To investigate the distribution and determinants of ciliary body inner diameter (CBID) in Chinese myopic adults using ArcScan Insight® 100 and evaluate its implication for Implantable Collamer Lens (ICL) sizing. 

This study was conducted at the Department of Ophthalmology in The First Affiliated Hospital of Xi'an Jiaotong University,  Xi'an, China

In this cross-sectional study, 107 myopic eyes (58 subjects) were enrolled. Anterior segment parameters, including CBID, were measured using ArcScan Insight 100. Regression analyses were performed to identify predictors of CBID. ICL sizes calculated via the Reinstein formula (incorporating CBID) were compared with those from the STAAR OCOS formula (based on white-to-white diameter). 

Mean CBID was 10.80 ± 0.48 (range 9.76 to 11.97) mm. Multivariate analysis revealed CBID was independently associated with younger age (P=0.020), lower crystalline lens rise (CLR, P=0.004), wider sulcus-to-sulcus diameter (STS, P<0.001), and smaller STS lens rise (STSL, P=0.013). Stepwise regression identified STS (partial R²=0.602) and CLR (partial R²=0.019) as primary contributors, explaining 62.1% of CBID variability. Reinstein formula-recommended ICL sizes differed significantly from OCOS-based sizes (χ²=9.232, P=0.010), with 28% of eyes requiring a 1-size reduction. 

This is the first study characterizing CBID in Chinese myopes. CBID is an important post chamber parameter influenced by multiple ocular anatomical parameters, among which the STS is the largest independent predictor. The Reinstein formula, which incorporates CBID, resulted in different ICL size recommendations for half of the eyes compared to the traditional WTW-based method. These findings highlight the potential of CBID to refine ICL sizing, though its direct impact on vault prediction accuracy requires future surgical validation.