Effect of hole size on fluid dynamics of a posterior-chamber phakic intraocular lens with a central perforation by using computational fluid dynamics.

Abstract

A modified implantable collamer lens (ICL) with a central hole with a diameter of 0.36mm, referred to as a hole-ICL, was created to improve aqueous humour circulation. The aim of this study is to investigate the ideal hole size in a hole-ICL from the standpoint of the fluid dynamic characteristics of the aqueous humour using computational fluid dynamics. Fluid dynamics simulation using an ICL was performed with thermal-hydraulic analysis software FloEFD V 12.2 (Mentor Graphics Corp.). In the simulation, three-dimensional eye models based on a modified Liou-Brennan model eye with a conventional ICL (Model ICM, Staar Surgical) and a hole-ICL were used. The hole-ICL was -9.0 dioptres (D) and 12.0mm in length, with an optic zone of 5.5mm. The vaulting was 0.50mm. The quantity of aqueous humour produced by the ciliary body was set at 2.80μL/min. Flow distribution between the anterior surface of the crystalline lens and the posterior surface of the ICL was calculated, and trajectory analysis was performed. With an increase in the central hole size, the velocity of the aqueous humour increased, with the peak velocity occurring at a diameter of approximately 0.4mm. Once the diameter had increased above 0.4mm, the velocity then decreased. The velocity difference between the cases of a central hole size of 0.1mm and 0.2mm was significant. The desirable central hole size was 0.2mm or larger in terms of flow dynamics. The current model, based on a central hole size of 0.36mm, was close to ideal. The optimisation of the hole size should be performed based on results from a long-term clinical study so as to analyse the incidence rate of secondary cataract and optical performance.