Fig. 14.1
IOLs are classified by haptic design. (a) Single-piece IOL; (b) three-piece IOL; (c) novel single-piece IOL made of two materials using a novel polymerization technology
14.1.3 IOL Implantation Site: Anterior Chamber IOLs and Posterior Chamber IOLs
Depending on the intended implantation position in the eye, IOLs can also be divided into anterior chamber (AC-) and posterior chamber (PC-) IOLs:
- 1.
AC-IOLs: Nowadays, it is widely believed that AC-IOLs (especially chamber angle-supported IOLs) are associated with multiple complications, such as corneal endothelial decompensation, hyphema, anterior uveitis, and secondary glaucoma. Thus, AC-IOLs are not recommended for children.
- 2.
PC-IOLs: The commonly used PC-IOLs can be divided into several types according to their haptic material, design, and shape (Fig. 14.2). Generally speaking, in-the-bag fixation and ciliary sulcus fixation are the preferred positions for implantation of PC-IOLs. The latter is often used when there is posterior capsule defect. In-the-bag IOL implantation has the following advantages: (1) the IOL is fixed at the physiological location of the crystalline lens, which enables to obtain good imaging quality, (2) the position of IOL is relatively stable for a long time, and (3) the IOL has no contact with surrounding tissues, which may reduce complications such as chronic inflammation of the ciliary body and the resulting IOL capture and dislocation.
Fig. 14.2
PC-IOLs. (a) Single-piece IOL with anti-vaulting haptics (AVHTM); (b) single-piece IOL with J-shaped haptics; (c) and (d) three-piece IOL with C-shaped haptics
14.1.4 IOLs for Pediatric Eyes
In 2007, the AAPOS conducted a questionnaire-based survey among US pediatric ophthalmologists to find out which kind of IOL was suitable for children’s eyes. Results showed that in-the-bag IOL implantation is routinely performed for children, with the use of single-piece PC-IOLs manufactured from soft materials, such as hydrophobic or hydrophilic acrylic. But silicone IOLs are not appropriate for children. When ciliary sulcus fixation or scleral-sutured fixation is planned, the use of three-piece PC-IOLs made of soft materials is recommended. Besides, AC-IOLs are usually not suitable for use in the pediatric population. The survey also indicated that as the axial length is likely to change under the age of 18 years, the refractive changes after surgery might significantly impair the effect of multifocal IOLs and increase the risk of amblyopia. Therefore, multifocal IOLs are not recommended for children.
14.2 Progress and Prospects
The basic theory, manufacturing technology, and clinical practice regarding IOLs have been rapidly evolving. Novel IOLs tailored to the anatomical and functional characteristics of children’s eyes have gained significant attention. Although so far, no IOLs specifically designed for children have been approved for clinical use, some innovative products seem to be quite promising.
Since eye development is rapid during childhood, the refractive change is much greater in children than it is in adults [12]. An ideal IOL for children should be able to adjust its diopter to the growing eye and the changing refraction, so as to keep both eyes as close to emmetropia as possible in the course of their development and thereby improve vision. All of the current clinically available IOLs, however, are designed with a fixed diopter and cannot adapt to the refractive changes of pediatric eyes. In view of this, Liu Yizhi and his colleagues have designed a new type of IOL, which is detachable in the capsular bag to adjust its diopter after surgery (China Patent No. 2006200564414) (Fig. 14.3). It comprises at least two IOL pieces that are adhered together with a potential space in between, which is connected to a sealed tube. When the child’s eye becomes fully developed with a stabilized refractive power, the following procedures can be performed to adjust the diopter of the IOL: cut open the sealed tube so that gas or liquid can pass through the tube to form a cavity and then grab the tube and peel off the IOL piece(s) above along a predefined peel-off line. These secondary procedures can bring the affected eye to or close to emmetropia by lowering the overall diopter of the IOL.
