**5. Determination of anatomic location of secondary IOL**

Choosing the best location and technique for secondary IOL implantation can be a difficult one. No clear guidelines are established for secondary IOL implantation. In 2003, Wagoner et al. reviewed the literature on secondary IOL implantation [10]. In this paper, the authors found no evidence to claim superiority of any one technique or anatomic location for fixation. Since 2003, secondary IOL surgery has continued to evolve dramatically and still no clear evidence exists to guide surgeons. As Wagoner's paper noted, the most important factor often is the surgeon's comfort with a secondary IOL technique.

There are however, some recommendations in ruling out certain anatomic locations for IOL fixation. For example, poor corneal endothelial status and/or abnormal angle/iris anatomy should discourage anterior chamber IOL implantation. Lack of adequate iris support would rule out other iris-fixated approaches (sutured or iris-claw). Lack of posterior capsular support or a fibrosed anterior/ posterior capsule would rule out in-the-bag PCIOL placement. Sulcus intraocular lens implantation requires adequate anterior capsular support. Scleral abnormalities (i.e., Marfan's, scleral thinning, etc.) would rule out scleral fixation techniques.

In-the-bag posterior chamber intraocular lens implantation remains the best anatomic location for an intraocular lens. However, even if during secondary IOL implantation the aphakic eye has an intact posterior capsule, the anterior/ posterior capsule is typically fibrosed, preventing IOL implantation inside the capsular bag. Brunin et al. evaluated the complication rates, visual acuity and refractive outcomes of different intraocular lens implantation techniques [11]. Their study noted that capsular bag implantation had the best refractive outcomes followed by sulcus IOL with optic capture and sulcus IOL without optic capture. There was no difference between transscleral-sutured IOL, iris-fixated IOLs, and ACIOLs.

If possible, in-the-bag implantation has the best outcomes given its closest proximity to normal anatomy. This requires a stable and intact capsular bag. If no posterior capsular exists but there is adequate anterior capsular support, sulcus IOL implantation can be performed, preferably with optic capture. However, if no capsular support exists, the guidelines for secondary IOL implantation remain controversial [12]. If a viable 3-piece IOL has been dislocated, the preference might be to reposition the lens with an iris-sutured or scleral fixation technique. Other options include ACIOL implantation, iris-fixation techniques, and scleral-fixation techniques. The following sections will explore these options in more detail.
