A Novel Algorithm To Determine The Optimal Preoperative Incision Size For Intraocular Lens Injector Models

Clear cornea incisions sized according to the manufacturers’ recommendation often enlarge during cataract surgery due to the insertion of an Intraocular lens (IOL) injector. The process of IOL injector manufacturers to determine their incision size recommendations is regularly undisclosed. The goal of this study was to propose a novel algorithm to determine the optimal preoperative incision size (IS) for intraocular lens injector models.

The David J Apple International Laboratory for Ocular Pathology, University of Heidelberg, Heidelberg, Germany.

This study analyzed 499 clear corneal incisions sized between 1.9 and 2.85 mm. In total 13 different injector models were included. The IS was measured right before and after IOL injector insertion with an incision gauge set ranging up to 3 mm. The IOL injectors were inserted into an incision using the into-the-bag implantation technique. To determine the optimal preoperative IS, the surgical challenge, the postoperative IS, and the intraoperative incision enlargement (IE) were considered. Differences of postoperative IS and intraoperative IE depending on the preoperative IS were statistically analyzed using a Games-Howell post-hoc test.

The minimal ISs that posed a reasonable surgical challenge ranged from 1.9 to 2.5 mm. The postoperative ISs ranged from 2.1 to >3.0 mm with a mean IS of 2.74 ± 0.20 mm. In 86.80% of all incisions intraoperative IE could be observed with a mean IE of 0.26 ± 0.18 mm. In small ISs the IE was significantly higher compared to larger ISs concerning an injector model (P < 0.05).  Five injector models needed to have a significant larger preoperative IS when applying the proposed algorithm compared to the IS recommendation by the manufacturer with an average difference of 0.3 mm (P < 0.05).

A transparent algorithm should be used to determine the optimal preoperative IS for each IOL injector model. Incision size recommendations should be validated by an independent laboratory to prevent needlessly small incisions associated with a more challenging surgery procedure. Future studies should evaluate the outcome of a high IE versus a large postoperative IS.