Size plays role in injection of IOLs during cataract surgery


Smaller corneal incisions made during cataract surgery are linked with better visual outcomes and less frequent postoperative endophthalmitis.

Maximilian Friedrich, MD, Gerd Auffarth, MD, and Patrick Merz, MD, from the David J. Apple Center for Vision Research, Department of Ophthalmology, University Hospital Heidelberg, Heidelberg, Germany, reported that despite using the specific incision size recommendations of the manufacturers of injector systems for intraocular lenses (IOLs), enlargement of the intraoperative incisions occurred with all injector systems analyzed, and some manufacturers’ recommendations did not specify an IOL implantation technique.1

The rationale behind this evaluation, the investigators explained, is that smaller corneal incisions made during cataract surgery are linked with a better visual outcome and less frequent postoperative endophthalmitis. The insertion of IOL injector systems into the anterior chamber to implant an IOL is associated with incision enlargement that impedes these positive effects.

In this study, they compared 126 IOL injectors of 13 IOL injector systems regarding the manufacturers’ recommended preoperative incision sizes to evaluate the intraoperative incision enlargement and postoperative incision sizes. A total of 499 corneal incisions in ex vivo porcine eyes were analyzed. The preoperative incision sizes depended on the recommended IS of the specific injector system. The incision size was measured before and after the IOL injector was inserted with an incision gauge set.

Results of incision analysis

The results showed intraoperative incision enlargement in 87% of the incisions (mean, 0.26 ± 0.18 mm). The incision enlargement often was significantly (p < 0.05) larger with small incisions compared to larger ones because of the injector system. Five injector systems needed to have a significantly larger incision than that recommended by the manufacturers, with an average difference of 0.3 mm when applying study criteria, a difference that reached significance (p < 0.05).

The investigators commented, “We found that despite using specific incision size recommendations, there was always an intraoperative incision enlargement in all 13 injector systems, and five manufacturers’ recommendations did not specify an IOL implantation technique.”

Based on their results, they recommended development of a transparent algorithm for finding a preoperative incision size recommendation, considering the surgical challenge, postoperative incision size, and intraoperative incision enlargement.

Another key result was their recommendation for the use of five study-based preoperative incision sizes that differ from the manufacturers’ recommendations. “This data should be included into the surgeon’s decision process regarding the choice of an adequate preoperative incision size to reduce intraoperative incision enlargement. In addition, the insertion depth of an IOL injector system into a clear corneal incision was measured and this could be used as a parameter in future studies to compare IOL implantation techniques or to explain variances in the postoperative incision size. In future studies, the clinical outcome between large preoperative incision sizes with small intraoperative incision enlargement and small preoperative incision sizes with large intraoperative incision enlargement should be compared,” they concluded.

1. Friedrich M, Auffarth GU, Merz PR. Experimental analysis of recommended corneal incision sizes in cataract surgery using 13 intraocular lens injector systems. Sci Rep. 2023;13: 2659;
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