Trapezoid incisions for phacoemulsification may reduce Descemet membrane detachment

Given the increased risk of incision-related Descemet membrane detachment (DMD) during phacoemulsification with a 2.2-mm corneal incision, the investigators examined whether the risk of DMD on the first postoperative day (POD 1) can be safely and effectively decreased with a trapezoid incision (modified 2.2-mm incision with the internal width enlarged to 3.0 mm).

Study design

This was a double-masked, randomized clinical trial in 130 Chinese patients aged 65–90 years who had a hard, nuclear age-related cataract with a nuclear opalescence grade of ≥4.0 based on the Lens Opacities Classification System III, a pupil size of ≥6 mm following dilation, and a corneal endothelial cell density of >1500 cells/mm². The primary outcome was the incidence of incision-related DMD at POD 1.

Outcomes

An equal number of patients were randomized to the modified group and to the conventional group; the mean patient age was similar between groups. The incidence of DMD in eyes in the modified group was significantly lower at POD 1 than in eyes in the conventional group (difference: 26.15). In addition, the modified group showed decreased maximal corneal thickness at the incision site and improved visual quality parameter modulation transfer function. No differences in best-corrected visual acuity, surgically induced astigmatism, or central corneal endothelium loss were noted between the groups, and no intraoperative complications were seen.

Limitations

All of the cataract surgeries were performed by one experienced surgeon; therefore, the results need to be verified among surgeons with a range of surgical skills and experiences using various phacoemulsification systems in a larger cohort. Since the enrolled patients had healthy corneas with normal endothelial cell density, the findings need to be validated in patients with corneal pathology who have a higher risk of DMD. While prior studies found that the highest incidence of DMD after phacoemulsification occurred on POD 1, and POD 1 was the primary outcome measure in this study, the clinical significance of these findings cannot be determined with certainty, as the authors could not confirm whether the differences seen at POD 1 definitively continued throughout the study duration.

Clinical significance

The findings of this study suggest that the incidence of DMD for advanced nuclear age-related cataract at POD 1 can be mitigated with a modified 2.2-mm trapezoid clear corneal incision, and therefore a trapezoid incision may be considered in at-risk patients. Enlarging the width of the clear corneal internal incision to 3.0 mm to create a trapezoidal tunnel can increase the range of motion for surgical instruments and decrease mechanical injury from wound compression by a smaller internal incision.