Laser Cataract Surgery Does Less Corneal Damage for Patients with Shallow Anterior Chambers

Femtosecond laser-assisted cataract surgery (FLACS) offers surgeons an option that exposes patients to lower ultrasound energies than conventional phacoemulsification techniques, and the literature is still parsing all the precise ways that could benefit patients. For instance, little evidence shows the impact of using FLACS for patients with shallow anterior chambers. These patients are more prone to postoperative inflammation and corneal edema. But new research published in the Journal of Cataract and Refractive Surgery now shows these patients experience reduced postoperative endothelial cell loss and corneal inflammation following FLACS, compared with conventional phacoemulsification.

The study looked at the outcomes of 40 eyes (of 40 subjects) with anterior chamber depths smaller than 2 mm undergoing age-related cataract removal. Half underwent FLACS while the other half had manual phacoemulsification. The investigators evaluated all subjects’ central corneal thicknesses (CCT); endothelial cell densities (ECD); basal epithelial cell (BEC) and Langerhans dendritic cell (LDC) densities; and keratocyte activation at baseline (preoperatively), 1 week, 1 month, and 6 months after surgery. Intraoperative parameters such as cumulative dissipated energy (CDE) and ultrasound (US) power were recorded. 

For the conventional phacoemulsification group, surgeons created 2 side-ports of 1.2 mm each with a keratome, and a clear cornea main incision was made at a temporal corneal site with a 2.2 mm angled keratome. For the FLACS group, the fragmentation patterns were composed of 3 radial cuts and 3 circular cuts.

The researchers noted a significant corneal thickening in the 2 groups 7 days after surgery compared with baseline (P <.001). But in the FLACS group, the CCT decreased to preoperative levels after 1 month. The conventional phaco group didn’t see CCT return to the preoperative ranges until after 6 months. Also, the mean CCT adjusted for the preoperative values was significantly lower in the FLACS group 7 days after surgery, with a difference of -4.4 µm (95% CI; -7.29 to -1.51, P =.003); this difference gradually decreased at 1 month (-2.65 µm; -5.54 to 0.24, P =.073) and 6 months (0 µm, -2.89 to 2.89, P =1.000) postoperatively.

ECD significantly decreased in both groups after surgery and the endothelial cell loss rate in the phaco group was significantly higher than the femto group at each follow-up. At 7 days postoperatively patients who received the conventional phaco approach saw 5.94% (± 1.72%) loss vs the femto groups’s 4.65% (± 1.94%; P =.033). At 1 month it was 7.97% (± 2.02%) vs the femto group’s 5.38% (± 1.82%; P <.001) and by 6 months it was 8.23% (± 2.11%) vs 5.85% (± 1.77%; P <.001). Endothelial cell loss was calculated as preoperative – postoperative)/preoperative x 100, where preoperative is preoperative cell density and postoperative is postoperative cell density.

BECs and LDCs significantly increased 1 postoperative week (P <.001), returning to preoperative values after 1 month in both groups. Keratocyte activation remained significantly higher 1 postoperative month only in the phaco group (P =.005).

This is only the second study to look specifically at patients with shallow anterior chambers and how they respond to FLACS. This is the first to focus on how each of these techniques damage the cornea. The team attributes the higher endothelial cell loss rate in the phacoemulsification group (in all postoperative visits prior to 6 months) to higher ultrasound vibrations in the phaco technique, which they say may induce more cellular stress. Indeed, cumulative dissipated energy (P =.001) and ultrasound power (P =.017) were significantly higher in the conventional phaco group than in the femto group. 

“The lower rate of endothelial cell loss, the faster recovery of preoperative pachymetric values and the level of activation of the keratocytes, suggest less damage and inflammation induced by the femtosecond laser-assisted technique compared to the conventional one,” the researchers explained. This study confirms that even for patients with shallow anterior chambers, FLACS reduces the traumatic impact of ultrasound on ocular tissues, as compared with conventional phacoemulsification. 

Reference

Mencucci R, De Vitto C, Cennamo M, et al. Femtosecond laser–assisted cataract surgery in eyes with shallow anterior chamber depth: comparison with conventional phacoemulsification. J Cataract Refract Surg. Published online September 3, 2020. doi: 10.1097/j.jcrs.0000000000000341