Comparison of Corneal Endothelial Cell Loss and Cumulative Dissipated Energy Between Femtosecond Laser Assisted Cataract Surgery and Standard Phacoemulsification With the Active Sentry or OZil Handpiece

Phacoemulsification (phaco) has been the standard technique for cataract surgery for several decades. It involves the removal of the lens nucleus after ultrasound fragmentation. Recently, Femtosecond Laser Assisted Cataract Surgery (FLACS) has become a new popular method amongst ophthalmologists.

The femtosecond laser (LFS) is a new technology that is being used for cataract surgery. The LFS has a femtosecond pulse duration, which reduces damage to collateral tissue and increases the efficacy and safety of the procedure. The LenSx laser (Alcon Laboratories Inc., USA) is one of the most widely used LFS for cataract surgery and is part of the CENTURION Vision system. The LFS automates key steps in the procedure including capsulorhexis, incision making and phaco, limiting human variability and potentially improving the efficiency and safety of the surgery. The Frequency Domain - Optical Coherence Tomography (FD-OCT) optical imaging system provides high-resolution, real-time visualization of ocular structures and their dimensions. The device sends the results to the interface which programs the laser and indicates the exact location, size and depth of the desired incisions.

Several handpieces are used to perform phacoemulsification. The traditional handpiece is named OZil and is part of the Infiniti Vision System (Alcon Laboratories Inc.) which was introduced in 2006 and has since revolutionized the phaco technique with its new rotational technology. This handpiece increased phaco efficacy by reducing core fragment repulsion, collateral tissue damage, and the amount of energy required. However, a new generation of handpiece called Active Sentry (Alcon Inc.), which is part of the new Active Fluidics technology, has now the added feature of detecting the pressure inside the eye in real time and adjusting it to avoid significant variations. This handpiece can also decrease the amount of fluid and energy used during the procedure, increasing the efficacy and safety of phacoemulsification.

Different methods to quantify the collateral damage caused by cataract surgeries are the count of endothelial cell loss (ECL) as well as the amount of energy required to fragment the lens (CDE: cumulative dissipated energy). FLACS may reduce the CDE required during phaco, thereby reducing the damage to the cornea of the eye (including the loss of endothelial cells of the cornea).

Despite a large number of publications on this topic, recent meta-analyses on the effect of FLACS on ECL and CDE were found to be inconsistent. Few studies have demonstrated a decrease in ECL as well as CDE required in patients undergoing FLACS when compared to standard phaco, but long-term results were not conclusive.