Alessandro Franchini, MD
Optical Physiopathological Department at the University of Florence
Stabilization of the capsule is key to the reduction of phacoemulsification complications. Many studies have suggested that there is a strong correlation between endophthalmitis, retinal detachment, cystoid macular edema and capsules that are not intact. Another area of importance for successful phacoemulsification is the maintenance of ocular pressure. My team and I at the University of Florence, Eye Institute, have recently completed a study examining the importance of ocular pressure during cataract extraction and why managing this has significant effects on minimizing complications.
During the course of our study we found that high pressures do occur during different phases of phacoemulsification, potentially leading to complications. Fluctuations in the anterior chamber pressure can cause an increase in postop macular thickness. Typically this effect will only occur in a small percentage of patients, but it is an important complication that all surgeons must be aware of due to its negative effects on visual acuity.
Evaluation of Phacoemulsification Technology
Many improvements in phaco technology have allowed surgeons to use little or no energy for the removal of nuclei as well as the ability to control pressure and flow changes. This was the basis of our study to investigate pressures in 15 people undergoing phacoemulsification with Sovereign with WhiteStar, Alcon Legacy, and Sovereign with WhiteStar ICE. Using the classic “stop and chop” technique we measured the various pressure spikes during all phases of surgery. What we found is that the group who underwent phaco with WhiteStar ICE experienced the least amount of pressure variations (8.5mm-Hg). Pressures increased to 15.5 mm-Hg in the WhiteStar group and to 16.3 mm-Hg in the Legacy group.
ICE with CASE technology featured in the latest version of the Sovereign system help to create the optimal environment for surgery. The ICE system allows for increased cutting power without a concomitant rise in energy. CASE (Chamber Stabilization Environment) aids in the maintenance of anterior chamber stability during phaco. By optimizing fluidics and ultrasound energy, it has been my experience that this software dramatically reduces post occlusion surge and improves nuclear fragment hold to the phaco tip.
Using Technique to Lower Pressure
We evaluated the tension during all phases of surgery in our study. To our surprise, we discovered a pressure spike as high as 120 mm-Hg at certain points of the procedure. While evaluating the pressure during phases of the procedure we found that during the first phase of surgery, while the viscoelastic was being refilled in the anterior chamber, pressure remained stable at 50 mm-Hg and continued to remain stable through the subsequent capsulorhexis phase.
Pressures began rising during the emulsification of the nucleus to about 90 mm-Hg and may rise as high as 100-120mm-Hg if we try to implant the lens through an incision that is much too small.
To minimize pressure and pressure fluctuations in the eye during surgery, it is imperative during each phase to pay attention to particular details.
These spikes in pressure are important to note because practitioners must keep in mind no matter what technique is used, fluctuations in pressures at the various phases of surgery will effect the end result; determining whether your patient will be happy with their visual acuity or not.
Future Studies
Further examination of different techniques and their correlation to IOP may reveal the best methods for managing pressure fluctuations. My colleagues and I are further evaluating the differences between pressure spikes using both standard and microincisional phaco. My initial impressions are that, due to the need to work in a closed chamber, the pressure will rise a bit more with microincisional techniques. As the rise appears to be small, I doubt it will provide a clinical difference.
Regardless of what technique is used, it is my belief that all practitioners must keep in mind the negative effects of pressure during cataract surgery in order to provide their patients with the best visual acuity as possible.
Allessandro Franchini, MD works in the Optical Physiopathological Department at the University of Florence, Eye Institute – Azienda Ospedaliera Careggi, Florence, Italy. He may be reached at +39 055 411765; [email protected]