EyeWorld Asia-Pacific September 2013 Issue

33 EWAP CAtArACt/IOL September 2013 GUO Haike, MD Chairman, Henan Eye Institute, Henan Eye Hospital Director, Guangdong Eye Institute, Guangdong General Hospital Zhengzhou, China Tel. no. +86-37165991123 guohaike@hotmail.com A ll steps of phacoemulsification are completed in a relatively closed space. To keep the balance and stability of the system, we can get smooth operation and obtain good effect. Therefore, the related concept of fluid dynamics is very important for surgeons. The basic factors of fluid dynamics include aspiration rate, vacuum, occlusion, surge and reflux. Aspiration rate represents the volume of fluid outflow from the eye in a unit of time. Actual rates affect the followability of the mobile objects. Followability is a phenomenon of the phacoemulsification technique in fluid dynamics. Objects can be moved in the eye to the tip by fluid. Even in the absence of occlusion, it can have a certain level of vacuum at a higher flow rate. Occlusion is an important component of fluid dynamics in the action of peristaltic pumps. When the tip is occluded, the vacuum increases. The vacuum attracts cataract material to the phaco tip. Holdability occurs. It allows the nucleus to be held on the tip for effective crushing. Eyeball volume is relatively fixed. The balance of fluid dynamics depends on the dynamic equilibrium of inflow and outflow. Throughout the operation, stable intraocular pressure is always needed. Any change will cause imbalance. In order to achieve continuous balance, the outflow must be matched by the inflow. In the absence of incision leakage, bottle height and aspiration rate influence the pressure within the eye. At fixed aspiration rate, adjusting the bottle height can change the pressure. For the same reason, at fixed bottle height, aspiration rate controls the pressure. The balance of fluid dynamics is the key to ensure the stability of the anterior chamber during the phaco process. It can also reduce damage to the cornea, posterior capsule and iris. The surgeon gets a smooth operation and the patient gets good vision. What can you do to optimize knowledge of fluid dynamics? In our training program for young doctors, understanding phacodynamics includes education on fluids, incision, tips and the machine. It is very important for surgeons to learn in order to achieve better postoperative outcomes. Editors’ note: Prof. Guo has no financial interests related to his comments. Mohan RAJAN, MD Chairman & Medical Director, Rajan Eye Care Hospital 5 Vidyodaya East 2nd Street, T. Nagar, Chennai, 600117, India Tel. no. +91-44-2834-0500 Fax no. +91-44-2834-3711 drmohanrajan@gmail.com H aving trained more than 400 ophthalmologists from around the world in phacoemulsification, I can confidently state that performing a successful phacoemulsification surgery needs lot of practice and patience. For a beginner, understanding the fluid dynamics in phaco is perhaps the most important aspect of this extremely complex surgery. Good hand–eye coordination under the operative microscope and foot switch control of the phaco machine are of utmost importance to get the best results. The need for a tunnel incision, good rhexis, and hydrodissection cannot be overemphasized. Using good fluidics and stabilizing the anterior chamber involve a simple balance between inflow from the phaco sleeve and outflow from the phaco tip and the side port and main port. Maintaining good bottle height and adequate aspiration flow rate help to achieve good fluid dynamics. Keeping a stable AC helps in preventing complications such as endothelial damage, posterior capsule rupture, wound burn and damage to non-target tissue such as the iris. Choosing the right settings for different grades of cataract is also vital to avoid complications. Using cold phaco technology, it is possible to reduce the insult on non-target tissue such as endothelium. A few important caveats would be to stay in the center of the chamber, avoid pushing the nucleus and applying phaco only after the nucleus occludes the tip. During I&A, aspirate the subincisional cortex first while the chamber is still deep before going all around. Some of the basic steps in phaco can be fine-tuned by watching videos of good surgeries being performed regularly and learning the techniques adapted by the masters until doing phaco becomes second nature. Editors’ note: Dr. Rajan has no financial interests related to his comments. Views from Asia-Pacific