Ultrasonic cataract aspiration is a surgical procedure that applies an ultrasonic emulsifier to crush and aspirate cataracts through a tiny incision. This procedure has the advantages of small incision, short time, light postoperative reaction and fast recovery of vision, and is currently recognized as the most advanced surgical method for cataract treatment.
The principle of ultrasonic emulsion cataract aspiration is to enter the eye through an incision in the cornea or sclera by means of an ultrasonic emulsion handle. The ultrasonic needle at its front end generates ultrasonic energy in the operated eye to crush the lens into an emulsion and aspirates the emulsified lens tissue with the help of a perfusion suction system that can maintain a constant fluid flow in the eye.
Before performing ultrasonic cataract aspiration, a thorough evaluation of the patient is required. It mainly includes: ①Evaluation of the timing of surgery: Surgery can be considered when the patient’s corrected visual acuity is below 0.3 or when the cataract significantly affects the patient’s life and work. ②Evaluation of surgical difficulty: Pre-operative examination of the patient to understand the type of cataract clouding and nuclear hardness, lens capsule integrity, pupil dilatability, corneal transparency and anterior chamber depth. The examination includes: visual acuity, slit lamp and fundoscopy, intraocular pressure measurement, corneal endothelial cell examination, and IOL determination. In addition, systemic diseases that cause surgical risk should be excluded. Evaluation of postoperative results: Other eye diseases affecting the recovery of postoperative visual function should be excluded, with the help of some special tests, such as laser retinal visual acuity, ultrasound examination, retinal current map (ERG), visual cortex evoked potential (VEP), laser retinal visual acuity, optical coherence tomography (OCT), etc.
Preparation of surgical items: The ultrasound emulsifier is the most important equipment to complete the ultrasound emulsification procedure. Surgical consumables include perfusion solution (balanced salt solution), viscoelastic and IOL. Auxiliary instruments include incisional constructing knife, tearing capsule forceps or needle, and nucleus splitter, etc.
Surgical procedure: First, the appropriate type of anesthesia will be selected preoperatively based on the patient’s specific situation. For most patients, surface anesthesia of the cornea, i.e., eye drops, is usually used. For complex cases and patients undergoing combined surgery, local anesthesia, i.e., by injection, may be used. General anesthesia, on the other hand, is indicated for children, psychiatric patients, and other patients who are less cooperative in surgery. Once the preoperative preparation is done, the surgery actually begins. The first step is to create the incision, usually using a scleral tunnel or clear corneal tunnel incision, made with a 3.0 mm tunneling knife. The second step is the avulsion of the capsule, using an avulsion needle or avulsion forceps to create a continuous circular avulsion opening with smooth edges of 5.0-5.5 mm in diameter right in the anterior lens capsule. The third step is the aqueous separation and aqueous layer. The aqueous separation is to separate the cortex from the capsule membrane. The aqueous separation layer is to separate the dense inner core of the lens from its outer superficial nucleus. The fourth step is ultrasonic emulsification, the central part of the entire procedure, which can be accomplished using various ultrasonic emulsion nucleus fragmentation techniques or splitting techniques with combined adjunctive instruments. The fifth step is cortical removal, which involves aspiration of the free cortex, followed by removal of the cortex adhering to the capsule membrane, and then polishing of the anterior and posterior capsule membranes to remove residual cortex and epithelium. In the sixth step incision closure, due to the self-closing nature of the small tunneling incision, it is sufficient to close the incision at the end of the intraocular operation by injecting water at the main incision with balanced salt solution. However, the following cases require suture closure of the incision: (i) obvious incision burn; (ii) edematous incision still not self-closing; (iii) infant or pediatric patients; and (iv) psychiatric or poorly cooperating patients. The sutures are usually removed 2-6 weeks after surgery.
Generally, IOL implantation is performed at the same time as cataract ultrasound emulsion aspiration. After preoperative IOL determination, an IOL of the appropriate degree is selected according to the patient’s specific situation and is performed after cortical and epithelial cell removal is completed.