Nonchopping phacoemulsification techniques, also known as nuclear- fracturing techniques, have facilitated cataract surgery immensely, allowing for safer and more efficient means of nucleus removal. The fundamental principle underlying all nuclear-fracturing techniques is the creation of “breaks” to divide the lens into smaller fragments for controlled removal through a small incision.
Gimbel was the first to propose a structured approach with the “divide- and-conquer” nucleofractis phaco technique This method involves the creation of 2 deep grooves in the nucleus that intersect centrally and are then cracked into 4 quadrants. These smaller sections of lens can be brought away from the capsule into a “safe zone” for emulsification and removal. Other interesting fracturing techniques include chip and flip, down slope sculpting, and phaco sweep. By using these methods, phacoemulsification can be performed safely and successfully on nearly all types of cataracts.
II. KEY POINTS IN DIVIDE-AND-CONQUER TECHNIQUE
A. Phaco Settings
The initial nuclear groove formation requires the use of a moderate degree of phaco energy with low aspiration and vacuum settings. Quadrant removal requires higher aspiration and vacuum settings to allow the phaco tip to engage the lens fragments. (The surgeon should always confirm the settings prior to entering the eye.)
B. Grooving Technique
Goal: Deep sculpting to facilitate cracking
The goal is to create a sulcus that is 90% of the depth of the lens. The sulcus depth is the most important aspect for facilitating a complete crack at the base of the lens. Groove length is not as important and should not extend into the far lens periphery. A good rule of thumb is to limit the length of the groove to the length of the capsulorrhexis.
C. Cracking Technique and Bisection of the Two Halves
Goal: Nucleofractis of the nuclear plate and rim and the remaining nuclear material
It is important to achieve a complete separation of the posterior nucleus. A complete crack of the periphery is not as important (leaving a portion of the cortex and epinucleus intact is not problematic). The phaco tip and second instrument must be positioned deep in the groove, and the second instrument is rotated to simulate a paddle-like movement while the phaco tip is moved in the opposite direction to create a crack. The grooving of the 2 halves requires a motion that is more posterior to anterior in nature. Far peripheral grooves are not necessary. Cracking of the posterior aspect of the lens is more important than cracking the periphery.
D. Quadrant Removal
Goal: Rotation, reposition, and removal of nucleus
Engage the quadrants in the region of the nucleus (the middle portion of the cataract). Occlude the tip and pull the fragment centrally. Once the phaco tip and nuclear fragment are positioned centrally and at the level of the iris, the quadrant can be safely removed.
III. PHACO SETTINGS
Creation of the initial sulcus is best achieved using a moderate degree of phacoemulsification energy with low aspiration and vacuum settings. The nucleus should not move during the sculpting phase. If it does, more power is needed to smoothly groove the nucleus. This includes not completely occluding the phaco tip while grooving. Become familiar with the type of machine that is used in your operating room. The most commonly used machines are those that are based on peristaltic technology, and the typical settings for initial grooving with these machines are a phaco power setting of 20% to 60%, vacuum of 60 mm Hg, and aspiration setting of 25 to 30 mm Hg. There is no aspiration action with Venturi-based machines, and phaco power setting of 20% to 60% and vacuum of 150 mm Hg. These settings prevent the phaco tip from engaging the lens material with significant vacuum, thus allowing the phaco tip to move smoothly through the groove without causing significant lens movement.
Typical settings for quadrant removal are phaco power setting of 20% to 60%, vacuum of 350 mm Hg, and aspiration of 25 mm Hg for the peristaltic machines and phaco power setting of 20% to 60% and vacuum of 350 mm Hg for Venturi-based machines. The phaco power can be increased or decreased depending on the ease of cutting. Phaco power greater than 60% is only rarely required and should be used only no significant motion by the most experienced surgeons and only when absolutely necessary. Vacuum settings for the divide-and-conquer technique are generally lower than for chopping tech- niques because the desired effect in the former is to engage the fragments and draw them into a central location where they can be safely phacoemulsified.
IV. GROOVING TECHNIQUE
In creating the initial lens sulcus, the depth of the groove is of the utmost importance because this will allow the surgeon to ideally position the phaco tip and second instrument to crack the base of the lens. In general, the groove does not need to extend into the periphery, maintaining the peripheral rim keeps the bag distended and the posterior capsule on stretch. A useful guide is to use the extent of the capsulorrhexis to gauge the length of the groove.
The sweeping arcuate movement of grooving should simulate the posterior curvature of the nucleus. Familiarity with the dimensions of the lens will provide the surgeon with a level of confidence that the posterior capsule is not at risk during this phase of the case. The average lens has a diameter of 9 mm and a thickness of 4.5 mm centrally. The rationale for limiting the length of the initial groove is that the lens thickness and the proximity of the posterior capsule decrease in the periphery. How do these dimensions compare to the length of the phaco tip? A useful guideline is to create a groove that is 1.5 phaco tips wide and 3 deep. The standard phaco tip is 1.2 mm in diameter, thus yielding a groove that is 1.8 mm × 3.6 mm centrally. In making smooth passes, there should be no ridges or step-offs in the groove. Widening the groove to 1.5 times the width of the thinner portion of the phaco tip will create adequate space to accommodate the phaco tip and second instrument for cracking. The goal of grooving should be to achieve 90% depth centrally with a length of approximately 6 mm (Figure 13-1). The power should be adjusted so that the nucleus is being sculpted and not rocked. There can be significant nuclear movement during the grooving step.
In soft lenses, the Y sign can be used to indicate that the groove is of adequate depth and that the nucleus is ready to be cracked. The Y sign has been described by Kurian et al and is used to describe the posterior embryonal Y suture that can be visualized at the center of the trench and can be used as an endpoint for grooving.
*Dikutip dari Buku Essentials Of Cataract Surgery 2nd Ed, halaman 125-128