EyeWorld Asia-Pacific March 2011 Issue

27 EW CATARACT/IOL March 2011 Navigating a rocky road by Abhay R. Vasavada, MD, FRCS Founder and director of Iladevi Cataract and IOL Research Center in Ahmedabad explains how he deals with hard cataracts W hen a patient comes to me with a hard cataract, I check the corneal health with specular microscopy and corneal thickness measurements. The hard cataract can contribute to the vulnerability of the cornea and the corneal clarity, thus the health of the eye must be established prior to surgery. The second thing I would check is the anterior chamber depth because it is within this pre-op space that I’m going to perform the lens removal in. If it is shallow, it could affect the cornea or the pupil and produce trabeculitis, thereby increasing intraocular pressure during surgery. Finally, I recommend getting a B-scan that will tell me if there is any vitreous opacification and if the retina is attached because it is not easy to visualize the retina through the dense cataract. The surgery During the surgery, I keep injecting a dispersive OVD such as Viscoat (sodium chondroitin sulfate, sodium hyaluronate, Alcon, Fort Worth, Texas, USA/ Hünenberg, Switzerland) inside the eye to protect the corneal endothelium. I then stain the endocapsule with Trypan Blue (figure 1) to make it more visible because the density of the cataract makes the red glow against which we perform the capsulorhexis is minimal or practically non-existent. I do a slightly larger rhexis than usual. A normal rhexis is about 4.5 mm; here I would go for 5.5 mm and then I would be careful in performing the hydrodissection. Normally, hydrodissection is routine in phacoemulsification in that we inject fluid that goes in the space between the posterior capsule and the cataract. However, with a very large and bulky cataract, the capsular bag is fully occupied, and if I inject excessive fluid, it can rupture the posterior capsule. So I will either not perform the hydrodissection at all or perform it very cautiously with a tiny amount of fluid. My strategy for lens disassembly takes place in three stages. The first stage of the lens removal is creating the space; that means I need to do some sculpting. The second stage is the division stage where I’ll completely divide the entire cataract into small segments. Having completed this division process, I will then proceed to the next stage, removal of the segments. Each of these three stages will have different parameter settings on the machine because their objectives are different. During the sculpting stage I do not need a very long tunnel but I do need a deep tunnel. The deeper it is, the easier it is for the second stage of division (figure 2). To achieve a good depth, the Kelman phaco tip is very useful. I recommend the 45-degree bevel phaco tip. It is a longer bevel, like a shovel, and can sculpt more effectively. In the second stage of division, the objective is to produce small fragments (figure 3a), so I use a technique I developed, which I call a step-by-step chop in situ and lateral separation. It combines two basic principles of division: the chop principle and the lateral separation principle. It is otherwise very stressful to the capsular bag and zonules. However, sometimes even with this technique, the division is not complete, and accomplishing this is critical. I have therefore devised a new technique in the last two years. It is a multi-level chop technique (figure 3b), where division is initiated at different levels. I initiate the division at the superficial lens, then remove that vacuum hold and apply the vacuum hold again posteriorly at deeper levels. During removal, I am very conscious that I do this away from the corneal endothelium so I try to confine the procedure to the posterior plane, either at the iris plane or behind the iris posterior. All of these processes require keeping the parameters low and making it very safe for the cornea and the posterior capsule. Surgeons should be careful not to use a very high aspiration flow rates, particularly in cases with dense cataracts. The capsular bags are very thin and have been overstretched by the bulk of the cataract and are therefore vulnerable to ruptures. Typically, before I begin each stage, I inject Viscoat so that there is additional continuous protection to the cornea throughout the procedure (figure 4). Until recently, all the machines we have had used longitudinal ultrasound technology, but with the development of torsional technology, low parameters have become very effective. With its low parameters, the torsional OZil (Alcon) is a great tool in dense cataracts in all three phases of sculpting, division, and removal. There is also improved cutting ability during the sculpting phase with its non-stop, left, right, left cutting. With the combination of Viscoat, OZil, and the step-by- step and multi-level chopping techniques, clear corneas have now become routine in dense cataract cases, which is the first requirement for enjoying premium IOLs like toric and multifocal IOLs. EW Editors’ note: Dr. Vasavada has not indicated any financial interests related to his comments. Contact information Vasavada: +91-79-27492303, icirc@abhayvasavada.com Figure 1. Trypan blue staining enhances anterior capsule visualization Source: Alcon Figure 2. A deep central trench is essential for dense cataract emulsification Figure 3a. In situ chop & lateral separation technique Figure 3b. Phaco tip is embedded at multiple levels to create multiple nuclear fragments Figure 4. Dispersive OVD injected during nuclear fragment removal protects endothelium Source: Abhay Vasavada, MD, FRCS