Performing MIVS in Eyes With a Fragile Ocular Surface
The latest instrumentation makes these procedures viable.
BY JAVIER ELIZALDE, MD
Since it is more comfortable for my patients, I prefer to use microincisional vitrectomy surgery (MIVS) instead of 20-g surgery whenever possible. However, in eyes with a fragile ocular surface, MIVS can be challenging. The force required to insert 23-g microcannulas in one step can increase the risk of perforation or reopening a freshly sutured incision in eyes that recently have undergone an anterior segment procedure, such as cataract surgery or keratoplasty, or have staphylomas or scleral thinning.
The amount of force required depends on intraocular pressure and surgeon expertise. It also depends on instrument design and quality, including the sharpness of the trocar blade, the shape and type of needle the system employs. Three 23-g systems for inserting microcannulas in one step are available in Spain (Alcon, DORC and Synergetics). Although the external diameters of the instruments presumably are the same in all of the systems (0.7 mm), their tip designs and geometries differ, making the ease of introducing them through the pars plana different as well.
Fragile Ocular Surfaces
I have tested the Alcon 23-g insertion system in an experimental model and have used it to perform vitrectomy in a series of 283 eyes with a fragile ocular surface. The eyes in the series included 276 with recent cataract surgery, 3 that had undergone penetrating keratoplasty, 3 with keratoprostheses and one with severe anterior uveal ectasia. The force required to insert the microcannulas in this system is low enough that I can use the system's 1-step technique in almost all cases of eyes with a fragile ocular surface. For example, I have been able to successfully use the 1-step cannula insertion technique in eyes with keratoprostheses (Figures 1 and 2).
Figure 1. A 23-gauge 1-step insertion technique and pars plana vitrectomy with the Alcon system were successfully performed in this eye with a temporal keratoprosthesis.
Figure 2. These images show endophthalmitis in an eye with a keratoprosthesis after a 23-gauge pars plana vitrectomy with the 1-step insertion technique, performed using Alcon instruments.
Insertion Technique: 1 Step or 2
While a 23-g 1-step microcannula insertion technique using the Alcon system is suitable for most eyes with a fragile ocular surface, you can choose a 2-step technique, as described by Eckardt,1 in cases where the risk of force-related complications is high. With this technique, incisions are made with a 23-g microvitreoretinal (MVR) blade before the cannulas are placed using a blunt inserter. One of the cases in my series, for example, involved an eye with late onset acute endophthalmitis and severe anterior multifocal uveal ectasia. Because I was concerned that the forces required to introduce the microcannulas in a 1-step approach could have perforated the eye, I used a 2-step approach before completing the 23-g vitrectomy.
Improved Instruments Foster Success
The design, geometry and sharpness of MIVS instruments have improved so that small-gauge surgery, including 1-step microcannula insertion, is a viable option in almost all cases, including in those eyes with a fragile ocular surface. In cases where 1-step insertion poses too great a risk, the surgeon can use the 2-step insertion technique and still maintain all of the advantages of a MIVS procedure.
Javier Elizalde, MD, is a member of the faculty, founder and coordinator of the eye oncology unit and coordinator of the vitreous-retina department at the Institut Universitari Barraquer in Barcelona, Spain.
1. Eckardt C. Transconjunctival sutureless 23-gauge vitrectomy. Retina. 2005;25:208–211.