Ординатура / Офтальмология / Английские материалы / Master's Guide to Manual Small Incision Cataract Surgery (MSICS)_Garg_2009

13.Lesiewska-Junk H, Malukiewiez-Wisniewska G. Late results of endothelial cell loss after cataract surgery. Klein Oezna 2002;104(5-6):374-6.

14.Phallip C, Ronald Laing, Richard Yee. Specular microscopy. In: Kracheu, Mamis, Holland, (Eds): The Cornea, 2nd edn, Mosby; 2005;261-81.

15.Quintana MC. Manual small incision ecce with nylon loop phakosection and fodable iol implantation. In:

Francisco J Gutierrez-carmona (Ed). Phaco Without Phaco, 1st edn 2005;310-8.

16.Yao K. Small incision extracapsular cataract extraction with a manual nuclear division technique and intraocular lens implantation. Chung Hun Yen Ko Tra Chin 1994;30:164-5.

INTRODUCTION

Now several years into the 21st century, the vast majority of cataract surgery is performed by phacoemulsification. However, there are numerous times in advanced centers when, for any number of reasons, ultrasound cannot be used (malfunction) and even more likely there are facilities where this technology is simply not available. For whatever reason, it is advantageous to have an alternative small incision technique at ones disposal. The ability to perform manual small incision sutureless cataract surgery is a great benefit. This alternative manual small incision pathway has been available for over two decades. Phacosection is a viscoelastic dependant technique that can be performed safely with the proper utilization of viscoelastics. Phacosection (manual fragmentation) has proven to be a safe, reliable small incision sutureless technique which allows excellent astigmatism control and rapid recovery similar to phacoemulsification. A well done, well healed phacosection procedure will be difficult to if not impossible to distinguish from a similarly well healed phacoemulsification procedure.

I started to develop a manual small incision technique in the early ‘80’s as an alternative to phacoemulsification with which I was struggling to master. The first renditions were with 7.0 to 7.5 mm incisions (superior scleral tunnels after Kratz) combined with fragmenting the nucleus into two pieces (nucleus bisection). These incisions were usually closed with one or two sutures. Encouraged by the good results, I went on to develop the instruments to fragment the nucleus into three pieces thus allowing the incision to be

Peter G Kansas (USA)

predictably 6 mm. During this period, one piece and three piece 6 mm PMMA IOLs were available.

When McPherson described his 6 mm superior sutureless scleral tunnel technique in 1990, I quickly made the necessary dissection adjustment to combine this wound architectural advance with the Kansas manual small incision cataract extraction technique.

INCISION

The Basics of Incision Construction

The incisional technique employed will have a profound affect on intraoperative wound behavior, selfsealing predictability and postoperative astigmatism stability. A superior incision will tend to reduce the vertical meridian curvature and a temporal incision will reduce the horizontal meridian curvature. Radial sutures will have the opposite effect, i.e. steepening the meridians in which they are placed. (To minimize sutural effect, very shallow bites should be taken or horizontal sutures utilized).

The maximum flexibility in incision construction is achieved by working superiorly. A frown type incisional configuration is placed 1.5 to 2.0 mm behind the corneal-conjunctival border. The frown configuration brings each end of the incision further from the limbus thus enlarging the lamellar intrascleral interface area. The greater the interface area, the greater the postoperative wound stability. Therefore, if a wider tunnel is needed, then a compensating adjustment can be performed for astigmatism control by bringing the groove further posterior. Koch’s rule (Figures 9.1 and 9.2). The incision width can be decreased over time as

Figure 9.5A: Keratome dimple down

intraoperative anterior chamber stability as well as postoperative wound stability. A vitally important point (Figures 9.5 and 9.6). The internal entry into the anterior chamber is made slightly larger (wider) than the external groove. The resultant tunnel profile is trapezoidal. The internal widening is accomplished by cutting on the IN stroke. A sawing type motion is to be avoided. Another important caveat, if the nucleus is expected to be larger, as in an elderly patient with dark brunescent nucleus, the nucleus has not only a longer diameter but is also thicker. So the cross-section volume of the tunnel most be larger. The 6 mm tunnel needs to be wider, sometimes vary much larger, up to 8 mm. In the presents of Fuchs corneal dystrophy, the tunnel always needs to be wider (6 to 7 mm is the safest). A wider tunnel tends to be more predictable since it will offer less resistance to fragment extraction, thus less trauma.

After the anterior chamber is entered, the anterior chamber is stabilized with 2% methylcellulose or a viscoelastic of the surgeons choice. A lateral and nasal paracentesis are created with a 15 degree blade (Figure 9.7). These openings are 1.75 mm and are self-sealing and astigmatism neutral. These paracentesis will allow 360 degree access to the anterior chamber thus providing better anterior chamber stability during I/A of the anterior and posterior epinucleus.

ANTERIOR CAPSULOTOMY

Following anterior chamber entry, the anterior chamber is stabilized with a viscoelastic. Although any visco-

Figure 9.5B: AC clear corneal entry

Figure 9.5C: Kuglen hook

Figure 9.6: Enlarging internal opening

elastic will do, 2% methylcellulose is adequate for the capsulotomy since it will get washed out during the next step (hydrodissection). I prefer doing the capsulotomy with a bent 22 g needle and a straight shaft. I feel I have maximum control as compared to the popular capsulorhexis forceps (Figures 9.8 and 9.9A, B]. There are any number of patterns that are possible but the important point is the size of the opening. If it is too small, it will promote capsulophimosis. There is absolutely no advantage to a small capsulotomy. It is

Figure 9.7: Nasal and temporal paracentesis with a 15 degree blade

Figure 9.8: Capsulorhexis with bent 2 gauge needle

Figure 9.9A: Start rhexis

Figure 9.9B: End capsulorhexis

an unwanted side affect of capsulorhexis forceps usage. Since today’s typical IOL diameter is 6 mm, a 5 mm rhexis opening is probably best. This size allows shrink wrapping of the IOL edge and helps retard posterior capsule opacification.

Another important consideration in regards to the capsulotomy size is that the delineated nucleus needs to be prolapsed through the capsulotomy and if it is too small it may tear the capsulotomy edge and disrupt the posterior capsule. Of course it is self-evident that avoiding the anterior zonular insertions while performing capsulorhexis is also important.

HYDRODISSECTION

Because of its simplicity, this is one of the more elegant steps in cataract surgery. A 27 g cannula on a 5 cc syringe is positioned well under anterior capsulotomy edge at 6 o’clock as BSS is injected (Figure 9.10). This dissects the posterior cortex and posterior epinucleus from the posterior capsule. This is followed by injecting into the more central anterior epinucleus for further delamination. Usually this can be repeated so that an onion skin affect is accomplished. The final hydrodissection step is nucleus delineation by simply injecting as centrally as possible to delineate the smallest diameter nucleus possible. Occasionally, a brightly illuminated ring or corona around the delineated nucleus is experienced (Figure 9.10A).

ANTERIOR CORTEX/EPINUCLEUS REMOVAL

The rational for removal the anterior epinucleus at this point is to maximize visualization of the delineated nucleus. Visualization is greatly enhanced and greatly

Figure 9.10A: Subcapsular cleavage

Figure 9.10B: Cornea

facilitates nucleus prolapse. Nucleus prolapse is an important precursor to nucleus fragmentation.

The anterior cortex and epinucleus is removed using a Kansas I/A handpiece which has a Simco type double barrel configuration with a 0.4 mm aspirating end opening on one cannula and an irrigating beveled opening on the other cannula (Figures 9.11 and 9.12). This handpiece fits snugly through the 1.75 mm paracentesis and provides a stable anterior chamber. I emphasize that the aspirating opening needs to be at least 0.4 mm and no smaller. This size allows good aspiration of both epinucleus and cortex.

Figure 9.11: Anterior epinucleus aspiration

Figure 9.12: Kansas- I and A handpiece

Incidentally, this 0.4 mm end opening aspirating port works well with soft cataracts where ultrasound is not needed.

NUCLEUS PROLAPSE

Following the completion of epinucleus removal, the anterior chamber is stabilized with a visco dispersive viscoelastic such as Viscoate, Discovisc, Amvisc plus or a thick viscocohesive as Healon 5.

Using two blunt modified Kuglen hooks (Kansas), the nucleus is displaced inferiorly with one hook until cleavage along the edge of the superior pole is visualized (Figures 9.13A to C). The second Kuglen hook is inserted into the cleavage, then gently sliding it posteriorly behind the nucleus. As the nucleus becomes lose from the posterior epinucleus, the two hooks are repositioned to alternately rotate the nucleus anteriorly. If the anterior chamber shallows before the nucleus is in the pupillary plane, the hooks are withdrawn and viscoelastic is injected behind the nucleus to complete

Figure 9.13B: Prolapsing into anterior chamber

the prolapse followed by injecting in front of the nucleus to deepen and stabilize the anterior chamber.

PHACOSECTION

At this critical junction, it is important for the anterior chamber to be stabilized to its maximum depth with a viscodispersive viscoelastic. Now, through the scleral

Figure 9.14: Trisector positioned on anterior face of nucleus

tunnel, the trisector is positioned first on the anterior surface of the nucleus (Figure 9.14). Placing the trisector first, prevents the nucleus from being displaced toward the endothelium when positioning the vectis (cutting board) behind the nucleus. Now the vectis is insinuated behind the nucleus while keeping the trisector stable and not letting the nucleus drift upward toward the posterior corneal surface (Figures 9.15A and B). The trisector is pressed through the nucleus while the posteriorly positioned vectis supports the nucleus thus accomplishing the fragmentation of the nucleus into

Figure 9.15A: Kansas vectis (cutting board)

Figure 9.15B: Vectis behind nucleus

three pieces (Figures 9.16A and B). The middle fragment usually remains captured in the trisector and both are withdrawn together (Figure 9.17). If it starts to float toward the endothelium, the vectis is removed and viscoelastic is injected anterior to the 1st fragment to avoid endothelial touch. After the fragment is stabilized, it can be removed with a Kansas fragment forceps that has been especially design for this task (these forceps have 8 mm tynes lined with two rows of teeth on each tyne).

Now that fragment one has been taken care of, fragments two and three remain to be removed. The anterior chamber is deepened with more viscoelastic. Fragment 2 is grasped by the fragment forceps (Kansas) (Figures 9.18 and 9.19). A little lift of the superior tunnel roof with a fine toothed forceps is usually helpful while extricating fragments. As the fragments are extracted through the scleral tunnel, very light posterior pressure on the back wall of the tunnel will facilitate fragment removal. Finally fragment 3 is removed after the anterior chamber is redeepened with viscoelastic (Figures 9.20A and B). If the remaining fragments or fragment seem too large for the width of the existing tunnel, then the fragments can be further subdivided

Figure 9.16A: Kansas fragment forceps

Figure 9.16B: Trisection completed with middle fragment ensnared

Figure 9.17: Removing trisector with fragment #1

Figure 9.18: Forceps removal fragment #2

Figure 9.19: Removal fragment 2

using the bisector (Kansas). In fact, the total fragmentation can be performed with the bisector but that necessitates more passes.

Sectioning with the bisector requires similar maneuvers as used with the trisector. In fact, the surgeon may opt for any number of reasons to just bisect the nucleus from the beginning but this requires a 6 to 7 mm tunnel. The wider tunnel still allows stable self sealing but it most likely will induce some degree of against the rule astigmatic change. A 6 or 7 mm tunnel may trigger one to one and half diopters of astigmatic change. The wider tunnel can of course still enjoy the advantage of having sutureless architecture. If the surgeon desires to maintain the smallest possible wound then fragmenting

Figure 9.20A: Forceps removal fragment #3

Figure 9.20B: Fragment 3 removal

with the bisector requires multiple steps, multiple fragmentations. Frequent replenishment of viscoelastic will be likely. Fragmenting can start from the center and work out or start on the end and fragment sequentially toward the center from left to right or right to left (similar to bread slicing).

Bisection combined with a 7 mm tunnel allows successful cataract removal in a Fuchs patient with a low cell count and still retain a clear cornea. Because phacosection is primarily is a viscodependent proce-