Tunnel-floor entry continuous curvilinear capsulorhexis technique: Rhexis in a controlled and stable anterior chamber always

Abstract

Continuous circular capsulorhexis (CCC) was demonstrated independently by Thomas Neuhann, Kimiya Shimizu, and Howard Gimbel in the 1980s and it finds mention in the landmark paper by Gimbel and Neuhann. The authors describe a technique of achieving the rhexis in a stable, viscoelastic-filled anterior chamber using the tunnel floor as the entry. This gets covered by the roof of the tunnel postoperatively and, therefore, does not leak. There is no oar-locking or striae even when cystitome goes beyond the edge of the tunnel. As there is no escape of the viscoelastic substance, there is no change in the pressure or shallowing of the anterior chamber. It is a useful technique for beginners. It is of great help in difficult cases like intumescent cataracts, shallow anterior chambers, hyperopes, nanophthalmos, pseudoexfoliation, small non-dilating pupils, intraoperative floppy iris syndrome (IFIS), and phacomorphic glaucoma.

Thomas Neuhann and Howard Gimbel published their paper on continuous circular capsulorhexis (CCC) in 1990.[1] The technique developed at different places in the 1980s. Inspired by Dr. James Gills, Dr. Howard Gimbel completed curvilinear capsular tear in 1983 in North America. His technique began the capsule tear around the 12 o’clock area. Then it extended continuously over the whole anterior capsule, naming it continuous tear capsulotomy. Thomas Neuhann, in Europe, created a smooth, circular capsular opening using his capsulorhexis technique (rhexis meaning to tear in Greek) in 1985. Kimiya Shimizu in Japan described his technique called circular capsulectomy in January 1987.[1,2] Finally the three contributors gave it a complete descriptive name from continuous tear capsulotomy by Gimbel, circular capsulectomy by Shimizu, and capsulorhexis by Neuhann and called it continuous circular capsulorhexis (CCC). CCC evolved to become continuous curvilinear capsulorhexis. It reduces tearing of the rim of the anterior capsule (AC) as the rhexis margins are much stronger and elastic. The elastic and stretchable rim gives a continuous opening with more smooth edges.[3] CCC keeps the intraocular lens (IOL) in the correct position by overlapping of anterior capsule over the optic, thereby making effective lens position (ELP) more predictable.[4,5] Reduced incidence of posterior capsular opacification (PCO), tilting, and decentration are other benefits of the technique.[4,5,6]

The authors describe a technique of continuous curvilinear capsulorhexis which can be done in difficult cases like intumescent cataracts, shallow anterior chambers, hyperopes, nanophthalmos, pseudoexfoliation, small non-dilating pupils, intraoperative floppy iris syndrome (IFIS), phacomorphic glaucoma, etc., It can also be used by beginners with immense success as the shallowing of the anterior chamber is prevented and the vector forces work in the most optimal way. The limbus is a reference for the cystitome to enter the anterior chamber and guide the capsulorhexis. Many surgeons do their rhexis through the side port and others do it through the main tunnel. The leaking of the viscoelastic agent out of the incision makes the process challenging for the beginner surgeon and also in cases where the anterior chamber is shallow or the capsular bag is tense. In such eyes, it becomes challenging to get a good side port entry.

Surgical Technique

In this technique, the 26-G needle is bent into a cystotome with a 45° bend. Conventionally, the needle tip is bent to 90°. As the needle tip has to perforate the floor of the tunnel at the limbus, it needs to be very sharp, and should not have touched any surface, including the needle holder or the plastic sleeve it comes in. As the routine cataract set does not have a needle holder in our setup, the technician bends the tip of a 26-G needle away from the bevel, reinserts it into the plastic sleeve, and autoclaves it along with the rest of the instrument set. The main tunnel is created using a 2.8 mm keratome, entering through the conjunctiva and anterior sclera about 1 mm behind the limbus, and advanced forwards across the limbus into the cornea for about 1 mm. The meridian is generally at the temporal sclerocornea, and the actual entry location is modified depending on the steep axis and presence of prominent vessels or pinguecula. The capsule is stained with trypan blue under-air staining, if required, and then the viscoelastic is injected into the anterior chamber to replace the aqueous or the stain. The bent needle cystitome is positioned so that the bent tip is directed toward the left, so that the tip would not drag on the floor of the tunnel. It is now advanced through the tunnel up to the beginning of limbus, and at posterior limbus the cystitome is axially rotated so that the tip faces down. With an anterior and downwards movement, the tip punctures the floor of the tunnel to gain needle cystotome entry into the anterior chamber as shown in Fig. 1. One must ensure that the floor of the tunnel is not pressed down, lest the visco leak out of the anterior chamber. The 45° bend instead of 90° bend of the tip gives the right vector force to move the cystotome forward, as well as, downwards without losing the anterior chamber as shown in Figs. 2 and 3. The entry through the floor of the tunnel should be quick and perpendicular instead of creating another tunnel that hinders the movement of the cystotome in the anterior chamber. As this entry through the floor is within the tunnel and is covered by the roof of the tunnel at the end of surgery, it will not leak postoperatively as shown in in Fig.4 and the videos of the technique Videos 1-4. Then the rhexis is made by starting with a small flap tear in the center as shown in the figure. The tear is converted into a flap which is rotated by shearing to complete the rhexis. The capsulorhexis trajectory depends on the balance of the tearing force along the tangent of the circle and the other is the pulling force perpendicular to the tangent towards the center of the circle. When the two forces are balanced, the trajectory proceeds curvilinear as planned and completes capsulorhexis successfully. If the tearing force along the circle tangent is larger, then the trajectory of the capsulorhexis shifts laterally resulting in a tear running off. With a larger pulling force, the trajectory of capsulorhexis deviates toward the center leading to a very small capsulorhexis opening. These two opposing forces are also determined by the depth of anterior chamber. If the cystotome pushes the lens backwards, or due to leaking of visco the chamber shallows, there will be an imbalance between centrifugal and centripetal forces, and the rhexis can run to the periphery or inwards. The position of the lens zonular complex is influenced by the presence of viscoelastic in the anterior chamber. The controlled rhexis requires a stable anterior chamber depth. However, this may not be achieved due to a variety of reasons like leakage of viscoelastic through the incision, ore-locking caused by the cystotome hitting the side wall of the tunnel, a long and anterior tunnel which makes the cystotome press the floor of the tunnel downwards allowing the visco to leak out, increased intraocular pressure (IOP), too shallow or deep anterior chambers, etc. A uniform and deep anterior chamber throughout is essential for a good rhexis. Several procedures are deployed to achieve this, like smaller initial side port for the cystotome or capsulorhexis micro-forceps. Increased pressure with viscoelasic makes the anterior chamber deep, and cystotome entry needs to be obliquely down. Also, as the cystotome or micro-forceps enters the anterior chamber centrally, the corneal striae may be formed when the shaft hits the side wall, obscuring the view. This is especially true when the rhexis is performed through the main tunnel, which is quite anterior as against the side port. These issues are completely overcome by the use of this tunnel-floor entry technique. A skilled surgeon can complete the capsulotomy in 3 to 4 regrasps but a beginner would be better off with a larger number of regrasps. This technique can be adapted to anterior limbal or posterior limbal or clear corneal tunnels as well. However, the conjunctival hood will be missing, and at the end or surgery proper stromal hydration and tunnel closure needs to be verified.

Figure 1.

(a) 2.8 mm Keratome entering through conjunctiva, sclera, limbus & cornea (b) HPMC visco is infused into the anterior chamber and Aqueous is let out. Anterior chamber is minimally deepened & the introaocular pressure is slightly above normal (c) 26 G Cystitome with its tip bent to 45 degrees enters anterior chamber at limbus, by perforating the floor of the tunnel (d) Note the pinpoint entry of Cystitome is at limbus and the tunnel remains closed, trapping visco inside AC (e) Rhexis in progress. Note the anterior chamber remains formed (f) Note that there are no striae in the cornea, and visibility is good throughout

Figure 2.

No oar-locking or striae even when cystitome goes beyond the edge of tunnel

Figure 3.

Cystitome 26-G needle. 1/3 to 1/2 of bevel portion is bent to 45°. Tip is not to be touched! Needle is bent at hub by 45°

Figure 4.

Schematic diagram of the technique. (a) External incision and partial thickness scleral tunnel dissected. (b) Internal lip of the tunnel opened. (c) Viscoelastic injected. (d) Cystitome entry from the bed of the tunnel into the pressurized anterior chamber. (e) Capsulorhexis. (f) Tunnel architecture explained. W- Internal incision. X- External groove. Y- Tunnel made by partial thickness scleral dissection. X- Entry track of the bent needle cystitome through the floor of the scleral tunnel. It gets covered by the tunnel roof after surgery and does not leak

This technique is of immense help in white intumescent cataracts with tense bags, and the incidence of Argentinian flag sign is reduced. Hypermature cataracts can be dealt with using this technique by a single-step rhexis when intracapsular pressure is not high. The mild pressure is withheld in the bag by visco pressure in the anterior chamber. In a very tense bag with convex anterior bulge, a two-step capsulorhexis with a smaller one created first is preferred. The anterior cortex and milk are aspirated and the nucleus is rotated to release the equatorial cortex before performing the second rhexis. The main benefit is that the depth and pressure environment in the anterior camber remains stable. While in an uncomplicated cataract, the anterior chamber depth can be minimally deeper than the normal with an IOP at about 25 mmHg, in a complex cataract, a relatively high unchanging pressure prevents the sudden egress of high intra-lenticular pressure. This sudden egress can be one of the causes for the tear to run out to the periphery. In small pupil and pseudoexfoliation, this technique helps as there is no change in the depth of the anterior camber or resultant stretch on the zonules.

Conclusion

Rhexis performed with a modified cystitome through tunnel floor is a valid, repeatable method of achieving stable anterior chamber and controlled rhexis with very small learning curve. It can universally achieve good well centered capsulorhexis in all the surgeries, and is of invaluable use in various complex cataract presentations.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.