Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001

112 THE ART OF PHACOEMULSIFICATION

Keiki R Mehta

Cyres K Mehta

HYDRODISSECTION

Hydrodissection is the creation of a cleavage plane between the nucleus and the cortex. It can also be defined as the separation, by a fluid dissecting wave, of the nucleus from the external cortex adhering to the capsule. It is important to appreciate that the cleavage plane is not between the capsule and the cortex. If that were so, then there would never be any need to do cortical aspiration. Hydrodissection is a very important step for endocapsular phacoemulsification. Its biggest advantage is that it permits free maneuvers on the nucleus in the bag without, in any way transgressing on the safety of the capsule. It must be clearly noted that effective and safe hydrodissection can only be done after a good rhexis. It is unsafe to do hydrodissection in a can-opener capsulotomy, or if the rhexis has, inadvertently, run away into the periphery. Injecting fluid at this time will cause the tear to spread backwards.

Hydrodissection Technique

The technique involves injecting a small amount of fluid (Ringer lactate or BSS) under the anterior capsule with a fine blunt cannula connected to a 3.00 ml syringe. Because of the fluid pressure and the dissecting ability of the fluid to take the path of least resistance, the fluid separates the cortex and the epinucleus and only partly between the capsule and the cortex. During the hydrodissection, the fluid wave can be seen clearly (unless it is a very hard cataract or an opaque one) to separate the cortex from the nucleus and is indicative of a successful hydrodissection. More hydrodissection is usually carried out in three sites commencing with the 4.00 O’clock position (Fig. 12.1) followed by the 2.00 O’clock position (Fig.12.2) and finally followed

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Fig. 12.1: Hydrodissection at 8 O’clock position Fig. 12.2: Hydrodissection at 2 O’ clock position

by hydrodissection at 8.00 O’clock position. It is important that small aliquots of fluid be utilized, as excess fluid especially in a hard brown cataract is liable to balloon the capsule posterior, rather than spreading as a wave, and may, if more fluidic pressure is applied, rupture the capsule.

It is important to visualize while injecting the fluid diffusion wave. The ideal syringe is a 3.00 ml Luer-Lok, plastic, disposable, Teflon-coated or siliconized. This type of a syringe permits a better control, prevents too much pressure from being applied, the plunger moves very smoothly, and does not stick. Too thin a cannula, (ideal is 24-26 G, flat cannula), even if it is blunt is liable to puncture the capsule if accidentally inserted too far into the periphery. Also a thin cannula permits the fluid to emerge in a sharp jet, at high velocity, which is not required. The one way to be sure the hydrodissection is complete is to check whether the nucleus rotates freely in the bag.

The ideal technique of cannula placement for effective hydrodissection is to place the cannula just within the capsulorrhexis edge, slightly tenting it or lifting it upwards. This technique termed as cortical cleaning hydrodissection was originally conceived by Dr Howard Fine. Injecting the fluid along the rhexis edge permits the fluid wave, literally to shear close to the capsule thus, significantly diminishing the quantum of cortical remnants which will need to be aspirated after the primary nucleus is removed by phacoemulsification.

In all cases hydrodissection should be followed by mechanical rotation (Fig. 12.3) of the nucleus to be sure that the nucleus rotates freely. Rotation confirms that all the adhesions between the epinucleus and the cortex have been broken. It is important to appreciate that if the lens does not rotate freely one must do hydrodissection again, till smooth rotation is achieved.

It is important that after every injection of fluid the lens should be gently pressed backwards. This technique is termed as compression hydrodissection, and works by causing the fluid to disperse and spread out as a flat lamellar zone at the back of the nucleus and thereby enhance the hydrodissection. This technique should be conducted gently following each injection of fluid under the capsular flap. Compression hydrodissection thus, decompresses a filled capsular bag, and at the same time hydrodissects or shears off any adhesions.

114 THE ART OF PHACOEMULSIFICATION

Viscohydrodissection

The parameters change radically when a viscous material (Healon, Provisc, Viscoat or hydroxypropylmethylcellulose–HPMC) is used. Since it takes much more force to inject, one has to be totally sure of the quantity injected; otherwise rupture of the posterior capsule becomes inevitable. In addition, the viscous fluid will force the iris-lens diaphragm forwards, shallowing the anterior chamber, to almost a mere chink. The fluid stays back as it is too viscous to escape from the sides of the 22 G opening normally used for the hydrodissection cannula (Fig. 12.4). Though it is easier to commence, fluid wave is rarely seen unless it is a very immature cataract. In a hydrodissected nucleus with an adequate sized capsulorrhexis, it tends to push the nucleus forwards and prolapse it out of the rhexis opening.

The authors utilize viscodissection only after hydrodissection is complete to rotate the edge of the lens forwards in their technique of vertical phacoemulsification. For safety purposes, viscodissection should only be done after hydrodissection with BSS is complete and it is certain that the lens is freely mobile. Caution would dictate that viscodissection, unless used for a specific purpose, may best be left in abeyance.

HYDRODELINEATION OR HYDRODELAMINATION

Hydrodelineation is the term coined by Anis Aziz to describe the cleavage of lens structures through the injection of fluid. It is also termed hydrodelamination or hydrodemarcation. The technique is fairly simple. A small bore cannula (26–28 G), blunt-tipped, attached to a Luer-lok 1.00 ml plastic syringe, filled with BSS or Ringer lactate, is placed in the middle of the nucleus, and pushed forward into the nucleus till it reaches the middle of the nucleus (in soft cataracts), or meets resistance (medium to hard cataracts).

The point of resistance is where the soft outer nucleus meets the harder central nucleus. At the point of resistance, the cannula is pulled back a fraction of a millimeter, and the fluid is injected. The fluid passes into the body of the cataract, and the dissected plane is usually identified by the appearance of a golden ring around the nucleus. This golden ring may not always be visible nor always clear depending on the density of the cataract. Sometimes only a dark separation plane may be noticed. As with hydrodissection, hydrodelamination must produce a cleavage and

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Figs 12.5 and 6: Hydrodelineation showing golden rings

a good separation of the nucleus from the epinuclear zone. If only a portion of the ring appears (Fig. 12.5 and 12.6), it may be necessary to reintroduce the cannula in a different place and try to inject the fluid again.

It is important to appreciate the differences between hydrodissection and hydrodelamination. Hydrodissection is done to permit phacoemulsification in the bag. If the nucleus did not rotate, it would not be possible to chop a lens, rotate the nucleus for further chopping, and it would also not be possible to allow each sequential piece of the nucleus to be rotated into its best place for removal. None of these techniques could be possible if the nucleus remained adherent to the capsule.

On the other hand, hydrodelamination is performed for safety. Hydrodelamination was a necessary preliminary step in the phacoemulsification technique of four-quarter grooving. It tells the surgeon how far he could groove with ultrasound into the periphery without taking any risks. In addition, hydrodelamination involves separation of the peripheral softer epinucleus from the deeper harder nucleus. Thus, in essence, the harder nucleus sits on a softer epinucleus bed. One can phaco the harder part with impunity knowing that the peripheral softer nucleus acts as a buffer safe zone. To recapitulate, the firm nucleus can be worked on within the softer nucleus of almost rubber-like consistency. This particular technique is especially useful with endocapsular phacoemulsification with nuclear cleavage and with the chip and flip technique.

Decompression of the Capsule Bag

Decompression of the capsule bag means reducing the pressure by allowing the excess fluid to leak out of the sides of the capsular bag and out of the anterior chamber.

If the nucleus is hard, hydrodelamination becomes an impossibility, and there even hydrodissection becomes technically difficult. In a dense nucleus the fluid wave is no longer visible and the fluid injection seems to have no effect. The surgeon is tempted to inject more and more at a higher pressure hoping to get a separation, but what does happen however is that the posterior capsule tents backward and as the pressures increases, the thin capsule gives way, rupturing. It is thus a disaster waiting to happen.

116 THE ART OF PHACOEMULSIFICATION

How does one recognize that this complication is impending? In a soft cataract even a single injection at a single site under the capsule while doing hydrodissection is adequate. However in the case of a hard or a suprahard cataract, it is important to inject at multiple points. This disperses the fluid and gives more sites for the fluid under pressure, to escape. The second important step is to compress on the nucleus, with the heel of the cannula after every injection, which disperses the fluid.

In case the fluid does not come out, two important signs have to be recognized: the chamber shallows very much, and the eye pressure rises sharply. The tendency of the surgeon is to reform the chamber by either injecting a viscoelastic, or still worse, by pressing on the nucleus with a repositor or cannula. Both techniques will lead to a posterior rupture. The correct way of handling this situation is to insert a thin blade iris repository under the edge of the capsule, at 5 O’clock and simply sweep it in both directions. Almost immediately the surgeon will be rewarded with a gush of fluid (which had been entrapped) and the eye immediately softens.

Hydrofracture

It is a technique, which involves possible separation of the lamella of the internal nucleus by a combination of ultrasonic needle penetration and a pressure injection of BSS. This method is known as a hydrosonic technique and was commenced by Dr Anis of USA. It has the advantage that it fragments the nucleus into little fine bits permitting easier phacoemulsification. However, with the advent of chopping technique it is now rarely utilized and is purely of academic interest.

CONCLUSION

Both the techniques of hydrodissection and hydrodelamination have the advantage that they also help the surgeon assess the degree of hardness of the lens and therefore, indirectly assess the quantum of ultrasound time, which would be required. Both techniques are essential and though in standard chopping methods hydrodelamination is not utilized, it still is a useful method especially if one expects difficulties to occur during the surgery. It also has the advantage that if a rhexis has been done a little too small, hydrodemarcation reduces the nucleus into its component parts diminishing the size thus, permitting the hard nucleus to be chopped and removed within the soft epinucleus buffer zone.

FURTHER READING

1.Fine IH: Cortical cleaving hydrodissection. J Cataract Refract Surg 18(5:) 508-12, 1992.

2.Mehta KR, SM Sathe, SD Karyekar: Computer Terminal Usage and Eye Fatigue, Xth Congress APAO. Soc Proc 2:946-48,1985.

3.Mehta KR: Pitfalls encountered in 1500 consecutive posterior chamber implant. All India Ophthl Soc Proc 165-6,1986.

4.Mehta KR: Phacoemulsification cataract extraction with foldable IOLS—first 50 cases. All India Ophthl Soc Proc 56-60,1989.

5.Mehta KR: Clear corneal phaco with injectable silicone IOL proc. All India Ophthl Soc Proc (Mumbai) 1995.

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6.Mehta KR: Mehta tangential chop (MTC) technique for phacoemulsification. All India Ophthl Soc Proc (Chandigarh) 1996.

7.Mehta KR: Combined astigmatic annular keratotomy and phaco—a corneal topographic analytical technique. All India Ophthl Soc Proc (Chandigarh) 1996.

8.Mehta KR: Phaco-levitation—a peaceful way. All India Ophthl Soc Proc (Chandigarh) 1996.

9.Mehta KR: Lollipop phaco cleavage—a new technique for hard cataracts. All India Ophthl Soc Proc (Bangalore) 1991.

10.Mehta KR: SICS mon-phaco—hydroexpression with an irrigating vectis. Proc of SAARC Conference, Nepal, 1994.

11.Mehta KR: Management of subincisional cortex in small incision cataract surgery (SICS). Proc of SAARC

Conference, Nepal, 1994.

12.Mehta KR: The new multiport phaco tip for safer, more effective phacoemulsification, with virtually zero capsular damage. Proc of SAARC Conference, Nepal, 1994.

118 THE ART OF PHACOEMULSIFICATION

Noshir M Shroff

Ranjan Dutta

Gurpreet Singh

Phacoemulsification:

The Quadrantic

Cracking, Chopping 13

and Stuffing Technique

INTRODUCTION

Phacoemulsification if it proceeds smoothly is an excellent procedure with early and extremely gratifying visual recovery. However, should a complication arise, the result can be disastrous with the patient’s sight under threat.

A surgeon’s skills may range from excellent to average. An excellent surgeon will not have much difficulty in adapting to any new procedure including phacoemulsification. Unfortunately not many surgeons belong to this category, where there is little or no difficulty in adapting to the new technique of phacoemulsification. The vast majority of us belong to the second group of “average surgeons”. Not uncommonly an average surgeon begins phacoemulsification, has a few complications in the first few cases, loses confidence and gives up.

Therefore, a nucleofractis technique which is useful for the vast majority of average surgeons, would be one which has a high order of safety with least chances of a posterior capsular rent and damage to the corneal endothelium, is easily reproducible and is easy to perform.

Modern nucleofractis techniques can broadly be divided into two types: (i) four quadrant cracking, and (ii) stop and chop technique.

Four-Quadrant Cracking (Shepherd’s Modification of Gimbel’s Divide and Conquer Technique)

It is easier to handle four small quadrants rather than two large halves. Hence, this technique is easier for the beginner. Moreover, central sculpting debulks the hard central nuclear core. However, the disadvantage is that this technique uses more phaco power and phaco time.

QUADRANTIC CRACKING, CHOPPING AND STUFFING TECHNIQUE 119

Stop and Chop (Koch’s Modification of Nagahara’s Phaco Chop Technique)

This technique has the advantage of using less phaco power and time as compared to quadrantic cracking. It is a very effective technique for hard nuclei.

However it is an inherently difficult procedure for the beginner. A nuclear half is simply too big a piece to tackle and most complications of this technique arise due to this fact. The large nuclear cumbersome fragment, if not impaled exactly midway, tends to rock sideways on the phaco tip, particularly if the occlusion is

not adequate. The lack of firm grip on the piece makes subsequent chopping frustratingly ineffective.

Moreover, the absence of a second trench in the Stop and Chop technique makes it difficult to convert each “half” into “quarters”. As the chopper moves toward the center from the periphery, the final portion (i.e. the central bulk of the nucleus) is difficult to chop. Interconnecting fibrils may at times pose difficulty in separating the fragments, necessitating the use of excessive force with the chopper (Fig. 13.1). Significant lateral forces are thus required for separating the fragments. This puts stress on the capsular bag and makes it an unsafe procedure. In contrast to this, the pre-existent second trench perpendicular to the first, in the quadrantic-cracking technique, makes fragment separation possible with minimal lateral force.

Fig. 13.1: In the Stop and Chop technique (above), the final portion i.e. the central bulk of the nucleus is difficult to chop. Interconnecting fibrils make separation of the fragments difficult. Significant lateral forces are thus created which put stress on the capsular bag. On the other hand in the Quadrantic cracking technique (below), pregrooving leaves a thin posterior nuclear plate and minimum force is required to crack each nuclear half into quarters

The danger of damage to the lens capsule in the Stop and Chop technique is very real. A forceful phaco chop can easily cause a posterior capsule rent. A large fragment will require a longer centripetal chop, which may inadvertently tear the edge of the rhexis and extend it. One may avoid the rhexis edge with a shorter centripetal chop (i.e. by starting at the midperiphery rather than the equator), but this will eventually require wider lateral separation of the nuclear fragments and put stress on the capsular bag.

Also, multiple phaco chops give rise to multiple fragments. These can act as splinters, and in conjunction with anterior chamber turbulence, cause endothelial damage.

Keeping in mind that most of the above complications occur only due to the large nuclear “halves”, we have devised a technique that combines the best features of both techniques.

QUADRANTIC CRACKING, CHOPPING AND STUFFING TECHNIQUE

Our technique of quadrantic cracking, chopping and stuffing starts with four-quadrant fracture followed by tackling each quadrant using low power and high vacuum settings. Thus it combines the safety of quadrantic cracking with the efficacy of Stop and Chop and is suitable for most grades of nuclei.

Preliminary Steps

Following suitable ocular anesthesia, a small conjunctival flap is made and a bloodfree zone is created with a bipolar cautery. The authors prefer prefer making a posterior limbal incision to a clear corneal incision, as it results in lesser induced astigmatism and provides a longer tunnel, which is self-sealing and watertight (due to its valve-like action). A limbal incision also has the advantage that it can be covered with the conjunctival flap at the conclusion of surgery, which acts as an additional barrier against intraocular microbial invasion.

The anterior chamber is filled with a high molecular weight cohesive viscoelastic substance and a side port incision is prepared. Capsulorrhexis is performed using a bent 26-gauge needle followed by hydrodissection (and sometimes hydrodelineation). These two steps are absolutely necessary and provide the key to successful phacoemulsification. Bimanual rotation using two lens hooks ensures that the nucleus has adequately been separated from the cortex.

Central Debulking and Pregrooving

The first step is to create a groove from the center of the nucleus towards 6 O’ clock, stopping just short of the edge of the rhexis. The parameters the authors use during sculpting are 50% U/S power (linear mode) and 30 mm Hg vacuum (Fig. 13.2). The bulk of phaco power is used in this step. The phaco tip is deep inside the central core of the nucleus. So, most of the phaco energy is dissipated within the nucleus far away from the endothelium and the posterior capsule. The groove is created by shaving in layers and is as wide as the sleeve of the phaco

QUADRANTIC CRACKING, CHOPPING AND STUFFING TECHNIQUE 121

Fig. 13.2: Sculpting is done by shaving layers towards 6 O’clock. Ultrasonic power is at 50% (linear mode) with vacuum at 30 mm Hg. The starting point of the first groove is slightly nearer the superior pole and not at the exact center

tip and as deep as possible. Using a spatula (second instrument) through the side port incision the nucleus is rotated by 90° and a second groove is created in a similar manner (Figs 13.3 and 13.4). This is followed by the third and the fourth grooves. One should ensure during sculpting that the starting point of each groove is slightly nearer the superior pole of the nucleus and not at the center itself (Fig. 13.5). Otherwise at the end of sculpting a thick central mound may be left on the center of the posterior nuclear plate and will make subsequent cracking difficult. In this regard a Kelman tip is very useful. Its tip has a bend close to its distal end and permits very effective and efficient downslope sculpting in the superior part of the nucleus, allowing prompt access to the posterior plate for fracturing. Thus there is no residual central mound and one is left with a thin and evenly shaved posterior plate. Additionally this shape allows working on either the left or right side of the central trench by simply turning the tip in either direction along its long axis. The authors have found this tip extremely useful in moderate to hard nuclei.

Another point that needs to be kept in mind while sculpting is that one should ensure adequate depth of the grooves so as to easily facilitate cracking. An indicator of adequate sculpting is the presence of red glow seen through the thin posterior nuclear plate (Fig. 13.6).

Finally, once the center has been debulked and all four grooves have been made, one is left with the nucleus resembling a Maltese cross.