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

In the event of an eye with a cataract that requires surgery, the presence of poor exposure and a fixed small pupil, may influence the surgeon to consider doing an extracapsular procedure rather than phacoemulsification. The majority of Asian cataracts are mature with a brunescent nucleus, whereas most Western cataracts are relatively immature. Current technology and newer techniques of surgery are enabling surgeons to do phacoemulsification on lenses with very dense nuclei, which would have been considered impossible some years ago. While the lens with a dense nucleus may be more difficult to phaco than a softer cataract it does have the advantage of being more brittle which makes its splitting and chopping easier.

Just as in cataract surgery there has been a shift from intracapsular to extracapsular and finally phacoemulsification, so in “phaco” itself there has been a progressive change in the procedure. In the original operation as described by Charles Kelman in 1968 the anterior capsule was opened with a”Christmas tree” configuration and the nucleus was dislocated into the anterior chamber of the eye, prior to phacoemulsification. The opening into the anterior capsule was modified into a “can-opener” by Robert Sinskey et al in 1972. With this larger opening in the anterior capsule, the nucleus could be phacoemulsified in the posterior chamber.

In 1987 Howard Gimble and Thomas Neuhnann introduced the concept of capsulorrhexis of the anterior capsule, with a circular tear opening being made. While considerably improving the surgical procedure, since it allowed a lens implant to be inserted totally within the confines of the capsular bag, it did cause some problems with the phacoemulsification of the nucleus. In the older techniques, the larger opening in the anterior capsule gave greater access for the removal of the nucleus. In the presence of a capsulorrhexis the surgeon had a much more limited access to the nucleus. This led to the introduction of advanced “phaco” procedures such as “divide and conquer”. For its removal the lens was divided and emulsified. The implosion procedure is a variant means of phacoemulsifying the nucleus in the presence of a capsulorrhexis.

The Surgical Approach

The eye for surgery is prepared with mydriatic drops to dilute the pupil and antibiotic guttae to kill any bacteria lying in the conjunctiva and fornices. A steridrape covers the lashes and a lid speculum exposes the globe (Fig. 16.1).

The incision into the eye may be made using, either the clear corneal or scleral tunnel approach (Fig. 16.2). The clear corneal incision described by Eric Arnott in 1975 and remodified by Howard Fine in 1992 may be either one or two step in style. It is made either in the corneal meridian with the steepest slope or

CATARACT EXTRACTION AND LENS IMPLANTATION: THE IMPLOSION TECHNIQUE 163

Fig. 16.2 Fig. 16.3

in the lateral meridian at 3 O’clock in the left eye and 9 O’clock in the right eye. A diamond keratome of some 3.2 mm width is used (Fig. 16.3)

If the scleral tunnel approach is to be used the incision is usually made in the 12 O’clock meridian. The opening into the anterior chamber is microscopic some 3.2 mm in cord width and three step in configuration, giving a water type seal at the end of the operation.

The initial incisions some 300 microns in depth [the tissue at the corneoscleral junction being some 700 microns in thickness] are made either at the corneoscleral junction or just posterior to it, in the sclera. From the depth of this incision a lamella split is made extending anteriorly into clear cornea for some 2 mm; the plane of this incision being parallel to the iris-lens diaphragm. From the anterior limit of this second portion of the section the anterior chamber is entered using a 3.2 mm keratome; this penetration being at right angles to the second part of the incision. When the tip of the keratome has just perforated into the anterior chamber it is pointed towards the apical anterior surface of the lens. In this way a self-sealing incision is obtained.

Reconstitution of AC with Viscoelastic Solution

A Wycroft cannula on a syringe filled with viscoelastic solution is inserted into the anterior chamber and passed over the anterior surface of the lens to lie just within the pupillary margin in the 6 O’clock meridian. In filling the anterior chamber with this viscoelastic solution the aqueous

humor is replaced, further pupillary dilation may be achieved, the anterior surface of the lens is flattened, and a protective layer is coated over the corneal endothelium.

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is one of the most important and precise part of the operation. The anterior capsule of the lens is perforated with a bent needle tip placed at the midpoint of the anterior capsule. A linear tear is made (Fig. 16.5), the upper edge of which is converted into a flap. This is held with forceps (Fig. 16.6), and with a continuing circular movement and repeated gripping of the torn flap near to the tearing edge, a capsulorrhexis is fashioned.

Hydrodissection

Before removing the lens contents it is necessary to free the nucleus from the surrounding capsule. The tip of a Wycroft cannula fitted to a 2 ml syringe filled with balanced salt solution (BSS) is placed under the lip of the anterior capsule and a little fluid is injected to flow around the inside of the lens capsule (Fig. 16.7).

The tip is moved to different meridians of the edge of the lens capsule each time injecting a little fluid. This has the effect of not only freeing the cortex from the lens capsule but also of washing away some of the equatorial cells; the removal of these germinal cells reduces the incidence of postoperative Elschnig pearl formation.

Phacoemulsification of Lens Contents

The next stage of the operation is to remove the hard central nucleus with the phaco handpiece tip. The phaco tip is some 1 mm in diameter, with a beveled edge. It is enclosed in a silicone sleeve, which has two side-port holes near its tip. One and a half mm of phaco tip is left exposed beyond the silicone sleeve. While ultrasonic agitation of the tip breaks up the nucleus, bit by bit, fluid enters the eye between the silicone sleeve and the phaco tip.The emulsified debris is aspirated up the phaco titanium tip.

Phacoemulsification has been markedly facilitated over the years by progressive improvements in the handpiece. The ultrasonic power, fluid inflow and outflow

CATARACT EXTRACTION AND LENS IMPLANTATION: THE IMPLOSION TECHNIQUE 165

can be modified according to the surgeon’s needs. The ultrasonic power can be varied from zero to 100 percent. The fluid inflow is normally 25 cu ml per minute but may be increased or reduced by raising or lowering the level of the inflow bottle. The fluid outflow has two parameters—“the vacuum pressure and the aspiration flow rate”. Variants between these two can be used at all stages of the operation. With the “pulsating pump” form of aspirating unit, the vacuum level will not rise within the system until the nucleus or other material occludes the phaco tip. The greater the level at which the aspirating flow rate has been preset, the more rapidly will the vacuum pressure build up once the tip has become occluded. With high aspiration levels there is more followability of the nucleus.

There are essentially three different techniques to phacoemulsify the nucleus of the lens.

•The divide and conquer

•The implosion method

•Chop and stop.

In most operations with phaco of the nucleus, a deep groove is made from 12 towards 6 over the anterior surface of the nucleus (Fig. 16.8). When making this groove the tip goes deeper towards the center of the nucleus and shallows towards the 6 O’clock meridian (Fig. 16.9), allowing for the convexity of the posterior capsule. While varying power, vacuum and aspirating levels may be chosen depending on the surgeon’s particular needs, average levels for this part of the procedure would be “phaco” power 70%, the vacuum level 60 mm Hg and an aspiration rate of 25 cu ml per minute. The phaco tip shaves the surface of the nucleus, with an action similar to the planing effect of a chisel. The softer the nucleus the deeper the tip may safely penetrate into its substance without disturbing the position of the nucleus, which could put tension on the zonule or capsule of the lens. With a hard nucleus the tip should shave superficially, with only a third or less of its diameter being embedded in its substance.

Divide and Conquer

In the divide and conquer technique once the initial deep groove has been made a spatula is inserted into the anterior chamber to join the phaco tip. The tips

166 THE ART OF PHACOEMULSIFICATION

of both instruments are placed deep into the groove and with counterpressure against the sides of the groove the nucleus is split into two. These two instruments are next used to rotate the nucleus some 90°. This process is repeated with another groove being made and the nucleus split yet again, so that it has now been divided into 4 quadrants, each of which can be individually emulsified. The vacuum level can be increased at this stage of the procedure to a much higher level. This enables the fragments to be drawn towards the center of the capsular bag where they can be emulsified using low phaco power.

The Implosion Method

In the implosion technique as with the divide and conquer the initial procedure is to make a deep groove across the anterior surface of the lens .The procedure differs in that the nucleus is not divided prior to its removal but is removed bit by bit in one piece. This has the safety factor in that if the capsule should inadvertently rupture, in an emergency situation, it is easier to deal with one lens fragment rather than multiple pieces of nucleus. The initial deep furrow is debulked on either side leaving intact a rim of nuclear bowl (Figs 16.10 and 11).The phaco tip should at all times be kept in view within the pupil margin in the “safe” triangular area between 4,6, and 8 O’clock. Keeping within this area, only the inferior half of the nucleus can be debulked. Access is gained to the superior half by rotating the nucleus some 90° at which time the debulking process is continued. Further rotation of the nucleus may be required to totally debulk its central contents.

When totally debulked the nucleus should resemble a salad bowl with intact rim and inferior nuclear plate (Fig. 16.12). The final part of the “phaco” process is to implode or break off fragments of the nuclear bowl into the cavity of the debulked nucleus, where they can be easily emulsified (Fig. 16.13). Since at this stage of the procedure the more peripheral softer portion of the nucleus is being dealt with, lower power levels may be used, averaging 40%. The vacuum and aspirating levels are left unchanged. This relatively high aspiration rate allows for the phaco tip to manipulate and mobilize the nuclear bowl rim.

The tip of the phaco impales the nuclear rim at 3 O’clock causing it to break, implode and rotate into the tip (Fig. 16.14). Due to the “followability” of the

168 THE ART OF PHACOEMULSIFICATION

The Chop

The chop technique may be combined with the “divide and conquer” and “implosion“ procedures or used as a primary procedure. It is best employed in cases with a very hard nucleus, which will be very brittle. High-vacuum pressure up to 200-400 mm Hg may be used. Using this high vacuum and with ultrasonic power the nucleus is impaled near the center of its anterior surface. Once impaled, the vacuum is maintained and the ultrasonic power turned off. A chopping hook is inserted into the anterior chamber and engages the nucleus 1 mm beyond the impaling phaco tip, and drawn towards it. The counterpressure of embedded hook against impaled phaco tip cracks the nucleus. The process can be repeated a number of times breaking the nucleus up into fragments which can be emulsified and aspirated from the capsular bag. It is important to ensure that the hook is at all times within, not over, capsular bag to prevent tension and partial disinsertion of the suspensory ligament of the lens. In the “implosion” technique if the nuclear bowl is particularly hard, the “chop” may be employed to help fracture the rim.

Aspiration of Residual Cortex

This is performed using the standard irrigating aspirating handpiece with 0.3 mm side port (Fig. 16.19).

Lens Implantation

With the lens contents removed the capsular bag is now ready to receive the implant. The lens implant may be made of several materials; foldable lenses that go through the phaco incision may be silicone, poly-HEMA (hydroxyethylmethacrylate), or acrylic. Polymethylmethacrylate (PMMA) lenses are more rigid and require the phaco incision to be a little enlarged for their insertion. Most implants have loops, which are attached to the optical portion and contract down when inserted into the capsular bag. Prior to the lens insertion the anterior chamber and capsular bag are filled with a viscoelastic solution.

With soft lenses a lens forceps is used to fold over the implant prior to insertion. With the implant folded in the forceps the inferior loop is guided through the

CATARACT EXTRACTION AND LENS IMPLANTATION: THE IMPLOSION TECHNIQUE 169

section and across the anterior chamber and into the inferior recess of the capsular bag. The forceps now release the lens allowing the optical portion to unfold half in the anterior chamber and half in the capsular bag. The upper loop may be either looped or dialled into the capsular bag.

Prior to inserting the PMMA lens the section is enlarged a further 1.75 mm.The insertion is similar to that of a foldable lens except that the lens is inserted in the unfolded state. The lens, held in forceps, is inserted through the section, across the anterior chamber. As with the soft implant the inferior loop is placed in the inferior recess of the capsular bag. A dialling hook is inserted into the upper crutch of the lens, at the junction of optics and loop. With a clockwise dialling motion the upper loop will be corkscrewed into the capsular bag. As an alternative the upper loop lying just within the section may be held with forceps and looped into the capsular bag. The PMMA lens with totally encircling loops has the advantage of giving great stability to the capsular bag (Figs 16.20 and 21).

C O N C L U S I O N

With this procedure the incidence of postoperative retinal detachments have been reduced from 2.5% with the old intracapsular operation to 0.15% with the small incisional and intercapsular technique. All other complications including late edema of the macula have also been reduced.

The small incisional phaco and implant procedure confers other benefits for the patient. The postoperative convalescence is minimal, the patient being able to return to normal activities immediately. A high percentage of visual acuity recovery is regained within the first 24 hrs. The rapid visual rehabilitation, limited postoperative convalescence and reduced postoperative morbidity have markedly changed the indications for cataract surgery.

170 THE ART OF PHACOEMULSIFICATION

Rasik B Vajpayee

Tanuj Dada

INTRODUCTION

Phacoemulsification has become the surgery of choice for a cataract extraction all over the world. Although the technique of phacoemulsification is more or less a standard one, there are certain special situations which warrant either a modification of the standard technique or the use of an additional device to facilitate the surgery. Some of these special situations include a small pupil, a subluxated lens, an intumescent lens, anterior uveitis, vitrectomized eyes and the pseudoexfoliation syndrome. Each of these conditions poses a unique intraoperative problem to the surgeon and demands a detailed preoperative planning on how to tackle them. In this chapter we describe the various innovative techniques developed to handle each of these special situations.

SMALL PUPIL

This is a frequently encountered problem during phacoemulsification. Although endolenticular phacoemulsification can be performed in the presence of a small pupil, it increases the degree of difficulty for the surgeon and is often a cause for complications. There are various intraoperative techniques that can be used to manipulate the size of the pupil, to facilitate phacoemulsification in a miosed pupil.

Intracameral Adrenaline

The use of 0.1 cc of 1:10,000 adrenaline, injected directly into the anterior chamber through the side port incision, is useful in dilating the pupil. Only preservative

PHACOEMULSIFICATION IN SPECIAL SITUATIONS 171

free drug is to be used. Since the drug is toxic to the endothelium, sodium hyaluronate should be used to coat the corneal endothelium before adrenaline is injected. This is helpful in eyes with an intact dilator pupillae muscle, with no synechiae, fibrosis or hyalinization of the iris musculature. Adrenaline is not to be used in hypertensive or cardiac patients.

Iris Hooks

Self-retaining iris hooks have been designed by Mackool (titanium) and De Juan (nylon). Three

to four hooks are placed through paracentesis sites and the pupil can be widely dilated to a triangular (Fig. 17.1) or square shape. With the use of these hooks, the pupil can be dilated to any size, regardless of the pre-existing pupillary diameter. Although this is an effective technique for pupillary dilatation, it is time consuming, leads to considerable iris manipulation and results in a large amount of leakage of fluid from

the paracentesis sites. The nylon hooks (Grieshaber and Co) are preferable since these incorporate an adjustable stop which allows the traction on the iris to be manipulated during surgery.

Iris Protector Ring

Siepser had designed a hydroview iris protector ring (Grieshaber and Co) which can be placed inside the pupil through a 3-mm incision. The ring expands with hydration and gradually ditates the pupil. It is removed at the end of phacoemulsification.

Stretch Pupilloplasty

This is our personal technique for dilating the pupil. After injecting a high viscosity sodium hyaluronate in the anterior chamber, two Sinskey hooks are employed from two paracentesis sites to engage the inner edge of the pupil. The hooks are placed diagonally opposite each other and then a bimanual stretching of the pupil is done. This stretch is done in the horizontal (3-9 O’clock) and vertical axis (6-12 O’clock) and creates micro tears in the sphincter pupillae, thereby dilating the pupil. A pupil size of up to 6 mm can usually be achieved with this technique.

Partial Thickness Sphincterotomies

Eight small sphincterotomies are performed using a Rappazzo scissors (used for vitreoretinal surgery) through two side port incisions. The cut is made up to half width of the sphincter pupillae muscle and then a hook is used to stretch the root of the iris in the different meridians in which the sphincterotomies have been made.