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

124 THE ART OF PHACOEMULSIFICATION

Fig. 13.7: Cracking is achieved with minimal horizontal force

Cracking

Since the central hard core of the nucleus has already been debulked and all four grooves have been created with adequate depth, cracking is easily performed using the phaco tip and the second instrument with minimal horizontal force (Fig. 13.7). Thus undue stress on the capsular bag has been avoided.

For this step the foot pedal is kept in position 1. The fracture is attained by the two instruments pushing away from each other (phaco tip to 9 O’clock and second instrument to 3 O’clock). Alternatively, beginners may find cracking easier by simply using two hooks. The first fracture divides the nucleus into two halves. Following this, the nucleus is rotated by 90° and the distal “half” is fractured into “quarters” using the pre-existent groove. The other nuclear half is rotated distally and similarly cracked till we achieve four separate quadrants (Fig. 13.8). Sometimes the first fracture does not completely divide the nucleus into two halves. In this case, the fracture is completed by rotating the nucleus by 180° and performing cracking on the undivided portion.

Segment Removal

The parameters are now changed. Ultrasonic power is reduced to 30% (pulse mode) and vacuum is increased to 120 mm Hg and the authors now proceed as one would in the Stop and Chop technique, i.e. engaging and holding each nuclear fragment and chopping it into smaller pieces.

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Fig. 13.8: The nucleus is rotated every 90 degree till four separate nuclear quadrants are obtained

One can engage each quadrant from the apex, the sides or the undersurface. However, the apex offers too small an area to ensure a good hold and the sides of the fragment have very irregular surfaces. Engaging a quadrant from an irregular surface can cause it to tumble and rent the posterior capsule (Fig. 13.9). Therefore, the authors prefer to engage the quadrant from its undersurface; its area is large and smooth and the phaco tip can be effectively occluded thus providing a good hold on the fragment. There are two ways of achieving this. One way is to depress the base of the fragment with a hook thus tilting up the apex and exposing the undersurface of the quadrant to the phaco tip (Fig. 13.10). The other way is to lift up the apex directly with the hook and guide the phaco tip to the undersurface (Fig. 13.11).

Once the quadrant has been effectively impaled onto the phaco tip, it is pulled to the center of the capsular bag away from the posterior capsule, and the endothelium and a chopper is introduced through the side port. With the phaco tip holding the quadrant steady, the chopper is sunk into the nuclear substance and retracted towards the phaco tip (Fig. 13.12). Just before it reaches the tip, the chopper is moved sideways and away from the tip (towards 3 O’clock). Simultaneously the

128 THE ART OF PHACOEMULSIFICATION

Fig. 13.13: As the chopper approaches the phaco probe it is moved sideways and away from the tip. Simultaneously the tip holding the nucleus is moved in the opposite direction

phaco tip is moved sideways in the opposite direction (towards 9 O’clock) dividing the quadrant into two fragments (Fig. 13.13). The chopper guides the engaged piece and then stuffs it into the phaco tip, all the time keeping the other fragments away (Fig. 13.14). The fragment is emulsified using a combination of this stuffing action, high vacuum and intermittent bursts of low phaco power. Likewise each quadrant is tackled in this manner by this method of chopping, stuffing and emulsification. One must all the time ensure that epinuclear and cortical matter is not aspirated during segment removal as this material acts as a protective buffer and prevents accidental posterior capsule rupture.

Epinucleus Removal

With ultrasonic power set at 10% (linear mode) and vacuum at 80 mm Hg the distal rim of the epinuclear shell is engaged by the phaco probe in pedal position 2 and pulled towards the center of the capsular bag. The epinucleus is pulled by the phaco tip towards the incision, while the second instrument simultaneously provides countertraction in the 6 O’clock direction. The epinucleus easily flips around the second instrument and is emulsified in the center of the capsular bag. Sometimes,

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Fig. 13.14: The smaller pieces are now stuffed into the phaco tip with the chopper and emulsified using bursts of low phaco power and high vacuum

the portion of the epinucleus engaged to the phaco tip breaks off from the rest of the epinuclear shell. In this case, after emulsifying the broken-off piece, the remainder of the shell is rotated to the 6 O’clock position, engaged by the phaco tip, brought to the center of the bag, and then finally emulsified. One should proceed very carefully in this delicate phase as the absence of the main bulk of the nucleus makes the posterior capsule relaxed and there is a danger of the floppy capsule coming into contact with the phaco tip.

Thereafter cortex is removed with the irrigation-aspiration tip. The authors prefer to remove 12 O’clock cortex by the bimanual method after creating a second side port incision. The anterior chamber is then filled with viscoelastic substance and a foldable IOL is implanted. Viscoelastic removal followed by testing the wound for its self-sealing nature concludes the operation.

CONCLUSION

The authors have been using this technique on most of their patients with gratifying results. It combines the safety of quadrantic cracking with the efficacy of Stop and Chop and is appropriate for most types of cataracts. This technique is reproducible and is ideal for the beginner as well as the experienced.

130 THE ART OF PHACOEMULSIFICATION

Richard Packard

Current

Phacoemulsification 14

Techniques

I N T R O D U C T I O N

Small incision cataract surgery was 30 years old in 1997. Since its inception the techniques involved have been constantly improving and this has been matched by innovations in phaco machinery and intraocular lens materials and design. At almost every meeting or edition of the throw-away papers somebody puts forward some new variation. It can be very confusing. The following shows my current techniques developed over 20 years experience in small incision cataract surgery.

PATIENT PREPARATION AND ANESTHESIA Preparation

Patients are not routinely given any premedication. They will have had a simple drop regime prior to reaching the operating theater as follows:

G. Phenylephrine 2.5% G. Homatropine 2%

Two drops of each 30 minutes preoperation G. Benoxinate 0.4%

Two drops every 10 minutes for 30 minutes preoperation

In the operating theater prior to administering any anesthetic, povidones iodine is instilled into the eye. This will then be in contact with the tissues for about 10 minutes before being washed out at the start of the operation.

Topical Anesthesia

The drop regime above is sufficient for topical anesthesia. This technique was not used often in our department until recently because the anesthetists prefer not to give any intravenous sedation, if required, without control of the airway. The advent of intraocular unpreserved lignocaine 1% at the start of the procedure and for hydrodissection has increased the number of patients operated upon without peribulbar injection. This is because the need for additional intravenous sedation is almost eliminated.

Peribulbar Anesthesia

Medication Mixture

Plain lignocaine 2% 8 ml mixed with hyalase.

Needle Long shank 23 gauge needle attached to 10 ml syringe.

Technique

3 ml are injected inferiorly back from the infraorbital notch and 3 ml superiorly over the supraorbital notch. Both injections point nasally. A mercury bag is then placed on the eye for about 5 minutes not to soften the eye but to help spread the local anesthetic.

PHACOMACHINES IN USE

1.Alcon Legacy

2.Allergan AMO Prestige

3.Allergan AMO Sovereign

The Legacy has the high vacuum cassettes in use and has been modified for bimodal and burst phaco. The microtip and ABS technology have improved the anterior chamber stability considerably compared with earlier configurations of this machine.

The Prestige has a unique pump monitoring arrangement. This helps to minimize postocclusion break surge in the anterior chamber by slowing the rate at which the pump regains full speed. This makes it very safe as the chamber does not collapse and intracameral contents are not sucked into the phaco tip. This machine is now available with a 21 gauge phaco needle.

The Sovereign is new and not yet available commercially though it is being launched shortly. It has developed on the microchip control of machine parameters seen in the Prestige and Diplomax machines. It has the ability to set different values for phaco with and without bursts of variable length, vacuum and pump speed which differs depending on whether the phaco tip is occluded or unoccluded. It is also possible to vary the pump speed in any setting depending on vacuum thresholds.