Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001
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132 
THE ART OF PHACOEMULSIFICATION
All these machines allow a slow rise time to maximum vacuum settings which is safer when teaching residents in training. The Sovereign will allow very rapid vacuum rise time on occlusion if so desired.
Tips and Sleeves
Current tips are 30 degree. This provides the best compromise for sculpting and nuclear fragment removal. These are used with both machines and are covered 
by silicone sleeves. The Legacy has the Kelman tip also which has very much greater cavitation than conventional straight tips and is particularly useful for
very hard nuclei.
INCISIONS
Side Port Incisions
Instruments Alcon 15 degree knife, toothed St. Martins forceps.
Technique The limbal conjunctiva is grasped with the forceps at about 11 O‘clock to steady the eye. The 15 degree knife is held in the right hand with blade parallel to the iris. The point of the knife is applied to the limbus at the capillary arcade approximately 60 degrees to the right of the tunnel incision (Fig. 14.1). The knife is advanced fully to produce an incision 1 ½ mm wide. This just the right size for the bimanual handpieces used for irrigation and aspiration. The second incision is made with the knife in the left hand at about 60 degrees to the left of the phaco incision (Fig. 14.2). They will easily self seal at the end of the procedure.
Figs 14.1 and 14.2: Side port
Note The incision is made at the edge of the capillary arcade so that the small amount of bleeding will mark its site for insertion of the nucleus manipulator later.
Temporal Incision
Instruments Colibri toothed microsurgical forceps, Alcon phaco slit blade 2.75 mm angled.
CURRENT PHACOEMULSIFICATION TECHNIQUES |
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Technique The Colibri forceps grasp the |
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limbus at the left end of the incision site to |
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steady the eye. A Fine Thornton ring will |
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also do this very well. The tip of the slit knife |
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is held against the limbus at an angle of 60 |
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degrees. The knife is pushed gently (Fig. 14.3) |
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forward until the bevel is just covered. The |
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knife is then angulated backwards so that |
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the blade is pointing up the slope towards |
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the center of the cornea. The blade is now |
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advanced (Fig. 14.4) very slowly. The progress |
Fig. 14.3: |
Starting the phaco incision |
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of the passage of the knife can be seen clearly. |
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When the tip of the knife is 2 mm into clear cornea the handle is lifted and the knife advanced again (Fig. 14.5) but this time pointing to the scleral spur opposite. When this last is done slowly a straight entry into the anterior chamber is produced which acts efficiently as an internal valve.
ANTERIOR CHAMBER MAINTENANCE
The chamber is now filled with viscoelastic through the side port. Provisc (sodium hyaluronate 1%) is what I use at present. I do not think there is much too choose between the various sodium hyaluronates, however HPMC does not perform as well in the eye but it is cheaper. Viscoat is reserved for problems during the phaco to tamponade a posterior capsule rupture.
Capsulorrhexis
Instruments Straight disposable cystitome, Duckworth and Kent titanium capsulorrhexis forceps.
Technique
•The eye is overfilled with viscoelastic elastic as above to flatten the anterior capsule.
Fig. 14.4: Advancing the slit knife |
Fig. 14.5: Making the internal incision |
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THE ART OF PHACOEMULSIFICATION
Fig. 14.6: Cystitome cutting capsule |
Fig. 14.7: Starting to tear with forceps |
Fig. 14.8: Folding the flap onto the |
Fig. 14.9: Finishing the rhexis |
untorn capsule |
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•Refocus the microscope on the anterior capsule and make sure there is good magnification, particularly if there is a less than helpful red reflex.
Note There is much less tendency for the capsular tear to move peripherally during the rhexis if the surface is flattened out. If the surgeon is worried about the rhexis getting out of control at any stage of the capsulotomy , more viscoelastic injected into the eye will usually arrest the problem.
•The cystitome is attached to the irrigation handpiece or the viscoelastic syringe and inserted through the tunnel. The instrument held in the right hand is steadied by the index finger of the left hand. The capsule in the center of
the lens is engaged with the tip of the cystitome and the sharp edge is used to cut the capsule for about 1 mm (Fig. 14.6). The capsule is then torn in a C-shape. The flap of capsule thus created is laid on top of the adjacent untorn capsule so that it can easily be grasped by the capsulorrhexis forceps.
•The capsulorrhexis forceps having been inserted into the eye are used to grasp the capsular edge. This is then torn in a circular manner constantly changing the angle of the vector forces by regripping the capsular edge as the tear progresses (Figs 14.7 to 14.9).
CURRENT PHACOEMULSIFICATION TECHNIQUES |
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Note The ideal angle of pull to produce the tear depends on both a horizontal and a vertical component. This is particularly important in young eyes with elastic capsules. Do not expect the capsule to tear in the direction you are pulling Capsules vary considerably in consistency and elasticity. As a general rule the younger the patient the more elastic and these capsules are much more difficult to control. The angle of pull is often at an obtuse angle to the direction of tear to prevent drift to the periphery. Aim to make these capsulotomies small (4mm)
and they will probably end up about 6 mm.
Capsulorrhexis Size
The ideal size for a capsulorrhexis is between 5 and 6 mm. In any event the capsulorrhexis should lie on the edge of the implant. Making it any larger can lead to difficulties with control and is unnecessary. With some implant materials (such as silicone) it is particularly important that at the end of the procedure the rhexis is not too small. A rrhexis of 4.5 mm or less may lead to contraction and capsulophimosis. The implant may then decenter and the patient experience glare from the opaque edge of the capsule.
Note If the rhexis looks too small after the I/A enlarge it.
Technique Inject viscoelastic into the anterior chamber; do not overfill it as this will put the capsule under tension. Use Vannas scissors to make an oblique cut at the rhexis edge, grasp this new tear with the capsulorrhexis forceps and tear carefully round.
Reasons for Problems with Capsulorrhexis
•The most common problem is loss of control of the tear so that it moves peripherally (Fig. 14.10). This may be due:
i.Elasticity of the capsule combined with lack of rigidity of the sclera as in younger patients (Figs 14.11 and 14.12).
ii.Excessive pressure from behind the lens.
iii.Any other cause for loss of the anterior chamber and escape of viscoelastic.
Fig. 14.10: Rhexis moving peripherally |
Fig. 14.11: Elastic juvenile capsule |
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THE ART OF PHACOEMULSIFICATION
Fig. 14.12: Preventing capsule going to periphery by pulling away from tear
Fig. 14.13: Leakage of liquid lens material as the capsule is punctured
The cure for all of these is to inject more viscoelastic, if the problem persists change to a high viscosity viscoelastic such as Healon GV.
•If the tear appears to stop this is due to anterior zonular fibers abnormally far forward. Do not persist with the rhexis in this direction or it will rapidly tear towards the equator. Start the rhexis the other way round by making a small cut with Vannas scissors and then joining it up again at the point where it had previously stopped.
•When there is a poor or no red reflex as in white cataracts or very advanced nuclear cataracts with extreme sclerosis capsulorrhexis can be very taxing. There are a few simple maneuvers which will improve visibility somewhat:
i.If you do not do so already, sit temporally, visibility is enhanced.
ii.Tilt the microscope so that the light is oblique to the capsule and will reflect from the torn edge. Or use the oblique (non-coaxial light) if available on the microscope.
iii.Increase the magnification so that the iris fills your field, focus accurately. What you lose in depth of field is gained by ease of vision of the capsular edge.
iv.In white cataracts (Figs 14.13 and 14.14) when liquid lens material fills the eye as the capsule is punctured, use the I/A to clear the chamber and suck out anterior cortex. Refill the eye with viscoelastic, your view of the capsule will then be much better.
•Small pupils, although they can be enlarged by various means, still make the rhexis more difficult. Viscoelastic may be used to push the pupil open and thus expose more capsule. Also the nucleus manipulator can push the iris aside (Fig. 14.15), in the area where the capsulorrhexis forceps are tearing the capsule
H Y D R O D I S S E C T I O N
Instruments Visitec hydrodissection cannula (with rectangular cross-section), 2 ml disposable syringe filled with BSS.
CURRENT PHACOEMULSIFICATION TECHNIQUES 
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Fig. 14.14: Using the I/A for removing excess soft lens matter
Fig. 14.15: Using the nucleus manipulator to hold aside the iris
Technique As the hydrodissection cannula is moved towards the rhexis start to inject BSS to lift its edge. The hydrodissection cannula is placed under the edge of the capsule at about the 3 O‘clock position. The capsule is tented up to peel it off the cortex and advanced 1 mm peripherally. BSS is injected rapidly but smoothly to produce cortical cleavage. This is seen as a fluid wave (Fig. 14.16) advancing rapidly under the nucleus and epinucleus.
The tip of the cannula is then placed on the center of the nucleus and then pushed backwards towards the posterior capsule (Fig. 14.17). This maneuver has the effect of helping to spread the fluid around the capsule and complete the cleavage. If it is felt that the hydrodissection is incomplete, a second injection of BSS can be made at the 6 or 12 O‘clock position.
In hard or medium cataracts it may be difficult to separate nucleus from epinucleus as in hydrodelineation and is often not necessary. If it is felt desirable to get the hard part of a nuclear fragment away from its attached epinucleus during phaco this can be done with the nucleus manipulator. However in soft cataracts, it is advantageous to see clearly the extent of the nucleus, so that the phaco tip does not inadvertently pass through soft nucleus, epinucleus and capsule.
Fig. 14.16: Fluid wave traveling behind |
Fig. 14.17: Pressing back on the nucleus to |
nucleus |
spread the fluid |
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THE ART OF PHACOEMULSIFICATION
Sometimes with very soft cataracts, part of the nucleus is pushed through the rhexis during the hydrodissection, this does not matter. It will facilitate the aspiration of the soft nucleus.
LENS REMOVAL
General Points
•Check that the machine is working satisfactorily before placing the phaco tip in the eye. This includes making sure the machine parameters are those desired.
•Check that the phaco tip is undamaged and that its bevel is at 90 degrees to the irrigation sleeve openings. The exposed tip should be about 1.5 mm beyond the end of the sleeve.
•Check that the foot pedal is comfortably placed.
Instruments Colibri toothed microsurgical forceps, phaco handpiece, Duckworth and Kent nucleus manipulator (actually called a Mackool iris repositor).
Technique for |
Soft Nuclei |
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Machine Settings |
Alcon Legacy |
AMO Prestige |
AMO Sovereign |
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Phaco tip bevel |
30° 21 gauge |
30° 19 gauge |
30° 19 gauge |
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Bottle height |
70 |
cm |
70 |
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70cm |
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Sculpting |
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Vacuum |
40 |
mmHg |
35 |
mmHg |
10 mmHg |
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Aspiration rate |
15 |
cc/min |
18 |
cc/min |
20 cc/min |
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Nuclear removal |
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Vacuum |
200 mmHg |
150 mmHg |
200 mmHg |
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Phaco power |
30% linear |
30% linear |
20% linear |
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Emulsification
The Colibri forceps are used to lift gently the edge of the wound and the phaco tip enters the eye bevel down. The machine should be in foot position 0 as the anterior chamber is still deepened by the viscoelastic.
Note If the eye has a shallow chamber, or the pupil is not well dilated and the iris is at risk of damage as the phaco tip enters the eye, redeepen the chamber with viscoelastic. If Viscoat is available and it is being used to protect the endothelium during phaco anyway then this problem will not arise.
Once the irrigation ports are safely in the eye, the foot pedal is depressed to position 1 allowing the irrigation fluid to deepen the anterior chamber.
•Sculpting: With soft cataracts it is very easy to pass straight through the lens if too much power is used when sculpting. It should be done with smooth movements and the edge of the delineated nucleus should not be passed. Make a deep central groove because even though it may not crack, it will facilitate the pulling of the edge of the lens centrally after it has been sliced.
CURRENT PHACOEMULSIFICATION TECHNIQUES 
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Fig. 14.18: Slicing the nucleus |
Fig. 14.19: Separating the sliced nucleus |
•Nucleus removal:
i.With the phaco tip in the eye in irrigation mode insert the nucleus manipulator through the side port incision.
ii.Pass the tip of the manipulator (turned on its side) under the rhexis and out to the equator of the nucleus in the 3 O‘clock position.
iii.Engage the nucleus with the manipulator and pull towards the central groove (Figs. 14.18 and 14.19), as the manipulator reaches the groove, use the phaco tip to separate the
two sides of the cut you have made. It does |
Fig. 14.20: |
not matter if there is full separation or not. |
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iv.Turn the nucleus with the manipulator and the phaco tip and repeat the chopping at intervals of two clock hours. This technique known as the “soft slice” will mean that the segments of nucleus even though they are not separated will fold in towards the center of the eye when they are engaged by the phaco tip.
v.Bury the phaco tip in one of the segments. No U/S power is needed for this because of the softness of the nucleus. Allow vacuum to build and when it has, pull the segment (Fig. 14.20) centrally for removal. The nucleus will peel apart along the preprepared cuts. Do this for each part of the nucleus.
vi.The epinuclear shell will still be in the eye, but because of the cortical cleavage hydrodissection, will be free to be aspirated. Pass the phaco tip under the rhexis edge into the epinucleus at 6 O‘clock and as vacuum builds pull it centrally for removal. Do not use U/S as this will break occlusion and also punch holes in the epinucleus. Sometimes the manipulator is needed to help the phaco tip to engage the epinucleus by moving it from the equator towards the center.
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THE |
ART OF PHACOEMULSIFICATION |
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Technique for Medium Hard Nuclei |
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Machine Settings |
Alcon Legacy |
AMO Prestige |
AMO Sovereign |
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Phaco tip bevel |
30° 21 gauge ABS |
30° 19 gauge |
30° 19 gauge |
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Bottle height |
70 |
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70 |
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70cm |
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Sculpting |
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Vacuum |
40 |
mmHg |
35 |
mmHg |
10 |
mmHg |
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Aspiration rate |
15 |
cc/min |
18 |
cc/min |
14 |
cc/min |
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Nuclear removal |
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Vacuum |
350 mmHg |
260 mmHg |
400 mmHg |
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Aspiration rate |
25 |
cc/min |
16 |
cc/min |
18 |
cc/min |
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Phaco power |
70% linear |
60% linear |
50% linear |
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This type of cataract is by far the easiest to remove. The nucleus offers some but not too much resistance to emulsification but also has enough substance to allow easy hydrodissection, manipulation and cracking. It is the ideal type of nucleus for beginners to learn on.
Emulsification
The eye is entered as already mentioned for the soft cataract.
•Sculpting: In medium hard cataracts the nucleus offers some resistance to sculpting. Accordingly, the amount of power needed to emulsify it is that which does not push the nucleus across the eye. It is better to press down with the foot and increase the phaco power than put the superior zonules at risk by pushing at the nucleus. The anatomy of the nucleus should be borne in mind during sculpting. Initially the anterior cortex is removed widely to expose the hard core. This core is then grooved to a depth of 90% of the nuclear thickness.
Note As nucleus hardness increases the passes of sculpting should attempt to remove thinner and thinner slivers of nucleus.
Note As the phaco tip advances it should be slightly elevated to avoid passing straight through the nucleus. It is important to remember that the center of the nucleus is 2.5-3.0 mm but that because of its elliptical cross-section this reduces rapidly as the phaco tip moves peripherally.
The grooves in the nucleus need not go beyond the edge of the 5.0 mm rhexis, provided that sufficient depth has been achieved cracking will occur easily with grooves of this length. It is also important that they are not significantly wider than the phaco needle or else cracking will be much less efficient.
Tips for Judging the Depth in the Nucleus when Sculpting
•Remember the diameter of the phaco needle (0.9-1.1 mm)
•Remember the anatomy of the lens with hard central nucleus surrounded by
epinucleus and cortex that are softer
• Watch the change in the red reflex, it gets brighter
•Refocus the microscope frequently so that the focus is at the plane of emulsification
CURRENT PHACOEMULSIFICATION TECHNIQUES 
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Fig. 14.21: Cruciate grooves |
Fig. 14.22: Cracking I |
When the first groove has been made, the nuclear manipulator is passed into the eye through the side port and placed in the groove. The nucleus is then rotated anticlockwise to present the next area of nucleus to be sculpted. These medium hard nuclei are generally easy to rotate.
Following the fashioning of all four grooves (Fig. 14.21) to create a cruciate shape of appropriate depth, the nucleus can be cracked.
Note Although I have used the chopping technique and still do to facilitate the removal of large nuclear fragments. I find that my technique for nucleofractis is the most predictable and consistent, also it is the easiest to teach our residents in training.
•Cracking
i.Using the manipulator to move the nucleus so that a groove is placed at the apex of the triangle formed by the phaco tip and the manipulator.
ii.These two instruments (Figs 14.22 and 14.23) are then put at the bottom of the groove.
iii.The phaco tip stabilizes the nucleus while the manipulator moves to the left. In a medium hard nucleus little effort should be needed to crack it. The crack should take place centrally but the effect should cause the equator to separate also. This is important for quadrant removal later.
•Quadrant removal
i.Each quadrant is split in turn and then the manipulator is used to lift the apex of the first quadrant to present it to the phaco tip (Fig. 14.24).
Note If the first quadrant that is approached for removal does not readily detach itself from its position, move to the smallest and try to engage it. Once one quadrant has been removed the others come easily.
ii.Initially the foot pedal is used in position 3 (phaco mode) to impale the nuclear quadrant on the phaco tip and thus cause occlusion. The foot pedal is now moved into position 2 (I/A) and vacuum is allowed to build. When it is felt that a good grip has been achieved on the nuclear quadrant it can be moved to the center of the capsulorrhexis. In this position using mostly vacuum assisted by low levels of linearly controlled U/S power, the quadrant is emulsified.