16 |
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|
J. L. Alió et al. |
Table 1.1 Fluid exiting from various irrigating choppers (mL/min) by Amar Agarwal |
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Irrigating |
Without gas |
With gas forced infusion at |
|
|
Air pump with |
Air pump with |
|
chopper |
forced infusion |
50 mmHg |
75 mmHg |
100 mmHg |
|
regulator at low |
regulator at high |
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|
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|
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0.9 mm Side opening |
25 |
36 |
42 |
48 |
37 |
51 |
|
0.9 mm End opening |
34 |
51 |
57 |
65 |
52 |
68 |
|
0.7 mm End opening |
27 |
39 |
44 |
51 |
41 |
54 |
|
0.7 mm Inferior opening |
32 |
45 |
55 |
66 |
50 |
66 |
|
Table 1.2 The differences between the two techniques of 0.9 and 0.7 mm MICS |
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|
Features |
0.9 mm MICS |
0.7 mm MICS |
Incision length (mm) |
1.2 |
1.0 |
Valve configuration of the incision |
Very important |
Important as incision is much smaller |
Hydrodissection |
Can be done from both incisions |
To be careful as there is very little space |
|
|
for fluid to exit the eye |
Irrigating chopper (mm) |
0.9 |
0.7 |
Diameter of the phaco tip (mm) |
0.9 |
0.7 |
Bimanual I/A (mm) |
0.9 |
0.7 |
Iris prolapse |
Can occur if corneal valve is not well done |
Very rare |
Intraoperative floppy iris syndrome |
Can be managed |
Absent |
prevention |
|
|
Pressured infusion |
Can be done without it, but better with it |
Mandatory |
Flow rate |
Can keep any value |
Do not keep it very high. 20–24 mL/min |
Control in surgery |
Very good |
Even better |
Closing incision |
Hydration is mandatory |
Hydration is not necessary |
The difference between 0.9 and 0.7mm surgery is not only the diameter of the instruments, but also the quality of the surgery. The smaller width of the tools gives us the opportunity to control more precisely the surgery and the maneuvers in the anterior chamber. The use of the pressured infusion and high vacuum MICS instruments provides control over anterior chamber stability. The problem with iris prolapse practically does not exist. Smaller incisions prevent leakage. The main features in 0.9 and 0.7mm MICS are shown in Table 1.2.
The second parameter that should be maintained is the vacuum. One of the authors (Jorge Alió) started
work with the Bausch & Lomb Stellaris platform. As
the 0.7 mm MICS requires higher parameters for suf- 1.3.3 Instrumentation ficient flow, this can be hazardous for anterior cham-
ber stability. The lack of inflow compensation after the occlusion can cause anterior chamber collapse. To prevent the surge during occlusion breaks at higher vacuum levels, the flow restrictor can be installed between the phacoemulsification handpiece and the aspiration tubing. Stable Chamber System® (Bausch &
1.3 0.7 mm Microincision Cataract Surgery |
17 |
The problem in the minimization of the phaco tip is not only the tip diameter, but also the fluid flow and energy transmission. If the diameter of the phaco tip becomes smaller, from a 0.9 mm phaco needle to a 0.7 mm phaco needle, the expected speed of the surgery would decrease. Flow rate aspiration would also decrease. The inner diameter of the tip regulates the flow rate. To obtain flow rate aspiration on the standard MICS level, the wall of 0.7 mm MICS phaco tip must be thinner and thus the internal diameter of the tip can be increased. The 0.7 mm MICS needle was designed for a 22 gauge (0.7 mm) chopper. The 30° tip end makes it even better. The special 0.7 mm phaco needle is currently produced by MST (cat. numb. PT-29130 MST, Redmond, Washington) (Fig. 1.12).
1.3.3.2 0.7 mm Irrigating Instruments
There are many designs of irrigating instruments. The construction of irrigating instruments can have an endopening, lateral-opening or inferior-opening hole. The rules of the fluidics flow are the same as in the aspiration tip. The previous set used was the 0.9 mm set. Now with the 0.7 mm MICS set, the new 0.7 mm bimanual irrigation-aspiration cannulas can be positioned in the anterior chamber without enlarging the incision after the nucleus removal.
All these instruments of the 0.7mm set fit onto the handles of the Duet System. These instruments are designed by MST. So, if a surgeon already has the handles and is using it for phakonit, the same handles can be used for microphakonit, and only the tips are needed.
The end-opening chopper has an advantage of more fluid coming out of the chopper, but greater turbulence of the fluid can occur in the anterior chamber. MST in their irrigating chopper increased the flow by removing the flow restrictions incorporated in other irrigating choppers. They have also developed control on incisional outflow by making all the instruments of one size and creating a matching knife of the proper size and geometry.
The first irrigating chopper for a 0.7 mm surgery was an end-opening irrigating chopper (Fig. 1.13). The idea was to diminish the diameter of the tool and to increase the infusion. The amount of fluid coming out of it would be less, so an end-opening chopper would maintain the fluidics better. With gas forced infusion, we thought we would be able to balance the entry and exit of the fluid into the anterior chamber and we succeeded in doing so.
Two different instruments are preferred by the authors:
The Agarwal Micro Phaconit 0.7 mm irrigating chopper (Cat. No. Du-02353 MST) is basically a sharp chopper which has a sharp cutting edge and helps in karate chopping or quick chopping. It can chop any type of cataract.
The Alio Stinger irrigating chopper Duet System (Cat. No. Du-02362 MST) is a 22 gauge inferior-open- ing instrument. It has one hole on the inferior side of the cannula and provides the infusion stream directly backward, forcing cataract fragments to levitate towards the phaco tip pointed towards masses and the posterior capsule. This allows maintaining the anterior chamber at
Fig. 1.12 0.7 mm Phaco tip as compared to a 0.9 mm phaco tip |
Fig. 1.13 0.7 mm Irrigating chopper |