No anesthesia Sub 1mm (700 micron)
Micro-Incision Cataract Surgery-
Microphakonit
EYE RESEARCH CENTRE
&
DR.AGARWAL'S GROUP OF EYE HOSPITALS
19 CATHEDRAL ROAD, CHENNAI- 600 086, INDIA
TEL- + 91 44 2811 6233
FAX- + 91 44 2811 5871
WEBSITE- http://www.dragarwal.com
E-MAIL- dragarwal@vsnl.com
HISTORY:
On August 15th 1998 the authors (Amar Agarwal) performed 1 mm cataract surgery by a technique called PHAKONIT1-13 (Phako being done with a Needle Incision Technology). Dr.Jorge Alio (Spain) coined the term MICS or Microincision cataract surgery 14 for all surgeries including laser cataract surgery and Phakonit. Dr.Randall Olson (USA) first used a 0.8 mm phaco needle and a 21 gauge irrigating chopper and called it Microphaco15-18. On May 21st 2005, for the first time a 0.7 mm phaco needle tip with a 0.7 mm irrigating chopper was used by the authors (Am A) to remove cataracts through the smallest incision possible as of now. This is called Microphakonit.
MICROPHAKONIT (0.7 mm) NEEDLE TIP:
When we wanted to go for a 0.7 mm phaco needle the point which we wondered was whether the needle would be able to hold the energy of the ultrasound. We gave this problem to Larry Laks from MST, USA to work on. He then made this special 0.7 mm phaco needle . As you will understand if we go smaller from a 0.9 mm phaco needle to a 0.7 mm phaco needle the speed of the surgery would go down. This is because the amount of aspiration flow rate would be less.
It was decided to solve this problem by working on the wall of the 0.7 mm phaco needle. There is a standard wall thickness for all phaco tips. If we say the outer diameter is a constant, the resultant inner diameter is an area of the outer diameter minus the area of the wall.
The inner diameter will regulate the flow rate/ perceived efficiency (which can be good or bad, depending on how you look at it). In order to increase the allowed aspiration flow rate from what a standard 0.7mm tip would be, MST (Larry Laks) had the walls made thinner, thus increasing the inner diameter. This would allow a case to go, speed wise, closer to what a 0.9mm tip would go (not exactly the same, but closer). With the gas forced infusion it would work very well. Finally we decided to go for a 30 degree tip to make it even better.
MICROPHAKONIT (0.7 mm) IRRIGATING CHOPPER:
There are two designs of 20 gauge (0.9 mm) irrigating choppers which we designed. (Figure 1). for phakonit when we used the 0.9 mm needle and irrigating chopper. One is the Agarwal irrigating chopper made by the MST (Microsurgical Technology) company. The opening for the fluid in this are end opening This is incorporated in the Duet system. The other irrigating chopper is made by Geuder, Germany. This has two openings in the side. Depending on the convenience of the surgeon, the surgeon can decide which design of irrigating chopper they would like to use. There are advantages and disadvantages of both types of irrigating choppers. The end opening chopper has an advantage of more fluid coming out of the chopper. The disadvantage is that there is a gush of fluid which might push the nuclear pieces away. The advantage of the side opening irrigating chopper is that there is good control as the nuclear pieces are not pushed away but the disadvantage is that the amount of fluid coming out of it is much less. That is why if one is using the side opening irrigating chopper one should use an air pump or gas forced infusion.The MST in their irrigating chopper increased flow by removing the flow restrictions incorporated in other irrigating choppers as a bi-product of their attachment method. They also had control of incisional outflow by having all the instruments to be of one size and created a matching knife of the proper size and geometry(Figure 2).
When we decided to go smaller to using a 0.7 mm irrigating chopper (Figure 3) we decided to go for an end-opening irrigating chopper. The reason is as the bore of the irrigating chopper was smaller the amount of fluid coming out of it would be less and 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 fluid into the anterior chamber and that is what happened.
We measured the amount of fluid coming out of the various irrigating choppers with and without an air pump (Table 1). We also measured the values using the simple aquarium air pump (external gas forced infusion) and the accurus machine giving internal gas forced infusion.
| IRRIGATING CHOPPER | WITHOUT GAS FORCED INFUSION |
WITH GAS FORCED INFUSION USING THE ACCURUS MACHINE AT 50 mm Hg | WITH GAS FORCED INFUSION USING THE ACCURUS MACHINE AT 75 mm Hg | WITH GAS FORCED INFUSION USING THE ACCURUS MACHINE AT 100 mm Hg | AIR PUMP WITH REGULATOR AT LOW |
AIR PUMP WITH REGULATOR AT HIGH |
0.9 m 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 |
The microphakonit irrigating chopper which we have designed 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. Table 2 shows the differences between C-MICS which is Co axial Microincisional cataract surgery and B-MICS which is Bimanual Microincisional cataract surgery.
| FEATURE | PHACO (C-MICS) | PHAKONIT (B-MICS) |
| 1. INCISION SIZE | 3 MM | SUB 1.4 MM |
| 2. AIR PUMP | NOT MANDATORY | MANDATORY |
| 3. HAND USAGE | SINGLE HANDED PHACO POSSIBLE | TWO HANDS (BIMANUAL) |
| 4. NON DOMINANT HAND ENTRY AND EXIT | LAST TO ENTER AND FIRST TO EXIT | FIRST TO ENTER AND LAST TO EXIT |
| 5. CAPSULORHEXIS | NEEDLE OR FORCEPS | BETTER WITH NEEDLE |
| 6. IOL | FOLDABLE IOL | ROLLABLE IOL |
| 7. ASTIGMATISM | TWO UNEQUAL INCISIONS CREATE ASTIGMATISM | TWO EQUAL ULTRASMALL INCISIONS NEGATE THE INDUCED ASTIGMATISM |
| 8. STABILITY OF REFRACTION | LATER THAN PHAKONIT | EARLIER THAN PHACO |
| 9. IRIS PROLAPSE- INTRAOPERATIVE | MORE CHANCES | LESS CHANCES DUE TO SMALLER INCISION |
AIR PUMP AND GAS FORCED INFUSION:
The main problem in phakonit we had was the destabilization of the anterior chamber during surgery. We solved it to a certain extent by using an 18-gauge irrigating chopper. Then Sunita Agarwal suggested the use of an antichamber collapser 19, which injects air into the infusion bottle . This pushes more fluid into the eye through the irrigating chopper and also prevents surge . Thus, we were able to use a 20/21 gauge irrigating chopper as well as solve the problem of destabilization of the anterior chamber during surgery. Now with a 22 gauge (0.7 mm) irrigating chopper it is extremely essential that gas forced infusion be used in the surgery. This is also called external gas forced infusion.
When the surgeon uses the air pump contained in the same phaco machine, it is called internal gas forced infusion (IFI). To solve the problem of infection we use a millipore filter connected to the machine. The Stellaris machine made by Bausch and Lomb have an inbuilt air pump to give pressurized infusion.When we are using a 0.7 mm irrigating chopper the problem is that the amount of fluid entering the eye is not enough. To solve this problem gas forced infusion is a must. We preset the infusion pump at 100 mm Hg when we are operating microphakonit.
BIMANUAL 0.7 mm IRRIGATION ASPIRATION SYSTEM:
Bimanual irrigation aspiration is done with the bimanual irrigation aspiration instruments (Fig). These instruments are also designed by Microsurgical Technology (USA). The previous set we used was the 0.9 mm set. Now with microphakonit we use the new 0.7 mm bimanual I/A set (Figure 4 and 5) so that after the nucleus removal we need not enlarge the incision.
DUET HANDLES:
All these instruments of the 0.7 mm set fit onto the handles of the Duet system. So if a surgeon has already got the handles and is using it for phakonit they need to get only the tips and can use the same handles for microphakonit (Figure 6)
DIFFERENCES BETWEEN 0.9 MM AND 0.7 MM SETS IN CATARACT SURGERY
Table 3 indicates the differences between the two techniques
| FEATURES | PHAKONIT | MICROPHAKONIT |
| IRRIGATING CHOPPER | 0.9 MM | 0.7 MM |
| PHACO NEEDLE | 0.9 MM | 0.7 MM |
| CONTROL IN SURGERY | GOOD | BETTER CONTROL |
| VALVE CONSTRUCTION | EXTREMELY IMPORTANT | NOT VERY IMPORTANT AS INCISION IS MUCH SMALLER |
| IRIS PROLAPSE | CAN OCCUR IF VALVE IS BAD | VERY RARE |
| INTRAOPERATIVE FLOPPY IRIS SYNDROME | CAN BE MANAGED | MUCH BETTER TO MANAGE AS INCISION IS MUCH SMALLER AND THERE IS BETTER CONTROL |
| HYDRODISSECTION | CAN BE DONE FROM BOTH INCISIONS | TO BE CAREFUL AS VERY LITTLE SPACE IS THERE FOR ESCAPE OF FLUID |
AIR PUMP (GAS FORCED INFUSION |
CAN BE DONE WITHOUT IT THOUGH BETTER WITH IT | MANDATORY. 0.7 MM IRRIGATING CHOPPERS EVEN WITH HIGHER END MACHINES NEED GFI |
| FLOW RATE | CAN KEEP ANY VALUE | DO NOT KEEP IT VERY HIGH. 20-24 ML/MIN |
| BIMANUAL I/A | 0.9 MM | 0.7 MM |
TECHNIQUE:
INCISION:
The incision is made with a keratome. This can be done using a sapphire knife or a stainless steel knife. One should be careful when one is making the incision so that the incision is a bit long as one would be using gas forced infusion in microphakonit. Before making the incision, a needle with viscoelastic is taken and pierced in the eye in the area where the side port has to be made . The viscoelastic is then injected inside the eye. This will distend the eye so that the clear corneal incision can be made easily. Make one clear corneal incision between the lateral rectus and inferior rectus and the other between the lateral rectus and superior rectus. This way one is able to control the movements of the eye during surgery.
RHEXIS:
The rhexis is then performed of about 5-6 mm. This is done with a needle (Figure 7. In the left hand a straight rod is held to stabilize the eye. This is the Globe stabilization rod. The advantage of this is that the movements of the eye can get controlled if one is working without any anesthesia or under topical anesthesia. One can use a micro rhexis forceps also (Figure 8 and 9)
HYDRODISSECTION:
Hydrodissection is performed and the fluid wave passing under the nucleus checked. Check for rotation of the nucleus. The advantage of microphakonit is that one can do hydrodissection from both incisions so that even the subincisional areas can get easily hydrodissected. The problem is as there is not much escape of fluid one should be careful in hydrodissection as if too much fluid is passed into the eye one can get a complication.
MICROPHAKONIT:
The 22 (0.7 mm) Gauge irrigating chopper connected to the infusion line of the phaco machine is introduced with foot pedal on position 1. The phaco probe is connected to the aspiration line and the 0.7 mm phaco tip without an infusion sleeve is introduced through the clear corneal incision . Using the phaco tip with moderate ultrasound power, the center of the nucleus is directly embedded starting from the superior edge of rhexis with the phaco probe directed obliquely downwards towards the vitreous. The settings at this stage are 50% phaco power, flow rate 20 ml/min and 100-200 mm Hg vacuum. Using the karate chop technique the nucleus is chopped. Thus the whole nucleus is removed. Cortical wash-up is then done with the bimanual irrigation aspiration (0.7 mm set) technique . During this whole procedure of microphakonit gas forced infusion is used.
SUMMARY:
With microphakonit a 0.7 mm set is used to remove the cataract. At present this is the smallest one can use for cataract surgery. With time one would be able to go smaller with better and better instruments and devices. The problem at present is the IOL. We have to get good quality IOL’s going through sub 1mm cataract surgical incisions so that the real benefit of microphakonit can be given to the patient.
REFERENCES:
- Agarwal A, Agarwal S, Agarwal At: No anesthesia Cataract surgery ; In Agarwal et als textbook Phacoemulsification, Laser cataract surgery and foldable IOL’s, First edition; Jaypee , India, 1998; 144-154
- Pandey S; Wener L,Agarwal A, Agarwal S, Agarwal At,Apple D : No anesthesia Cataract surgery ; J Cataract and Refractive Surgery; 2001; 28:1710
- Agarwal A, Agarwal S, Agarwal At: Phakonit: A new technique of removing cataracts through a 0.9 mm incision; In Agarwal et als textbook Phacoemulsification, Laser cataract surgery and foldable IOL’s, First edition; Jaypee , India, 1998; 139-143
- Agarwal A, Agarwal S, Agarwal At: Phakonit and laser phakonit: Lens surgery through a 0.9 mm incision; In Agarwal et als textbook Phacoemulsification, Laser cataract surgery and foldable IOL’s, Second edition; Jaypee, India,2000; 204-216
- Agarwal A, Agarwal S, Agarwal At: Phakonit; In Agarwal et als textbook Phacoemulsification, Laser cataract surgery and foldable IOL’s, Third edition; Jaypee , India, 2003; 317-329
- Agarwal A, Agarwal S, Agarwal At: Phakonit and laser phakonit; In Boyd/Agarwal et als textbook Lasik and Beyond Lasik, Higlights of Ophthalmology, Panama, 2000; 463-468
- Agarwal A, Agarwal S, Agarwal At: Phakonit and laser phakonit- Cataract surgery through a 0.9 mm incision; In Boyd/Agarwal et als textbook Phako, Phakonit and Laser Phako, Higlights of Ophthalmology, Panama, 2000; 327-334
- Agarwal A, Agarwal S, Agarwal At: The Phakonit Thinoptx IOL; In Agarwals textbook Presbyopia, Slack, USA, 2002; 187-194
- Agarwal A, Agarwal S, Agarwal At: Antichamber collapser; J Cataract and Refractive Surgery; 2002; 28:1085
- Pandey S; Wener L,Agarwal A, Agarwal S, Agarwal At,Hoyos J: Phakonit: Cataract removal through a sub 1.0 mm incision with implantation of the Thinoptx rollable IOL ; J Cataract and Refractive Surgery; 2002; 28:1710
- Agarwal A, Agarwal S, Agarwal At: Phakonit: phacoemulsification through a 0.9 mm incision ; J Cataract and Refractive Surgery; 2001; 27:1548-1552
- Agarwal A, Agarwal S, Agarwal At: Phakonit with an acritec IOL ; J Cataract and Refractive Surgery; 2003; 29:854-855
- Agarwal S, Agarwal A, Agarwal At: Phakonit with Acritec IOL; Highlights of ophthalmology 2000
- Jorge Alio: What does MICS require in Alios textbook MICS; Highlights of Ophthalmology 2004; 1-4
- Soscia W, Howard JG, Olson RJ: Microphacoemulsification with Whitestar. A wound-temperature study; J Cataract and Refractive Surgery 2002, 28; 1044-1046
- Soscia W, Howard JG, Olson RJ: Bimanual phacoemulsification through two stab incisions. A wound-temperature study; J Cataract and Refractive Surgery 2002, 28; 1039-1043
- Randall Olson: Microphaco chop in David Changs textbook on Phaco Chop; Slack , USA 2004; 227-237
- David Chang: Bimanual phaco chop in David Changs textbook on Phaco Chop; Slack , USA 2004; 239-250
- Agarwal A: Air pump in Agarwal’s textbook on Bimanual phaco: Mastering the phakonit/MICS technique; Slack , USA 2005
