The main problem we had in bimanual phaco/ phakonit 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, which injects air into the infusion bottle (Fig. 1.1). This pushes more fluid into 3the eye through the irrigating chopper and also prevents surge. Thus, we were able to use a 20 gauge or 21 gauge irrigating chopper as well as solve the problem of destabilization of the anterior chamber during surgery. Now with microphakonit because of gas forced infusion we are able to remove cataracts with a 0.7 mm irrigating chopper. Subsequently we used this system in all our co-axial phaco cases to prevent complications like posterior capsular ruptures and corneal damage.
A locally manufactured automated device, used in fish tanks (aquariums) to supply oxygen, is utilized to forcefully pump air into the irrigation bottle. This pump is easily available in aquarium shops. It has an electromagnetic motor which moves a lever attached to a collapsible rubber cap. There is an inlet with a valve, which sucks in atmospheric air as the cap expands. On collapsing, the valve closes and the air is pushed into an intravenous (IV) line connected to the infusion bottle. The lever vibrates at a frequency of approximately 10 oscillations per second. The electromagnetic motor is weak enough to stop once the pressure in the closed system (i.e. the anterior chamber) reaches about 50 mm Hg. The rubber cap ceases to expand at this pressure level. A micropore air filter is used between the air pump and the infusion bottle so that the air pumped into the bottle is clean of particulate matter.4
When an occluded fragment is held by high vacuum and then abruptly aspirated, fluid rushes into the phaco tip to equilibrate the built up vacuum in the aspiration line, causing surge. This leads to shallowing (Figs 1.2A and B) or collapse of the anterior chamber). Different machines employ a variety of methods to combat surge. These include usage of noncomplaint tubing, small bore aspiration line tubing, microflow tips, aspiration bypass systems, dual linear foot pedal control and incorporation of sophisticated microprocessors to sense the anterior chamber pressure fluctuations.5
Figs 1.2A and B: Illustration showing surge and chamber collapse when the nucleus is being removed and the air pump is not used. Note the chamber depth has come down. When we use the air pump this problem does not occur
The surgeon dependent variables to counteract surge include good wound construction with minimal leakage, and selection of appropriate machine parameters 6depending on the stage of the surgery. An anterior chamber maintainer has also been described in literature to prevent surge, but an extra sideport makes it an inconvenient procedure.
To prevent anterior chamber collapse during phacoemulsification and phakonit we increase the velocity of the fluid inflow into the anterior chamber. This is achieved by an automated air pump which pumps atmospheric air through an air filter into the infusion bottle thereby preventing surge. We stumbled upon this idea when we were operating cases with phakonit where we wanted more fluid entering the eye, but now also use it in all our phaco cases.7
Before we enter the eye, we fill the eye with viscoelastic. Then once the tip of the phaco handpiece in phaco or irrigating chopper in phakonit is inside the anterior chamber we shift to continuous irrigation. This is very helpful especially for surgeons who are starting phaco or phakonit. This way, the surgeon, never comes to position zero and the anterior chamber never collapses.8
Fig. 1.3B: Flow of fluid through the irrigating chopper with an air pump. Note when the air pump is on the amount of fluid coming out of the irrigating chopper is much more
Even for excellent surgeons this helps a lot.
When the air pump is switched on, it pumps air into the infusion bottle. This air goes to the top of the bottle and because of the pressure, it pumps the fluid down with greater force. With this, the fluid now flows from the 9infusion bottle to reach the phaco handpiece or irrigating chopper. The amount of fluid now coming out of the handpiece is much more than what would normally come out and with more force (Figs 1.3A and B).
The advantages are:
- With the air pump, the posterior capsule is pushed back and there is a deep anterior chamber.
- The phenomenon of surge is neutralized. This prevents the unnecessary posterior capsular rupture.
- Striate keratitis postoperatively is reduced, as there is a deep anterior chamber.
- One can operate hard cataracts also quite comfortably, as striate keratitis does not occur postoperatively.
- The surgical time is shorter as one can emulsify the nuclear pieces much faster as surge does not occur.
- One can easily operate cases with the phakonit technique as quite a lot of fluid now passes into the eye. Thus, the cataract can be removed through a smaller opening.
- It is quite comfortable to do cases under topical or no anesthesia.
Internal gas forced infusion was started by Arturo Pérez-Arteaga from Mexico. The anterior vented gas forced infusion (AVGFI) system of the Accurus surgical system is used (Fig. 1.4). This is a system incorporated in the Accurus machine that creates a positive infusion pressure inside the eye; it was designed by the Alcon engineers to control the intraocular pressure (IOP) during the anterior and posterior segment surgery. It consist of an air pump and a 11regulator who are inside the machine; then the air is pushed inside the bottle of intraocular solution, and so the fluid is actively pushed inside the eye without raising or lowering the bottle. The control of the air pump is digitally integrated in the Accurus panel; it also can be controlled via the remote. Also the footswitch can be preset with the minimal and maximum of desired fluid inside the eye and go directly to this value with the simple touch of the footswitch. Arturo Pérez-Arteaga recommends to preset the infusion pump at 100 to 110 mm Hg; it is enough strong irrigation force to perform a microincision phaco. This parameter is preset in the panel and also as the minimal irrigation force in the footswitch; then he recommends to preset the maximum irrigation force at 130 to 140 mm Hg in the foot pedal, so if a surge exist during the procedure the surgeon can increase the irrigation force by the simple touch of the footswitch to the right. With the AVGFI the surgeon has the capability to increase even more these values.12
Fig. 1.5: Eye with cataract. Needle with viscoelastic entering the eye to inject the viscoelastic. This is the most important step in no anesthesia cataract surgery. This gives an entry into the eye through which a straight rod can be passed to stabilize the eye. Note no forceps holds the eye
On June 13th 1998 at Ahmedabad, India the first No anesthesia cataract surgery was done by the author (Amar Agarwal) as a live surgery at the phako and refractive surgery conference. This has opened up various new concepts in cataract surgery. In this surgery the technique of karate chop was used. Unlike the peripheral chopping of Nagahara or other stop and chop techniques we have developed a safer technique called “Central anterior chopping” or “karate chop”. In this method the phaco tip is embedded by a single burst of power in the central safe zone and after lifting the nucleus a little bit (to lessen the pressure on the posterior capsule) the chopper is used to chop the nucleus. In soft nuclei, it is very difficult to chop the nucleus. In most cases, one can take it out in toto. But if the patient is about 40 years of age then one might have to chop the nucleus. In such cases we embed the phaco probe in the nucleus and then with the left hand cut the nucleus as if we are cutting a piece of cake. This movement should be done three times in the same place. This will chop the nucleus.
A temporal clear corneal section is made. If the astigmatism is plus at 90 degrees then the incision is made superiorly. First of all, a needle with viscoelastic is injected inside the eye in the area where the second site is made 14(Fig. 1.5). This will distend the eye so that when you make a clear corneal incision, the eye will be tense and one can create a good valve. Now use a straight rod to stabilize the eye with the left hand. With the right hand make the clear corneal incision.15
Fig. 1.6: Clear corneal incision. Note the straight road inside the eye in the left hand. The right hand is performing the clear corneal incision. This is a temporal incision and the surgeon is sitting temporally
When we started making the temporal incisions (Fig. 1.6), we positioned ourselves temporally. The problem by this method is that, every time the microscope has to be turned which in turn would affect the cables connected to the video camera. Further the theater staff would get disturbed between right eye and left eye. To solve this problem, we then decided on a different strategy. We have operating trolleys on wheels. The patient is wheeled inside the operation theater and for the right eye the trolley is placed slightly obliquely so that the surgeon does not change his or her position. The surgeon stays at the 12 O’ clock position. For the left eye the trolley with the patient is rotated horizontally so that the temporal portion of the left eye comes at 12 O’ clock. This way the patient is moved and not the surgeon.
We had been wondering whether any topical anesthesia is required or not. So we then operated patients without any anesthesia. In these patients no xylocaine drops were instilled. The patients did not have any pain. It is paradoxical because we have been taught from the beginning that we should apply xylocaine. We never use any one-tooth forceps to stabilize the eye. Instead what we use is a straight rod which is passed inside the eye to stabilize it when we are performing rhexis, etc. The first 17step is very important. In this we first enter the eye with a needle having viscoelastic and inject the viscoelastic inside the eye. This is done in the area of the side port. Now, we have an opening in the eye through which a straight rod can be passed to stabilize the eye. Francisco Gutierrez-Carmona from Spain modified the technique using cold fluid and has termed it as Cryoanalgesia.18
Capsulorhexis is then performed through the same incision (Fig. 1.7). While performing the rhexis it is important to note that the rhexis is started from the center and the 19needle moved to the right and then downward. This is important because today concepts have changed of temporal and nasal. It is better to remember it as superior, inferior, right or left. If we would start the rhexis from the center and move it to the left then the weakest point of the rhexis is generally where you finish it. In other words, the point where you tend to lose the rhexis is near its completion. If you have done the rhexis from the center and moved to the left, then you might have an incomplete rhexis on the left hand side either inferiorly or superiorly. Now, the phaco probe is always moved down and to the left. So every stroke of your hand can extend the rhexis posteriorly creating a posterior capsular rupture. Now, if we perform the rhexis from the center and move to the right and then push the flap inferiorly-then if we have an incomplete rhexis near the end of the rhexis it will be superiorly and to the right. Any incomplete rhexis can extend and create a posterior capsular tear. But in this case, the chances of survival are better. This is because we are moving the phaco probe down and to the left, but the rhexis is incomplete up and to the right.
Hydrodissection is then performed. We watch for the fluid wave to see that hydrodissection is complete. We do not perform hydrodilenation unless operating on a posterior 21polar cataract. In such a case we do only hydrodilenation and not hydrodissection. Viscoelastic is then introduced before inserting the phaco probe.
We have devised our own chopper. The other choppers, which cut from the periphery, are blunt choppers. Our chopper is a sharp chopper. It has a sharp cutting edge. It also has a sharp point. The advantage of such a chopper is that you can chop in the center and need not go to the periphery. In this method by going directly into the center of the nucleus without any sculpting ultrasound energy required is reduced. The chopper always remains within the rhexis margin and never goes underneath the anterior capsule. Hence, it is easy to work with even small pupils or glaucomatous eyes. Since we don't have to widen the pupil, there is little likelihood of tearing the sphincter and allowing prostaglandins to leak out and cause inflammation or cystoid macular edema. In this technique we can easily go into even hard nuclei on the first attempt.
We then insert the phaco probe through the incision slightly superior to the center of the nucleus (Fig. 1.8). At that point apply ultrasound and see that the phaco tip gets embedded in the nucleus. The direction of the phaco probe should be obliquely downwards toward the vitreous 22and not horizontally towards the iris. Then only the nucleus will get embedded. The settings at this stage are 70% phaco power, 24 ml/minute flow rate and 101 mm Hg suction. By the time the phaco tip gets embedded in the nucleus the tip would have reached the middle of the nucleus. We do not turn the bevel of the phaco tip downwards when we do this step, as the embedding is better the other way. We prefer a 15° tip but any tip can be used.23
Fig. 1.9: Phaco probe embedded in the nucleus. We started from the superior end of the rhexis and note it has got embedded in the middle of the nucleus. If we had started in the middle then we would have embedded only inferiorly that is at the edge of the rhexis and chopping would be difficult. Left hand chops the nucleus and splits like a laterally reversed l, that is downwards and to the left
Now stop phaco ultrasound and bring your foot to position 2 so that only suction is being used. Now lift the nucleus. When we say lift it does not mean lift a lot but just a little so that when we apply pressure on the nucleus with the chopper the direction of the pressure is downwards. If the capsule is a bit thin like in hypermature cataracts you might rupture the posterior capsule and create a nucleus drop. So when we lift the nucleus the pressure on the posterior capsule is lessened. Now, with the chopper cut the nucleus with a straight downward motion (Fig. 1.9) and then move the chopper to the left when you reach the center of the nucleus. In other words, your left hand moves the chopper like a laterally reversed L.
Once you have created a crack, split the nucleus till the center. Then rotate the nucleus 180 degrees and crack again so that you get two halves of the nucleus. In brown cataracts, the nucleus will crack but sometimes in the center the nucleus will still be attached. You have to split the nucleus totally in two halves and you should see the posterior capsule throughout.25
Fig. 1.10: Phaco probe embedded in one-half of the nucleus. Go horizontally and not vertically as you have now a shelf of nucleus to embed. Chop and then split the nucleus
Now that you have two halves, you have a shelf to embed the probe. So, now place the probe with ultrasound into 26one-half of the nucleus (Fig. 1.10). You can pass the direction of the probe horizontally as now you have a shelf. Embed the probe, then pull it a little bit. This step is important so that you get the extra bit of space for chopping. This will prevent you from chopping the rhexis margin. Apply the force of the chopper downwards. Then move the chopper to the left so that the nucleus gets split. Again, you should see posterior capsule throughout so that you know the nucleus is totally split. Then release the probe, as the probe will still be embedded into the nucleus. Like this create three quadrants in one-half of the nucleus. Then make another three halves with the second-half of the nucleus. Thus, you now have 6 quadrants or pie-shaped fragments. The settings at this stage are 50% phaco power, 24 ml/minute flow rate and 101 mm Hg suction.
Once all the pieces have been chopped, take out each piece one by one and in pulse phaco mode aspirate the pieces at the level of the iris. Do not work in the bag unless the cornea is preoperatively bad or the patient is very elderly. Always use the air pump at this stage as surge is prevented and the chamber becomes deep. The setting 27at this stage can be phaco power 50-30%, flow rate 24 ml and suction 101 mm Hg.
Fig. 1.11: Cortical aspiration completed. Note the straight rod in the left hand which helps control the movements of the eye
The next step is to do cortical washing (Fig. 1.11). Always try to remove the subincisional cortex first, as that is the most difficult. Note the left hand has the straight rod 29controlling the movements of the eye. If necessary use a bimanual irrigation aspiration technique. Then inject viscoelastic and implant the foldable IOL.
At the end of the procedure, inject the BSS inside the lips of the clear corneal incision. This will create a stromal hydration at the wound. This will create a whiteness, which will disappear after 4-5 hours. The advantage of this is that the wound gets sealed better.