Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001
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THE ART OF PHACOEMULSIFICATION
Fig. 7.9: (Hayashi) Mean (standard deviation) induced keratometric cylinder following superolateral incision and superior incision surgery using the vector analysis method. The mean induced keratometric cylinders in group 1 were significantly less than those in group 2 throughout the six month follow-up. The standard deviations in group 1 were also smaller than those in group 2
month after surgery. Consequently, in group 1, the averaged maps of the corneas, after 1 month were virtually the same as the map of preoperative corneas.
The averaged maps of group 2 patients show a marked steepening of the upper and lower corneas, in the vertical meridian, one week after surgery. This induced steepening gradually decreased but remained upto three months. The averaged map of the cornea at “six“ months after surgery, was almost the same as the preoperative map (as compared to one month, group 1).
Absolute scale maps of a patient in Group 1 reveal remarkable changes in the corneal shape after surgery. There was prominent corneal steepening in the 10 O’clock meridian and the map shows an asymmetric horizontal bow-tie configuration one week after surgery. This steepening quickly disappeared; at three and six months after surgery the cornea had almost recovered it’s preoperative shape, although a focal steepening in the horizontal meridian remained (Fig. 7.10). In group 1 19.7 percent of corneas showed this prominent steepening, just after surgery.
Figure 7.11 shows a patient from group 2. Marked steepening of the upper and lower corneas occurred at one week and is shown as a vertical bow-tie configuration. The steepening did not change substantially during the six-month follow-up. In group 2, 68.4 percent of corneas, showed this marked corneal steepening.
Thus, superolateral incision cataract surgery induced minimum changes in the corneal shape, as well as SIA, and the changes decreased quickly and stabilized in the early postoperative period. One cannot explain why the induced corneal shape changes are less with the superolateral approach. The differences between
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Fig. 7.11: (Hayashi) Absolute scale maps of a cornea in the superior incision group: (A) Preoperatively and (B) at 3 months postoperatively. At three months the steepening in the upper and lower corneas, did not change substantially
Fig. 7.10: (Hayashi) Absolute scale maps of a cornea in the superolateral incision group: (A) Preoperatively, and (B) at 3 months postoperatively. After 3 months the map was almost same as preoperatively
the semilateral and superior incision surgeries were only related to the wound site. There are a few anatomical differences between the horizontal and the superior limbus. Alternatively, some unknown physiologic and/or optical factor may exist. The rapid stabilization with the superolateral incision appeared to be rather easy to explain.
Continuous stroking of the upper eyelid causes pressure on the superior corneoscleral wound. Therefore corneal distortion by the superior wound persists longer. A superolateral incision is relatively free from such eyelid pressure and corneal shape changes stabilize faster. Thus, superolateral incision surgery appears to have advantages, although the exact mechanism remains unproven.
The temporal location has been shown to be the most astigmatically stable of these three locations, achieving stability almost immediately and maintaining stability for life or until further astigmatic interventions. First, the temporal location is furthest from the visual axis, and so there will be less impact on the corneal curvature at the visual axis. Second the wound is parallel to the effects of both lid blink and gravity. The temporal location has an added advantage in that it provides the easiest anatomic access to the surgical site, being unimpeded by the bony orbital rim.
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Fig. 7.13: Limbal incision, 1 week postsurgery demonstrating significant fibroblastic activity completely sealing the incision
Fig. 7.12: Clear corneal incision, 1 week postsurgery showing no wound healing
Fig. 7.14: Two-month postsurgery, clearcorneal incision demonstrating the incision is healed through binding of the stromal keratocytes as seen in corneal transplant surgery
LIMBUS vs CLEAR CORNEA
In their fourth cadaver study of clear corneal incisions Ernst et al reported that when clear corneal incisions of exactly the same dimensions were made at the limbus and anterior to the limbus, the one nearer the limbus demonstrated greater
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Fig. 7.15: Two-month postsurgery, limbal incision, 
showing the same fibroblastic activity and the
same degree of healing as 1 week postsurgery
wound stability. The reason of this is not completely clear. It may be that the architecture of the limbus, with its circumferential fibers allows greater resistance than the radial fibers of the cornea. The limbus also contains more elastic fibers than the cornea, which has none.
Histologic evaluations at 1 week showed no healing activity of the clear-corneal incision (Fig. 7.12). The limbal incision, whether it was placed anteriorly or posteriorly, showed a significant fibroblastic response causing the wound to seal (Fig. 7.13).
Both limbal and corneal incisions heal by fibroblast response. The key is the timing of the healing process: 7 days for vascular origin (limbal incisions) and 60 days for avascular origin (corneal incisions). Limbal incisions heal by an influx of fibroblasts in the vascular arcade or through the differentiation of stem cells into fibroblasts. They heal faster than corneal incisions, which heal in a way similar to that of corneal transplants, in which binding stromal keratocytes transform into fibroblasts (Figs 7.14 and 7.15). The advantages of moving to a temporal approach and more posterior into a vascular region (limbal incisions) allow an earlier fibroblast response that seals incisions faster than the 60 days required for incisions made in an avascular region (corneal incisions).
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Amar Agarwal |
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Athiya Agarwal |
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Sunita Agarwal |
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No Anesthesia |
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Cataract Surgery |
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I N T R O D U C T I O N
On June 13th, 1998 at Ahmedabad, India the authors (Amar Agarwal) did the first No anesthesia cataract surgery at the Phaco and Refractive Surgery Conference. This was performed as a live surgery in front of 250 delegates. This has opened up various new concepts in cataract surgery.
Phacoemulsification
Since the introduction of phacoemulsification as an alternative to standard cataract extraction techniques, surgeons throughout the world have been attempting to make this new procedure safer and easier to perform while assuring good visual outcome and patient recovery. The fundamental goal of phaco is to remove the cataract with minimal disturbance to the eye using least number of surgical manipulations. Each maneuver should be performed with minimal force and maximal efficiency should be obtained.
The latest generation phaco procedures began with Dr Howard Gimbel’s “divide and conquer” nuclear fracture technique in which he simply split apart the nuclear rim. Since then we have evolved through the various techniques namely four quadrant cracking, chip and flip, spring surgery, stop and chop and phaco chop.
The phaco chop technique was developed and introduced by Dr Nagahara to reduce total phaco time and power needed to remove the cataractous lens. In this technique the tip is embedded in the superior half of the nucleus using shallow sculpturing motion. The tip of the chopper is introduced into the nucleus at the 6 O’clock position by penetrating the lens cortex and epinucleus. The two
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Fig. 8.1: Eye with cataract |
Fig. 8.2: Left hand injects viscoelastic using a |
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26-gauge needle |
instruments create the nuclear fracture. The nucleus is rotated and the process repeated to get 4 to 6 fragments. Each quadrant is then emulsified. This chopping does peripheral chopping. In other words, the nucleus is chopped from the periphery.
Agarwal Karate Chop Technique
Incision
A temporal clear-corneal section is made. If the astigmatism is plus at 90 degrees then the incision is made superiorly. first of all, in the cataractous eye (Fig. 8.1) a needle with viscoelastic is injected inside the eye in the area where the second site is made (Fig. 8.2). 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 (Fig. 8.3).
When we started making the temporal incisions, 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
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Fig. 8.3: Clear corneal incision. Note the straight |
Fig. 8.4: Rhexis being done with a needle |
rod inside the eye in the left hand. The right hand |
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is performing the clear corneal incision. This is a |
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temporal incision and the surgeon is sitting |
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temporally |
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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.
Rhexis
Capsulorrhexis is then performed through the same incision (Fig. 8.4). While performing rhexis it is important to note that the rhexis is started from the center and the needle moved to the right and then downwards. This is important because today concepts have changed to temporal and nasal. It is better to remember it as superior, inferior, right or left. If we would start 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
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Fig. 8.5: Hydrodissection
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.
If you are a left-handed person start the rhexis from the center and move to the left and then down.
Hydrodissection
Hydrodissection is then performed (Fig. 8.5). We watch for the fluid wave to see that hydrodissection is complete. We do
not perform hydrodelineation or test for rotation of the nucleus. Viscoelastic is then introduced before inserting the phaco probe.
Karate Chop—Two Halves
We then insert the phaco probe through the incision slightly superior to the center of the nucleus (Fig. 8.6). At that point apply ultrasound and see that the phaco tip gets embedded in the nucleus (Fig. 8.7). The direction of the phaco probe should be obliquely downwards toward the vitreous and not horizontally towards the iris. Then only the nucleus will get embedded. The settings at this stage are 70 percent phaco power, 24 ml/minute flow rate and 101 mm of 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-degree tip but any tip can be used.
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
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Fig. 8.6: Phaco probe placed at the superior end of the rhexis
Fig. 8.7: 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. Note the tip of the phaco is not seen as it is fully embedded
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. 8.8) 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 an inverted L.
Remember—do not go to the periphery for chopping but do it at the center.
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.
Karate Chop—Further Chopping
Now that you have two halves, you have a shelf to embed the probe. So, now place the probe with ultrasound into one half of the nucleus (Fig. 8.9). You can
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Fig. 8.8: Left hand chops the nucleus and splits like an inverted L shape, that is downwards and to the left. When the crack is complete, you should see posterior capsule throughout the crack
Fig. 8.9: Embed the probe in one-half of the nucleus. Go horizontally and not vertically as you have now a shelf of nucleus to embed
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 percent phaco power, 24 ml/minute flow rate and 101 mm of Hg suction.
Remember 5 words—embed, pull, chop, split and release.
Pulse Phaco
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