Ординатура / Офтальмология / Английские материалы / LASIK and Beyond LASIK Wavefront Analysis and Customized Ablation_Boyd_2001

One can inject Blurhex directly or first inject air into the anterior chamber. This prevents waterlike dilution of the Trypan blue. Then the Trypan blue is withdrawn from the vial into a syringe. This is then injected by a cannula into the anterior chamber between the air bubble and the lens capsule. It is kept like that for a minute or two for staining of the anterior capsule to occur. Next viscoelastic is injected into the anterior chamber to remove the air bubble and the Trypan blue.

Now, rhexis is started with a needle (Figure 42-14). One can use a forceps also. We prefer to use a needle as it gives better control on the size of the rhexis. Note the left hand holding a rod stabilizing

the eye while the rhexis is being performed. The rhexis is continued with the needle. Note the contrast between the capsule, which has been stained, and the cortex, which is not stained. The rhexis is continued and finally completed (Figure 42-15). When the rhexis is complete, we can see the stained anterior capsule lying in the anterior chamber .

Air Pump to Prevent Surge

One of the main bugbears of phacoemulsification is Surge1. The problem is that as the nuclear piece gets occluded in the phaco tip and we emulsify

Figure 42-14: Blurhex (Trypan Blue) used to stain the anterior capsule. Note the blue staining of the anterior capsule and the needle performing the rhexis.

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Figure 42-15: Rhexis completed. Note the white nucleus in the center and the stained anterior capsule in the periphery.

NO ANESTHESIA CATARACT / CLEAR LENS EXTRACTION

Figure 42-16: Diagrammatic representation of the air pump and infusion bottle. Note two infusion bottles connected to a transurethral resecton tubing (tur set). Also note the air pump connects to one of the infusion bottles.

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it, surge occurs. Many people have tried various methods to solve this problem. Some Phaco machines like the Sovereign have been devised with the help of I. Howard Fine, Barry Seibel and William Fishkind to solve this problem. Others have tried to use an anterior chamber maintainer to get more fluid into the eye. The problem with the anterior chamber maintainer is that another port has to be made. In other words now, we have three ports and if you are doing the case under topical or no anesthesia (as we do in our hospital) it becomes quite cumbersome. Another method to solve surge is to use more of phacoaspiration and chop the nuclear pieces with the left hand (non-dominant hand). The problem by this is the surgical time decreases and if the case is of a hard brown cataract, phacoaspiration will not suffice.

Surge occurs when an occluded fragment is held by high vacuum and is then abruptly aspirated with a burst of ultrasound. What happens is that fluid from the anterior chamber rushes into the phaco tip and this leads to a collapse of the anterior chamber.

One of us (Sunita Agarwal), then thought of

a method to solve surge using an air pump. We got Help ? this idea as when we were operating cases with

Phakonit (a new technique in which cataract is removed through a 0.9 mm opening); we wanted more fluid entering the eye. Now we, routinely use the air pump to solve the problem of surge.

The Method

1.First of all (Figure 42-16), we use two BSS bottles and not one. These are put in the IV stand.

Chapter 42

2.Instead of using an IV set for the fluid to move from the Bottle to the phaco hand piece, we use a TUR set. This is a Transurethral Resection (TUR) tubing set, which is used by urologists. The advantage of this is that, the bore of the tubing is quite large and so more fluid passes from the infusion bottle to the phaco hand piece. The TUR set has two tubes, which go into each infusion bottle, and then the TUR set becomes one, which then passes into the phaco handpiece.

3.Now we take an air pump. This air pump is the same air pump, which is used in fish tanks to give oxygen to the fishes. The air pump is plugged on to the electrical connection.

4.An IV set now connects the air pump to the infusion bottle. The tubing passes from the air pump and the end of the tubing is passed into one of the infusion bottles.

5.What happens now is that 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 TUR set also is in place and so the fluid now flows from the infusion bottle into the TUR set to reach the phaco handpiece. The amount of fluid now coming out of the hand piece is much more than what would normally come out and with more force.

6.One can use an air filter between the air pump and the infusion bottle so that the air which is being pumped into the bottle is sterile.

7.This extra amount of fluid coming out compensates for the surge which could occur.

Conclusion

As in any other field, progress is inevitable in ophthalmology more so in refractive surgery. We have started to look on refractive surgery as a craft and should constantly try to improve our craft and become better every day. By this, we will be able to provide good vision to more people than any one dared dream a few decades ago. It also goes without saying that we are and will be forever grateful to all our patients because without their faith, we would never have had the courage to proceed.

Keeping this in mind, we hope and wish that

realized and practiced thereby making the technique of phacoemulsification safer and easier providing good visual outcome and patient recovery.

REFERENCES:

1.Sunita Agarwal, Athiya Agarwal, Mahipal S Sachdev, Keiki R Mehta, I Howard Fine, Amar Agarwal: Phacoemulsification, Laser Cataract Surgery & Foldable IOL’s; Jaypee Brothers; 1998, Delhi, India

Introduction

Since Charles Kelman started phacoemulsification, various new modalities have developed which have made this technique more refined. One problem still persists which is the size of the incision. The normal size of the incision is 3.2 mm. With time and more advances in phaco machines and phaco tips this reduced to 2.8 mm and then to 2.6 mm. Today certain phaco machines like the Alcon’s Legacy and the Staar phaco machine have produced a 1.9-mm phaco probe. In other words cataract surgery has become a sub 2-mm incision. The authors (Sunita Agarwal) worked on Laser cataract surgery and have achieved cataract removal through an incision below 2-mm (1.8-mm) using laser phaco energy coupled with high aspiration. But the problem of the incision still remained and the 1-mm barrier could not be broken. Today, the authors have started a new technique called PHAKONIT in which the size of the incision is below 1 mm. In other words the size of the incision through which the cataract is removed is 0.9 mm. The authors (Amar Agarwal) performed this technique for the first time in the world on August 15th 1998. It was performed without any anesthesia. No anesthetic drops were instilled in the eye nor was any anesthetic given intracamerally. The first live surgery in the world of Phakonit was performed on August 22nd 1998 at Pune, India by the authors (Amar Agarwal) at the Phako & Refractive surgery conference. This was done in front of 350 ophthalmologists. This technique will revolutionize cataract surgery because now the foldable Intraocular lenses which pass into the eye through a size of below 2 mm (1.9 mm) will have to pass through a below

used in the left (nondominant) hand. Once the soft nucleus is removed, bimanual cortical aspiration is done. An IOL is not implanted if the myopia is very high (depending upon the Biometry). Thus the chances of creating astigmatism is very less.

Terminology

The name PHAKONIT has been given because it shows phaco (PHAKO) being done with a needle (N) opening via an incision (I) and with the phako tip (T).

TECHNIQUE OF PHAKONIT FOR CATARACTS

Anesthesia

All the cases done by the authors have been done WITHOUT ANYANESTHESIA. In these cases no anesthetic drops were instilled in the eye nor was any intracameral anesthetic injected inside the eye. The authors have analyzed that there is no difference between topical anesthesia cataract surgery and No anesthesia cataract surgery. They have stopped using anesthetic drops totally in all their hospitals in India (Bangalore and Chennai) and Dubai (UAE).

Incision

In the first step a needle with viscoelastic is taken and pierced in the eye in the area where the side port has to be made (Figure 43-1). The viscoelastic is then injected inside the eye. This will distend the eye so that the clear corneal incision can be made. Now a temporal clear corneal incision is made. The problem here is that the diamond knives are all 2.6 mm or larger. Since our aim is to make only a 0.9-mm opening the diamond knives are not sufficient. So a Microvitreoretinal (MVR) blade is used (Figure 43-2). This creates an opening of 0.9 mm. With time when companies start manufacturing diamond knives to create a 0.9-mm opening, one can start using them. When this incision is made it should be done in such a fashion that a clear corneal valve is made. The authors have devised a sapphire knife

keratome of 0.9 mm which they now use. This keratome creates a good valve.

Rhexis

The rhexis is then performed. This is done with a needle (Figure 43-3). In the left hand a straight rod is held to stabilize the eye. The advantage of this is that the movements of the eye can get controlled as one is working without any anesthesia.

Hydrodissection

Hydrodissection (Figure 43-4) is performed and the fluid wave passing under the nucleus checked. Check for rotation of the nucleus.

Phakonit

The phaco tip without the infusion sleeve is kept in the right hand (Figure 43-5) In the left hand an irrigating chopper of 18 gauge is taken (Figure 43-6) . The irrigating chopper is then passed through the side port into the eye. This is connected to the phaco machine. When the foot switch is in position 1 fluid passes into the eye and the eye gets distended. Now the phaco tip is passed into the eye. This is passed through the 0.9-mm incision. Remember the phaco needle has no infusion sleeve.

The foot switch is pressed for phacoemulsification. Karate chopping is done with the left hand (Figure 43-7) and the nucleus removed.

Figure 43-1: Viscoelastic injected inside the eye to distend the eye. This is done with a 26 guage needle.

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Figure 43-2: Clear corneal incision made with the microvitreoretinal blade (0.9 mm). Note the left hand has a straight rod to stabilize the eye as the case is done without any anesthesia.

Figure 43-4: Hydrodissection

Figure 43-3: Rhexis started with a needle.

Figure 43-5: Phaco probe without an infussion sleeve.

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Figure 43-6: Irrigating probe with a fork, irrigating chopper and irrigating probe. One can use either of these instruments in the left (nondominant hand).

Figure 43-7: Phakonit started. Note the Phako needle in the right hand and an irrigating chopper in the left hand. Phakonit being performed. Note the crack created by Karate Chopping. The assistant continuously irrigates the Phaco probe area from outside to prevent corneal burns.

The assistant injects fluid over the phaco tip at the area of the clear corneal incision to prevent thermal burns of the eye.

Cortical Washing, Foldable IOL

Implantation and Stromal Hydration

Cortical washing is done with the bimanual irrigation aspiration technique. Note in Figure 43-8 the nucleus has been removed but there are no corneal burns. Figure 43-9 shows the bimanual irrigation aspiration probes. This is like the irrigating chopper but does not have the chopper in it. The advantage of this is that as the chopper is not present the posterior capsule will not be cut accidentally. If one wants they can also use the aspiration probe of the phaco machine but take out the sleeve of the probe. In cases of small pupil irrigation aspiration is difficult with this set up so the authors devised an irrigating probe with a fork at the tip. The advantage of the fork is that it can push the iris with the left hand and the right hand with the aspirating probe can go under the rhexis and remove the trapped cortex. Figure 43-6 shows all three instruments, which can be, used in the left handthe irrigating probe with a fork, the irrigating chopper and the blunt irrigating probe. The cortical aspiration is completed with the bimanual irrigation aspiration probes (Figure 43-10).

Then the foldable IOL is implanted depending upon the biometry.At present one has to extend

Figure 43-9: Bimanual irrigation aspiration probes.

Figure 43-8: Phakonit completed. Noth the nucleus has been removed and there are no corneal burns.

(Figure 43-11) and then implant the foldable IOL (Figure 43-12). If the cases is of a cataract with high myopia and an IOL is not necessary then no lens is implanted. At present, the lowest available is the Staar sub 2 mm foldable IOL’s so one has to increase the size of the incision from 0.9 mm to 2 mm. With time the foldable IOL’S will come to less than 1 mm and the size of the incision will not have to be increased. The authors prefer the Staar plate haptic foldable IOL’s with large fenestration’s. Finally the viscoelastic is removed with the bimanual irrigation aspiration technique and stromal hydration done. Injecting

Figure 43-10: Bimanual irrigation aspiration. Note the clear corneal wound does not have any corneal burns.

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Figure 43-11: Incision enlarged to implant the foldable IOL.

fluid into the sides of the clear corneal incisions does stromal hydration. No subconjunctival injections or pad are applied in the eye. The patient walks out of the operation theatre and is seen the next day. The next follow up is after a month and suitable glasses prescribed if necessary.

PHAKONIT IN CLEAR LENS EXTRACTION

If one is performing a clear lens extraction as a refractive procedure, then Phakonit is a good alternative as the incision is only 0.9 mm. If necessary one can implant an IOL depending on the Biometry. If the case is a high myope then one need not implant an IOL. The pre and post topographic pictures are nearly the same of cases who have undergone Phakonit indicating the advantage of having a very small incision of 0.9 mm.

Discussion

This technique of Phakonit can change various concepts of cataract surgery. One of the main bugbears of cataract surgery was to break the 1-mm barrier. With Phakonit the barrier is broken. There are various questions , which come to one’s mind on this technique, and these will have to be answered with time as this procedure is so new.

Figure 43-12: Foldable IOL being implanted.

The first is of the left hand. The amount of fluid flowing into the eye normally in phaco is about 40 ml / minute. If we have a 20-gauge cannula in our left hand enough fluid does not flow inside the eye. So one has to use an 18 gauge irrigating chopper, otherwise when doing phakoemulsification the anterior chamber will collapse as the amount of fluid passing into the eye is very less compared to the suction. This problem can be solved with the use of an air pump which we always use in our cases.

The next problem is of the foldable IOL. At present the lowest one can go is to 1.9 mm. Remember phaco came before the foldable IOL’s. So obviously once Phakonit will catch on the companies will have to manufacture foldable IOL’s which pass through an incision less than 1 mm.

Another solution to solve the thermal burn could be to paint the tip of the phaco needle to insulate it from heating any structures.

The solution to the problems of Phakonit could be the surgery of a Three-Port Phakectomy in which an anterior chamber maintainer could be like the infusion cannula, an irrigating chopper could be the second port and the phako needle the third port just akin to a three-port vitrectomy.

Another modification of Phakonit is the technique of Laser Phakonit. In this the laser probe is passed into the phaco probe so that one can use a two port technique.

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Another technique by which one can perform Phakonit is to use an anterior chamber maintainer. The authors started this technique. They call it ThreePort Phakectomy. Just as a three port vitrectomy, here also we have three ports, hence the nameThreePort Phakectomy.

There are pros and cons in every technique. The problem in three port phakectomy is that it is too cumbersome. Surgeons prefer to have two ports only. Some surgeons prefer three ports as an anterior chamber maintainer is present in the eye and thus the anterior chamber is always formed.

Laser Phakonit

Laser Phakonit uses laser energy (coupled with ultrasound energy in hard nuclei) to remove the nucleus. This technique was started first time in the world by the authors (Sunita Agarwal). The laser machine used is the Paradigm Laser Photon. In these cases, two ports are used. One port has fluid (BSS) flowing through an irrigating chopper of 20 gauge and in the other hand is the phaco probe without a sleeve. In the center of the phaco probe is passed the laser probe. The diameter of the phaco probe is 900 microns. The laser probe reduces the orifice opening to 550 microns. Thus the nucleus can be removed through a very small 0.9 mm opening.

There are various problems, which are encountered, in any new technique and so also with Phakonit. With time these will have to be solved. The important point is that today we have broken the 1 mm barrier for cataract removals. This can be done easily by separating the phaco needle from the infusion sleeve. As the saying goesWe have miles to go before we can sleep.

REFERENCES

1. Sunita Agarwal, Athiya Agarwal, Mahipal S Sachdev, Keiki R Mehta, I Howard Fine, Amar Agarwal: Phacoemulsification, Laser Cataract Surgery & Foldable

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Limitations of LASIK in Very High

Myopia

The general consensus is that although, initially, different prestigious refractive surgeons from various countries performed and recommended LASIK for all degrees of myopia (low, moderate, moderately high and very high) it is now clear that this procedure is not recommended in very high myopias (greater than -10 diopters). This is because of important limitations in night vision, loss of best spectacle-corrected visual acuity, some visual aberrations and diminished quality of vision.

The surgeon’s goal is to provide his/her patient not only a satisfactory postoperative visual acuity as measured in the Snellen chart, but also to sustain a very good quality of vision.

Some ophthalmologists have seen patients operated with LASIK for myopia larger than - 10.50 D who end up with a postoperative vision of 20/25 without spectacles or contact lens correction but, at day’s end, they must rush back home because they cannot drive at night or go about normal activities in surroundings with low illumination.

The Important Role of Phakic

Intraocular Lenses

We are entering a new age with this procedure. We are moving away from an exclusively extractive concept with the crystalline lens being replaced by a posterior chamber intraocular lens for aphakia, toward a refractive concept of implanting an intraocular lens leaving the crystalline lens intact.

Contributions of Phakic IOL's

In these specific patients (-10-50 D or higher) phakic IOL’s provide the following: 1) excellent refractive accuracy; 2) preservation of corneal sphericity and the patient’s accommodation; 3) reversibility or adjustability; 4) predictable healing and; 5) rapid visual recovery and a stable postoperative refraction.

High myopes are usually very satisfied. Their post-op uncorrected visual acuity is generally better than their pre-op best-corrected visual acuity.

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