Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001

182 THE ART OF PHACOEMULSIFICATION

Moderately Dense Nuclei

This group of lenses represents the bulk of the cataracts that the average phaco surgeon will encounter. As stated previously, I routinely use divide and conquer nucleofractis.1 In this technique, one begins with the sculpting of a deep central trench just slightly off center, toward the side of one’s dominant hand (Fig. 18.3). I have found down-slope sculpting to be extremely useful in cases without zonular compromise (Fig. 18.4).16 After sufficient depth is obtained the second instrument (i.e. cyclodialysis spatula) is placed deep within the trench adjacent to the phaco probe and the two instruments are positioned on opposite walls of the groove and moved away from each other to crack the nucleus into hemisections (Fig. 18.5). It has been my observation that most surgeons sculpt further into the periphery than is necessary. This is both dangerous and inefficient. When the initial sculpting of the trench is sufficiently deep, it is rarely necessary to sculpt beyond the rim of the capsulorrhexis opening to facilitate complete and consistent cracking.

After a small rotation of the nucleus, the phaco probe is used to burrow into the inferior section of the nucleus with a short burst of ultrasonic power. Next, using foot position two on the phaco machine, aspiration is used to engage and stabilize the nucleus. The second instrument is held adjacent to the phaco probe and using a small down and away movement with the second instrument, the phaco probe breaks off a pie-shaped fragment (Fig. 18.6). One may think of this maneuver as similar to phaco chop in attempting to visualize the required hand movements. However, the two instruments are moved away from one another rather than toward each other as with phaco chop. The lens is then rotated and the fracturing maneuver is performed again. This is repeated several times until the cataract is broken into multiple wedge-shaped fragments (Fig. 18.7). These are then engaged with the phaco handpiece and emulsified in the safe central area of the capsular bag, approximately at the level of the capsulorrhexis opening.12

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Dense Nuclei

In these lenses a variation on the trench technique is used. Deep central sculpting is used to create a central crater with the phaco probe, deep enough to thin the posterior plate sufficiently to facilitate cracking (Fig. 18.8). The inferior portion of the nuclear rim is engaged with a burst of phaco energy and the second instrument is used to create a fracture, as described above (Fig. 18.9). The lens is then rotated and the nucleofractis technique is repeated until the lens is completely divided into wedge-shaped pieces. Each wedge is then drawn centrally and emulsified.17

Recently, I have been increasing my use of the phaco chop technique in these cases (Fig. 18.10). Chopping is a very efficient technique for nuclear division, particularly in dense lenses.13-14 Care must be taken, however, to preserve the anterior capsular rim. Because phaco chop puts the capsule at some additional risk so, I reserve the technique for denser nuclei or for cases with compromised zonules.

184 THE ART OF PHACOEMULSIFICATION

Posterior Capsule Rupture

Early identification of this event is critical to a good outcome. Initially, when one recognizes a small tear in the posterior capsule, a dispersive viscoelastic should be injected through the tear, in an attempt to keep the vitreous face from

prolapsing through the defect in the posterior capsule. When the tear is small, it is sometimes possible to engage the tear with a capsulorrhexis forceps and create a posterior capsulorrhexis. This will

Fig. 18.10: Phaco chop stabilize the defect and prevent it from enlarging. If a large portion of the

nucleus is still present in the eye and the rupture is small, one may occasionally rotate the remaining nucleus over the rent (using the nuclear segment to block the defect), and emulsification may continue more or less as before. In this situation, phaco chop may allow more efficient disassembly of the nucleus, minimizing total phaco energy and turbulence. An alternative method involves the use of a sheets glide placed over the capsular opening to create a “pseudo-posterior capsule.”In either of these situations extreme care should be exercised to prevent prolapse of the vitreous into the capsular space. Lowering both the bottle height and the aspiration flow rate will reduce turbulence in the eye and reduce the chance of vitreous prolapse. If large fragments exist one may attempt to engage the lens with the phaco probe and prolapse the nucleus into the anterior chamber where phaco chop may be used to divide the remaining nucleus and remove it from the eye. However, one should use extra care to avoid “post-occlusion surges” as these may increase the incidence of prolapse of vitreous. Once vitreous prolapse is recognized, phacoemulsification should be stopped and one should attempt to manually remove the remaining fragments through the main incision followed by careful and complete anterior vitrectomy. One should consider conversion to an extracapsular extraction at this point if the remaining nuclear segments cannot be safely removed through the original incision.

IOL Insertion

I routinely use foldable IOLs through a slightly enlarged clear corneal incision. However, I alter the lens that I use depending on the individual needs of the patient. For example, larger optics for diabetics and younger patients or those with large pupils, or acrylic lenses for patients with an increased probability of needing silicone oil and vitrectomy in the future (diabetics and patients with HIV/AIDS).

After IOL insertion, if I notice that a tear in the anterior capsule has occurred, I place a small matching incision 180 degrees away in the anterior capsule in the hope of balancing capsular contraction forces and maintaining IOL centration.11

ZEN IN THE ART OF PHACO 185

If zonular dehiscence has occurred, the IOL can be rotated so that the orientation of one of the haptics is toward the area of the dehiscence using the haptic to push the area of the capsule with the dehiscence back toward its original anatomic location. A PMMA capsular tension ring has been developed by Morcher and has been used with much success for this same purpose.20 Unfortunately, till now of this writing the ring has still not obtained FDA approval for use in the United States. In the case of severe zonular dialysis or loss of large amount of posterior

capsule alternative approaches become necessary. These include the placement of an anterior chamber lens, a sulcus-fixated lens (with or without optic capture

to facilitate IOL centration), and the suturing of a posterior chamber IOL.21-24

C O N C L U S I O N

The ability to recognize and to manage complications during surgery and to have good outcomes is what separates excellent from average surgeons. The willingness to teach oneself a variety of techniques and to understand the most appropriate occasions to use them is very important if one hopes to become a competent phaco specialist. Just as important however, is to be flexible enough to depart from one’s most comfortable techniques and to utilize new approaches to reduce complications and to properly manage them, so as to maximize the visual potential of the patient.

When a surgeon has knowledge of many different techniques of nuclear removal and the flexibility to use them, it becomes possible to use phacoemulsification and small incision surgery for even the most dense and complicated cataract cases that one may encounter.

R E F E R E N C E S

1. Gimbel HV: Divide and conquer nucleofractis phacoemulsification, development and variations.

J Cataract Refract Surg 17:281-91, 1991.

2. Arshinoff SA: Dispersive-cohesive viscoelastic soft shell technique. J Cataract Refract Surg 25:16773, 1999.

3. Gimbel HV, Neuhann T: Developments, advantages, and methods of the continuous curvilinear capsulorrhexis technique. J Cataract Refract Surg 16:31-37, 1990.

4. Koch P, Davidson JA: Advanced Phacoemulsification Slack: Thorofare, 1991.

5. Gimbel HV, Kaye GB: Forceps-puncture continuous curvilinear capsulorrhexis. J Cataract Refract Surg 23:473-75, 1997.

6. Maloney WF, Dillman DM, Nichamin LD: Supracapsular phacoemulsification—a capsule-free posterior chamber approach. J Cataract Refract Surg 23:323-28, 1997.

7. Hoffer KJ, McFarland JE: Intracameral subcapsular fluorscein staining for improved visualization during capsulorrhexis in mature cataracts (letter). J Cataract Refract Surg 19:566, 1993.

8. Nahra D, Castilla M: Fluorescein-stained capsulorrhexis (letter). J Cataract Refract Surg 24:1169, 1998.

9. Melles GRJ, De Waard PW, Pameyer JH et al: Trypan blue capsule staining to visualize the capsulorrhexis in cataract surgery. J Cataract Refract Surg 25:7-9, 1999.

10.Gimbel HV, Willersheidt AB: What to do with the limited view. J Cataract Refract Surg 19:65761, 1993.

11.Gimbel HV, Chin PK, Ellant JP: Capsulorrhexis. Ophthalmol Clin North Am 4:441-55, 1995.

12.Gimbel HV, Ellant JP, Chin PK: Divide and conquer nucleofractis. Ophthalmol Clin North Am 4:45769, 1995.

186 THE ART OF PHACOEMULSIFICATION

13.Koch PS, Katzen LE: Stop and chop phacoemulsification. J Cataract Refract Surg 20:566-70, 1994.

14.Koch PS: The stop and chop phacoemulsification technique. Ophthalmol Clin North Am 4: 497507.

15.Mackool RJ: Eccentric capsulorrhexis and bidirectional endocapsular phacoemulsification. J Cataract Refract Surg 17:221-32, 1991.

16.Gimbel HV: Downslope sculpting. J Cataract Refract Surg 18:614-18, 1992.

17.Gimbel HV: Trough and crater divide and conquer nucleofractis techniques. Eur J Implant Refract Surg 3:123-26, 1991.

18.Castaneda VE, Legler UFC, Tsai JC et al: Posterior continuous curvilinear capsulorrhexis—an experimental study with clinical applications. Ophthalmology 99:45-50, 1992.

19.Gimbel HV: Posterior capsule tears using phacoemulsification—causes, prevention, and management.

Eur J Implant Refract Surg 2:63-69, 1990.

20.Cionni RJ, Osher RH:Management of profound zonular dialysis or weakness with a new endocapsular ring designed for scleral fixation. J Cataract Refract Surg 24:1299-1306, 1998.

21.Uthoff D, Teichmann KD: Secondary implantation of scleral-fixated intraocular lenses. J Cataract Refract Surg 24:945-50, 1998.

22.Oshima Y, Oida H, Emi K: Transscleral fixation of acrylic intraocular lenses in the absence of capsular support through 3.5 mm self-sealing incisions. J Cataract Refract Surg 24: 1223-29, 1998.

23.Neuhann T, Neuhann TH: The rhexis-fixation lens. Film ASCRS, 1991.

24.Lyle WA, Jin JC: Secondary intraocular lens implantation—anterior chamber vs posterior chamber lenses. Ophthalmic Surg 24:375-81, 1993.

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Keiki R Mehta

PREOPERATIVE PREPARATION

The pati ent is dilated with 5% Neo-Synephrine eyedrops with 1 percent homatropine eyedrops. Both the drops are commenced 40 minutes prior surgery. In case the pupil is tardy in dilatation, place a drop of methylcellulose on the cornea, instill a drop of Neo-Synephrine and homatropine on it, lift the lid and shut it over the methylcellulose, tape the eye shut for 5 minutes. Usually after that period, the pupil is well dilated. Another alternate technique to dilate a tardy pupil is to instill a drop of Xylocaine 4%, and then to instill the dilating drops. It functions as the epithelial cells’ closed junctions become tenuous, permitting easier diffusion into the anterior chamber of the dilating drops.

I also favor preoperatively treating the patient with a topical antibiotic-NSAID (nonsteroidal antiinflammatory drug) combination for a day prior surgery. The rationale for it is that surgical insult is much less likely to demonstrate any postoperative inflammation. In addition the use of preoperative antibiotics to reduce the risk of postoperative endophthalmitis.

ANESTHESIA TECHNIQUE

Topical anesthesia is my choice for 98 percent of all cataract surgeries. I use topically, Xylocaine 4% eyedrops (Lidocaine). The Xylocaine is drawn in two syringes through a Millipore (20 micron) filter. One syringe is left outside the operating field to be used prior draping and washing the patient, and kept with the circulating nurse. The second sterile syringe is left on the operating trolley after clearly labeling it.

A drop is instilled three minutes prior surgery so that the eye may be washed out with Betadine solution (5% Betadine mixed with distilled water in a 50% dilution).

After washing the eye out, a final drop of Xylocaine is instilled on the cornea prior commencing the case.

Normally topical anesthesia is all that I use in virtually all cases. However, if intraoperatively the patient has a problem and the case is likely to take longer (inadvertent vitreous loss, a complaining patient, one who keeps rotating his or her eye like a metronome, etc) I also keep a 5 ml syringe with 2% Xylocard (intravenous Xylocaine, preservative free, normally used by the cardiologists) with a blunt

parabulbar cannula. All syringes are plastic, disposable and Luer-Lok type. At that stage it is a simple procedure to give 1.00 ml as a parabulbar injection. It is virtually painless, no pressure needs to be applied to the eye to diffuse the anesthetic agent, and takes effect almost immediately. Though the movement of the eye will take about a minute or so to decrease and stabilize down, the anesthetic agent takes effect almost immediately.

I normally like to instill a final drop of 4% Xylocaine after the lid retractor has been placed, just prior starting. I lift the retractors just a little to enable the drop to go all the way up to the fornix. Wait for about 30 seconds, wash off the eye with BSS and commence surgery. I normally do not use the Xylocaine 4% drops again at all.

In the younger anxious patients or in those in whom I am not sure of achieving their full cooperation, a little sedation is given intravenously. The amount of sedation being such that the patient does not drop of to sleep but just becomes a little more amenable to control. I like my patients to be able to respond to commands during the surgery. In those cases which need further supplementation, I/V Propofol administered in 10 mg increments induces a transient hypnosis with amnesia which clears rapidly in minutes.

In cases where the papillary dilatation is inadequate, despite best efforts at dilatation of the pupil, and where intracameral surgical manipulations will involve iris touch, or in cases where I would intend to use iris retractors (Grieshaber), I like to inject little Xylocard 2% (preservative free Xylocaine) diluted 50% with BSS, to convert it to Xylocard 1%, 0.5 ml injected immediately after the side port opening is made, prior injection of viscoelastic. Wait for a minute, wash out the chamber, and proceed with the surgery. It reduces the iris sensitivity and reduces ciliary proprioception (Grabow). I also like to use intracameral Xylocard in cases where the cataract is very hard and where the surgery is likely to last much longer with more ultrasound energy in the anterior chamber and much more lens manipulation.

I am a little hesitant to use topical anesthesia with patients who I cannot converse with during the surgery, like mentally retarded patients, or even patient speaking a language which I am not familiar with. In these patients, I prefer to give a peribulbar injection of 2% Xylocaine with 150 units of hyaluronidase admixed, a single injection administered through a 24 G, 1 inch disposable needle, the injection given through the upper lid. I feel it is important when giving the peribulbar block to insert the tip of the index finger between the orbital ridge of the frontal bone and the eye, which deflects the eyeball away. The patient is requested to look straight upwards at the operating microscope light (visible through the closed lid), and the injection

of 3.00 ml is given at the point 1/3 towards the nasal point of a line drawn between the two canthi. No massage is given. The eye is taped shut (to prevent accidental corneal abrasion) and the balancing weights (Tony Fernandez, 1992) are placed on the eye. I personally do not prefer to use either Honan Oculopressor, the Super Pinky ball as I feel that in cases of an inadvertent venous leak by a slow hemorrhage in the socket, the pressure induced is likely to compromise the ocular circulation. The balancing weights balls are safer since they are not a constrictive device.

The pressure from the balancing balls, is kept on the eye for 5 minutes, the IOP is checked with the Schiotz tonometer. The ideal pressure should be a minimum

of 10 deflection using no weight (5.5 gm).

The patient should be made comfortable on the operating table. It is preferable that the hands be loosely restrained so that accidentally during the procedure in case the patient falls asleep and suddenly awakes, he should not move his hands up and make an unexpected moment.

PREFERRED PHACOEMULSIFIER

My present personal choice is the Legacy 20,000 (Alcon). The Alcon Legacy has exceptional fluidics, maintains the chamber well, has excellent ultrasound power, with a sensitive, balanced, stable, 4 crystal handpiece, rarely induces bubble formation and works very well. I usually use the Max-Vac setup with a, 30 degree, 0.9 mm diameter, straight tips which work very well on the hard cataracts common in India. The Kelman 30 degree bent, 0.9 mm tip also works well but sometimes a bit unpredictable. Perhaps the biggest advantage of the Kelman is that, since the tip is curved down, the surgeon does not need to hold the handpiece at a steep angle. The Legacy has superior followability making the procedure much simpler. In addition the dynamic range of fluidics allow the surgeon to really individualize settings at every single phase of cataract removal depending upon the grade of the nucleus.

DRAPING AND PREOPERATIVE PREPARATION OF THE EYE

The patient’s eye is washed out with 10 ml of Betadine 5% solution diluted with distilled, sterile water (not tap), half and half (50% dilution), taken in a 10 ml plastic syringe. The assistant keeps the lids open widely to permit a proper wash. Subsequently cotton swabs soaked in full strength Betadine, are swept along the lash line to be sure that the lashes are clean and properly prepared. Next the entire area of the eye is again flushed out with distilled water, dried with a sterile towel. Two drops of an antibiotic solution are instilled in the eye (at present I use tobramycin eyedrops).

A highly adherent plastic drape, termed as Opsite (Johnson and Johnson) Tegaderm (3M) which is commonly used to isolate the skin for surgical procedures, is placed over the fully opened eye such that it drapes the lashes, deflected outwards and away from the field, and drapes all crevices around the eye and the surrounding area.

It is important that there should be adequate oxygenation under the drapes. An ideal device to maintain it are silicone nasal prongs. The tubes are looped around

the ear to stabilize them and the prongs placed in the nostrils. Oxygen (of if not available, even normal air) at a flow rate of 8 volumes/minute. It is very reassuring to the patient to feel air under the drapes which otherwise may make a patient very apprehensive and asphyxiated. In addition it assures adequate oxygenation which is very useful to a patient who has limited respiratory ability (asthmatics or those with chronic pulmonary conditions.)

Over the draped eye, a second self-adhesive drape can be utilized, and over that a sterile, absorbent, thick cotton drape with a small hole is fitted over. The head is draped in a double layer of cloth to isolate the forehead and the face away from the site to be operated. It is important to tape a piece of rolled absorbent gauze just in front of the ear on the operating side so accidentally water does not trickle in the ear during surgery, leading to discomfort and sudden head movement.

The normal eye (the one not to be operated) is taped shut, gauze placed on it and a protective plastic shield taped over it. The tape directly on the eye is to prevent the gauge from irritating it, and the shield is to protect the eye in case, accidentally the surgeon does apply inadvertent pressure, which may cause the patient discomfort and again may be the cause for the patient fidgeting under the drapes.

MONITORING PATIENTS IN THE THEATER

I strongly feel that all patients, even if they are under topical anesthesia must be suitably monitored in the theatre. All my patients have a finger-probe oxygen saturation monitor with simultaneous cardiac monitoring. A safety intravenous line is commenced with a 23G Vent-Flo (silicone indwelling venous catheter) which is much more stable and safer than a butterfly venous needle, which tends to be displaced at the slightest movement. I use an anesthesiologist as a standby in all cases. He normally only gives the I/V antibiotics on the table and monitors the patient, but gives supplementary sedation and analgesics if required.

In the balance salt solution (BSS plus, considering its high cost, is not really required for short procedures unless the endothelial cell count is significantly low) is added ½ ml of a cardiac, preservative free, epinephrine 1/1000 (without sodium bisulfate) instilled in a 500 ml bottle to maintain the dilatation of the pupil, and to keep a good clean, bloodless field. In addition to the 500 ml bottle of BSS add 10 mg of vancomycin or 40 mg of garamycin. The use of these antibiotics, in my opinion, significantly reduces the risk of endophthalmitis. Other authorities too concur (Linda Strong, 1999, Kraff, Gills 1999).

A final drop of Xylocaine is added and the procedure is now commenced. I do not like to utilize more drops as Xylocaine 4% used excessively will lead to punctate epithelial keratitis, corneal erosion and a delayed postoperative rehabilitation, and is said to lead to endothelial cell damage (Marr WG, Wood R 1957).

I prefer also to connect dual BSS bottles, connected to each other and to the phacomachine by a thick walled ¾ cm bored, plastic tubing (normally used by Urologists, it is known as a TUR set). The advantage of using this tubing is that

it gives a good flow and cuts down on surge developing which is critical in the high flow techniques used (Bangkok system). In addition in the BSS bottles the airways are special long needles which reach right up to the clear air space on top rather than being put in below. It is important for the suction generated in a glass bottle to suck in the air very often leads to fluidic imbalance and suction variables especially if one is operating at low suction near the capsule or in removing the final little bit of cortical or cortex material.

OPERATIVE PROCEDURE

The patient is requested to look into the operating light and advised that he keeps his eye stable and fixed at the light. It is clearly explained to him that at the time phaco is done he must not move at all. The operating light intensity is kept low until such time that Phacoemulsification is commenced.

The plastic drape is incised, and a reversible spring speculum is utilized to give the eyes open. An ideal speculum is the Kratz modified, Barraquer speculum. The spring speculum is preferable to fixed screw speculums, because it has a certain amount of ‘give’ which enhances patient comfort. Another advantage is that with a flexible spring retractor the patient does not fight it. He blinks a few times, tiring the orbicularis, and then keeps the eye wide open.

THE INCISIONS

A side port incision is made with a Alcon V-lance blade (1.2 mm spear) (Fig. 19.1), made with the blade as parallel to the cornea as possible to get a good self-sealing shelf. The chamber is refilled with BSS from a 3 ml syringe to reform the chamber and repressure the eye in preparation for the main phaco incision.

Almost all my implants utilized are flexible and in most of the cases a SI40

Allergan silicone foldable lens inserted via an injector (Unfolder in Allerganese), which goes through a 2.8 mm incision. Hence, virtually all my cases have a pure corneal tunnel. In case I will put in a PMMA 5.25 mm IOL, I prefer to do a semiscleral incision in a curved ‘V or chevron ’ incision after reflecting back the conjunctival flap.

CORNEAL ENTRY

The correct point of entry is posterior to the clear cornea, utilizing the perilimbal capillary plexus as a landmark and slightly anterior to the insertion of the conjunctiva (Fig. 19.2). I always prefer to see a faint capillary bleed where I make my entry. Since the incision is into a slightly vascular area, better long-term wound healing