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

the rhexis using the split rotation technique described elsewhere. Since the quantum of ultrasound energy liberated in the anterior chamber is very low, it can be used safely in Fuch’s dystrophy, patients with a low endothelial cell count, or prior keratoplasty, where the regular options do not apply.

The important question, often asked is whether doing a regular phacoemulsification as compared to a vertical phacoemulsification shows any disparity in endothelial cell loss. It is often thought that since, in coring U/S energy is used more, the

endothelial cells may be affected. But in fact the extra energy is masked off the cells by the fact that a phaco needle buried in the substance of a lens does not radiate any energy out. A Topcon endothelial specular non-contact microscope coupled with its own special “ImageNet” software, showed no cell loss of any significance in a series of 125 consecutive cases. Though, in theory, endothelial cell changes must occur in any surgery, in practice there is hardly a +/- 3.00% variation change in the endothelial cell count.

Perhaps the greatest application of this technique is that it is an exceptional transition technique for teaching residents, fellows and young pledging surgeons the art of phacoemulsification without inducing any complications. It is easy to do, minimizes the risks of capsular damage, removes the chances of inadvertent iris contact, and enables even a hard cataract be done with safety in a short period of time. It is thus the technique of choice in eye camps where, I am sure, it will supplant the regular technique in time.

FURTHER READING

1.Mehta KR: Pitfalls encountered in 1500 consecutive posterior chamber implant. All India Ophthl Soc Proc 165-166,1986.

2.Mehta KR: Posterior capsular capsulorrhexis with shallow core vitrectomy following implantation in paediatric cataracts. All India Ophthl Soc Proc 207-210,1995.

3.Mehta KR: An advanced but simple keratometer for control of postoperative astigmatism. All India Ophthl Soc Proc 122-123,1990.

4.Mehta KR: The new clover leaf stabiliser (CLS) for the safe and effective insertion of posterior chamber IOL over a broken capsular face. All India Ophthl Soc Proc 251-253,1995.

5.Mehta KR: Shelve and shear phacoemulsification: All India Ophthl Soc Proc (Mumbai) 1995.

6.Mehta KR: Mehta tangential chop (MTC) technique for phacoemulsification. All India Ophthl Soc Proc (Chandigarh) 1996.

7.Mehta KR: HEMA intracameral hood—corneal turbulence control in phaco. All India Ophthl Soc Proc (Chandigarh) 1996.

8.Mehta KR: Phaco-levitation—a peaceful way. All India Ophthl Soc Proc (Chandigarh) 1996.

9.Mehta KR: Lollipop phaco cleavage—a new technique for hard cataracts. All India Ophthl Soc Proc (Bangalore) 1991.

10.Mehta KR: Phaco with flexible IOL—is it a step forward. All India Ophthl Soc Proc (Bangalore) 1991.

11.Mehta KR: The prephaco split technique using the contrasplit forceps–a new technique. All India Ophthl Soc Proc 1998.

12.Mehta KR: Intralenticular “hubbing” technique for simple eye camp phacoemulsification–a simple technique. APIIA Conference, 1997.

13.Mehta KR: Astigmatic control using the new curved—laminating keratotomy technique. APIIA Conference 1997.

14.Mehta KR: The tripod posterior chamber foldable acrylic lens. Proc of SAARC Conference, Nepal, 1994.

15.Mehta KR: Phacoemulsification, the “roller-flip” way for suprahard cataracts—it works great. Proc of SAARC Conference, Nepal, 1994.

MY PERSONAL TECHNIQUE OF VERTICAL “HUBBING” PHACOEMULSIFICATION 203

16.Mehta KR: Intralenticular phacoemulsification—a new technique. Proc of SAARC Conference, Nepal, 1994.

17.Mehta KR: Management of subincisional cortex in small incision cataract surgery (SICS). Proc of SAARC Conference, Nepal, 1994.

18.Mehta KR: Intralenticular “hubbing” phaco technique for safe phaco. Proc of SAARC Conference, Nepal, 1994.

19.Mehta KR: Effective endothelial cell protection during phacoemulsification with HEMA intracameral contact lens (HICL). Proc of SAARC Conference, Nepal, 1994.

20.Mehta KR: The new multiport phaco tip for safer, more effective phacoemulsification, with virtually

zero capsular damage. Proc of SAARC Conference, Nepal, 1994.

204 THE ART OF PHACOEMULSIFICATION

I N T R O D U C T I O N

Phacoemulsification is now the most preferred modality for cataract extraction according to the latest ASCRS survey.1 The various nucleotomy techniques are generated to avoid complications and to ensure safe phacoemulsification procedure. We herein, describe the following nucleotomy techniques.

•Modified phacoemulsification in situ, for weak zonular apparatus.

•Petalloid phacoemulsification, for hard cataracts

•Sinus fracture and intranuclear nucleotomy, for semihard cataracts, and

•Slit nucleotomy technique for soft cataracts.

MODIFIED PHACOEMULSIFICATION IN SITU

A modified methodology of in situ phacoemulsification is described which imparts minimal stress on the zonular apparatus. This is especially relevant in cases of zonular weakness where undue stretch may cause partial or total zonular dialysis during rotation.

The phaco procedure is begun by inserting the phaco tip into the chamber prior to emulsification. Central sculpting a groove approximately 2½ to 3 phaco tips wide with specific attention to down sculpting, approximately 90% of nucleus depth, is done in order to consume part of the posterior plate or the backbone of the nucleus (Fig. 20.1A), thus, the central hard nucleus, epinucleus and cortex within the confines of the capsular bag. For this debulking procedure, the phaco power is initially kept at 50% and increased further as per the hardness of the nucleus. The aspiration flow of fluid is 20 cc/min and vacuum is 11 mm Hg.

INNOVATIVE NUCLEOTOMY TECHNIQUES 205

Fig. 20.1A: Central debulking, sculpting to 90% depth

Fig. 20.1B: Horizontal fracture along 3 and 9’O clock meridian

A deep groove facilitates instruments to be in place for a subsequent fracture and increases the working space. During this part of phaco it is imperative not to rock or move the nucleus so as to keep the zonules and anterior capsule intact.

Following an adequate debulking, the second instrument (chopper) is inserted through the side port and a horizontal fracture is created by karate fracture at 6 O’ clock to divide the lower half of the nucleus into 2 quadrants. Right

INNOVATIVE NUCLEOTOMY TECHNIQUES 209

into 2 quadrants (Fig. 20.1G). The bevel of the phaco tip is turned down to pick up each quadrant separately which is emulsified in situ (Fig. 20.1H).

This modified methodology of central debulking and in situ phacoemulsifcation is particularly suitable in cases where degree of stress imparted to the zonular apparatus has to be minimized. It is especially relevant in cases of anticipated weak zonular apparatus, like pseudoexfoliation, uveitis, hypermature or traumatic cataracts and glaucoma. This technique further ensures minimal lens rotation and eliminates the need to sculpt in the periphery. A remarkable index of safety is entailed as each fragment is emulsified in the central safety zone in a stable environment with the phaco tip. Moreover, as no sharp instruments approach the posterior capsule, this technique is safer than the conventional chopping technique.

PETALLOID PHACOEMULSIFICATION

Transitional phaco surgeons may hesitate to deeply chop the central core of hard cataracts which resists complete division even in expert hands due to elasticity and tenacity of the posterior nuclear plate. If the instruments are placed too anteriorly in the trench, the bottom of the bridge is not split, because the inappropriate placement of instruments creates a torque in the area rather than a splitting force.2 On the other hand, an inappropriate deeper fracture may inadvertently rupture the posterior capsule. We herein, describe a useful technique for phaco surgeons who are still in the learning curve for performing phacofracture of hard nuclei.

Technique

Debulking of the central hard nucleus is facilitated by sculpting a crater (75% depth) with the phaco tip (Figs 20.2A and B). The phaco parametres are: power— 70% and vacuum—10 to 12 mm Hg. This removes the hardest core tissue from within the middle of the hard cataract and provides enough room for the working of the instruments and subsequent manipulation of the nuclear fragments. The 2nd instrument (chopper) is introduced via the side port and Nagahara chopping3 is facilitated within the confines of the capsulorrhexis to separate out a petal shaped nuclear fragment still attached to the unchopped intact central disc (Fig. 20.2C). The nucleus is then rotated by 2 to 3 clock hours and another petalshaped fragment is chopped. Each ‘petal’ constitutes predominantly the nuclear rim, the base of which is formed by the central disc, giving it a petalloid configuration. The same technique of rotation, chopping and rotation is performed to form 6 to 12 such “petals” depending on the hardness of the nucleus (Fig. 20.2D). The vacuum is raised 100 to 110 mm Hg during nuclear emulsification. Each petal may be emulsified in the central capsular bag separately or all may be left in place until all “petals” have been formed. The advantage of waiting until all “petals” have been formed is the maintenance of maximal capsular distention which keeps the capsular bag stretched and helps to avoid inadvertent posterior capsular tear. However, the advantage of removing each fragment separately is

210 THE ART OF PHACOEMULSIFICATION

to allow more space for easy chopping of the other segments of the remaining rim. Nevertheless, caution is mandatory while doing the latter since, as more segments are removed, less lens material is available to expand the capsule and the lax capsule has a greater tendency to be aspirated into the phaco tip especially if high aspiration rates are used. Following consumption of the nuclear rim (Fig. 20.2E), the central mobile disc of the nucleus (Fig. 20.2F) is emulsified.

Twenty eyes underwent petalloid phacoemulsification with foldable silicone intraocular lens implantation (SI30NB:Allergan ) with no untoward intraoperative complications. The mean phaco time was 1.02 ± 0.06 minutes and the mean percentage endothelial cell loss was 4.2 ± 0.8% at the end of 3 months follow-up. Postoperatively, all eyes achieved a visual acuity of 20/20 at the end of first week.

Figs 20.2A to F: (a and b) Central debulking upto 75% depth, (c) Karate chop at the paracenter to create the edge of a petal, (d) Chopping, rotation and chopping create the petalloid configuration, (e) The central disk and the base of the petal remains following emulsification of the petals, and (f) central disk and the base of the petal are emulsified in the end

This technique is based on the anatomic relationship between the lens fibers and the lenticular sutures. During embryologic development lens fibers elongate and join forming 2 sutures, one anteriorly and one posteriorly.4,5 With time, as more fibers are added these sutures branch off into increasingly complex patterns. The radially oriented fibers create potential cleavage planes that are amenable to separation.5 The lens epithelial cells lay down concentric layers of nuclear tissue which become dense centrally and less dense peripherally. These concentric layers resemble the lamellar organisation of a tree trunk. Thus the peripheral area of a hard cataract offers less resistance and a more predictable shearing stress as compared to the center which is much more dense.

This modified method of “petalloid” phacoemulsification is particularly suitable and comfortable for transitional phaco surgeons who are as yet hesitant to completely chop the dense central core of hard nuclei. An experienced surgeon may be able to determine and gauge the depth of the central crater and the density of tenacious and elastic fibers of the posterior plate. However, this may not be true for the beginners. For learning phaco surgeons chopping in the center of a hard nucleus is difficult, as the hardness of the nucleus precludes the depth at which the fracture has to be facilitated. On the other hand, chopping the relatively softer “paracenter” may allow a better perception of depth. The fracture which is radial is more physiological with the arrangement of the lens fibers as compared to the one which is horizontal. In an untoward situation, the traditional horizontal fracture may cause an unexpected and unequal break in the nucleus so that the phaco probe directly impinges on the posterior capsule. The process of partial central debulking, peripheral chopping and emulsification and then central disc emulsification offers a more graduated effect and is thus more predictable.

A greater predictability is attributed to impaling from less hard periphery towards a more hard central core. Thus this procedure works on progressive harder gradient by going from periphery towards the paracenter. The small residual nucleus core is phacoemulsified separately with ease due to its small size and larger room for manipulation and movement.

We recommend this procedure as an alternative to technique of performing phacofracture of a hard nucleus during phacoemulsification.

SINUS FRACTURE AND INTRANUCLEAR NUCLEOTOMY

The technique of sinus fracture and intranuclear nucleotomy facilitates and accomplishes a successful phacoemulsification in dense or hard nuclei.

Technique

Using a 30o phaco tip a central crater is sculpted approximately 2.5 to 3 phaco tips wide and upto 90% of the nuclear depth. The central hard nucleus is debulked, leaving a peripheral rim of nucleus, epinucleus and cortex within the confines of the capsular bag. A deep groove allows instruments to be in place for a subsequent horizontal fracture of the nucleus into two halves.

The phaco probe with bevel upwards is then inserted into the center of the inferior hemisection to create a sinus (Fig. 20.3A). The lateral wall of the sinus is widened to accommodate the phaco tip and the chopper (Fig. 20.3B). A mechanical force is then applied along the lateral wall of the sinus with these two instruments (Fig. 20.3C). Thus the inferior hemisection is divided into two quadrants (Fig. 20.3D). The individual fragments may then be cleaved further in a similar manner and aspirated out. The superior nuclear hemisection is dealt with, in a similar way.

In intranuclear nucleotomy, 4 such sinuses are made (Figs 20.3E and F) each at 90° to each other. This is followed by the breaking of the 4 sinuses so that 4 quadrants are generated which are then subsequently emulsified.