Ординатура / Офтальмология / Английские материалы / The Art of Phacoemulsification_Mehta, Alpar_2001
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THE ART OF PHACOEMULSIFICATION
It is perfectly feasible to combine phacoemulsification and astigmatic surgery on the table. However this is acceptable only provided, the cornea is quite regular (< 2.00 D astigmatism) and the maximum width of the incision to be utilized is 3.00 mm, or smaller. If the astigmatic component is more or if one is going to be enhancing the incision to 4.00 or more, it makes more sense to do it as a twostep procedure. Do phaco as a primary procedure, allow the cornea to stabilize postoperatively, and only then after doing a computerized corneal topography , 
plan and complete the astigmatic procedure.
CONCLUSION
Clinically, clear corneal incisions have now become the most popular option for cataract extraction IOL implantation throughout the world. Spearheaded by phacoemulsification and the now sub-three (< 3.00 mm ) sized incisions, significant improvements in surgical techniques have resulted in a keen appreciation of astigmatism, how it is induced and what can be done to reduce, if not eliminate it entirely. Being naturally anastigmatic, phacoemulsification incisions serve as an ideal background datum to achieve a zero refractive status, and at the same time, in managing residual astigmatism, obviate the necessity for complex calculations.
Clear corneal incisions have had an outstanding record of safety with exceptional cosmetic outcome and should increase in popularity with time.
FURTHER READING
1.Kirk S, Burde RLM, Waltman SRL: Minimizing corneal endothelium damage due to intraocular lens contact. Invest Ophthalmol Vis Sci 16:1053, 1977.
2.Ernst PH, Kiessling LA, Lavery KT: Relative strength of cataract incision in cadaver eyes. J Cataract Refract Surg 17(suppl):668-71, 1991.
3.Ernst PH, Lavery KT, Kiessling LA: Relative strengths of scleral corneal and clear corneal incisions constructed in cadaver eyes. J Cataract Refract Surg 21:39-42, 1994.
4.Ernst PH, Neuhann T: Posterior limbal incision. J Cataract Refract Surg 22:78-84, 1996.
5.Ernst PH: The corneal lip tunnel incision. J Cataract Refract Surg 20:154-57, 1994.
6.Ernst PH: The self-sealing sutureless wound: Engineering aspects and experimental studies. In Gills JP, Martin RG, Sanders DR (Eds): Sutureless Cataract Surgery. SLACK Inc: Thorofare 23-39, 1992.
7.Edelhauser HF, Gonnering R, Van Horn DL: Intraocular irrigating solutions—a comparative study of BSS plus and lactated Ringer’s solutions. Arch Ophthalmol 96:516-20, 1978.
8.Edelhauser HF, Van Horn DL, Schultz RO et al: Comparative toxicity of intraocular irrigating solutions on the corneal endothelium. Am J Ophthalmol 81:473-81, 1976.
9.Edelhauser HF, Van Horn DL, Hynduiuk RA et al: Intraocular irrigating solutions—their effect on the corneal endothelium. Arch Ophthalmol 93:648-57, 1975.
10.Edelhauser HF, Rosenfeld SI, Waltman SR et al: Discussion of comparison of intraocular irrigating solutions in pars plana vitrectomy. Ophthalmology 93:114-15, 1986.
11.Fine IH, Finchman RA, Grabow HB (Eds): Clear Corneal Cataract Surgery and Topical Anesthesia Slack Inc: Thorofare 1993
12.Fine IH: The Rhein 3-D diamond knife. Eye World 1:2-24, 1996.
13.Fine IH, Fichman RA, Grabow HB: Clear Corneal Cataract Surgery and Topical Anesthesia Slack Inc: Thorofare 1993.
14.Fine IH: Architecture and construction of a self-sealing incision for cataract surgery. J Cataract Refract Surg 17(suppl): 672-76, 1991.
15.Fine IH: Cortical cleaving hydrodissection. J Cataract Refract Surg 18:508-12, 1992.
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16.Mehta KR: Pitfalls encountered in 1500 consecutive posterior chamber implant. All India Ophthl Soc Proc 165-66,1986.
17.Mehta KR: Phacoemulsification cataract extraction with foldable IOLS—first 50 cases. All India Ophthl Soc Proc 56-60, 1989.
18.Mehta KR: Endocapsular phacoemulsification and posterior chamber IOL implantation. All India Ophthl Soc Proc 217-20, 1989.
19.Keiki R Mehta: Post-cataract astigmatism—a comparison between phacoemulsification and ECCE procedure—cataract with and without intraocular implantation. All India Ophthl Soc Proc 226-29, 1989.
20.Mehta KR: Posterior capsular capsulorrhexis with shallow core vitrectomy following implantation in paediatric cataracts. All India Ophthl Soc Proc 207-10, 1995.
21.Mehta KR: The clear corneal phacoemulsification with injectable silicone lenses. All India Ophthl Soc Proc 218-22, 1995.
22.Mehta KR: The new shelve and shear technique for simplified phacoemulsification. All India Ophthl Soc Proc 222-24, 1995.
23.Mehta KR: Posterior chamber implantation. All India Ophthl Soc Proc 143-44, 1990.
24.Mehta KR: YAG Laser damage to intraocular implants—an evaluation. All India Ophthl Soc Proc 14750, 1990.
25.Mehta KR: Phacoemulsification—is it the true III world answer for eye camps. All India Ophthl Soc Proc 301-03, 1990.
26.Mehta KR: An analysis of causative faction leading to eye strain caused by computer monitor screens.
All India Ophthl Soc Proc 334-36, 1990.
27.Mehta KR: Single stitch elliptical funnel incision for cataract surgery. All India Ophthl Soc Proc 25354, 1991.
28.Mehta KR: Bifocal intraocular implants—a functional evaluation based on 425 cases. All India Ophthl Soc Proc 271-74, 1991.
29.Mehta KR: Phacoemulsification with flexible PC IOL—is it really a step forward? All India Ophthl Soc Proc 287-88, 1991.
30.Mehta KR: The New Phaco cleave technique for hard cataracts. J Intraocular Implant and Refractive Society India, 1(1): 74-75, 1996.
31.Mehta KR, Sathe, SN, Karyekar SD: The new soft intraocular lens implant. Am Intra-Ocular Implant Society J 4(4):200-205, 1978.
32.Mehta KR, Sathe SN, Karyekar SD: New soft posterior chamber implant. X Congress of the AsiaPacific Academy of Ophthalmology. New Delhi,1985.
33.Keiki R Mehta: When not to do an anterior chamber implant. All India Ophthl Soc Proc 164 -165,1986.
34.Mehta KR: Mehta Tangential Chop (MTC) technique for phacoemulsification. All India Ophthl Soc Proc (Chandigarh) 1996.
35.Mehta KR: Phaco-levitation—a peaceful way. All India Ophthl Soc Proc (Chandigarh) 1996.
36.Mehta KR: Comparison of centration stability and capsular response to AcrySoft and silicone S130 lenses. All India Ophthl Soc Proc 1998.
37.Mehta KR: Intralenticular “hubbing” technique for simple eye camp phacoemulsification—a simple technique. APIIA Conference 1997.
38.Mehta KR: Management of subincisional cortex in small incision cataract surgery (SICS). Proc of SAARC Conference, Nepal, 1994.
39.Mehta KR: Intralenticular “hubbing” phaco technique for safe phaco. Proc of SAARC Conference, Nepal, 1994.
40.Mehta KR: The new multiport phaco tip for safer, more effective phacoemulsification, with virtually zero capsular damage. Proc of SAARC Conference, Nepal, 1994.
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THE ART OF PHACOEMULSIFICATION
Shashi Kapoor
Capsulorrhexis (CCC): |
10 |
A Beginner’s Guide |
I N T R O D U C T I O N
Continuous curvilinear capsulorrhexis (CCC) is one of the revolutionary innovations of modern cataract surgery. It was presented to the ophthalmic, surgical community in 1985 and 1986 by Fercho, Graether, Gimbel, and Neuhann. These ophthalmologists were able to use and appreciate CCC because they had developed methods for performing phacoemulsification totally within the capsular bag, i.e. they were not using an iris plane approach in which the superior pole of the cataract is tipped superiorly out of the bag for tip access.
Terminology
CCC—continuous, circular, capsulorrhexis. The border does not need to be “circular”, but may be ovoid or elliptic.
Hence, the more generic word “curvilinear” has replaced “circular”, leaving the abbreviation the same—CCC.
Anatomy of Lens Capsule
The posterior zonular fibers are inserted 1.0 to 1.5 mm from the equator, while the anterior zonular fibers are attached approximately 2.0 mm from the equator.
Since the diameter of the adult crystalline lens is 9.5 to 10.0 mm, the “zonulefree” area, on the anterior capsule is approximately, 6.0 mm in diameter only. It is therefore ideal to create a tear limited to the zonule-free area, preferably slightly inside the zonular frontier, as zonular fibers have been observed more centrally than has previously been considered.
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Technique
Prerequisites
Absence of positive pressure— facilitated by use of viscoelastic agents, air, irrigation, or a “closedchamber” technique, where a bent needle, used to perform the CCC, perforates the preplaced incision, before any other entry is made into the anterior chamber.
Instruments
Cystotomes, bent needles or forceps, can all be used effectively. Existing ultrasonic or thermal devices, are not believed to offer any advantages.
Initiation of Tear
Beginning of CCC peripherally, carries a greater liability than beginning centrally. With the initial cuts made centrally, radial stress vectors across the anterior capsule are interrupted, resulting in less tendency for the tear to extend towards the equator. It is always easier to spiral the initial tear out to enlarge a capsulotomy, than it is to pull a peripheral tear back towards the center.
Technique
Using a bent needle, of 23 G to 25 G, a perforation is made in the center of the anterior capsule. By extending this with the sharp edge of the needle, a horizontal incision is made (Fig. 10.1A). The tip of the needle is now used to redirect the tear in a counterclockwise direction.
This creates a flap with a smooth curve as it is beginning. The flap is then pulled along in a circular manner by means of gentle traction with the needle tip. If the tear starts to extend peripherally, it is usually the result of positive vitreous pressure
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and can be counteracted by reinflating the anterior chamber with viscoelastic. A light touch is needed, because if one presses too hard on the flap, it creates a responding increase in vitreous pressure, which forces the tear outward. As the flap progresses, large amounts of capsular folds will present and must be pushed out of the way, so that one can visualize the exact point at which to place the tip of the needle (Fig. 10.1C).
When completing the CCC, one should overlap the tear such that the last part of the tear joints the first part from the outside towards the center, thus resulting in a continuous edge. If the overlap is created from the center towards the outside, it will result in a small triangular flap, with a tendency to tear towards the equator or beyond.
The best control of the progressing tear is achieved by grasping the developing capsular flap, with the desired instrument close to where the capsule is tearing at the time. The direction of the tear can be controlled by the position of the instrument. Placing the tip of the instrument a little peripheral to the advancing tear, will direct it outwards. Placing it a bit central to the tear will direct it towards the center.
Tear patterns may vary, and progress clockwise or counterclockwise. There are cases however, when no form of CCC may be achieved. These include capsules that are heavily fibrosed and shrunken, as in certain congenital, secondary, and traumatic cataracts. In these patients, a continuous, curvilinear opening often still may be achieved by using a capsule scissors to cut through the fibrosed part of the anterior capsule. In the nonfibrosed area, the smooth edge border of the CCC is achieved by the usual methods.
A Kraff-Utrata forceps can be used to perform CCC. The initial puncture in the anterior capsule is made with a bent needle, (or with the forceps itself, if the tips of the forceps are sharp enough), and the rest of the CCC is continued with the forceps. Using the forceps requires a larger opening into the anterior chamber as compared to a bent needle, and viscoelastic is usually necessary.
Two-staged CCC
In this procedure, the original capsulotomy is just large enough to admit the smaller endocapsular phaco probe and a second instrument for lens manipulation. After the
Figs 10.2A and B: Two-staged continuous curvilinear capsulorrhexis (CCC)
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lens material is removed a small initial opening is converted to a larger one, of the desired diameter, while still maintaining the continuous tear edge. The second capsulotomy is started with a tangential snip on one side of the opening with a Vannas scissors (Figs 10.2A and B). This requires a viscoelastic agent in the anterior chamber and lens capsule. It is important to prevent the side of the capsule opening from folding over or under at the scissors tip so as to prevent a V-cut. Also, the snip is not taken to the scissors point, because the point may create an irregularity in the line of the cut. Such a notched cut destroys the integrity of the continuous tear.
Once the tangential cut is successfully achieved, the second continuous tear is then extended, using Utrata forceps to complete a larger circle, which is centered in the pupil, and is of the desired diameter. The forceps enlarges the original capsulotomy by removing a strip or ribbon of additional capsule.
Two-staged CCC is Particularly Useful
•In patients with small pupils, when an originally small CCC requires subsequent conversion to a larger CCC.
•When the original CCC is made inadvertently small.
•For corneal endothelial protection in intercapsular and endocapsular cataract extraction.
A similar technique may be used in blunting or turning back, short inadvertent tears of the anterior capsular border.
Posterior CCC (PCCC)
Posterior CCC uses the principle of CCC and is used to advantage, when a small linear or triangular tear inadvertently occurs in the posterior capsule, in order to convert it into a smooth CCC that is resistant to radial extension.
The PCCC is accomplished just as one does an anterior CCC. The size of the PCCC is kept as small as possible to preserve the maximum support by the posterior capsule. Equatorial capsular tears, posterior capsule tears near the equator or with extensions to the equator are not suitable for PCCC.
PCCC may also be used, for making primary posterior capsulectomies, in removing posterior plaques, or to blunt, small extending tears with posterior continuous.
Intumescent Cataracts and CCC
Intumescent cataracts are a special problem for any form of capsulotomy, especially CCC. The internal lens pressure simply splits any rent towards the equator. A useful technique in such cases, is to decompress the lens by first aspirating some lens cortex.
Another difficulty is the poor visualization of the tearing edge, in milky white cataracts, where there is no red reflex. In such instances, Lee has found it extremely useful to perform CCC under air. The distortion of the tearing capsule under an air-lens interface is apparently, exceptionally clear.
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Advantages of CCC
There are several advantages of CCC:
•In-situ phacoemulsification is facilitated, and the ultrasonic turbulence is contained within the lens capsule.
•IOL implantation and verification in the bag is greatly facilitated because of the smooth-edge visible rim.
•IOL rotation with no chance of decentration caused by loops coming out of
the bag is allowed.
•No capsular tags or V-shaped tears are left that can extend into the posterior capsule, under even minimal, mechanical stress.
•A diaphragm quality of the capsule for sulcus placed lenses is maintained or preserved in the event of a ruptured posterior capsule.
•Chances of posterior synechiae are reduced.
•In-the-bag IOL implantation in the very elastic capsule of children is facilitated.
ECCE and CCC
Most surgeons recommend one or two “relaxing incisions” in the CCC, prior to nuclear expression in extracapsular cataract extraction (ECCE). The relaxing incision helps prevent untoward complications as zonular tears, vitreous loss, unintended ICCE, or even prolapse of lens into the vitreous cavity. Hydrodissection, hydrodelineation, and hydroexpression techniques are useful adjuncts, when using CCC along with ECCE.
Complications of CCC
These include:
•Shrinkage of anterior capsular opening
•Capsular bag hyperdistention
•Epithelial cell hyperproliferation on the posterior capsule.
CAPSULAR |
CONTRACTION |
S Y N D R O M E |
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Capsular contraction syndrome is seen after ECCE using can-opener capsulotomy or CCC. While rarely with can-opener capsulotomies, with anterior radial capsular tears, it is relatively frequent with CCC. The syndrome consists of an exaggerated reduction in the anterior capsulotomy opening and equatorial capsular bag diameter. This may also
Fig. 10.3: (Davison) Capsular contraction syndrome with capsulorrhexis opening displaced inferiorly and open to only 2.0 mm several months after surgery in eye with pseudoexfoliation
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Fig. 10.4: (Davison) Excessive capsular contraction has shrunk the capsulorrhexis opening to approximately 2.0 mm. The opening is decentered as is the silicone optic and the capsular bag; so the zonular fibers are visible below. Pseudoexfoliative material can be seen on the fibers
Fig. 10.5: (Hansen) Red reflex of an eye with dense anterior capsular fibrosis and well-centered, but extensively constricted capsular opening (1.3 mm). Note the radial stress lines and the broad fibrous rim of the circular capsulotomy. The three-piece posterior chamber IOL is completely within the capsular sac and shows a mild inferotemporal decentration
lead to a malposition of the IOL. These effects seem more exaggerated in small CCC openings and the older patient (Figs 10.3 to 10.6). It is due to capsular bag contraction from fibrous dysplasia of residual lens epithelial cells, countered by relatively unopposed weak zonular support. This is particularly seen, in pseudoexfoliation, advanced age, and in association with uveitis, pars planitis, and myotonic muscular dystrophy.
Role of IOL Material
Hayashi et al showed the reduction in the area of anterior capsule opening at various postoperative intervals after continuous capsulorrhexis and compared any differences in the area reduction between polymethylmethacrylate (PMMA), silicone, and soft acrylic IOLs.
Figure 10.7 shows retroillumination photographs, which illustrate the typical postoperative changes in the anterior lens capsule of the three optic materials. Figure 10.7 top left, shows an eye after undergoing PMMA IOL implantation. A slight degree of contraction and fibrosis of the anterior capsule opening occurred over the PMMA optic. Figure 10.7, top right, shows an eye after undergoing silicone IOL implantation.
The contraction of the anterior
capsule progressed markedly up to 3 months after surgery. The degree of fibrosis in the anterior capsule was also extensive. Figure 10.7, bottom shows an eye after soft acrylic IOL implantation. The anterior capsule contraction was very slight. Surprisingly, no fibrosis in the anterior capsule was evident in some cases in the soft acrylic IOL group. The study clarified that the area of the anterior capsule opening gradually decreased for up to 3 months after surgery. However, after 3 months, the area reduction in the anterior capsule opening showed no further progression. The percentage of the area reduction with the silicone IOL
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Fig. 10.6: (Hansen) Photograph of a case immediately after Nd: YAG laser anterior capsulotomy in a cross pattern, cutting through the fibrous rim of the constricted opening
Prevention
was greater than that with the polymethylmethacrylate and soft acrylic intraocular lenses. No significant difference was observed between the PMMA and soft acrylic intraocular lenses. Furthermore, although it could not be quantitated in this study, the degree of fibrosis in the anterior capsule was most extensive in the silicone IOL, followed by the PMMA IOL. On the other hand, the anterior capsule fibrosis over the soft acrylic optic was extremely slight.
Capsular fibrosis is caused by metaplastic lens epithelium. The more epithelium that is left, the greater the potential for capsule contraction. Since twice as much epithelium is removed with a 5.5-mm capsulectomy as with a 4.00-mm capsulectomy,
Fig. 10.7: Retroillumination photographs showing postoperative changes in the anterior lens capsule. (Top left) after a polymethylmethacrylate (PMMA) IOL implantation. A slight degree of contraction and fibrosis in the anterior capsule was observed over the PMMA optic. (Top right) An eye after a silicone IOL implantation. A marked contraction of the anterior capsule opening occurred for up to 3 months. The degree of fibrosis in the anterior capsule was also prominent, especially along the capsulorrhexis edge. (Bottom) An eye after soft acrylic (AcrySof) IOL implantation. The anterior capsule contraction over the soft acrylic optic was very slight. It was surprising that no fibrosis in the anterior capsule was evident
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one should make the larger anterior capsulectomy in vulnerable eyes. The sphincter effect of an intact capsulorrhexis is important in creating significant capsule shrinkage. A can-opener capsulotomy with deliberately created anterior radial capsular defects may be appropriate in lose eyes with zonular weakness.
Another influence in maintaining capsular bag size and shape and good functional IOL position is the use of a one-piece, all-PMMA IOL with a relatively firm broad haptic structure. Nishi suggested vacuuming the undersurface of the anterior capsule to significantly reduce the amount and effect of residual lens epithelial cells. 
Fig. 10.8: Six anterior YAG capsulotomies are almost not visible, three weeks after creation in a patient with pseudoexfoliation
Fig. 10.9: Same eye as in Figure 10.8 six anterior YAG capsulotomies have been redefined with more YAG separation
Role of Nd:YAG Laser
Early anterior radial YAG laser, relaxing capsulotomy helps resolve the ultimate contraction of the anterior capsulectomy opening (Figs 10.8 and 9). These anterior capsulotomies may also reduce the incidence of more rare complications of excessive zonular traction and its sequelae, IOL dislocation and retinal detachment.
If capsule contraction is noted, consider YAG laser relaxing anterior capsulotomies at 2 to 3 weeks postoperatively. Active capsular fibrosis and attendant contracture of the anterior capsule and indeed the entire capsular diameter can be influenced with early YAG laser intervention, whereas later intervention may not help really as much.
CAPSULAR BAG HYPERDISTENTION
“Capsular block” implies fluid hyperdistention of the capsular bag from occlusion of the circular anterior capsule opening by the IOL optic; the resulting anteriorplacement of the optic induces an artificial myopia; the source of the fluid is unclear, although some have suggested that it is retained viscoelastic (Fig. 10.10). Other possibilities include transudation through the lens capsule or exudation from the lens epithelial cells. Capsular block is generally self-limiting and is only associated with capsulorrhexis and IOLs flexible or mobile enough to move forward against the capsule opening; it has not been observed with the traditional can-opener