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

172 THE ART OF PHACOEMULSIFICATION

A pupillary size of 6 to 7 mm can be achieved with this method. Postoperative miotic therapy is required to decrease the pupil size and prevent iridocapsular synechiae between the sphincterotomy sites and the anterior edge to the capsulorrhexis.

Manipulation with the Chopper

The second instrument or the chopper can be employed to stretch the pupil in the area of interest while performing phacoemulsification. The chopper can be placed at the edge of the pupil and the iris manipulated to expose the nucleus that is being currently engaged by the phaco probe. The process is then repeated in the

other quadrants till the nucleus is completely emulsified.

UVEITIS

Anterior uveitis is often associated with a small, bound down pupil with a pupillary membrane and dense posterior synechiae. A fibrinoid reaction with pigment deposition over the surface of the IOL is also a common postoperative problem, specific to cases with uveitis.

Phacoemulsification should be attempted only if there has been no sign of activity in the past three months. Preoperative topical and systemic steroids can be started 48 hours prior to the surgery. Since the surgeon often encounters a pupillary membrane in such cases, membrane dissection (a technique first described by Osher) is a prerequisite for pupillary dilatation. In this technique, a bent 26/27 g needle or a capsulorrhexis forceps is used to perform a blunt dissection and stripping of the membrane from the edge of the pupil. After the membrane has been removed the pupil usually dilates to an adequate size for phacoemulsification to be performed. All manipulations in the anterior chamber should be performed under a cohesive viscoelastic like sodium hyaluronate, which also binds to the corneal endothelium and gives protection to the endothelial cells, already compromised due to the intraocular inflammation.

Intracameral low molecular weight heparin (Fragmin) can be added in the irrigating fluid (10 IU per ml) to decrease the postoperative reaction. A heparin coated/Smart IOL should be used in such cases, to minimize deposits on the surface of the IOL.

SUBLUXATED LENS

The stabilization of the capsular bag and implantation of the IOL is an important challenge for the phaco surgeon. If the zonular loss is limited to less than one quadrant a standard phacoemulsification may be attempted safely. If the zonular loss is more extensive, lens manipulation may cause further loss of zonular support and lens dislocation into the vitreous. Although an intracapsular extraction was traditionally performed in such eyes, it is now possible to perform phacoemulsification surgery in a subluxated cataractous lens using the PMMA endocapsular ring (ECR). The ring was introduced by Witschel and Legler in 1993 to provide an intraoperative and postoperative stabilization of the capsular bag. The ring currently in use is

the one modified by Morcher (Fig. 17.2) and consists of an open, flexible PMMA filament with eyelets present at the open ends. It is dialled with a Sinskey hook (using the eyelets to insert the hook) under the edge of the anterior capsulorrhexis. The ring expands and occupies the equator of the lens, circumferentially distributing the tension inside the capsular bag and thus acting as an artificial zonule. One can then proceed with phacoemulsification using a setting of low flow and low vacuum, to minimize turbulence in the anterior chamber and subsequent zonular stress.

Cionni has recently introduced another modification

in the ring with the introduction of a separate fixation element or a hook that extends centrally from the ring (Fig. 17.3). At the free end of the hook is an eyelet for manipulation and suture placement, which can be used to allow scleral fixation without disturbing the integrity of the capsular bag. This is helpful in eyes with an extreme loss of zonular support where the endocapsular ring itself may require a scleral support. Since implantation of the IOL may be associated with an excess pressure on the zonules due to the large inflexible PMMA haptics, these haptics can be tied to the surface of the optic using a 10-0 nylon suture prior to insertion into the anterior chamber. The suture can be cut once the IOL is inside the capsular bag for a gentle unrolling of the two haptics.

Another method described by Merriam and Sheng makes use of the flexible nylon iris retractors to hook the edge of the anterior capsulorrhexis to support the lens during the surgery. Two to four retractors can be used for this purpose depending upon the degree of subluxation. The retractors are removed at the end of the surgery and while it may be possible to insert one of the haptics in the ciliary sulcus, the second haptic can be sutured to the sclera with a 10-0 prolene suture for better stabilization.

POSTVITRECTOMY

Cataract development in phakic eyes after a pars plana vitrectomy is a common occurrence, with reported rates as high as 80 to 100% especially if silicone oil has been used. Phacoemulsification in vitrectomized eyes is a difficult task. Poor pupillary dilatation, posterior synechiae, deep anterior chamber requiring a steep angulation of the surgical instruments, zonular damage, posterior capsular plaques, excessively mobile posterior capsule and capsular tears are some of the problems faced by the surgeon. In addition due to absence of the anterior hyaloid, there is loss of posterior lenticular support and alteration in intraocular fluid dynamics. This leads

a collapse and sagging of the capsular bag during phacoemulsification due to a low vitreous pressure. The use of a superpinky is to be avoided in such eyes and the height of the infusion bottle should be decreased. An infusion port made in the region of the pars plana prior to proceeding with the cataract surgery may prove useful, although this is more relevant to extracapsular cataract extraction (ECCE). The constant inflow of fluid through the infusion cannula maintains a positive vitreous pressure, prevents scleral collapse and allows a comfortable surgery. The infusion port is taken out as the last step during surgery and the sclerotomy port is closed with the preplaced 8-0 Vicryl suture.

The integrity of the posterior capsule and the zonules may be disturbed by vitreous surgery. This can lead to a dehiscence of the posterior capsule and zonular dialysis at any time during the phacoemulsification. In such eyes, the endocapsular ring may be required to facilitate a successful IOL implantation.

In operated eyes with silicone oil left in the vitreous cavity, a silicone foldable IOL should not be used.

INTUMESCENT CATARACT

Phacoemulsification in intumescent cataracts is a challenge for the phaco surgery primary because of the difficulty in performing a capsulorrhexis. There is a lack of the red reflex, making the perception of the capsular flap difficult. In addition, since the lens is swollen, there is an increased tension on the anterior capsule and a greater tendency for the margin of the capsulorrhexis to escape towards the periphery of the lens. In such cataracts it is advisable to perform an initial cut in the central capsule to permit escape of the liquid cortex, to decompress the swollen lens. The cortical matter is aspirated out and the anterior chamber filled with a high viscosity viscoelastic substance (Healon GV). Then one proceeds with the capsulorrhexis under condition of high magnification and illumination, using a capsulorrhexis forceps. The surgeon may find it helpful to turn off the light of the operation theater and the microscope, and use an endoilluminator for oblique illumination of the capsule.

Another alternative in such cases is to perform the capsulorrhexis under air. This helps to tamponade the egress of liquefied cortical material after an incision in the anterior capsule. A bent 26 g needle is used in performing the capsulorrhexis, if air is to be used. The rhexis forceps requires a large opening and air escapes rapidly if this instrument is used. After completion of the capsulorrhexis, the rest of the procedure is similar to a routine phacoemulsification surgery.

PSEUDOEXFOLIATION

The pseudoexfoliation syndrome is associated with a weak zonular apparatus with an increased risk of zonular dehiscence during phacoemulsification. Poor pupillary dilatation, a fragile capsule prone to rupture, a degenerated iris, pathological iris vasculature and an increased inflammatory response after surgery are some of the problems encountered in eyes with pseudoexfoliation. The basic tenant of surgery

in such cases is to minimize stress on the zonules. A number of modifications are suggested to facilitate a smooth phacoemulsification in eyes with pseudoexfoliation.

The capsulorrhexis should be done with a Rhein or Utrata forceps, that can pinch the capsule and initiate the tear in the capsule. The needle or cystitome, traditionally used to perform the initial tear on the capsule, exerts much more mechanical pressure on the zonules and there may be a possibility of rupture of the zonules. The endocapsular tension ring and an anterior chamber IOL should be kept in reserve since there is a high incidence of zonular and capsular tears. Hydrodissection should be performed with minimal injection of fluid in several different quadrants to decrease intracapsular pressure. The technique of depressing the nucleus down, to complete the hydrodissection should be avoided.

The use of the endocapsular ring offers the safest method of phacoemulsification. The insertion of this ring creates a circumferential distribution of forces around the entire zonular apparatus, thereby reducing the localized pull on the zonules, during any intraocular manipulation.

The nucleus should be elevated away from the capsular bag with the second instrument to decrease the zonular traction while manipulating the nucleus in the capsular bag.

The implantation of the IOL prior to cortical aspiration is also useful because the PMMA haptics stabilize the capsular bag. In such cases the cortical clean up takes a much longer time and this technique is to be used only if the endocapsular ring is not available.

Intense postoperative steroid therapy and adequate cycloplegia may be required to control the postoperative reaction.

FURTHER READING

1.Bartholomew RS: Lens displacement associated with pseudocapsular exfoliation—a report on 19 cases in southern Bantu. Br J Ophthalmol 54:744-50, 1970.

2.Carpel EF: Pupillary dilation in eyes with pseudoexfoliation syndrome. Am J Ophthalmol 105:692-94, 1988.

3.Cionni RJ, Osher RH: Endocapsular ring approach to the subluxated cataractous lens. J Cataract Refract Surg 21:245-49, 1995.

4.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.

5.De Juan E Jr, Hickingbotham D: Flexible iris retractor (letter). Am J Ophthalmol 111:776-77, 1991.

6.Eckardt C: Pupillary stretching—a new procedure in vitreous surgery. Retina 5:235-38, 1985.

7.Fischel JD, Wishart MS: Spontaneous complete dislocation of the lens in pseudoexfoliation syndrome.

Eur J Implant Refract Surg 7: 31-33, 1995.

8.Fuller DG, Wilson DL: Translimbal iris hook for pupillary dilation during vitreous surgery (letter).

Am J Ophthalmol 110:577, 1990.

9.Goder GJ: Our experiences in planned extracapsular cataract extraction in the exfoliation syndrome. Acta Ophthalmol 184(suppl): 126-28, 1988.

10.Grusha YO, Masket S, Miller KM: Phacoemulsification and lens implantation after pars plana vitrectomy. Ophthalmology 1998; 105: 287-94.

11.Hutton WL, Pesacka GA, Fuller DG: Cataract extraction in the diabetic eye after vitrectomy. Am J Ophthalmol 1987; 104: 1-4.

12.Lacalle VD, Garate FJO, Alday NM et al: Phacoemulsification cataract surgery in vitrectomized eyes.

J Cataract Refract Surg 24: 806-09, 1998.

176 THE ART OF PHACOEMULSIFICATION

13.Lumme P, Laatikainen L: Exfoliation syndrome and cataract extraction. Am J Ophthalmol 116: 51-55, 1993.

14.McCuen BW II, Hickingbotham D, Tsai M et al: Temporary iris fixation with a micro-iris retractor.

Arch Ophthalmol 107:925-27, 1989.

15.McDermott ML, Puklin JE, Abrams GW et al: Phacoemulsification for cataract following pars plana vitrectomy. Ophthalmic Surg Lasers 28: 558-64, 1997.

16.Meldrum ML, Aaderg TM, Patel A, Davis J: Cataract extraction after silicone oil repair of retinal detachments due to necrotizing retinitis. Arch Ophthalmol 114:885-92, 1996.

17.Merriam JC, Zheng L: Iris hooks for phacoemulsification of the subluxated lens. J Cataract Refract

Surg 23:1295-97, 1997.

18. Meyers SM, Klein R, Chandra S et al: Unplanned extracapsular cataract extraction in postvitrectomy eyes. Am J Ophthalmol 86:624-26, 1978.

19.Miller KM, Keener GT Jr: Stretch pupilloplsty for small pupil phacoemulsification (letter). Am J Ophthalmol 117:107-08, 1994.

20.Naumann GOH: Exfoliation syndrome as a risk factor for vitreous loss in extracapsular cataract surgery (preliminary report). Acta Ophthalmol 184(suppl): 129-31, 1994.

21.Nichamin LD: Enlarging the pupil for cataract extraction using flexible nylon iris retractors. J Cataract Refract Surg 19:793-96, 1993.

22.Saunders DC, Brown A, Jones NP: Extracapsular cataract extraction after vitrectomy. J Cataract Refract Surg 22: 218-21, 1996.

23.Shepherd DM: The pupil stretch technique for miotic pupils in cataract in cataract surgery. Ophthalmic Surg 24:851-52, 1993.

24.Skuta GL, Parrish RK II, Hodapp E et al: Zonular dialysis during extracapsular cataract extraction in pseudoexfoliation syndrome. Arch Ophthalmol 105:632-34, 1987.

25.Smiddy WE, Stark WJ, Michels RG et al: Cataract extraction after vitrectomy. Ophthalmology 94: 48387, 1987.

26.Sneed S, Parrish RK II, Mandelbaum S, et al: Technical problems of extracapsular cataract extraction after vitreous surgery (letter). Arch Ophthalmol 104: 1126-27, 1986.

27.Whitsett JC, Stewart RH: A new technique for combined cataract/glaucoma procedures in patients on chronic miotics. Ophthalmic Surg 24: 481-85, 1993.

28.Wilbrandt HR, Wilbrandt TH: Pathogenesis and management of the lens-iris diaphragm retropulsion syndrome during phacoemulsification. J Cataract Refract Surg 20: 48-53, 1994.

178 THE ART OF PHACOEMULSIFICATION

when situations arise that are not routine, I do not hesitate to alter my technique and use one which is safer or more efficient.

Incision

As I stated, I routinely use a temporal hinged clear corneal incision. When properly created this incision is refractively neutral, stable and easy to perform. Furthermore, it preserves the conjunctiva in case glaucoma filtering procedures need to be performed in the future and is bloodless which is particularly important for patients taking anticoagulants or aspirin. When a patient has greater than 1.25 diopters of with-the-rule (WTR) or oblique astigmatism, I move my incision toward the steep axis and depending on the axis and degree of astigmatism I decide where to place the incision. When the astigmatism is greater than 45 degrees away from the horizontal meridian, I use a corneoscleral tunnel; usually, this results in a more or less superior corneoscleral incision.

Viscoelastic

Much has been written about the advantage of one viscoelastic over another. Recently a great deal of research has begun to quantify the precise differences in cohesiveness between the different agents.2 Routinely I will use one of the agents that is in the middle of the cohesive/dispersive spectrum. However, in a patient with significant endothelial dysfunction I am careful to select an agent that is more dispersive. I want this viscoelastic to coat the endothelium as well as possible and to remain in the eye to protect the endothelium throughout the case. Cohesive agents tend to be removed in a bolus during phacoemulsification and do not adequately protect the compromised endothelial cells. In those cases where I use a more dispersive agent, I take a few extra seconds at the end of the case to try to remove any residual viscoelastic that may remain in the eye.

Capsulorrhexis

Continuous curvilinear capsulorrhexis has elegantly transformed the way in which cataract extraction is performed.3 It is arguably the critical step which will determine the ultimate success of the phacoemulsification and IOL placement. Before beginning the CCC, I inject additional viscoelastic into the anterior chamber to try to enlarge the pupil and to flatten the anterior capsule. At this point it is wise to evaluate the adequacy of pupillary dilation. Good dilation of the pupil is very important for safe and efficient phacoemulsification. I have observed extremely talented individuals perform CCC in eyes with small pupils with the leading edge of the rhexis under the pupil, essentially unseen. While this is a most impressive maneuver, I do not recommend it for mere mortals such as myself. I believe that for most of us this is just asking for trouble, and there is not much more trouble than a radial extension of the CCC at this point in the case.

I have found that pupil stretching techniques to be extremely useful when the pupil is small.4 I use a bimanual technique with an iris hook through the

original incision and a Kuglein manipulator through the side port incision. Occasionally I create an additional paracentesis incision approximately 120 degrees away from the main incision on the side opposite the original paracentesis incision for cases where extensive posterior synechiae are present. In these extreme cases I also use the viscoelastic with its cannula to viscodissect the synechiae. It is very unusual to not obtain adequate pupillary dilation after carefully engaging segments of the pupillary margin 180 degrees from each other with these two

(or two similar) instruments and moving the two opposite one another, toward the direction of the trabecular meshwork. The two instruments are then moved

to different areas of the pupillary margin and the action is repeated, three or four times is usually adequate. Occasionally, small hemorrhages may occur at the pupillary margin, they are self-limited however, and resolve without any further treatment. Additional viscoelastic is then instilled into the eye to evaluate the adequacy of the pupil dilation. Stretching can be repeated if necessary, but care must be taken to avoid damaging the anterior capsule during any iris manipulation.

Several devices have been developed to facilitate dilation including the Beehler pupil dilator and disposable iris retractors. I used the latter during my residency and found them to be quite useful, now however, I rarely use anything other than the technique described above. Minisphincterotomies may also be performed, however these significantly disrupt the blood-aqueous barrier and seem overly traumatic in my view. However, cases may exist where they are necessary and one should keep this option in mind.

I usually begin the CCC with a cystitome, and continue it with capsulorrhexis forceps, aiming for a 5 mm opening, or slightly smaller than the optic. If one is seeking additional efficiency, the capsulorrhexis forceps may be used to initiate and complete the CCC.5 During the rhexis I observe the lens for any phacodenesis or zonular dialysis, if any is observed I change my mindset. This is a situation where having flexibility and the knowledge of alternate techniques enables one to perform safer surgery and avoid potentially significant complications. When loss of zonular integrity is recognized, I create a larger CCC, and alter my technique, planning to prolapse the nucleus during hydrodelineation, and perform supracapsular phacoemulsification of the nucleus.6 In this way, one may reduce stress on an already compromised zonular apparatus and complete the case without disinserting more of the zonules.

White nuclei and hypermature nuclei present special challenges because no red reflex is present and visualization of the leading edge of the capsular tear is extremely difficult. Many different techniques have been described, including the injection of intracapsular fluorescein, capsule staining with trypan blue, side illumination (with a flashlight or similar illumination device), reducing the overhead lighting, and endoscopic illumination.7-9 In these cases I usually turn off the room lights and increase the magnification of the microscope. I then attempt a smaller than normal CCC (approximately 3-4 mm). By reducing the diameter I am able to increase my margin of error, should the CCC begin to extend radially. The CCC can then be enlarged secondarily after removal of the cataract and implantation of the IOL.10 At times

180 THE ART OF PHACOEMULSIFICATION

it is not possible to successfully perform an intact CCC in these cases. When the rhexis begins to extend radially, one may have to convert to a can-opener type capsulotomy for the remainder of the circle. If this occurs, additional care must be taken during hydrodissection and phacoemulsification to prevent a radial tear from being created. One should again consider supracapsular phaco in this instance. After IOL implantation it is occasionally possible to convert the can-opener portion of the capsulotomy to a continuous tear for additional IOL stability and centration.10

CCC in hypermature or Morgagnian lenses can sometimes be performed with relative ease with the use of a little trick. Occasionally after the initial puncture of the anterior capsule in these cases, liquefied cortical material may leak into the anterior chamber and obstruct one’s view. If this occurs after the anterior capsule is pierced with a cystitome, one can place a 27-gauge cannula on an empty syringe, place the tip of the cannula through the opening created in the capsule, into the anterior cortex and aspirate some of the liquefied cortex. Usually the anterior chamber must be re-expanded with additional viscoelastic. After sufficient amounts of cortex have been aspirated, a red reflex is often seen and a careful CCC may be performed in the usual manner.11

Hydrodissection and Hydrodelineation

These two steps are extremely important, both to preserve the zonules and to facilitate removal of the nucleus and cortex. I begin using a J-shaped cannula for subincisional hydrodissection. This has proved to be of invaluable assistance to me in removal of subincisional cortex. I then proceed with standard hydrodissection and hydrodelineation using a straight cannula (Fig. 18.1). Before attempting any phacoemulsification, I will use the cannula tip or a cyclodialysis spatula to rotate the

nucleus to ensure that adequate hydrodissection has been performed.

Nucleus Removal

Numerous techniques have been described, but as I mentioned in the introduction, most surgeons utilize few of them. The more techniques that one is aware of, the more flexible and efficient one can be when intraoperative challenges present themselves. No matter how many techniques one knows, there will always be one or two that are most familiar and with which one has the most experience. I believe that as one obtains more experience, it is possible to use subtle maneuvers to encourage the cataract to behave as one wants it to, but until that time, knowledge of alternative techniques, and the flexibility to use them, will enable the beginning or intermediate phaco surgeon to handle challenging cases with greater safety