Ординатура / Офтальмология / Английские материалы / The Art and the Science of Cataract Surgery_Boyd, Barraquer_2000

Detachment of Descemet's

Membrane

An occasional but important complication is detachment of Descemet’s membrane, as shown in Fig. 143. The main causes are: 1) ocular hypotension while dissecting the tunnel or while constructing the internal part of the tunnel to make the valve-like incision. The injection of viscoelastic through the side port of the incision before performing the primary incision can prevent this from happening. 2) The introduction of the blade in the wrong direction when constructing the internal part of the incision (Figs. 140, 142 and 143). 3) The forced introduction of the phaco tip or foldable lenses in a tight incision. This may be avoided by being very careful during entry of the tip, by

lubricating the tunnel with viscoelastic and by very careful folding of the IOL and lubrication either of forceps or the injector, in order to attain a non-traumatic introduction and implantation of the IOL.

Important: During the dissection of the internal step of the incision which leads to the formation of the internal valve (V), the intraocular pressure must be either normal or slightly high and the tip of the blade must be directed towards the pupil and follow a parallel path toward the pupil as shown in Figs. 140, 142 and 143. Use abundant viscoelastic in order to keep Descemet’s membrane where it belongs until the conclusion of the surgery.

A detachment of Descemet’s membrane discovered postop, is an important complica-

tion when it occurs because it may be followed by corneal edema and even inflammation. If it occurs, topical antiinflammatory medications are sometimes useful. If the detachment is significant, however, (Fig. 143) there may be corneal decompensation progressing to bullous keratopathy which may eventually require a penetrating graft.

Precautions with Closure of the Incision Upon Conversion

Conversion to extracapsular is not infrequent when you start in the transition period and may be necessary even in the hands of a more experienced surgeon upon the development of complications. If the incision is corneal, move to the limbus. Other surgeons prefer the scleral tunnel incision or the tunnel starting at the limbus or about 1 to 1.5 mm from the limbus. When converting, enlarge the

incision for the extracapsular at the limbus. The nucleus and cortex are removed and the IOL implanted. When suturing, it is important to close the wound by placing the interrupted sutures radially. Whenyouget tothejunction between the part of the incision where the tunnel was started and the limbus, suture it as shown in Fig. 144. The arrow shows conversion when the initial incision was a sclerocorneal tunnel. Unless properly sutured, the valve may leak at this site.

Heating the Wound

Very occasionally, if one is not careful, you can heat the wound. It looks like you cauterized the cornea. That is not such a problem during the surgery but this wound may well leak. If that occurs, at the end of the operation, the surgeon has to close the wound by suturing but will not be able to perfectly

approximate the edges of the incision because this may induce a large astigmatism. The most practical approach is to suture the anterior edges of the tunnel to the posterior surface of the wound using a mattress suture. A little gap will remain in almost every setting but you can create a sealing incision. You should expect a small to moderate amount of astigmatism, but the good news is that it will go away with time. It is only a temporally induced astigmatism. The difficulty is to get that incision to seal.

Management of Leaking Incisions with a Positive Seidel

Infrequently, a clear cornea incision or a scleral tunnel incision larger than 3 mm in width may show leaking of fluid one day postoperatively. This is either secondary to an incision larger than planned and not sutured, or by too much trauma in the lips of the wound usually by the phaco tip.

When this leaking occurs, it may be immediately detected by instilling a drop of fluorescein and observing the patient under ultraviolet light. The problem with these patients is that the constant escape of aqueous humor keeps the wound open and may require suturing of the incision which certainly is a nuisance.

Prof. Juan Murube, M.D., from Madrid recommends a very ingenious maneuver in order to close the leaking wound without having to re-suture the incision. He places a Honan balloon (Fig.96) over the eye for 30 minutes at a pressure of 35 mm Hg and at the same time administers 1 tablet of acetazolamide, 250 mg orally (Diamox). The hypotony produced when the Honan balloon is removed makes the aqueous humor (that is

constantly being produced and was causing the positive Seidel) remain in the anterior chamber. The anterior chamber has the opportunity to reform. After a few minutes, when the intraocular pressure returns to normal, the walls of the incision have come together and adhered, without any further positive Seidel. This ingenious maneuver is simple and avoids having to re-suture the patient.

COMPLICATIONS RELATED TO ANTERIOR CAPSULORHEXIS

It is generally agreed that this is the procedure of choice to open the anterior capsule. In most cases, it allows the phaco technique to be performed within the capsular bag and, consequently, the maneuvering and instrumentation does not affect the surrounding tissues particularly the corneal endothelium. Capsulorhexis also allows an almost perfect positioning of the intraocular lens. As emphasized by Centurion, when the surgeon dominatesthetechniqueofcapsulorhexis,cases of decentration, capture and/or subluxation of the IOL are rare.

Main Complications

The main complications may be related to: 1) the size of the capsulorhexis. It may be either too large or too small. This is due to a technical mistake either in the judgment of the surgeon or in performing the technique. The ideal diameter of capsulorhexis ranges from 5to6mm. Centurion advisesthat,whenthere is doubt, check the diameter of the capsulotomy by holding a compass over the cornea. When the capsulorhexis is too small, less than 5mm(Fig.145),problemsmayariseduringthe manipulation of the nucleus and the IOL im-

plantationmaybemoredifficulttotheextentof compromising the final result of the surgery.

If it is considered to be small, perform a small lateral cut in the capsulorhexis with Vannas scissors at 10 o'clock (Fig. 146). Afterwards, perform a second and wider anterior capsulorhexis with the Uttrata forceps at 12 o'clock which will prevent or eliminate the likelihood of stenosis of the opening (Fig. 147). This is also a good option on what to do if there is some discomtinuity or small tear identified in the anterior capsulorhexis.

When the capsulorhexis is too large (Fig. 148), larger than 6 mm, some difficulties may arise in stabilizing the nucleus after hydrodissection with a tendency for the nucleus to move into the anterior chamber. Thic could possibly endanger the corneal endothelium and other surrounding structures and emulsification would need to be done in the anterior chamber. Maintain sufficient viscoelastic between the lens and the endothelium.

Lindstrom considers that if the capsulorhexis is really large (Fig. 148) it is not a major problem although there is a tendency to develop a higher rate of capsular opacity because the border of the capsulorhexis is not placed over the edge of the posterior capsule.

Another problem that Lindstrom has commonly encountered is the chamber will shallow as you are doing the capsulorhexis, particularly in younger eyes. The way to avoid this is that as you see the chamber shallowing, put more viscoelastic in it and put it more centrally in the younger eye.

Another complication is that the capsulorhexis will tear into the zonules. If

that occurs, Lindstrom goes back to the beginning, makes a little cut with Vannas scissors at the edge of the rhexis (Fig. 146) in the other direction from where the extension into the zonules occurred and enlarges the rhexis around the opposite way (Fig. 147). In these cases, the surgeon may have to presume that there was a little radial tear to start and must be very careful with the next step, the hydrodissection, because most probably there is a weak spot in the anterior capsule. In that case you should probably not use a plate haptic lens.

Preventing Rhexis Complications by Tinting

One of the major advances in performing circular continuous capsulorhexis (CCC) in hypermature cataracts which are either totally white or very dark is the tinting of the anterior capsule. In these eyes, the fundus reflex cannot be seen by the coaxial light of the microscope. When the reflex is not present, it is extremely difficult to see in order to complete the circular capsulorhexis. Tinting of the anterior capsule through various substances such as Fluorescein 2%, Indocyanine Green, Trypan Blue, Gentian Violet, or Methylene Blue is a new development to improve the visibility of the anterior capsule during CCC. Professor Juan Murube, M.D., in Madrid and Professor Carlos Nicoli, M.D., in Buenos Aires both definitely prefer the use of Trypan Blue as the best coloring substance for this purpose. Theyplacethetinting substance over the anterior capsule when the anterior chamber is full of air as advised by Murube. The technique is shown in (Figs. 101, 102, page 173).

Figure 146 (above): Management of Small

Anterior Capsulorhexis

If it is considered to be small, perform a smalllateralcutinthecapsulorhexiswithVannas scissors at 10 o'clock.

Figure 148 (below): Complications Related to Anterior Capsulorhexis - Too Large

The ideal size ranges from 5 to 6 mm. In this surgeon's view you may observe a large capsulorhexis (C). This may induce tears of the posterior capsule during the stage of phacoemulsification or a tendency for the nucleus to move to the anterior chamber during the operation.

Figure 147 (center): Enlarging a Small Capsulorhexis - Managing a Discontinuity of the Rhexis

Perform a second and wider anterior capsulorhexis with the Uttrata forceps which will prevent or eliminate the likelihood of stenosis of the opening. This figure also serves to show what to do when there is a discontinuity or small tear identified in the anterior capsulorhexis (C). The best option first is the injection of viscoelastic. Next, try with the forceps

(F) to perform a second anterior capsulorhexis (arrow) leaving a regular surface with no weak points in order not to alter the correct evolution of the surgery. The white arrow identifies the small discontinuity of the rhexis which is being repaired.

COMPLICATIONS WITH

HYDRODISSECTION

What we try to accomplish with hydrodissection is that by irrigating with a stream of BSS immediately under the anterior capsule, we produce a separation of the rest of thelensfromtheanteriorcapsule,includingthe nucleus and cortex, and separation of the cortex from the epinucleus.

If you are doing an endocapsular technique,sometimesitisdifficulttogetthenucleus loosebyhydrodissection. Sometimessurgeons will stop because they find it is taking them longer than they expected and are not sure how to proceed. If the surgeon stops to the extent of discontinuing hydrodissection, this makes the rest of the operation much more difficult and risky. Lindstrom emphasizes that one should continue to hydrodissect and do so in different

areas until one is sure the nucleus is loose and will rotate. Having a loose nucleus by hydrodissection is one of the keys to success with the endocapsular technique. If the surgeon does not get the nucleus loose it leads to complications in the next step.

Centurionemphasizesthatif thenucleus does not spin freely within the capsular bag it is due to incomplete hydrodissection. It is important not to try to rotate the nucleus mechanically at this stage but, instead, repeat the hydrodissection maneuver and/or introduce in the anterior chamber a Sinskey hook through the main incision and another hook through an ancillary incision as shown in Fig. 149. The hooks are fixed at opposite sides of the nucleus. In Fig. 149 the arrows indicate the direction of the spin of the nucleus when a slight traction is applied but this is done after a repeat hydrodissection. For this procedure, the anterior chamber should be filled with viscoelastic.

Centurion emphasizes not to proceed to the next stage, which is nucleus removal through phaco, without being sure that the nucleus is free. In traumatic or congenital cataracts be particularly careful when performing hydrodissection due to the possible fragility of the posterior capsule.

COMPLICATIONS DURING NUCLEUS REMOVAL

Before proceeding with phacoemulsification of the nucleus, it is assumed that the surgeon has performed correctly all the previous phases of the operation. Upon entering this crucial stage of the operation, the surgeon may have difficulty in fracturing the nucleus. That usually is caused by having performed

too shallow a groove within the lens, not deep enough to allow fracturing of the remaining nuclear bed.

If the surgeon is using the "Divide and Conquer" technique, the reliable point of reference when performing the groove, is the tip of the phacoemulsifier as shown in Fig. 150. The tip of the phacoemulsifier should penetrate the central region of the nucleus 1 1/2 to 2 times the diameter of the tip of the phacoemulsifier (Fig. 150). The arrows in this figure show the direction of opposing forces applied to both sides of the groove in order to fracture the nucleus. As this proceeds, the red reflex becomes redder (Also see Figs. 104 page 178, and 106 page 182). The most serious complication of nucleus removal is rupture of the posterior capsule, which we address separately in this chapter.

Surgeon's Fatigue

Lindstrom points out that another preventive measure to avoid complications during nucleus removal is that in the more difficult eyes, the surgeon fatigues, or gets tired. When this happens, he stops and rests. The minute you think you do not seem totally comfortable and your movements get a little awkward he recommends stopping and put some viscoelastic in the eye. Use two instruments to rotate the nucleus into a more favorable position (Fig. 149) and then start again. In some difficult eyes Lindstrom may restart and stop even two or three times. Maybe that means the case took four minutes longer but this is not important. In those really difficult eyes it can mean the difference between success and failure. In some complications symposia, if you observe the live surgery you can see the tremors of some surgeon's hands when it is taking them a long time in difficult cases, and they get awkward and uncomfortable, they just cannot get the nucleus into the right position. In those cases Lindstrom thinks if you just stop and rest for a minute, put a little viscoelastic, take your time and be patient until being able to rotate the nucleus (or other difficult maneuvers) you can save yourself and the patient a great deal of problems.

COMPLICATIONS DURING REMOVAL OF THE CORTEX

After the nucleus has been removed, it is importantthatthesurgeonremainconcentrated on proceeding with skill and attention to every detail to the end stages of the operation. It is natural for some surgeons to consider that immediately after removing the nucleus, the main steps of the operation have been con-

cluded and it is time to relax. Not so. An unpleasant rupture of the posterior capsule may occur during the following step, which is removal of the cortex.

Lindstrom emphasizes that for most people removing the cortex is "easy" but many of the series in the world literature will show that as many posterior capsules are torn during cortical removal as are during the nucleus removal. The hard part is over but do not loose concentration. Slow down, and make sure you do this step properly. The cortex usually is quite easy to remove but most of the difficulty and risk occurs when trying to vacuum clean the posterior capsule. Lindstrom is not convinced that it makes any difference to vacuum clean the posterior capsule because this is not where the source of the eventual opacification of the posterior capsule. He discourages aggressive vacuuming of the posterior capsule. If you are going to do it be very certain that there is no barb or sharp point on the tip of the I/A. He has seen many capsules torn by a little barb or sharp tip on the I/A tip particularly during the vacuum cleaning.

COMPLICATIONS DURING FOLDABLE IOL's IMPLANTATION

Wrong IOL Power and

Decentration

To prevent complications, the key is to get the lens symmetrically into the capsular bag or symmetrically into the ciliary sulcus if for some reason the surgeon feels insecure about the capsular bag being intact. This requires being very observant that there is a good capsular rim and certain that you are placing the complete lens at the bottom of the capsule.

Also, be sure you have the correct lens and correct lens power. Surgeons who receive many referrals from other colleagues consider that the most common reasons they have to operate in order to change an IOL are: 1) error in lens power calculation during the previous operation and 2) late decentration or subluxation.

Asymmetric Capsulorhexis

Sometimes, a decentration of the IOL occurs because there is an asymmetric capsulorhexis. The margins of the rhexis are not over the optic on all sides. Consequently, one side gets underneath the lens, it fibroses and pushes the lens aside. If for some specific reason the haptics were placed in the sulcus, sometimes the sulcus can be very large, as in myopes, and there can be an area of disinsertion.

DeficientIntraoperativeHandling

Carlos Nicoli, M.D., one of Argentina's most prestigious cataract surgeons, finds that the intraoperative complications with foldable IOL`s are not significant but we do have to be alert as to problems arising from intraoperative handling of the lenses, the instruments used to fold the lenses, the injectors and the forceps. Heavy or high density viscoelastics placed withintheplasticinjectorshaveledtobreakage of the injector at the time of insertion. In addition, if the surgeon does not have enough experience with the injectors, he may scratch the lens optic. Also, if we grasp the lenses with forceps without a stop at the tip, the optics can be scratched at the time of folding.

Nicoli points out that tears may occur in lenses at the time of insertion. They may be: 1) partial tears where vision is not affected

because they are not within the central zone; and 2) others have suffered significant tears and have had to be removed during surgery, requiring that a new lens be inserted. These tears might have been due to the lack of lubrication with viscoelastic or because the surgeon did not use the proper technique of insertion.

Importance of Warming Acrylic

IOL's

Upon using acrylic lenses, they should be warmed before folding and implantation. This measure provides easier folding and a slower unfolding. If we attempt to fold and implant an acrylic IOL at room temperature, the lens presents resistance to folding and a certain resistance to unfolding.

Management of Complications with Array Multifocals

As emphasized by Fine and Hoffman, in situations in which the first eye has already received an Array lens implant, complications management must be directed toward finding the way to implant an Array IOL in the second eye. Under most circumstances, capsule rupture will still allow for implantation of an Array lens as long as there is an intact capsulorhexis. Under these circumstances, thelenshapticsareimplantedinthesulcus,and the optic is prolapsed posteriorly through the anterior capsulorhexis. This is facilitated by a capsulorhexis that is slightly smaller than the diameter of the optic (Fig. 145) in order to capture the optic in essentially an in-the-bag location. If full sulcus implantation is used, then an appropriate change in the IOL power will have to be made to compensate for the more anterior location of the IOL within the