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

membrane; hemorrhage into the vitreous; separation of the vitreous from the retina; and retinal detachment, which are obscured to direct examination (Fig. 199).

Combined Injuries of Anterior and

Posterior Segment

A damaged lens mixed with blood and vitreous needs prompt and adequate surgery. Failure to remove this debris encourages fibrosis with a cyclitic membrane causing ciliary body detachment and hypotony eventually leading to retinal detachment and phthisis bulbi.

Traumatic Cataracts in the

Presence of Anterior Segment

Penetrating Wounds

Main Objectives

In anterior segment injuries the initial objectives are watertight repair of the corneal wound, restoring normal depth to the anterior chamber, intensive antibiotic treatment to prevent infection and intense antiinflammatory therapy from the very start. The further goals are to manage the cataract adequately, reduce secondary damage by minimizing excessive corneal scarring; assuring a clear, adequately sized and cosmetically and optically desirable pupillary opening; and preventing further damage to the anterior chamber angle that could result in glaucoma.

Often all of these objectives can be achieved at the time of initial wound repair although in some cases further surgical procedures are needed. The traumatic injury may have caused a lens anterior capsular

defect either from a blunt rupture or a sharp laceration.

MANAGEMENT OF TRAUMATIC CATARACT

Robert Stegmann, M.D., has very extensive experience in trauma cases. He believes that the prognosis for a traumatic cataract can be the same as for a routine senile cataract if the traumatic cataract is handled properly. This excludes cases in which there is damage to the posterior segment, the vitreous has become cloudy, or the retina is damaged from the same trauma, or where infection has occurred.

Small Wounds in Anterior

Capsule

In many cases a penetrating wound in the cornea and lens is small, the lens material still remains within the capsule and, even though cloudy, it may not escape through the tiny capsular tear (Fig. 200). Prof. Giora Treister from Israel recommends that in such cases, the lens be left alone during the first surgical intervention. He repairs the primary wound and goes no further at this time because generally these are the worst conditions for operating on the eye. The tissues are swollen and irritated, and perhaps even infected. The trauma may have occurred at night. In case of unexpected complications, the most experienced surgeons are not on duty.

If it is not absolutely necessary to go further with the initial procedure, Treister recommends that it will suffice to close the primary wound and to concentrate on proper reconstruction later.

If Anterior Capsule More Widely

Damaged

If the anterior capsule is more widely damaged and lens material is present in the anterior chamber, (Fig. 201) Treister removes all the lens material during the first surgical intervention and examines the posterior segment with the indirect ophthalmoscope. If the trauma is confined to the anterior segment, the vitreous is clear, the retina is attached without retinal tears and no foreign body is seen, a posterior chamber lens is implanted .

Timing for Primary Lens Extraction

John Alpar, M.D., who has extensive experience with traumatic cataracts, considers that a primary lens extraction should occur any time the lens is so damaged that its particles are mixed with anterior chamber or vitreous material. The lens should also be removed in cases of subluxated lens following trauma. The advantages of a primary operation in these cases are that postoperative inflammation is reduced, rehabilitation time is faster, and later examinations, including the evaluation of the retina, are easier to perform.

The most important indications for primary operation are signs that point to the likelihood of a ruptured posterior capsule with vitreous already entering the chamber.

More Extensive Damage

Affecting Posterior Capsule

In case of perforation of the lens with an opening also in the posterior capsule,

Treister as well as Stegmann in South Africa remove the vitreous from the anterior chamber (if present) with a vitrector together with the lens material but try to preserve the posterior lens capsule, or part of it, for sulcus-placed posterior IOL implantation.

Specific Problems with

Traumatic Cataracts

Paul Koch, M.D., points out that zonules are often torn and there may be significant risk of collapse of the posterior capsule as well as vitreous prolapse around the equator of the lens. Consequently, in the preoperative evaluation with the slip lamp, look carefully for evidence of zonulysis.

HIGHLIGHTS OF SURGICAL TECHNIQUE

The Incision

A sclero-corneal tunnel (Fig. 40-B) is definitely the incision to be used. A corneal tunnel incision is contraindicated. The conjunctiva must be treated very delicately. Some of these patients may develop second-

ary glaucoma and might need a filtering operation at a later date.

Anterior Capsulorhexis

In many cases the anterior capsule has been perforated. A CCC may be quite difficult and sometimes risky. Paul Koch has advocated that a better way to open the unsupported part of the anterior capsule ruptured zonules is to use capsule scissors. A puncture can be made in the anterior capsule, scissors introduced with one blade through the puncture, and a snip capsulotomy performed. Koch points out that pulling inward to create a capsulorhexis with a needle or forceps could be dangerous, dislocating the lens beyond the point of recovery.

Other parts of the capsule, where the zonules are intact, may be opened in the usual fashion.

The circular anterior capsulotomy should be made large enough so that the nucleus can be floated out of the bag with hydrodissection. Typically this occurs easily because the nucleus is white, soft and fluffy.

In performing the anterior capsulotomy, if the cataract is white, the use of Trypan Blue as shown in Figs. 101 and 102, page 173 may increase the possibility for performing a successful capsulotomy.

Lens Removal

In the presence of traumatic cataract, phacoemulsification is done in the anterior chamber. Once the nucleus enters the anterior chamber, viscoelastic can be placed above and below it, protecting the cornea and pushing the flaccid capsule as far posteriorly as

possible. In a young patient the nucleus is usually very soft and is amenable to many different options. For a patient with an intact capsulorhexis, phaco-aspiration of the nucleus is safe and effective. If an anterior or posterior capsular tear is present, then manual aspiration with a Simcoe-style cannula affords greater control. «Dry» aspiration of the soft nucleus under viscoelastic material offers excellent control, especially in the most complicated cases, as advocated by Snyder and Osher.

Role of Intracapsular Tension

Ring in Traumatic Cataracts

This is an important advance in cataract surgery. The ring is a relatively

recent development, as advocated by Robert J. Cionni, M.D., in the U.S. and Okihiro Nishi, M.D., in Japan. This device maintains the shape of the bag during and following extracapsular surgery or phacoemulsification in traumatic cases or in patients with subluxation or pseudoexfoliation. It has important implications in terms of preventing IOL dislocation, decentration, tilting, further zonular dehiscence, and posterior capsule opacification. The capsular tension ring (or intracapsular ring), is an open circular PMMA haptic (Fig. 202). It can distribute the forces inside the capsular bag, thereby making it possible to perform surgery safer, and decentration of the IOL is prevented.

In the management of traumatic cataracts, the ring is placed in the bag for support,

provided that there is an intact anterior capsulotomy and posterior capsular bag. In some cases it will be easy to place it prior to emulsification of the nucleus, while in other patients it is better to place it prior to cortical aspiration. This will stabilize the capsule and support the areas lacking zonules. Once the capsule is secure, the cortex can be removed and the implant placed. If necessary the ring can be sutured transsclerally..

Removal of Cortex

After nucleus removal, before proceeding with cortical aspiration, inspect the posterior capsule carefully to be sure that there are no tears as a result of the injury, particularly a blunt injury, where tears might be hidden.

If the capsule is intact, proceed as usual, following the principles and techniques outlined in Figs. 127 and 128. In case of doubt about the effects of automated irrigationaspiration, you may use the manual aspiration with the Simcoe-type cannula, as shown in Fig. 128. This allows a greater degree of control.

Selection of IOL

Traumatic cataracts may be associated at a late date with some vitreoretinal complications. PMMA and acrylic lenses are well tolerated by the eye and preferred by the vitreoretinal surgeons. Since traumatic cataracts are not uncommonly associated with some degree of traumatic mydriasis, a 6.0 mm or larger diameter IOL optic is a prudent choice.

IOL Implantation

With the support and stability of an intracapsular tension ring, the placement of

the IOL in the capsular bag is indicated and desirable. If an intracapsular ring is not available and only a small area of zonular dehiscence is present, slowly unfolding the implant or very gently placing a rigid lens with soft loops will minimize the stress on the intact remaining zonules.

Ciliary sulcus placement of a posterior chamber implant is still possible in the setting of a posterior capsular tear or zonular dialysis (Figs, 153, 154, 156). If the anterior capsulorhexis is intact, yet a severe posterior capsule break exists, the haptics should be placed in the sulcus. It may be possible to capture the lens optic posteriorly into the capsulorhexis. This will provide adequate support and will prevent the lens from subsequently dislocating.

If the capsulorhexis is incompetent or larger than the implant optic, sulcus fixation with a large diameter implant can be utilized.

Selection of Viscoelastic in

Traumatic Cataracts

In those eye centers where the two main types of viscoelastics are available (dispersive and cohesive), the following are good choices as advocated by Snyder and Osher: 1) When the hyaloid face is partly exposed, a highly retentive (dispersive) viscoelastic agent such as Viscoat (Alcon) or Vitrax (Allergan), may tamponade the vitreous and keep it back. The dispersive agents also protect the endothelium well. This may be particularly important in cases in which the endothelial cell density has been reduced by the trauma. 2) On the other hand, the space retaining qualities and ease of removal typical of highly cohesive viscoelastic agents, such as Healon GV (Pharmacia & Upjohn), make these agents more appropriate for the lens implantation stage of the procedure.

Phacoemulsification Advantages in Traumatic Cataract

Traumatized eyes with potentially weakened zonules are at greater risk for suprachoroidal hemorrhage. Maintaining a closed system as provided by phacoemulsifi-

cation reduces the risk of expulsive hemorrhage. In addition, a closed system allows compartmentalization within the anterior segment. If the posterior capsule is broken or if a zonular dehiscence is present, viscoelastic tamponade of the vitreous can be best maintained in the setting of a closed system.

Strategic Management

Phacoemulsification is performed in a totally closed system, where the ultrasound tip blocks the incision, allowing the volume of aspirated masses to equal the volume of liquid injected into the anterior chamber, thus maintaining stable intraocular pressure throughout the surgery. The space available for disassembling the cataract is extremely small, limited anteriorly by the corneal endothelium and, posteriorly, by the posterior capsule.

If the zonules sustaining the crystalline lens are weak, broken or nonexistent, in part or totally, or when the posterior capsule is ruptured, a delicate and risky situation may arise unless we are ready to manage it effectively.

MANAGEMENT DEPENDING ON SIZE OF ZONULAR DIALYSIS

When confronted with a zonular rupture, Padilha recommends adopting the following strategies: 1) If during biomicroscopy at the office, under mydriasis and with a slit lamp, a small or moderate zonular dialysis is detected, which does not

extend to more than 45º of the crystalline lens circumference, and we can see an excellent red retinal reflex, it is almost certain that a phacoemulsification can be accomplished safely.

The hydrodissection must separate the lens capsule from the cortex by injecting balanced salt solution (BSS) under the anterior capsule, and the hydrodelamination must attain consistent detachment of the nucleus from the epinucleus (Fig. 203).

The sharp separation of these structures will significantly reduce the tension on the fragile zonules during disassembling of the nucleus and aspiration of the residual cortex.

2. a) If the damage to the zonular fibers extends to more than 45º and the cataract has a hard nucleus with a retinal reflex turning brown, or b) the dialysis extends to 180º, the insertion of an intracapsular tension ring (Fig. 202) will be extremely useful to better support the crystalline bag throughout the surgical procedure, reducing the chances of dislocation of the cataract into the vitreous. This is true even in cases of soft cataract. The use of the intracapsular tension ring is also valid for cases with pseudoexfoliation and ectopia lentis – as in the Marfan syndrome and others.

very extensive damage to the zonular fibers with a dialysis of more than 180º, Padilha considers that phacoemulsification or even a planned extracapsular extraction may not be sufficiently safe, even with the help of the intracapsular tension ring (Fig. 202), espe-

patients, Padilha advocates performing an intracapsular extraction associated with a Kelman anterior chamber implant, or a posterior chamber lens fixated to the sclera (Fig. 156). He considers this to be a more prudent solution.

Special Precautions with Subluxated Cataracts

Padilha points out that some important issues should be considered when subluxated cataracts are approached.

Anterior Capsulotomy

Anterior capsulotomy should be performed as a continuous curvilinear capsulorhexis (CCC). The surgeon needs to use extreme caution starting with a bent needle and completing it with this same instrument or with the Uttrata’s or similar forceps.

If any problem arises at the time of the anterior capsule perforation with the cystotome (bent-needle) the surgeon may begin the capsulorhexis with a pinch-type forceps such as the Kershner capsulorhexis cysto- tome-forceps (Rhein Medical). The maneuvers should be executed very carefully and smoothly so as to prevent further damage to the zonules. The diameter of this capsulotomy should not be very large. Reaching the equatorial region must be avoided at all costs. (Editor’s Note: I also refer you to the discussion of Traumatic Cataracts complicated by some zonular dialysis, in which Paul Koch recommends using scissors to perform the anterior capsulotomy so as to not exhert further pressure on the weakened zonules with the maneuvers of a standard capsulorhexis.)

Characteristics of Viscoelastics Used

Another important issue involves the use of viscoelastic substances. It is important to combine one viscoelastics with cohesive

properties, with another of dispersive properties, which scatters and adheres to instruments or tissues. While the latter will protect the damaged zonular area, by adhering to adjacent tissues of that region and helping prevent an eventual escape of the vitreous, the cohesive viscoelastic will press down upon the anterior face of the crystalline lens, transforming it into a convex surface, and facilitate making the CCC. Such convexity will help channel the zonular tear in the direction of the center of the capsule and not toward the periphery because of the centrifugal force generated above the surface (Fig. 204). (Editor’s Note: A very clear definition of the qualities of the cohesive and the dispersive viscoelastics, and how they differ from one another, is presented at the beginning of this Chapter).

Additional Measures to Reduce Risks

1)Padilha recommends that the phacoemulsification incision, whether in clear cornea or a scleral tunnel, should be placed as far away (circumferentially) as possible from the damaged zonular region. This is to prevent extension of the zonular dialysis by the insertion and withdrawal of instruments in the interior of the eye precisely in the most affected area. If the zonular rupture is located in the superior quadrants a superior temporal incision will make surgery more demanding and risky.

2)To further reduce risks, Padilha advises the use of disposable plastic flexible iris retractors, which will help sustain and stabilize the crystalline bag. The flexible hooks are anchored in the borders of the CCC, in exactly the way we use them in