Purpose of chapter

Contemporary phacoemulsification techniques usually provide excellent outcomes. However certain situations present a challenge to the cataract surgeon, which may compromise the outcome due to poor visualization or tissue stabilization problems leading to disruption of normal anatomical relationships. These include poor capsule visualization, small pupils, and loss of capsular or zonular support. An array of adjunctive devices is available to facilitate the achievement of surgical goals in these complex situations. This chapter reviews the devices which are used to manage these situations including capsular dyes, pupil expansion devices, tools and implants for capsular bag stabilization, and implantation of posterior chamber IOLs when capsular support is inadequate.

Epidemiologic consideration and terminology

Large multi-surgeon series report intraoperative complications rates in the order of 2% with up to 5% of eyes with no prior co-pathology (and 9% of all eyes) not achieving vision better than 20/401. Many of these are ascribable to the situations described above.

Clinical features, diagnosis and differential diagnosis

The creation of a continuous curvilinear capsulorrhexis (CCC) is critical for safe phacoemulsification and secure IOL implantation in the capsular bag. Poor visualization due to a poor red reflex, as in mature or white cataracts, opaque lens material, dense nuclear or subcapsular opacification, vitreous opacities, or corneal pathology, can make the CCC difficult to achieve. The use of a capsular stain can greatly enhance the safety of this procedure by enhancing visualization and increasing contrast.

Adjunctive devices are useful in the setting of small pupils not responding to mydriatics, iris prolapse, or intraoperative floppy iris syndrome (IFIS)2 to maintain pupil dilatation whilst stabilizing iris tissue allowing safe phacoemulsification to be completed. Usually risk factors will be apparent in the preoperative assessment, including a history of uveitis, posterior synechiae, use of alpha antagonist drugs such as tamsulosin and a history of trauma or previous intraocular surgery, but the pupil can sometimes miose intraoperatively without any predisposing conditions. It is therefore imperative for all cataract surgeons to be conversant with strategies to deal with small pupils and IFIS.

Zonular support may be deficient in conditions like PXF, or the lens may be frankly subluxed due to trauma or in conditions like Marfan syndrome. Preoperative examination will often show phacodonesis in such situations, forewarning the surgeon, but zonular loss can also be sustained during surgery or become apparent in a lens which seemed stable preoperatively.

Fundamental principles

Numerous dyes have been used for the purpose of capsular staining, including indocyanine green (ICG), fluorescein, crystal violet, gentian violet, and brilliant blue G. Trypan blue marketed as Vision Blue (DORC International, Zuidland, The Netherlands) is by far the most popular in contemporary practice and is FDA (US Food and Drug Administration) approved. The Ophthalmic Technology Assessment Committee Anterior Segment Panel of the American Academy of Ophthalmology published their recommendations on capsular staining for cataract surgery in 2006 finding considerable data on the safety of trypan blue in the anterior chamber3. This dye has a well-established safety record; none the less occasional concerns have been raised about its safety, with some apoptotic cell death having been reported4. It is therefore important to use dyes only when needed and in the smallest amount which achieves the surgical outcome.

A vast array of tools for pupil expansion and stabilization are available, and the choice of device used is often based on personal preference and familiarity. Mechanical stretching using a pair of hooks (e.g. Kuglen; Katena Products), or specialized instruments like the Beehler pupil dilator (Ambler Surgical Corp, Exton, PA, USA) often results in adequate dilatation, but does not prevent progressive miosis or increased iris prolapse related to IFIS. In these situations mechanical devices are preferred to maintain intraoperative dilatation and stabilization of the pupil.

Flexible iris hook-retractors5 are versatile; aside from their use in small pupil, iris prolapse, and IFIS, they are also useful in the setting of iridoschisis and as a capsular support in cases of zonular loss or subluxed lenses.

A range of ring expanders are available including The Perfect Pupil Device (Milvella, Sydney, Australia), which is a flexible ring with a flanged groove and scalloped tabs to hold a billowing floppy iris through 315° leaving an open area of 45° to accommodate the passage of instruments. The Morcher pupil-dilator ring (Morcher, Stuttgart, Germany) is a fixed 7.5 mm polymethyl methacrylate (PMMA) ring. It is a rigid device which can be difficult to insert and remove. The Graether pupil-expander system (Eagle Vision, Memphis, TN, USA) is another option. This is an incomplete soft silicone ring, with a grooved outer surface to engage the iris which is preloaded in a disposable insertion tool. More recently, the Malyugin ring (MicroSurgical Technology, Redmond, Washington) has gained popularity and is now the device of choice for most surgeons6. This rectangular device, made of 5-0 polypropylene, uses the scroll principle to catch the pupillary margin. It is available in two sizes, 6.25 mm and 7 mm. The main advantages of this device include gentle and less traumatic fixation of the iris margin and controlled stretching of the pupil. The single use package includes a holder and inserter with the ring. The inserter is used to withdraw the ring from the holder. It also introduces the ring into the anterior chamber and removes the ring from the eye.

Capsule tension rings (CTR) are invaluable in situations where zonular support is deficient. CTRs are available from various manufacturers including Morcher (Morcher, Stuttgart, Germany) and Ophtec (Groningen, The Netherlands). They can be inserted manually or through an injector. CTRs are available preloaded in an injector (e.g. AMO (Santa Ana, CA, USA)). The CTR stabilizes the zonular apparatus through centrifugal force, which expands and centrates the capsular apparatus, supporting the weak zonules by recruiting tension from existing stronger zonules. The diameter of the CTR slightly exceeds that of the capsular bag allowing the ends to overlap. The standard CTR was modified by Cionni to allow for capsular support in the setting of extensive or progressive instability. This modification, the M-CTR, is manufactured by Morcher. Both the standard CTR and the M-CTR should be used only in the setting of an intact anterior capsulorrhexis and posterior capsule. The modification consists of one or two fixation eyelets mounted on the open ring, which lie in a plane just above the anterior capsule. The eyelets allow for suture fixation of the capsular bag to the eye wall.

A 10-0 Prolene suture on CIF-4 (Ethicon, USA) needles is the preferred suture for most surgeons. The suture should be placed under a scleral flap or within a scleral pocket7. The M-CTR can increase zonular damage when it is being implanted as the ring has to be dialled into a position where the fixation islet is in the area of maximal zonular loss. Ahmed introduced the capsular tension segment (CTS)8, which is a smaller device; this can be positioned directly into the area of zonular loss, which reduces the potential to cause further damage to the zonular apparatus during implantation. The CTS is very versatile and can be used in combination with a standard CTR to achieve the same result as an M-CTR, but with less traumatic surgery (Fig. 16.1 a,b).

Fig. 16.1 (A) Subluxed lens due to Marfan syndrome. Two ‘iris’ retractors are supporting the capsulorrhexis edge. A capsule tension ring is being inserted. (B) Same eye as in part (A). Iris retractors engaging the capsulorrhexis and a standard capsule tension ring is stabilizing the capsule. A capsule tension segment is being positioned in the area of maximal zonular weakness. A 10-0 Prolene suture has been preplaced through the central eyelet, to allow scleral fixation.

Goals of surgery

The secure placement of an intraocular lens within the capsular bag is the goal of cataract surgery. Techniques should minimize tissue damage even when complex situations are managed.

Indications for surgery

Indications to use capsular stains include a poor red reflex as in a mature or white cataract, or other cause of media opacity such as a dense posterior capsular cataract or a vitreous hemorrhage. A less well-publicized reason is to use it when corneal opacities preclude a good view of the capsule or for surgeons practicing a technique new to their armamentarium (e.g. chopping), when enhanced visualization of the capsule is desirable.

Iris stretching is required to get adequate mydriasis when operating on an eye with a small pupil unresponsive to mydriatics, and mechanical fixation may be needed to combat progressive miosis or a tendency to iris prolapse.

Scleral fixation of a posterior chamber lens is indicated when capsular support is deficient, especially if co-pathology such as uveitis or glaucoma precludes the use of an angle supported or iris fixated anterior chamber lens.

Preoperative assessment

Preoperative assessment including a detailed history allows the surgeon to anticipate problems in most situations. A history of trauma including previous intraocular surgery should point to the potential need for adjunctive devices. History of drug use including warfarin and alpha agonists (e.g. tamsulosin) should be noted. PXF syndrome, high myopia, and mature cataracts are other findings which can signify the need for adjunctive devices and techniques to be deployed.

Anesthesia

The vast majority of cataracts, even when challenging, can be dealt with under topical anesthesia, supplemented with intracameral anaesthetic if iris manipulation is required. However if lengthy surgery is anticipated a regional block or general anesthesia should be considered. General anesthesia is also required when dealing with pediatric cataracts. The anaesthetist should be aware of systemic conditions such as Marfan syndrome which have cardiovascular associations.

Operation techniques

Trypan blue has traditionally been applied in the anterior chamber after it has been filled with air, to allow it to stain the capsule whilst minimizing contact with other tissue. The air bubble limits contact of dye with the central corneal endothelium, but the meniscus encourages contact with the iris and the peripheral corneal endothelium. A more elegant technique is to fill the anterior chamber with an ophthalmic visco-elastic device (OVD) and then apply a very small aliquot of dye under OVD directly onto the capsule. This can then be spread by the applying cannula, akin to painting the anterior capsule9. This minimizes the contact of dye with other structures and is more time-efficient. A ‘top-up’ with OVD following this maneuver pushes excess dye into the periphery and allows the CCC to be initiated and completed in a controlled manner (Fig. 16.2). Trypan blue can also be deployed after the CCC has been initiated if visibility deteriorates or the edge of the CCC cannot be visualized. This is best done directly under OVD by applying a drop of dye in the area of the tear to aid visualization and retrieval of the developing CCC edge, a strategy which is very beneficial when combined with techniques to retrieve a CCC which is tearing out.

Fig. 16.2 Trypan blue is used to stain the anterior capsule to allow visualization of the tearing edge of the capsule.

Use of flexible iris hook-retractors needs attention to technique to avoid complications such as a wide, raised iris platform between hooks, iris prolapse, or iridodialysis. Tears of either the anterior capsule or Descemet’s membrane and irregular postoperative pupil function can also ensue. The paracentesis used should be parallel to the iris plane to avoid drawing the iris forward when the hooks are engaged. OVD is used to deepen the sulcus plane and create space between the capsule and iris to avoid damaging the capsule. Overstretching of the pupil should be avoided and hooks should be placed symmetrically (Fig. 16.3). Placing the hooks in a diamond configuration with one of the hooks placed in a subincisional location allows for good surgical access.

Fig. 16.3 Four flexible iris retractors are placed in a diamond configuration in a patient with a small pupil and anterior capsular phimosis.

The Malyugin ring can be deployed at any stage of the procedure, either before capsulorrhexis has been done, or at a later stage if progressive miosis or IFIS is encountered. The ring is loaded into the inserter. Then, it is inserted through a 2.2 mm or larger incision. Surgeons using microincision surgery should use a separate 2.2 mm clear corneal incision as the injector will not pass through an incision smaller than 2.2 mm. The tip of the inserter is positioned at the center of the anterior chamber. As the ring is injected, it is released from the tip until the distal scroll is engaged with the distal iris. Both lateral scrolls then emerge from the tube of the inserter and simultaneously catch the iris margins. The proximal scroll is expelled from the inserter lying on top of the iris. The inserter is withdrawn from the eye, and a hook is used to push the proximal scroll into the pupillary space and engage the iris margin. Once the phacoemulsification and IOL implantation are done, the ring is then removed from the eye in the reverse order. The Malyugin ring is a flexible device which is easy to insert without the need for multiple incisions; it is particularly useful in patients in whom cutting or tearing of the iris tissue needs to be avoided, e.g. in the presence of rubeosis, chronic anterior uveitis, or systemic coagulopathy. The device provides a controlled stretching of the pupil and engages a wider area of the pupillary margin than iris hooks and is therefore less prone to tearing the sphincter. The iris rim is safely fixed in the ring’s loops, eliminating the risk of iris aspiration during phacoemulsification (Fig. 16.4).

Fig. 16.4 The Malyugin ring is in place with the four scrolls engaging the iris margin providing good mydriasis.

Scleral fixation of a posterior chamber lens is an elegant technique to manage aphakia or to secure a posterior chamber lens when capsular support is inadequate. Rigid PMMA IOLs with eyelets incorporated in the haptics are available to allow secure suturing to the sclera. Foldable lenses can also be sutured to the ciliary sulcus. Late suture breakage leading to IOL decentration or frank luxation remains a concern in the long term. The use of scleral pockets without conjunctival dissection reduces the risk of late suture exposure compared with the use of scleral flaps7. Recently techniques of sutureless scleral fixation using scleral tunnels into which haptics are buried have gained popularity and potentially eliminate the potential for suture related complications10.

Postoperative care

Careful monitoring and management of postoperative inflammation and intraocular pressure are required in these eyes due to the increased amount of tissue handling compared with standard uncomplicated phacoemulsification. If vitreous has been disturbed with or without a posterior capsular rent, a dilated peripheral retinal examination is mandatory prior to discharging the patient. The patient should be given a full explanation of all implanted devices, to avoid confusion arising if they are seen elsewhere at a later date.

Assessment of surgery

Good outcomes are possible even in very challenging situations with the use of appropriate adjuncts. All cataract surgeons should be conversant with the use of trypan blue, iris hook retractors, the Malyugin ring, and capsule tension rings.