Adjuncts for challenging cases

Published on 08/03/2015 by admin

Filed under Opthalmology

Last modified 08/03/2015

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CHAPTER 16 Adjuncts for challenging cases

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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.

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