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CATARACT & REFRACTIVE
SMALL PUPILS Everything you ever wanted to know about small pupil phacoemulsification – Part 2. Dr Soosan Jacob reports
M
y last column (EuroTimes December 2016/January 2017, Vol 21 Issue 12/ Vol 22 Issue 1, Page 8-9) dealt with preoperative and intraoperative considerations for small pupil phacoemulsification. This column deals with the various pupil expander devices available for aiding surgery.
IRIS STRETCHING DEVICE: The Beehler Pupil Dilator™ (Moria, USA) is a tri-pronged device that utilises three retractable micro-fingers together with an external micro-hook to stretch the iris. Once stretched, the instrument is removed and phacoemulsification continued. Cycloplegics must be given preoperatively. An irrigating model with two flexible U-shaped retractors, together with an external micro-hook, is also available that provides three-point stretch.
IRIS HOOKS: Prolene iris hooks were introduced by de Juan and metal hooks by Mackool. Prolene hooks are the most commonly used, are disposable, and the degree of dilatation depends on the amount that the silicone tyre is slid down over the hook. Iris hooks should be introduced through
Iris hooks
EUROTIMES | FEBRUARY 2017
small, short, peripheral paracenteses parallel to the iris plane in order to expand the pupil sideward towards the limbus. Creating paracenteses that are more clear corneal and angled downwards tents the iris upwards towards the cornea, causes obstruction to the passage of instruments, produces iris chafing, thermal damage and also shallows the anterior chamber. The most commonly used configuration is that of four hooks applied in a square or diamond (Oetting et al) configuration, the latter having advantages of better visualisation and manoeuvre-ability of the phaco probe. Iris hooks may cause damage to the pupillary margin, especially in rigid pupils and also if the iris has been stretched excessively. Dilatation should therefore be done only to the degree required to uneventfully perform phacoemulsification, generally 5mm. The Assia Pupil Expander (APX Ophthalmology Ltd, Israel) utilises two tiny, spring-loaded devices inserted 180 degrees from each other, perpendicular to the phaco incision. Each device is like a miniature blunt scissor, the arms of which open out to hold the iris expanded.
EXPANDING RINGS: There are many ring designs available. These have advantages of being able to be inserted through the phaco incision and not requiring
Malyugin Ring
additional paracentesis incisions. These mechanically dilate the pupil and have advantages of creating the least amount of sphincter damage, providing vertical stability to iris tissue, preventing undue movement, iris billowing or iris prolapse during surgery. They are very useful in intraoperative floppy iris syndrome (IFIS). Malyugin Ring® (MicroSurgical Technology, USA): The Malyugin Ring, which has proven very popular, was designed by Boris Malyugin. It has a square design with loops at all four corners which engage the iris margin. It has the advantage of retaining a round pupillary shape when the device is in situ by giving eight points of fixation. It is available in two sizes – 6.25mm and 7mm and is also now available in a newer model that allows insertion through less than 2.2mm incisions. A special injector allows safe implantation and explantation. Care should however be taken while explanting that the edges of the loop go inside the injector before withdrawing the ring. I-Ring® Pupil Expander (Beaver Visitec, USA): This is a single-use pupil expander made of polyurethane. It gives uniform pupillary expansion of about 6.3mm. It has hinges that enhance flexibility and fold-ability, channels that safely hold the pupillary margin, four corners that hold the iris stroma in place and positioning holes for safe positioning with the Sinskey Hook. There is an inserter for easy implantation and explantation. B-HEX Ring™ (Med Invent Devices, India): Created by Suven Bhattacharjee, this has a uniplanar design that engages the pupil in the same plane as the device. It is waferthin (0.075mm) and comes in a preloaded carrier which presents the device sterile at the incision. Simple manoeuvers with a Sinskey Hook are used to glide the device through the incision (0.9–2.8mm) and tuck alternate flanges under the pupil margin. The eyelets