The Malyugin ring is a safe alternative to traditional pupil-expansion approaches in cataract surgery. Here, best practice for safe surgery and a case study are described
Thorough visualisation of the lens is important for safe and effective cataract surgery. This is best achieved when pupils are adequately dilated throughout the procedure. Although mydriatic eye drops produce the required dilation in most cases, mechanical intervention, namely hooks and additional incisions, is required when these pharmacological agents fail.
The Malyugin ring (MicroSurgical Technology) was developed as a safe alternative to traditional pupil-expansion approaches. It is square in shape and has four circular scrolls with eight points of fixation that ensure an evenly dilated circular pupil is achieved. The latest version is made of 5.0 polypropylene.
A stand-out advantage of the device is that the ring, with its diameter of 6.25 or 7.0 mm, can be inserted through main corneal incisions as small as 2.0 mm – a feature that enables the ring’s use at any time during the surgery and eliminates the need for additional incisions.
However, although the ring offers such advantages and reduces the challenges associated with operating on eyes with small pupils, it has an associated learning curve and must be mastered to avoid difficulties or complications during surgery.
The ring, which has been designed to make minimal contact with the iris during insertion and removal, is introduced into the eye using its own injector. Specifically, it is inserted through the primary corneal incision at the start of the phacoemulsification stage of surgery, although for eyes that experience unexpected intraoperative pupillary constriction, such as in intraoperative floppy iris syndrome (IFIS), the ring can be safely inserted at a later stage.
The injector must be used to move the ring forward and engage its distal scroll with the iris. It is important to then continue inserting the ring while moving the injector in a backward direction towards the primary incision.
Once the lateral scrolls emerge from the injector, they will latch onto the edge of the iris and the proximal scroll will emerge smoothly from the injector. The injector can then be completely removed from the eye in a quick and fluid motion.
I have used the ring for around 3 years and have operated on many eyes with conditions in which it is difficult to maintain pupillary expansion throughout surgery, such as pseudoexfoliation syndrome, traumatic iris and IFIS. While doing so, I have found that although the ring is easy to insert, care must be taken when attaching the proximal scroll as its correct engagement with the iris is important for avoiding complications.
Failure to do so creates a small risk of iris damage if the ring unexpectedly disengages during surgery. Furthermore, an accompanying device called the Malyugin Ring Manipulator (designed specifically to assist placement of the ring) or a Lester hook should be used in conjunction with the injector to ensure correct attachment of the fourth edge – the injector alone will not suffice.
Once correct attachment of the ring has been achieved, the next potential challenge to a surgeon new to the Malyugin ring is removal of the injector from the eye. While the injector usually exits from the eye with no problem, sometimes, resistance may be felt. If this happens, the surgeon simply needs to move the ring to the side a little to overcome the resistance.
Just as care needs to be taken to correctly insert the ring to avoid ocular tissue damage, the iris can be damaged if the ring is not removed with due care. The Malyugin ring is removed from the eye by reversing the process by which it was inserted, with a Lester hook required to lift the disengaged proximal and lateral scrolls from the iris.
The injector can then be inserted through the main corneal incision and hooked onto the proximal scroll. Once the injector and the scroll are firmly attached, the surgeon simply has to push the injector’s button backwards to start retracting the ring into the injector.
Iris damage can occur at this stage if the ring is removed too quickly and without checking that the last scroll is fully disengaged before beginning retraction. To avoid this, a Lester hook must be used to disengage the ring edges at 12 o’clock and 9 o’clock.
Once these are free, the ring can be retracted with complete confidence that the iris edge will not be caught and pulled. As soon as the ring is fully retracted, the injector can be removed from the eye.
This is the case of a 72-year-old male patient with exfoliative glaucoma. Given his history of tamsulosin use, he was identified as being at high risk of IFIS and I knew a Malyugin ring would most likely be required for his surgery.
Indeed, preoperative pupil dilation was poor and a Malyugin ring was used to produce sufficient dilation to proceed with surgery as safely as possible. Insertion and removal of the ring was performed following standard protocol and no iris damage occurred.
The Malyugin ring is an effective pupil-expansion device with minimal risk of intraoperative damage and no need for additional corneal incisions. It exhibits highly predictable behaviour throughout surgery.
Its injector facilitates the non-traumatic introduction and removal of the ring, and its square shape ensures that, once engaged, the pupil remains adequately dilated without being overstretched to a level that causes iris sphincter damage. By maintaining dilation, even in cases of IFIS, the device provides the room needed for a surgeon to complete phacoemulsification and fragment removal.
Despite these advantages, skill, experience and care are still required to use this ring in a manner that ensures iris damage is not caused by incorrect scroll engagement during insertion or disengagement prior to removal of the ring. However, having used this ring for several years without incident, it is clear that the risk of iris damage is minimal if care is always taken and a specific hook is used in conjunction with the injector during insertion and removal.
Dr CÃ©dric Schweitzer, MD, PhD
Dr Schweitzer is an ophthalmologist based at the University Hospital Bordeaux in France.