Making a Case: Iris Hooks vs. Malyugin Ring
Non- and poorly-dilating pupils can pose a challenge during and after cataract surgery. In milder cases, a careful surgical approach and application of intracameral phenylephrine might suffice. However, moderate and severe cases require a pupil expander.
In this part of the Complex Cases, Simplified series, Paul Ursell, MBBS, MD, FRCOphth, explains his view of the management of small pupils, comparing iris hooks with pupil expansion rings (Malyugin Ring). He also touches on the thought process behind adopting new surgical techniques. You can also check out some of the practical tips Mr. Ursell shared in one of our webinars (watch Mr. Ursell’s presentation on the link below from 0:15:00).
Managing Small Pupils
There are two main approaches for small pupils in cataract surgery: iris hooks and expander rings, such as the Malyugin Ring.
Iris hooks have been around for many years; most of today’s senior surgeons learned with them. We usually use 4 or 5 flexible nylon hooks per surgery, inserting each one through a separate incision. The secret is to place them as peripherally as possible about 1mm distal to the limbus, so you are parallel to the iris plane. One advantage of hooks is that you can choose where to place them, which is very useful if the patient has an asymmetric or a post-traumatic pupil, for example.
An alternative to hooks is the Malyugin Ring, designed in 2007 by Professor Boris Malyugin. In my experience, the procedure goes significantly faster when using the Malyugin Ring. You are also causing less sphincter trauma, probably because the contact area is larger with the Malyugin Ring and the material has a broader profile compared to iris hooks. Another great advantage of the ring is that there is no need for extra incisions which may lead to more post-operative inflammation and possibly an infection risk.
Iris Hooks vs. Expansion Ring
Recently, we published a paper in which we compared iris hooks with a pupil expansion ring, examining operating times, complications, and visual acuity outcomes [1]. Our sample included 9552 patients who had primary phacoemulsification cataract surgery, of which 425 (4.4%) had a small pupil and required a pupil expander. In almost three-quarters of the cases (N=314) the surgeon used a Malyugin Ring, while the hooks were used 95 times.
When we examined the characteristics of patients who required pupil expanders of any type, we found that on average, they were older, and the majority were male (55%). Moreover, they had a shallower anterior chamber (AC) and shorter axial length compared to patients who did not need a pupil expander.
When we compared the operating times, we detected significant differences between the three groups (no expander/hooks/Mayugin Ring). When there was no need for expanders, the average operating time was 16 minutes. If a Malyugin Ring was used, the time increased by four minutes.
However, when iris hooks were used, the operating time went up to 30 minutes, adding an extra 14 minutes to the surgery. In a busy clinical environment, time is a luxury; therefore, operating lists can quickly overrun when using iris hooks. Also, posterior capsular (PC) ruptures were more common with hooks (but not significantly) and took longer to manage when they occurred. However, following the surgery, the visual acuity gains (BCVA) were similar between iris hooks and the Malyugin Ring.
Tips for Using the Malyugin Ring
I have been using the Malyugin Rings for about eight years now. In the webinar, I described some of my practical tricks; for instance, how to insert the Malyugin Ring using a second instrument, and how to remove it using either a standard technique or a technique that avoids putting the instruments into the periphery to take the scrolls off. With the shallower AC, I prefer to keep the surgical manoeuvres in the deeper parts of the chamber. I use a rotational movement that enables the removal of the ring without going into the periphery too much and also protects the endothelium.
I find that the newer version, the Malyugin Ring 2.0, is easier to take off the iris compared to version 1.0. The scrolls are wider, which makes it easier to engage and disengage without causing iris trauma. The instrument is made of thinner polypropylene and comes in two sizes, 7mm and 6.25mm. We usually use the 7mm as we want a bigger pupil. Both Malyugin Ring 1.0 and 2.0 can be used by trainees as well.
How to Transition from Hooks to Rings?
It can sometimes be challenging to venture out of your comfort zone and adopt a new surgical technique for a procedure you are already comfortable with. I suggest the following protocol for evaluating new techniques or instruments:
1. Review academic/clinical data: Is there evidence to support the change
2. Acknowledge that you will have a learning curve with every new technique: To get over the learning curve, commit to do at least 10 cases in a new way. Then decide if the technique works for you.
3. Re-evaluate your premise: Merge your theoretical and practical experiences to make the final decision about adopting the new technique.
Conclusion
Malyugin Rings are quicker than hooks and can be successfully used by both consultants and trainees for the management of small pupils and IFIS during cataract surgery. Their use results in fewer PC ruptures that are quicker to manage.
Most surgeons have a preferred technique that works for them, so it is not always easy to transition to a new instrument. To improve and progress, it can be useful to systematically evaluate new trends and adopt them if deemed clinically superior.
Key learnings
- When planning cataract surgeries, keep in mind that about 4.5% of the cases will require a pupil expander.
- It takes significantly longer to perform cataract surgery using iris hooks compared to using the Malyugin Ring (30 min vs. 20 min).
- The Malyugin Ring 2.0 has certain advantages over the Malyugin Ring Classic, such as wider scroll gaps, higher material flexibility, and smaller incision size.
- Carefully evaluate new techniques and instruments and allow some time to get over the learning curve.
[1] Nderitu P, Ursell P. Iris hooks versus a pupil expansion ring: Operating times, complications, and visual acuity outcomes in small pupil cases [published correction appears in J Cataract Refract Surg. 2019 Feb;45(2):257]. J Cataract Refract Surg. 2019;45(2):167–173. doi:10.1016/j.jcrs.2018.08.038
