Overcoming the small-pupil FLACS challenge with the Malyugin ring

Femtosecond laser-assisted cataract surgery (FLACS) entered the ophthalmic field around 8 years ago, and in doing so, it helped advance the safety and predictability of cataract surgery. However, every physician knows that while new technologies help address existing problems, they can also create new challenges.

In the case of FLACS, operating on eyes with a small pupil size is that challenge. Indeed, the procedure is contraindicated in eyes with pupil diameters smaller than 5 mm in order to minimise the risk of hitting the pupillary edge during capsulotomy or creating an insufficiently sized capsulorhexis.^1,2

A further challenge posed during FLACS is the occurrence of intraoperative miosis secondary to prostaglandin release into the aqueous humour. As such, even eyes with adequate preoperative pupil sizes carry the risk of becoming problematic during surgery.

Fortunately, cataract surgeons have a variety of options for expanding small pupils, including iris retractor hooks and intracameral injection of adrenergic receptor agonists. However, in some patients, these conventional expansion strategies are ineffective, unpredictable or unsafe. And when miosis occurs intraoperatively-a phenomenon that literature shows can occur in up to 30% of eyes undergoing FLACS-options become even more limited.^3-5

The solution to the small-pupil problem

I developed the Malyugin ring (Micro Surgical Technology) as a solution for such difficult eyes. It is estimated that 5% of patients presenting for FLACS have small pupils-defined as ones with diameters smaller than 5.5 mm-and require a pupil expansion device intraoperatively.³

The square-shaped ring is an ideal pupil expansion tool in these situations. The device, which is available in diameters of 6.25 and 7.0 mm, consists of four circular scrolls that provide eight points of fixation to facilitate uniform pupil dilation. 

A standout benefit of the device is the gentle, evenly dispersed contact made with the iris, thus minimising the likelihood of iris sphincter damage, as seen with other expansion rings. Furthermore, as it is introduced into the eye via an injector that is inserted into the primary corneal incision, it ensures there is no need to create additional incisions, as is neccessary with iris hooks.

The new-generation ring

While the initial model of the ring was composed of 4.0 polypropylene, the second generation of the version is made with 5.0 polypropylene, making it even more flexible, and easier to insert and remove from the eye. In fact, it is this ease of insertion and removal through small corneal incisions that allows surgeons to routinely perform FLACS through 2-mm corneal incisions – incisions small enough to remain watertight during the docking and laser phase of the procedure.

Just before inserting the second-generation ring, I like to inject a small amount of ophthalmic viscosurgical device (OVD) under the iris in the meridian perpendicular to the main incision. This helps to ease engagement of the lateral ring scrolls with the iris.

I regularly use the ring with appropriate patients and find that once I have made the 2-mm incision with the blade, injected the viscoelastic and implanted the ring, I can place my patient under the femtosecond laser, create the capsulorhexis, remove the cataract and implant the IOL – all through the same 2-mm incision. I prefer doing FLACS with the ring in place after I have completely filled the anterior chamber with dispersive OVD (Viscoat, Alcon).

Doing so perfectly maintains the chamber and protects the corneal endothelium during aspiration of lens fragments. Of course, the surgeon has to be sure that there are no air bubbles trapped in the OVD, as such bubbles may divert the laser beam and lead to an incomplete capsulotomy.

In some circumstances, the corneal tunnel may be too short, and when this happens, there is a chance that the wound may not self-seal as expected. In these situations, I place a single 10-0 nylon suture before docking to maintain the anterior chamber. However, I find that I need to use this additional step in no more than one in 15 cases.

When the procedure is completed and the IOL has been placed securely in the capsular bag, the ring is simply removed by disengaging the distal scroll first, followed by the proximal scroll. There is usually no need to adjust the lateral scrolls because they automatically disengage on retracting the ring.

The device in clinical practice

I have used the new-generation ring in over 60 FLACS patients over the past 2 years. Below are a few interesting cases I have come across.

Case Study 1

This 67-year-old male presented to me with a history of pseudoexfoliation syndrome. He was taking tamsulosin and had a pupil size of 5 mm. Given the four-fold higher risk of intraoperative floppy iris syndrome (IFIS) in eyes with pupils smaller than 7 mm compared with pupils of 8 mm or more, the Malyugin ring was chosen as the device most likely to minimise the risk of adverse intraoperative events in this patient.

A 2-mm corneal incision was created and the viscoelastic injected. I then injected the ring, engaging the distal scroll first, and then the lateral scrolls and proximal scroll. I repositioned the ring to centre it and then placed the patient under the laser.

I was able to create a capsulorhexis of 4.7 mm because the ring provided enough space and allowed me to maintain the distance between the edge of the iris and the capsulorhexis (therefore avoiding damaging the iris with the laser).

Case study 2

A 46-year-old female attended my clinic with a history of corneal transplant to treat keratoconus. She had a very small pupil – no more than 2.0 mm, cataracts, 12 D of against-the-rule corneal astigmatism and she needed a custom-made IOL to be implanted.

On assessment in the operating room at the beginning of the surgical step of the procedure, her small pupils responded slightly to intracameral phenylephrine and OVD. However, the level of enlargement achieved was not enough to safely proceed with the surgery.

It is in situations like this that the Malyugin ring is invaluable. Insertion of the ring achieved sufficient pupil expansion, allowing suitable exposure of the capsulotomy for thorough assessment of its adequacy. In my opinion, a good capsulotomy is one that is free of tags and adhesions within the capsule and capsulotomy flaps.

On confirming that the capsulotomy was indeed suitable, I was able to proceed with removal of the opaque lens and replaced it with the custom-made toric IOL.  

Adequate pupil expansion is critical for toric IOL alignment. After the IOL is oriented along the strong corneal meridian, OVD is removed from the capsular bag-especially from behind the IOL-to ensure that the lens will not rotate postoperatively.

However, OVD must not be removed from the anterior chamber at this time because its presence is required for safe removal of the ring. Once the ring has been withdrawn from the eye, residual OVD can then be aspirated and the wound’s water tightness checked.  

Case study 3

In this case involving a 79-year-old male with a pupil size of 5.5 mm, the pupil remained stable and of normal size during femtosecond laser application and the initial steps of phacoemulsification, allowing me to aspirate the cortical material. But on starting to open the cleavage planes created with the laser, the pupil began to collapse and constrict – a classic sign of IFIS.

I initially chose to proceed by injecting viscoelastic through the paracentesis in order to expand the pupil a little, but I was met with constant pupillary constriction – most probably due to the combined effect of IFIS and the laser encouraging prostaglandin release into the channel. Given the unrelenting constriction, I chose to change tactics and use the Malyugin ring, knowing it would be a safer and more predictable option than trying to irrigate and aspirate at least some of the cortical material.

On injecting the ring, the pupil stabilised and expanded, allowing safe completion of the procedure. I could then dry aspirate the cortical material, insert the IOL into the capsular bag and remove the ring.

Conclusion

As these case studies demonstrate, the second-generation Malyugin ring is a versatile pupil expansion ring with high efficacy in FLACS. Having used it on a variety of classically difficult eyes and in complicated surgical cases, it remains the device I can safely turn to, in order to ensure predicable and effective pupil expansion when other techniques fail.

Studies involving the ring, such as an 850-patient trial conducted by Conrad-Hengerer et al, support my own personal observations. The German study found that cases with 5.5-mm pupils or smaller required a ring 68% of the time.

In short, the device is poised to help bring about a paradigm shift in FLACS, allowing the procedure to become suitable and safe even in those with notoriously difficult eyes.

References

1.     Donaldson KE, et al. Femtosecond laser-assisted cataract surgery. J Cataract Refract Surg, 2013;39,1753–1763.

2.     Nagy Z. New technology update: femtosecond laser in cataract surgery. Clin Ophthalmol. 2014;8:1157–1167.

3.     Conrad-Hengerer I, Hengerer FH, Schultz T, Dick HB. Femtosecond laser-assisted cataract surgery in eyes with a small pupil.  J Cataract Refract Surg. 2013;39:1314-20.

4.     Jirasková N, Rozsíval P and Lešták L. Use of Malyugin pupil expansion ring in femtosecond laser-assisted cataract surgery. J Clin Exp Ophthalmol. 2013;4:6.

5.     Hatch KM, Talamo JH. Laser-assisted cataract surgery: Barriers of the femtosecond laser. Curr Opin Ophthalmol. 2014;25:54-61.

Professor Boris Malyugin, MD

E: boris.malyugin@gmail.com

Prof. Boris Malyugin is the deputy director general (R&D, Edu) of the S. Fyodorov Eye Microsurgery Institution (Moscow, Russia). Prof. Malyugin is president of the Russian Ophthalmology Society (ROS), ESCRS Board member, as well as the member of International Intraocular Implant Club and Academia Ophthalmologica Internationalis, AAO and ASCRS. He has financial interest in the products mentioned.