Novel design for pupil dilation device expands realm of surgical options

Take-home:

A novel device for pupil dilation offers several advantages over current devices, including the ability to be inserted through smaller sizes and lesser numbers of incisions in procedures, noted its inventor.

A novel device for pupil dilation can expand the pupil wiht a single 20-gauge (0.9 mm) incision and no sideports, according to Suven Bhattacharjee, MS, DO, DNB, FRF. (Video courtesy of Suven Bhattacharjee, MS, DO, DNB, FRF)

By Nancy Groves; Reviewed by Suven Bhattacharjee, MS, DO, DNB, FRF

Kolkata, India-A novel device for pupil dilation (Bhattacharjee pupil expansion ring)-which can be inserted and removed through a 0.9-mm incision-is easier and faster to use and is safer than existing devices, according to its inventor.

“I had the impression that the Malyugin ring could be improved upon for our present-day needs because it has a biplanar design,” said Suven Bhattacharjee, MS, DO, DNB, FRF, an ophthalmologist from Kolkata, India. “I started working on a design that would be simpler and could be inserted through a much smaller incision.”

He also wanted a ring that would not snag on the incision.

Both the square and hexagonal designs of this new single-plane device effectively dilate the pupil for phacoemulsification. The hexagonal model, however, is preferred for small eyes and is less likely to cause injury to the cornea, iris, angle, and sphincter, according to Dr. Bhattacharjee.

How the device, design works

The result of several years of work is a single-plane device with alternating notches and flanges on a closed ring made of a single strand of 5-0 nylon, which is stiff-yet-flexible, regains its shape quickly, and is durable enough to withstand a lot of handling during a procedure. While the notches engage the pupil margin, alternate flanges are tucked under it. The pupil margin and the iris bend as they pass through the notches and above and below the flanges. The notch corners straighten as they pass through the incision, so there is no snagging. The ring can be inserted and removed with a 23-gauge forceps when a 20-gauge incision is used or a long blade McPherson’s forceps if a 2.2-mm incision is used.

In a recent study, Dr. Bhattacharjee evaluated both square and hexagonal ring designs, assessing the incision size, insertion, removal, pupil size, capsulorhexis size, stability, ease of instrumentation, pupil shape on removal, and complications of 6.5- and 7-mm square and 6- and 7-mm hexagonal devices. The devices were used in 33 consecutive eyes with non-dilating pupil (less than 5 mm) or larger pupil (up to 6 mm) with a history of intraoperative floppy iris syndrome in the other eye. The square device was used in 17 eyes and the hexagon in 16.

The incision size ranged from 0.9 to 2.2 mm, the average enlarged pupil size was 5.7 mm, and the average capsulorhexis was 4.9 mm. The insertion and removal process was easy after a short learning curve, Dr. Bhattacharjee said, and phacoemulsification probe movement and sideport instrumentation were unhindered.

A round pupil was achieved on removal of all the devices, and no device-related complications were reported. For any given pupil dilation, the appropriate hexagonal device was smaller than the square device. Based on this comparison, Dr. Bhattacharjee concluded that both devices effectively dilated the pupil, although the hexagon would dilate the pupil more.

“The hexagon eventually is going to be the device of choice for the future, but I’m working on both of them and use both of them alternately,” Dr. Bhattacharjee said.

While developing the ring, Dr. Bhattacharjee studied the geometry of pupil expansion devices to come up with the square and hexagonal shapes. He determined that an incircle of 6 mm is required within the regular polygon for a 5-mm capsulorhexis. A square with an incircle of 6 mm lies within an 8.48-mm circumcircle, whereas a hexagon with an incircle of 6 mm lies within a 6.92-mm circumcircle. Therefore, the hexagonal expansion device has a geometric advantage in small eyes.

Exploring future applications

Dr. Bhattacharjee believes the new pupil expansion ring will be useful in several procedures, including 2.2-mm standard coaxial phacoemulsification, 1.4-mm bimanual microincisional cataract surgery, and sub-2-mm coaxial microincisional cataract surgery.

The device is expected to be especially valuable in femtosecond laser-assisted small pupil phacoemulsification, in which the ring can expand the pupil with a single 0.9-mm sideport incision and a Kuglen hook, he noted. In contrast, the Malyugin ring requires a 2.2- to 2.75-mm manual keratome incision and two 1.2-mm sideports.

“Femtosecond laser-generated corneal incisions are truly triplanar and better than manual keratome incisions,” Dr. Bhattacharjee said. “This advantage is retained if the pupil can be dilated with a single 0.9-mm sideport incision.”

Inserting the ring through a smaller incision would also reduce the risk of infection and inflammation as well as the risk of anterior chamber shallowing during imaging and laser treatment, Dr. Bhattacharjee said.

Further, the new dilating device reduces the severity and complications of intraoperative floppy iris syndrome since its anterior flanges dampen the billowing of the iris.

Suven Bhattacharjee, MS, DO, DNB, FRF

P: +91 9830060348 or +91 33 24651391

E: suvenb@gmail.com

Dr. Bhattacharjee has a pending PCT patent application for his pupil expanding devices, which are not yet commercially available. He has been talking with prospective industry partners about the manufacture and marketing of the rings and expects a product to be globally available later this year.