The silicone ring with a micro-patterned surface may help make this part of cataract surgery more reproducible.
A silicone ring with a micro-patterned surface facilitated creation of a precise continuous curvilinear capsulorrhexis through a small incision in ex vivo eyes, according to a laboratory study.
Such a device may offer an alternative to other capsulorrhexis creation aids such as Nd:YAG and femtosecond lasers, the study authors said.
“[The capsulorrhexis] is really the toughest part of teaching cataract surgery, and creating a perfectly sized and centered capsulorrhexis is hard for even the most seasoned surgeon,” corresponding author Malik Y. Kahook, MD, said in an interview with Ocular Surgery News. “There’s a big need for assistive devices that would make this part of cataract surgery more reproducible.”
The study was published in the Journal of Cataract and Refractive Surgery.
Kahook and co-investigator Matthew A. Powers tested five devices in bovine and human eyes in an ex vivo setting.
Malik Y. Kahook
The designs were a flexible circular blade of nickel-titanium alloy (nitinol), a flexible nitinol guide wire, a flexible elastomeric suction device, a combination approach of a nitinol guide wire and flexible silicone ring, and a free-standing micro-patterned silicone ring.
Each device was used to either cut an opening in the capsule or to serve as a guide for creating a continuous curvilinear capsulorrhexis (CCC) using Utrata forceps.
Kahook and Powers assessed ease of inserting each device through the corneal incision and ability to successfully complete a 5.5-mm CCC.
The first three designs were difficult to insert through a sub-2.4-mm corneal incision and failed to bear enough downward force to cut the capsule and/or prevent radial tears.
The fourth design was successfully inserted through a 2.4-mm incision and exerted adequate downward pressure and contact to guide a manual CCC without radial tears.
“The four iterations that we went through before getting to number five each had their own limitations that would not allow them to translate into real patient care,” Kahook said.
Figure 1. The micro-patterned device rests on top of the anterior capsule, and additional viscoelastic is injected over it to enhance stability.
Figure 2.The resulting capsulorrhexis follows the dimensions of the internal diameter of the device, allowing for a precisely sized and positioned capsulotomy.
Images: Kahook MY
After filling the anterior chamber with viscoelastic, the final device (Figure 1) was inserted through a 2.4-mm incision over the anterior capsule and exhibited excellent stability and resistance to lateral stress, he said.
“The reason for the final iteration working the best is that there was very little, if any, downward pressure from the device itself on the anterior capsule, which would lead to a change in the vectors when performing a manual capsulorrhexis,” Kahook said. “The key to the efficacy of this device was the micro-patterning on the bottom of it, which acts as a built-in breaking system to lateral stress.”
The micro-pattern enhances adhesion to the anterior capsule.
“Once you put it in place and put viscoelastic over the device, the micro-pattern acts as a break, preventing the device from moving outward when performing the capsulorrhexis,” Kahook said. “Once in place, the surgeon is then able to center it on the corneal light reflex so that the capsulorrhexis is perfectly centered where the surgeon wants it to be (Figure 2).”
The surgeon uses the internal edge of the device as a guide, Kahook said.
“Essentially, the surgeon can start a flap and walk it along the edge of the internal diameter of the device, similar to cutting a piece of paper against a flat ruler,” he said.