This article is more than 5 years old. Information may no longer be current.
Calibrated gauge simulates force of patient manipulation after cataract surgery
Studies show that wound construction plays a significant role in stabilizing the main incision.
Click Here to Manage Email Alerts
Using a calibrated gauge to deliver a controlled amount of force to the ocular surface after clear corneal cataract surgery simulated the effects of patient-induced manipulation of the eye with resultant IOP elevation, according to three studies.
In each study, the Dontrix gauge (GAC International), an aluminum spring gauge used to measure forces in orthodontics, was customized by Ocular Therapeutix.
“The distal and proximal ends of the Dontrix gauge were modified so that the gauge could be applied to the eye for a measured, reproducible force of deformation,” lead investigator Samuel Masket, MD, said.
The studies were reported in the Journal of Cataract & Refractive Surgery.
Samuel Masket
Stability of the incision
With clear corneal cataract surgery, the stability of the incision and how to quantitatively assess that stability are two main concerns, Masket said.
The first study was akin to a proof-of-concept test and consisted of 30 eyes of 30 healthy volunteers.
“We wanted to determine how much force would be approximated on the eye when a patient would forcibly blink, for example,” Masket said. In this study, the gauge was used to ascertain how much force was needed to elevate IOP to the average level that has been reported in the literature when patients squeezed their eyes.
“We found that approximately 1 ounce of external force raised pressure to an average of 43.44 mm Hg,” Masket said. Mean baseline was 17.49 mm Hg.
In the second study, 30 eyes of 29 patients underwent temporal main incisions, and stromal hydration was used to seal the incision. The leak rate was 67% for the main incision using up to 1 ounce of force.
The 21 patients who demonstrated leakage were enrolled in the third study, for which the leak rate was 23.8% when using sutures.
“Four of the five patients who leaked had a single-plane incision, whereas only one leak was from a multi-plane incision,” Masket said.
Postoperative concerns
During the early postoperative period after clear corneal cataract surgery, there is always a concern that the patient could potentially deform the incision and cause it to leak by rubbing or squeezing his or her eye, Masket said.
“Stability of the incision is paramount, and wound architecture definitely plays a role,” he said.
Once an incision leaks, the eye can become hypotonous, and fluid can flow in reverse, from the outside of the eye in. This occurrence has been theorized to cause postoperative infection, according to Masket.
Masket also said there is an approximately 40 times higher chance for infection if the incision is noted to be leaking during the first postoperative day. Therefore, Masket recommended that surgeons evaluate the stability of their incisions with a force gauge.
“If incision stability is demonstrated with the force gauge, then one needs not to be concerned with the need for a suture,” he said. “However, if leakage is demonstrated by deformation of the eye with the force gauge, I recommend that the incision be sutured or, hopefully in the near term, sealed with a tissue adhesive.” – by Bob Kronemyer