Micro transscleral pars plana vitrectomy using high-speed, 25-gauge instruments is an effective new way to handle an old challenge: performing phacoemulsification in patients with very shallow anterior chambers.
Dr. Fine, clinical professor of ophthalmology, Casey Eye Institute, Oregon Health and Science University, Portland, shared his insights at the annual meeting of the American Society of Cataract and Refractive Surgery here.
In some cases, anterior chambers are so shallow that the slit-lamp beams are hardly separated, and no room for equipment exists in the angle recesses.
"These instruments operate at 1,200 cuts per minute, so if you don't maintain tactile contact, you can overly soften the eye," Dr. Fine said.
He added that although concern about endophthalmitis following vitrectomy often occurs, he avoids that problem by pre-treating his patients with antibiotics for 3 days prior to their cataract surgery.
"Sometimes, in very small eyes, the chamber remains pretty shallow even after performing a vitrectomy, and the small size of these instruments facilitates the phaco," he said.
Dr. Fine cited a case of a patient in whom a dense cataract had developed in an eye with a very shallow anterior chamber. The cataract was mobilized very easily and quickly, and there was adequate space following the vitrectomy to proceed with the case, although preoperatively "it had looked nearly impossible when we looked through the slit lamp at the peripheral angle," he said.
"I tend to lift the conjunctiva a little as I'm doing the stab incision, so the conjunctiva will slide back over the scleral incision," he said. "Then, in this patient, we freed the synechiae. And this is the only time I will stretch a pupil; all other pupils are potentially at risk for intraoperative floppy iris syndrome.
"In this case, we performed a coaxial phacoemulsification, basically a simple divide-and-conquer technique, which we've done so often."
Another useful device when performing phacoemulsification in eyes with shallow anterior chambers is a pupil expander ring, which is injected into the eye. The ring has facets that surround the pupil and positioning holes within the facets.