Jean-Marie Parel, Ing.ETS-G, Ph.D., FARVO
Lasers and Devices
Corneal Disease, Cataract, Glaucoma, Retinal Disease
Surgical Restoration of Accommodation:
Starting at age 45, the eye starts loosing its ability to focus on near objects and, by age 50, most peoples require reading glasses. The hardening of the crystalline lens with age is thought to be responsible for this loss in reading ability. A surgical technique, named Phaco-Ersatz, was conceived by the OBC team to replace the content of the crystalline lens with a polymeric substitute that has the properties of a infant’s crystalline lens. The technique was shown by the team to restore accommodation, results that were later confirmed by other investigators. Presently, the OBC team studies the dynamic biomechanical and optical properties of young and aged human lenses to design advanced polymers and further improve the technique to correct ametropia when restoring accommodation.
Over 10 million people world-wide are bilaterally blind due to corneal diseases not amenable to transplantation or for lack of donor tissue. The OBC team developed a synthetic cornea, a mesoplant, made to fit onto Descemet’s membrane and replace the corneal stroma. The team studies the biocompatibility of polymers they designed to mimic the natural cornea optical and biomechanical properties as well as laser surgical means designed to improve the visual acuity of prosthesis implanted patients.
Controlled Drug Release Implants:
Biodegradable controlled drug release of antimetabolite 5-FU is an adjunct treatment in glaucoma filtering procedures. A small “c” shaped cylindrical implant was designed to release 5-FU for 3 weeks and biodegrade in 2 months. It is placed under the conjunctival flap at the end of a trabeculectomy or deep sclerectomy procedure. In vitro and in vivo studies were performed at Bascom Palmer Eye Institute and a 300-patient multi-center Phase I clinical study is underway. The results at 6 months proved the safety of the implant. The efficacy study is ongoing. The 5-FU implant was studied by Dr. Scott Cousins and associates as an adjunct to prevent recurrent PVR. The group plans to develop CDRi loaded with other drugs to address the patient compliance challenge in glaucoma medical therapy.
MESH, a new surgical approach to lower IOP:
The MESH is an artificial meshwork made of porous hydrophobic material (polytetrafluoroethylene, ePTFE) and shaped as a glove to regulate aqueous outflow. A custom-made inserter allows its placement across the scleral wall into the anterior chamber angle, shunting aqueous to the subconjunctival space. The procedure takes about one minute. In vitro and in vivo tests were performed at Bascom Palmer and a Phase I clinical study is underway to demonstrate safety and efficacy in glaucoma patients. Recent long-term pre-clinical studies performed at Bascom Palmer Eye Institute have shown ePTFE to produce a minor subclinical inflammatory reaction of 2 to 4 cell thickness in subtenon tissues. Being more inert than ePTFE, polymers treated by laser photochemistry are being studied as potential materials for MESH-like implant fabrication.
Implants for reduction of IOP:
Tubes and valves are currently used to lower the intraocular pressure in patients with failed trabeculectomies and deep-sclerectomies. Made of polypropylene and polydimethylsiloxanes, these implants become encapsulated by a dense fibrous cocoon which stops aqueous outflow within two to three years. A pre-clinical biocompatibility pilot study designed to quantify the thickness and density of the encapsulation identified one high water content hydrogel as the best material, and a novel implant is being developed.
Non-conventional laser wavelengths in glaucoma surgery:
Selective Laser Trabeculoplasty (SLT) is a promising new treatment procedure for open angle glaucoma as it targets melanin-loaded TM cells while avoiding damage to the delicate framework of the trabecular meshwork ™ and thus offers the possibility of retreatment. Selectivity was attributed to the short laser wavelength (532nm) where melanin strongly absorb and the short pulse duration (3ns) which does not allow heat to propagate to the TM collagen structure. However, in a 48patient clinical pilot study done with a Titanium:Sapphire laser, selectivity was also observed even though the wavelength (790nm) is well off the melanin absorption peak and the pulse duration (~200ns) much longer. To elucidate the SLT phenomenon, the group is studying the laser effect in a controlled laboratory situation with SEM and will study these effects on live TM cells present in fresh ex-vivo tissues using a custom-made inverted microscope laser delivery system that will allow to quantify cell expression.
Training of researchers is an integral component of our mission at Bascom Palmer Eye Institute, especially in the Ophthalmic Biophysics Center. Our comprehensive research training program offers mentored training experiences in biomedical engineering, biomedical sciences and clinical research at all levels offering both short and long-term opportunities. Recently, two University of Miami enginerreing students, Noël Ziebarth and Stephanie Delgado were honored with awards for their contributions to the Ophthalmic Biophysics Center.