Franck Villain

Reticulated hyaluronic acid implant in nonperforating trabecular surgery

PURPOSE To evaluate experimentally and clinically the tolerance and efficacy of a reticulated hyaluronic acid implant in nonperforating trabecular surgery (NPTS). SETTING Bascom Palmer Eye Institute, Miami, Florida, USA, and Clinique Sourdille and Clinique Ophtalmologique Universitaire, Nantes, France. METHODS In experimental surgery, NPTS was performed with and without a hyaluronic acid implant in 25 rabbit eyes. In a pilot study, the results of NPTS with a hyaluronic acid implant in 72 human eyes were retrospectively analyzed in terms of visual acuity, intraocular pressure (IOP), external filtration, postoperative inflammation, and gonioscopy. Mean follow-up was 13.8 months (range 6 to 24 months). RESULTS In the experimental surgery, the rabbit eyes with the implant showed a different healing process than the eyes without the implant. The implant was slowly bioabsorbed and remnants were seen at the operative site (where the tissue was removed) up to day 56 postoperatively. This site was detectable at all histology study periods. Intraocular pressure reduction was longer in the implant group: greater than 5 months versus 3 weeks (P < .05). In the pilot study, visual acuity remained stable, IOP decreased from a mean preoperative level of 26.3 mm Hg +/- 5.22 (SD) to a mean postoperative level without treatment of 15.4 +/- 3.1 mm Hg (P < .0001). No external filtration was detected in 60 eyes, a slightly elevated conjunctiva was noted in 12 eyes. Postoperative inflammation (laser flare and cell measurements) was low. Gonioscopy consistently demonstrated the persistence of a decompression space behind the trabeculum. CONCLUSION Comparative experimental surgery results showed excellent tolerance and efficacy in the rabbit eyes with a hyaluronic acid implant. Clinical results, to be confirmed by a randomized comparative study, also showed excellent biocompatibility and encouraging efficacy.

Deep sclerectomy with and without implant: an in-vivo comparative study

Purpose: Establish the effects of pre-Descemetic sclero- keratectomy, a new nonpenetrating Deep-Sclerectomy filtration procedure, with and without crosslinked sodium hyaluronic acid (SKgel) implant in the rabbit animal model. Materials and Methods: Ten adult NZW rabbits had surgery only (group A) and 15 other had surgery and a crosslinked sodium hyaluronate implant inserted under the scleral flap (group B). Weekly intraocular pressure (IOP), outflow facility, and central and peripheral corneal thicknesses were measured in both the operated and the contralateral eye over a period of five months in Group A and six months in Group B. Results: IOP was consistently lower until POD 21 for Group A and POD 161 for Group B, respectively (P less than 0.05). Outflow facility was significantly higher than control eyes until POD 14 in Group A and until POD 84 in Group B. Peripheral corneal thickness returned to normal by POD 14 in Group A and POD 28 in Group B. By POD 35, there was no statistical significance between both groups in the mean of peripheral corneal thickness. Conclusion: Pre-Descemetic Sclero-Keratectomy with crosslinked sodium hyaluronate implant is effective in reducing IOP and safe operation in rabbit eyes.

Measuring ocular characteristics after gel injection adjustable keratoplasty (GIAK) in the rabbit

Gel Injection Adjustable Keratoplasty (GIAK) is a refractive surgery procedure which uses an ocular ring implant made of a polyethylene oxide hydrogel to cause a refractive change in the cornea. Unlike laser photo refractive keratectomy, GIAK does not interfere with the central cornea because the ring lies around the optical axis. Thus, vision can be assessed immediately after surgery. Our in vivo study was designed to quantify GIAKs effects on tissues, the biocompatibility of the polymer and in the process investigate which ocular changes in the rabbit model can be monitored with precision using current technology. Thirty-two young rabbits underwent a delamination in one eye, 22 of which were injected with a new polymeric gel. Corneal topography, keratometry, pachymetry, and tonometry were performed on both eyes for up to 105 days. All corneas flattened with growth. In GIAK animals, we found an average flattening of 6.51 +/- 1.23 diopters (p < 0.0001) relative to the fellow eye. No statistically significant regression over the 102 days was observed. Intraocular pressure dropped slightly by 0.69 +/- 1.21 mmHg (p equals 0.025), a clinically insignificant value, while no significant change was detected in corneal thickness. Keratometry can be tracked in rabbits after GIAK surgery from POD 1. Measuring unoperated fellow eyes allows for the effects of surgery to be assessed without bias from growth. Using this protocol, GIAK was shown to be stable. It was more difficult to draw conclusions from pachymetry, tonometry, and topography data.

Design improvement in keratoprosthesis

One of the major problems of keratoprosthesis (KPro) is postoperative expulsion resulting from inadequate haptic fixation. To overcome this obstacle, a new design was conceived using a retrocorneal fixation. An earlier version of our KPro was made of two pieces: an optical element threaded in a surrounding haptic. Both pieces were made of medical grade PMMA. Although encouraging results were obtained, some anatomic failures occurred (20% at 5 years). To improve fixation and sealing, a biocolonizable skirt was recently added to the keratoprosthesis. This skirt should prevent migration of biocontaminants inside the eye. Made of porous PTFE, the skirt was ultrasonically held inside a one-piece PMMA keratoprosthesis by ultrasonic microwelding. Thus far, implantations carried out in 8 patients show a good tolerance.

Laser sclerectomy and 5-FU controlled-drug-release biodegradable implant for glaucoma therapy

Laser sclerectomy, a simple filtering procedure performed to alleviate high intraocular pressure in glaucoma patients, was taught to offer longer lasting effect and therefore improve the patients outcome when compared with the standard trabeculectomy procedure. Recent clinical trials have shown that this was not the case and pharmacologic wound healing modulation is also required with this new procedure. Five-Fluorouracil (5-FU) is useful as an adjunct treatment for glaucoma filtering surgery. However, efficacy depends upon maintaining sustained drug levels, currently achieved by repeated daily injection of the drug for several weeks. To overcome this limitation, we designed a biodegradable implant for the sustained release of 5-FU. After laser sclerectomy, the implant is inserted through the same 1 mm wide conjunctival snip incision and positioned below the open channel. Implantation takes less than a minute. The implant releases the drug for over 15 days and totally biodegrades in less than 100 days. The combined laser surgery and implantation procedure show great potentials for the treatment of glaucoma.

ArF photorefractive correction of keratoprostheses

Keratoprostheses (KPro) are optical elements replacing a cornea that is opacified and which cannot be replaced by transplantation. This occurs, for example, after severe burn or in trachoma. The KPro that consists of an optical cylinder mounted on a supporting plate (haptics) is implanted approximately in the middle of the cornea. It is intended to restore vision, i.e., should give a sufficient visual acuity and a comfortable field of view. Failures are due to rejection (expulsion) and optical decentration of the prosthesis. Postoperative corrections of the refractive power are possible with spectacles. However, in view of the rapid expansion of corneal reshaping with the ArF excimer laser emitting at 193 nm, a direct correction of the anterior surface of the KPro can be envisaged. For that purpose, various designs are analyzed in terms of image magnification and field of view. The possibility of a postoperative adaptation of the keratoprostheses by photoablation with the ArF is then presented.