Novel vitreous substitutes: the next frontier in vitreoretinal surgery.

PURPOSE OF REVIEW: After removing the native vitreous during vitreoretinal surgery, an adequate substitute is required to ensure homeostasis of the eye. Current clinically used endotamponades (silicone oil, gases, semifluorinated alkanes) are effective in promoting retinal reattachment, but lead to complications such as emulsification, prolonged inflammation, blurred vision, raised intraocular pressure, cataract formation or the need for revision surgery. The aim of this review is to provide an update on novel vitreous substitutes with a focus on polymer-based systems. RECENT FINDINGS: Polymeric hydrogels provide favourable properties such as high water content, optical transparency, suitable refractive indices and densities, adjustable rheological properties, injectability, biocompatibility and their ability to tamponade the retina via viscosity and swelling pressure, comparable to the native human vitreous body. Here, vitreous replacement strategies can be divided into chemically or physically crosslinked hydrogel systems that are applied as preformed or in-situ gelling matrices. SUMMARY: Several hydrogel-based vitreous substitutes have already been positively evaluated in preclinical tests and have the potential to enter the clinical phase soon.

Rate and timing of spontaneous resolution in a vitreomacular traction group: should the role of watchful waiting be re-evaluated as an alternative to ocriplasmin therapy?

INTRODUCTION: The incidence of spontaneous resolution of vitreomacular traction (VMT) is low in studies of Ocriplasmin that have had a limited follow-up. Previous studies did not look for morphological parameters in the natural history using spectral-domain ocular coherence tomography (SD-OCT) imaging. The purpose of this study was to investigate how often and when spontaneous VMT resolution occurs in candidates for Ocriplasmin therapy. METHODS: The study is a retrospective chart review of patients who would have high chances of a benefit by an Ocriplasmin injection, without epiretinal membrane or vitreomacular adhesion of 1500 µm or more on SD-OCT. Main outcome measures were the frequency of complete VMT resolution and the best corrected visual acuity seen in the natural history. RESULTS: Out of the 46 patients that were included after screening 889 SD-OCT images, 20 were found to exhibit spontaneous resolution during the follow-up period (median: 594 days, 95% CI 567 to 719 days), the majority after 6-12 months of observation (95% CI 266 to 617 days). The group with spontaneous VMT resolution and a mean improvement of one line in best corrected visual acuity included a few patients losing vision by macular hole formation. In the absence of resolution, patients lost on average one early treatment diabetic retinopathy study letter per year. Younger age was found to increase the chance of spontaneous resolution. CONCLUSIONS: A shorter follow-up might underestimate the incidence of spontaneous VMT resolution as the functional outcome of watchful waiting. The likelihood of resolution does not seem to decrease after 12 months.

Comparing the effects of two different irrigation solutions on an isolated perfused vertebrate retina.

PURPOSE: To compare the effect of a taurine-containing intraocular irrigation solution (PuriProtect TM) to a standard irrigation solution (BSS TM) we evaluated the retinal function using an electroretinogram (ERG) and analyzed the survival of retinal ganglion cells on isolated whole mount retinas. MATERIALS AND METHODS: During ERG recordings, each irrigation solution was superfused for 45 min with the relevant irrigation solution. To investigate the effects on photoreceptor function, 1 m M asparate was added to obtain a-waves.The recovery of the a- and b-wave was monitored after superfusing the retinas with standard medium again. To evaluate the percentage of dead ganglion cells, retinas were stored for 24 h at 4°C in darkness and after staining the retinas with ethidium homodimer-1 the retinas were analyzed using fluorescence microscopy. RESULTS: The application of standard medium supplemented with 2 m M taurine resulted in a significant increase of the b-wave amplitude compared to standard medium alone. The a-wave amplitudes showed no significant changes under taurine supplementation. Compared to standard medium BSS showed no significant decrease in b-wave amplitudes, but a significant decrease ina-wave amplitudes. In contrast to BSS there were no significant changes in the a- or b-wave amplitudes detectable after the application of PuriProtect. At the end of the washout period no significant changes in a- or b-wave amplitudes were recorded for any tested irrigation solution. Retinas stored for 24 h in PuriProtect or in standard medium with taurine had a statistically significant smaller amount of dead cells than retinas stored in standard medium without taurine supplementation. CONCLUSIONS: BSS does not seem to be an ideal irrigation solution, because it compromises the a-wave in the ERG. In contrast to BSS, PuriProtect showed no significant impact on the ERG and showed a better long-term effect on ganglion cell survival. Taurine supplementation,therefore, seems to be neuroprotective and its supplementation to an intraocular irrigation solution favorable for the retina.

Neuroprotective effects of a taurine-containing irrigation solution for vitrectomy.

BACKGROUND: During pars plana vitrectomy, the retina is exposed to several iatrogenic risk factors, including excitotoxicity. A taurine-containing irrigation solution for pars plana vitrectomy (PURI PROTECT) has been developed and is claimed to have neuroprotective properties. METHODS: Retinal ganglion cells (RGC-5) and retinal whole mounts were incubated in standard irrigation solution (SIS) and SIS supplemented with 3 mM taurine (SIS-taurine). Excitotoxicity was induced by the addition of 8, 10, and 12 mM or 250 µM glutamate. Cell viability and cell survival were assessed by the MTT test and Annexin-V/propidium iodide flow cytometry. Whole mounts were stained with the Live/Dead staining assay. Pars plana vitrectomy with SIS or SIS-taurine was performed in rabbits. Animals were followed-up by electroretinography. RESULTS: RGC-5 incubated in SIS-taurine showed a 4.3-fold (P < 0.0005) better overall cell viability and an up to 8.5-fold (P < 0.05) increased cell survival under excitotoxic conditions compared with that incubated in SIS. Whole mounts incubated in SIS-taurine showed a 1.7-fold (P < 0.0005) and 1.6-fold (P < 0.0005) better cell survival under excitotoxic and nonexcitotoxic conditions, respectively. In the immediate postoperative period, b-wave amplitudes were significantly better in animals operated with SIS-taurine compared with control (P < 0.01). CONCLUSION: A taurine-containing irrigation solution may protect retinal ganglion cells against excitotoxicity.