A Tenon's capsule/bulbar conjunctiva interface biomimetic to model fibrosis and local drug delivery.

Glaucoma filtration surgery is one of the most effective methods for lowering intraocular pressure in glaucoma. The surgery efficiently reduces intra-ocular pressure but the most common cause of failure is scarring at the incision site. This occurs in the conjunctiva/Tenon's capsule layer overlying the scleral coat of the eye. Currently used antimetabolite treatments to prevent post-surgical scarring are non-selective and are associated with potentially blinding side effects. Developing new treatments to target scarring requires both a better understanding of wound healing and scarring in the conjunctiva, and new means of delivering anti-scarring drugs locally and sustainably. By combining plastic compression of collagen gels with a soft collagen-based layer, we have developed a physiologically relevant model of the sub-epithelial bulbar conjunctiva/Tenon's capsule interface, which allows a more holistic approach to the understanding of subconjunctival tissue behaviour and local drug delivery. The biomimetic tissue hosts both primary human conjunctival fibroblasts and an immune component in the form of macrophages, morphologically and structurally mimicking the mechanical proprieties and contraction kinetics of ex vivo porcine conjunctiva. We show that our model is suitable for the screening of drugs targeting scarring and/or inflammation, and amenable to the study of local drug delivery devices that can be inserted in between the two layers of the biomimetic. We propose that this multicellular-bilayer engineered tissue will be useful to study complex biological aspects of scarring and fibrosis, including the role of inflammation, with potentially significant implications for the management of scarring following glaucoma filtration surgery and other anterior ocular segment scarring conditions. Crucially, it uniquely allows the evaluation of new means of local drug delivery within a physiologically relevant tissue mimetic, mimicking intraoperative drug delivery in vivo.

Supplementary intracameral lidocaine for phacoemulsification under topical anesthesia. A meta-analysis of randomized controlled trials.

TOPIC: We consider a meta-analysis of randomized controlled trials (RCTs) comparing topical anesthesia alone with topical and intracameral anesthesia for phacoemulsification. CLINICAL RELEVANCE: Topical anesthesia has become an increasingly popular option for day-case cataract surgery. Many surgeons now use supplementary intraoperative intracameral lidocaine, but the evidence base for the supplementary use of intracameral anaesthetic during cataract surgery has never been reviewed systematically. METHODS/LITERATURE REVIEWED: The primary objective is to compare intraoperative pain for phacoemulsifications under topical anesthesia with and without intracameral anesthesia. The secondary objectives are to assess both adverse effects and complications attributable to choice of anesthesia and the need for additional anesthesia during surgery. Searches were made from the Cochrane Central Register of Controlled Trials, Medline, Excerpta Medica database, and Latin American and Caribbean Health Science Information Database up to and including June 8, 2006. RESULTS: Eight RCTs, recruiting a total of 1281 patients, were identified. Our data comparison showed significantly lower intraoperative pain perception in patient groups using supplementary intracameral lidocaine. No significant difference in intraoperative adverse events, corneal toxicity, or the need for supplemental anesthesia was identified. CONCLUSION: Intraoperative pain during cataract surgery under topical anaesthetic is reduced by intracameral lidocaine. Possible adverse effects of intracameral lidocaine cannot be excluded due to significant heterogeneity in outcome measures between different RCTs. Although a statistically significant reduction in intraoperative pain has been demonstrated, it is not yet possible to recommend this additional intervention without reservations.