Precipitants of 5-Fluorouracil in Trabeculectomy Bleb Management: A Comparative Laboratory Study.

AIM: Concerns regarding 5-Fluorouracil (5-FU) corneal toxicity have resulted in various ways of reducing its corneal exposure during post-operative trabeculectomy bleb manipulation. This study investigates the properties of various topical agents used to induce the precipitation of this compound. MATERIALS AND METHODS: This is a double-blind, descriptive, laboratory study comparing five different potential precipitants of 5-FU (proxymetacaine (proxy), oxybuprocaine (oxy), ametho-caine (ameth), fluorescein (flor), proxymetacaine + fluorescein (proxy-flor) to a control group (normal saline). A 0.01 mL of each anonymized agent was applied next to a clear round comparison marker in a transparent sterile container set on a dark background. 5-FU (0.01 mL of 50 mg/mL) was subsequently applied to each agent. The induced changes in transparency were imaged and compared to the transparency of the central marker. For each application, pH changes were also noted. RESULTS: Proxy, flor and proxy + flor did not result in any discernible 5-FU precipitation. Oxy resulted in a moderate visible change, and ameth produced very significant precipitation. Application of proxy, oxy, ameth, and proxy + flor resulted in the neutralization of the 5-FU's alkaline pH. CONCLUSION: We propose using a cotton-tipped bud dipped in ameth applied at the injection site as the recommended method to avoid 5-FU corneal exposure in these cases. CLINICAL SIGNIFICANCE: Practitioners should be aware of the differences in precipitation of 5-FU by different types of topical anesthetics and modify techniques of anesthesia and 5-FU administration accordingly.How to cite this article: Mercieca KJ, Fenerty CH, Steeples LR, Drury B, Bhargava A. Precipitants of 5-Fluorouracil in Trabeculectomy Bleb Management : A Comparative Laboratory StudyJ Curr Glaucoma Pract 2018;12(2):64-66.

Trabeculectomy bleb needling and antimetabolite administration practices in the UK: a glaucoma specialist national survey.

AIMS: To evaluate, describe and quantify the diversity in postoperative antimetabolite administration and bleb needling practices among glaucoma specialists performing trabeculectomy surgery within the UK and Ireland. METHODS: A cross-sectional online survey was distributed to all consultant glaucoma specialists who are on the United Kingdom and Eire Glaucoma Society (UKEGS) contact list. Participants were asked specific questions about their current practices for post-trabeculectomy antimetabolite administration followed by questions directly related to bleb needling procedures. RESULTS: 60 (83%) of UKEGS glaucoma subspecialty consultants completed the survey. 70% of respondents administered 5-fluorouracil (5-FU) in their clinic room while 30% used a separate treatment room. Doses of 5-FU varied considerably but 70% used 5 mg as standard. Techniques used to reduce corneal toxicity included precipitation with amethocaine (44%) or benoxinate (14%), saline wash (14%) and modified injection technique (8%). Topical antibiotics and/or betadine were used to prevent infection following 5-FU injection in just over 50%. Bleb needling was exclusively performed in operating theatre by 56% of respondents and solely at the slit lamp in the clinic room by 12%. A further 30% used a combination of both theatre and outpatient clinic rooms. Anti-metabolites used were 5-FU (72%) and mitomycin C (22%) with 12% using either of the two substances. CONCLUSIONS: There is a significantly wide variety of current practices for antimetabolite administration and bleb needling within the UK and Ireland. This may be influenced by a glaucoma surgeon's specific experience and audit results as well as particular clinical set-up, availability of antimetabolite and clinic room space.

Short-term intraocular tamponade with perfluorocarbon heavy liquid.

BACKGROUND: Inferior retinal detachment pathology can be difficult to manage due to inadequate tamponade with low specific gravity tamponade agents and the propensity for the development of proliferative vitreoretinopathy (PVR). We report the efficacy and adverse effects associated with the use of perfluorocarbon heavy liquid as a short-term tamponade in managing such pathologies. METHODS: Retrospective analysis of 17 eyes treated with short-term perfluoro-n-octane tamponade for complex inferior retinal pathology, including inferior detachment and PVR. Mean follow-up time was 14 months and mean tamponade duration was 7 days. RESULTS: Reattachment of the retina during the study period was achieved with a single set of operations in 13/17 (76%) eyes, with four eyes requiring a subsequent set of vitreoretinal operations. Postoperative visual acuity (VA) was equal to or better than preoperative VA in 14 (82%) of 17 eyes. Complications arising during the follow-up period included superior redetachment, atrophic macular changes, minor macular haemorrhage, cataract, elevated intraocular pressure, corneal defects, PVR, epiretinal membrane and retained perfluorocarbon heavy liquid. One case of intraocular inflammation occurred >6 months after removal of perfluoro-n-octane tamponade. CONCLUSION: Short-term perfluoro-n-octane tamponade achieved a stable reattachment rate of 76% when used to manage challenging retinal pathologies.

Amino acid patterns around disulfide bonds.

Disulfide bonds provide an inexhaustible source of information on molecular evolution and biological specificity. In this work, we described the amino acid composition around disulfide bonds in a set of disulfide-rich proteins using appropriate descriptors, based on ANOVA (for all twenty natural amino acids or classes of amino acids clustered according to their chemical similarities) and Scheffé (for the disulfide-rich proteins superfamilies) statistics. We found that weakly hydrophilic and aromatic amino acids are quite abundant in the regions around disulfide bonds, contrary to aliphatic and hydrophobic amino acids. The density distributions (as a function of the distance to the center of the disulfide bonds) for all defined entities presented an overall unimodal behavior: the densities are null at short distances, have maxima at intermediate distances and decrease for long distances. In the end, the amino acid environment around the disulfide bonds was found to be different for different superfamilies, allowing the clustering of proteins in a biologically relevant way, suggesting that this type of chemical information might be used as a tool to assess the relationship between very divergent sets of disulfide-rich proteins.

Conformational characterization of disulfide bonds: a tool for protein classification.

BACKGROUND: Throughout evolution, mutations in particular regions of some protein structures have resulted in extra covalent bonds that increase the overall robustness of the fold: disulfide bonds. The two strategically placed cysteines can also have a more direct role in protein function, either by assisting thiol or disulfide exchange, or through allosteric effects. In this work, we verified how the structural similarities between disulfides can reflect functional and evolutionary relationships between different proteins. We analyzed the conformational patterns of the disulfide bonds in a set of disulfide-rich proteins that included twelve SCOP superfamilies: thioredoxin-like and eleven superfamilies containing small disulfide-rich proteins (SDP). RESULTS: The twenty conformations considered in the present study were characterized by both structural and energetic parameters. The corresponding frequencies present diverse patterns for the different superfamilies. The least-strained conformations are more abundant for the SDP superfamilies, while the "catalytic" +/-RHook is dominant for the thioredoxin-like superfamily. The "allosteric" -RHSaple is moderately abundant for BBI, Crisp and Thioredoxin-like superfamilies and less frequent for the remaining superfamilies. Using a hierarchical clustering analysis we found that the twelve superfamilies were grouped in biologically significant clusters. CONCLUSIONS: In this work, we carried out an extensive statistical analysis of the conformational motifs for the disulfide bonds present in a set of disulfide-rich proteins. We show that the conformational patterns observed in disulfide bonds are sufficient to group proteins that share both functional and structural patterns and can therefore be used as a criterion for protein classification.