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OBJECTIVE: To report the surgical outcomes of a modified trabeculectomy technique involving implanting the Tenon's layer under the scleral flap. DESIGN: Prospective, interventional case series. PARTICIPANTS: 51 eyes with medically uncontrolled glaucoma were enrolled for this study. A new trabeculectomy technique, the Tenon's filtration technique for trabeculectomy (TFT-LEC) was used in 26 eyes, while a conventional procedure, normal trabeculectomy (N-LEC), was used for 25 eyes. METHODS: Intraocular pressure (IOP) control, the number of glaucoma medications, the need for additional interventions, and postoperative complications were assessed. RESULTS: Twelve months postoperatively, the mean IOP was 13.5 ± 0.5 mmHg in the TFT-LEC group and 15.4 ± 0.5 mmHg in the N-LEC group (p = 0.13). The TFT-LEC group required an average of 1.3 ± 1.0 additional glaucoma medications (21 cases required only ripasudil) postoperatively, with no cases of bleb needling revision or reoperation. The N-LEC group required an average of 1.7 ± 1.5 glaucoma medications (p = 0.43) compared to TFT-LEC group, eight cases (32%) required bleb needling revision (p = 0.002), and one case (4%) of reoperation (p = 0.49). The complications in the TFT-LEC group included shallow anterior chamber in six (23 %) cases (p = 1.00) compared to N-LEC group, choroidal detachment in two (8%) cases (p = 0.42), and anterior chamber hemorrhage in seven (27%) cases (p = 0.29). None of these complications affected visual function. CONCLUSIONS: This new technique involving implanting the Tenon's layer under the scleral flap may improve the postoperative outcomes of trabeculectomy.

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BACKGROUND: Polyhydroxyalkanoates (PHAs) are microbial polyesters synthesized by PHA synthases. Naturally occurring PHA copolymers possess a random monomer sequence. The development of PhaCAR, a unique sequence-regulating PHA synthase, has enabled the spontaneous biosynthesis of PHA block copolymers. PhaCAR synthesizes both a block copolymer poly(2-hydroxybutyrate)-b-poly(3-hydroxybutyrate) [P(2HB)-b-P(3HB)], and a random copolymer, poly(3HB-co-3-hydroxyhexanoate), indicating that the combination of monomers determines the monomer sequence. Therefore, in this study, we explored the substrate scope of PhaCAR and the monomer sequences of the resulting copolymers to identify the determinants of the monomer sequence. PhaCAR is a class I PHA synthase that is thought to incorporate long-main-chain hydroxyalkanoates (LMC HAs, > C3 in the main [backbone] chain). Thus, the LMC monomers, 4-hydroxy-2-methylbutyrate (4H2MB), 5-hydroxyvalerate (5HV), and 6-hydroxyhexanoate (6HHx), as well as 2HB, 3HB, and 3-hydroxypropionate (3HP) were tested. RESULTS: Recombinant Escherichia coli harboring PhaCAR, CoA transferase and CoA ligase genes was used for PHA production. The medium contained the monomer precursors, 2HB, 3HB, 3HP, 4H2MB, 5HV, and 6HHx, either individually or in combination. As a result, homopolymers were obtained only for 3HB and 3HP. Moreover, 3HB and 3HP were randomly copolymerized by PhaCAR. 3HB-based binary copolymers P(3HB-co-LMC HA)s containing up to 2.9 mol% 4H2MB, 4.8 mol% 5HV, or 1.8 mol% 6HHx were produced. Differential scanning calorimetry analysis of the copolymers indicated that P(3HB-co-LMC HA)s had a random sequence. In contrast, combining 3HP and 2HB induced the synthesis of P(3HP)-b-P(2HB). Similarly, P(2HB) segment-containing block copolymers P(3HB-co-LMC HA)-b-P(2HB)s were synthesized. Binary copolymers of LMC HAs and 2HB were not obtained, indicating that the 3HB or 3HP unit is essential to the polymer synthesis. CONCLUSION: PhaCAR possesses a wide substrate scope towards 2-, 3-, 4-, 5-, and 6-hydroxyalkanoates. 3HB or 3HP units are essential for polymer synthesis using PhaCAR. The presence of a 2HB monomer is key to synthesizing block copolymers, such as P(3HP)-b-P(2HB) and P(3HB-co-LMC HA)-b-P(2HB)s. The copolymers that did not contain 2HB units had a random sequence. This study's results provide insights into the mechanism of sequence regulation by PhaCAR and pave the way for designing PHA block copolymers.

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Chimeric polyhydroxyalkanoate synthase PhaCAR is characterized by the capacity to incorporate unusual glycolate (GL) units and spontaneously synthesize block copolymers. The GL and 3-hydroxybutyrate (3HB) copolymer synthesized by PhaCAR is a random-homo block copolymer, poly(GL-ran-3HB)-b-poly(3HB). In the present study, medium-chain-length 3-hydroxyhexanoate (3HHx) units were incorporated into this copolymer using PhaCAR for the first time. The coenzyme A (CoA) ligase from Pseudomonas oleovorans (AlkK) serves as a simple 3HHx-CoA supplying route in Escherichia coli from exogenously supplemented 3HHx. NMR analyses of the obtained polymers revealed that 3HHx units were randomly connected to 3HB units, whereas GL units were heterogeneously distributed. Therefore, the polymer is composed of 2 segments: P(3HB-co-3HHx) and P(GL-co-3HB-co-3HHx). The thermal and mechanical properties of the terpolymer indicate no contiguous P(3HB) segments in the material, consistent with the NMR results. Therefore, PhaCAR synthesized the novel block copolymer P(3HB-co-3HHx)-b-P(GL-co-3HB-co-3HHx), which is the first block polyhydroxyalkanoate copolymer comprising 2 copolymer segments.

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