Wound modulation after trabeculectomy by different formulations of antimetabolites in rabbits

Effect of Topical 5-Fluorouracil on Lacrimal Drainage System: Histopathological Evidence From Animal Experiments and Potential Clinical Implications

PURPOSE

The purpose of this study is to investigate the histopathological changes in the lacrimal drainage system of rabbits following the application of 1% topical 5-fluorouracil (5-FU) for 4 weeks.

METHODS

Ten eyes of 10 healthy New Zealand white rabbits were subjected to topical instillation of 1% (10 mg/mL) 5-FU, 1 drop 4 times a day for 4 weeks. Rabbits underwent a detailed ocular examination including eyelids, ocular surface, punctal, peri-punctal changes, and nasolacrimal duct patency at baseline and after 4 weeks of 5-FU. The rabbits were then sacrificed, and the eyelid, conjunctiva, lacrimal gland, and the entire lacrimal drainage system were retrieved for histopathological analysis as per standard protocols.

RESULTS

Clinically demonstrable peripunctal changes and canalicular stenosis were noted in 6 (60%, 6/10) rabbits. Two of these (20%, 2/10) had additional complete regurgitation of clear fluid, indicating a nasolacrimal duct obstruction. The remaining 4 (40%, 4/10) clinically did not demonstrate lacrimal drainage changes and were patent on irrigation. The conjunctiva showed focal loss of goblet cells in several areas. Significant changes were noted in the canalicular, lacrimal sac, and the nasolacrimal duct tissues in the form of epithelial hyperplasia, subepithelial inflammation, edema, dilated and congested vessels, and fibrosis. The lacrimal gland, eyelid tissue (excluding tarsal conjunctiva), and cornea showed no significant histopathological changes.

CONCLUSIONS

Clinical and histopathological changes were noted in the lacrimal drainage system of rabbits subjected to topical 5-FU application. These findings can have potential clinical implications for patients receiving 5-FU therapy.

Clinical outcomes of amniotic membrane loaded with 5-FU PLGA nanoparticles in experimental trabeculectomy

AIM

To evaluate the effect of amniotic membrane loaded with 5-fluorouracil poly (lactic-co-glycolic acid) (PLGA) nanoparticles (5-FU-NPs) in the surgical outcomes of experimental trabeculectomy in rabbits.

METHODS

Thirty-two New Zealand white rabbits were randomly categorized into four groups with 8 rabbits in each group. Group 1, the control group, performed traditional trabeculectomy without adjuvant treatment. While the experimental groups performed compound trabeculectomy with different implantations including amniotic membrane (group 2), 5-FU-NPs (group 3) and amniotic membrane loaded with 5-FU-NPs (group 4). Clinical evaluations including IOP measurement and filtration bleb analysis were performed in all groups postoperatively.

RESULTS

There is no significant difference of mean IOP in all groups at first 7d after surgery. While at P14, mean IOPs of experimental group 2 (9.8±2.1 mm Hg), groups 3 (8.9±2.8 mm Hg) and group 4 (7.6±2.3 mm Hg) were significantly reduced compared to control group (12.4±2.6 mm Hg; n=8, P<0.05). At P21, mean IOPs of groups 3 (11.7±3.2 mm Hg) and group 4 (9.9±1.6 mm Hg) were significantly decreased compare to control group (17.9±1.6 mm Hg) and group 2 (16.6±2.8 mm Hg; n=8, P<0.05). At P28, mean IOPs of groups 3 (13.8±3.3 mm Hg) and group 4 (10.6±2.0 mm Hg) were also significantly reduced compare to control group (19.4±2.3 mm Hg) and group 2 (18.5±2.4 mm Hg; n=8, P<0.05). Meanwhile mean IOP of group 4 is significantly decreased compared to group 3 at P28 (n=8, P<0.05). Survival analysis of functional filtration blub in all groups revealed the longest survival time in group 4 (24.9±5.1d) compared to that in group 3 (20.6±4.3d), group 2 (15.0±5.2d) and control group (10.1±5.7d).

CONCLUSION

Amniotic membrane loaded with 5-Fu-NPs may function as an effective anti-scarring implant and provides improved long-term surgical outcomes for experimental trabeculectomy in rabbits.

Tower microneedle minimizes vitreal reflux in intravitreal injection

Intravitreal injection is widely used for easy control of drug levels in posterior segment of the eye by injecting the drug directly with hypodermic needles. Patients, however, often experience complications from intravitreal injection due to repeated injections, increased intraocular pressure, and infection. In addition, injected drug reflux after intravitreal injection makes it challenging to maintain predetermined drug dose due to the drug loss through backward effusions. Here, we described that the Tower Microneedle can reduce initial reflux and bleb formation due to its smaller outer diameter compared to a traditional hypodermic needle. Furthermore, we use phenylephrine hydrochloride for pupil expansion and demonstrated that Tower Microneedle induced similar pupil expansions using only half the drug volume, in the same period of time, compared to the 31 Gauge hypodermic needle. Consequently, Tower Microneedle achieves the same therapeutic effect in the vitreous body using fewer drugs than a traditional hypodermic needle due to the decreased backward drug effusion. Tower Microneedle described herein holds great promise for intravitreal injection with less reflux and lower drug dosage.

Topical silver nanoparticles result in improved bleb function by increasing filtration and reducing fibrosis in a rabbit model of filtration surgery

PURPOSE

To compare the effects of silver nanoparticles (AgNPs) and mitomycin C (MMC) on intraocular pressure (IOP) and external, histologic, and immunohistochemical bleb characteristics in a rabbit model of filtration surgery.

METHODS

Filtration surgery with concurrent topical application of either AgNPs or MMC was performed on 14 pigmented Dutch Belted rabbits. IOP and bleb characteristics were compared on postoperative day 1 and at weeks 1 through 6. Hematoxylin and eosin staining and smooth muscle actin (SMA) immunohistochemistry were performed at postoperative week 6.

RESULTS

Average IOP across all time points was reduced 5.8 and 3.8 mm Hg in AgNP- and MMC-treated eyes, respectively. At week 6, IOP was reduced 4.1 and 0.2 mm Hg in AgNP- and MMC-treated eyes, respectively. Blebs were smaller, thicker, and less ischemic in AgNP-treated eyes. AgNP-treated eyes showed less fibrosis and more stromal edema, suggesting increased filtration, and also had fewer SMA-positive myofibroblasts, suggesting reduced bleb contraction. AgNP-treated eyes showed more lymphocytes than MMC-treated eyes. There were few complications in both groups.

CONCLUSIONS

In a rabbit model of filtration surgery, AgNPs are a reasonable alternative to MMC as adjunctive therapy. Compared to MMC, AgNPs result in an improved and sustained reduction of IOP and promote blebs with decreased fibrosis and ischemia as well as increased filtration despite a smaller overall size. This combination may offer an opportunity to promote long-term surgical IOP reduction with an improved complication profile.

Post-trabeculectomy topical bevacizumab preventing bleb failure: a preliminary study

This study aims to evaluate the efficacy and safety of post-trabeculectomy topical bevacizumab, in preventing bleb failure. A total of 11 females and 12 males were enrolled for the study. After a complete ophthalmic evaluation, the patients underwent trabeculectomy. Full ophthalmic examination was done the next day, which included visual acuity, intraocular pressure (IOP), and bleb morphology. Next, two drops of bevacizumab [0.25 mg (0.01 ml)] were instilled over the wound area with a tuberculin (1 ml) syringe. Pressure was applied at the medial canthus to prevent it from going into the lacrimal passage. Similar postoperative procedures were repeated at 1, 2, 3, and 4 weeks. So in all, five instillations of bevacizumab were completed. Later, the patients were followed at 1-month interval for 6 months. Target IOP was achieved in all eyes and was maintained during the study period of 6 months without any anti-glaucoma medication. Average IOP before trabeculectomy was 27.27 ± 8.92 mmHg, which decreased postoperatively to 8.77 ± 0.97 mmHg at 3 months and 9.27 ± 1.16 mmHg at 6 months. This drop in IOP was statistically significant on both occasions (p = 0.00). A nice low filtering bleb was formed after the surgery, and it remained the same during the study period. The other parameters like cup-to-disc ratio and visual field did not change during the 6 months of study as expected because glaucoma is a slow progressive disease. Modulating the wound at multiple sites by bevacizumab (inflammation, proliferative, and remodeling stages) can lead to success of trabeculectomy.

Subconjunctival bevacizumab as an adjunct to trabeculectomy in eyes with refractory glaucoma: a case series

This prospective observational case series study included 6 eyes of 6 consecutive glaucomatous patients. Each patient underwent trabeculectomy with mitomycin C, and received a 1.25 mg of subconjunctival bevacizumab injection at completion of the trabeculectomy. Study eyes included two with neovascular glaucoma, three with uveitic glaucoma, and one with secondary glaucoma following vitrectomy. All eyes had undergone failed glaucoma laser/surgical treatment or an intraocular surgical procedure. Intraocular pressure (IOP) at the following postoperative visits: preoperative, 1 week, 1 month, 2 months, 3 months, and 6 months, was measured. We also evaluated postoperative bleb findings and complications. IOP measured at each visit was 37.5±14.4 mmHg, 6.2±3.4 mmHg, 8.3±7.2 mmHg, 12.0±4.4 mmHg, 10.8±3.1 mmHg, and 12.2±3.3 mmHg, respectively, for each visit. All eyes had functioning blebs with normal IOP at postoperative 6 months with no additional IOP-lowering medication.

Physicochemical Properties and In Vivo Assessment of Timolol-Loaded Poly(D,L-Lactide-co-Glycolide) Films for Long-Term Intraocular Pressure Lowering Effects

Timolol-loaded poly(D,L-lactide-co-glycolide; PLGA) films were prepared for achieving the long-term intraocular pressure (IOP) lowering effect on glaucoma treatment. The physicochemical properties and in vivo effects of films were determined and characterize the delivery system. PLGA, span 20, propylene glycol (PG), and timolol base were dissolved in dichloromethane (DCM) and kept in a stainless mold; timolol films were prepared after the evaporation of DCM. Timolol disc-shape film preparation (TDF), containing 1 mg of timolol in 0.37 cm(2) area, was fabricated by using a trephine and placed onto the cul de sac of alpha-chymotrypsin-induced ocular hypertension rabbits for assessing the IOP lowering effect. The prepared films characterized a Young's modulus ranged from 1.13 to approximately 2.49 MPa, and related to the content percentages of PLGA, PG, and the residual DCM. The timolol film could maintain drug release for 1 week. Following a single-dose application in ocular hypertension rabbits, the prepared TDF could achieve a long-term IOP lowering effect and maintain the IOP change (in comparison with baseline) of approximately 7 mmHg within 1 week. The aqueous humor levels of timolol were low within a range of 0.8 to approximately 0.24 microg/mL for the initial 24 h and less than 0.15 microg/mL for 4-7 days. The investigated film formulation might be potentially developed for the application of long-term ocular delivery systems.