Prevention of ocular scarring post glaucoma filtration surgery using the inflammatory cell and platelet binding modulator saratin in a rabbit model

Using a Novel, Subconjunctival, Sustained-Release Mitomycin C Formulation in a Rabbit Model of Filtration Surgery with Gel Stent Implantation

Purpose: To investigate gel stent implantation with and without intraoperative sustained-release mitomycin C (MMC SR) in a rabbit model for gel stent implantation, and to examine aqueous humor outflow (AHO) postimplantation. Methods: Four groups of rabbits were included. Group 1 was untreated (control). Groups 2, 3, and 4 received the gel stent without MMC, with MMC solution (subconjunctival injection), and with MMC SR (subconjunctival injection), respectively. Intraocular pressure (IOP) and AHO were assessed via tonometry and indocyanine green-based angiography, respectively. The main efficacy measure was change in IOP from baseline. Results: Following gel stent implantation, Groups 2, 3, and 4 maintained ≥20% IOP reduction (response) for a median duration of 1 week, 6.5 weeks, and 30 weeks, respectively. Angiography showed normal aqueous humor drainage (Group 1) beginning at the perilimbal trabecular plexus and continuing posteriorly to episcleral outflow vessels. Following implantation, drainage occurred preferentially and directly into the subconjunctival bleb. Conclusions: Gel stent implantation with MMC SR was most effective in achieving sustained, long-term IOP reduction in the rabbit model, compared with implantation with or without MMC solution. Bleb presence and the postimplantation aqueous angiography results indicated redirection of the AHO to the subconjunctival vasculature and presumed lymphatics, suggesting efficient glaucoma filtration to lower IOP in this model. This rabbit model and aqueous angiography may help refine understanding of the mechanism of action of minimally invasive glaucoma surgeries and ultimately translate to improved surgical devices and procedures for patients with glaucoma.

Molecular cloning and functional analysis of HnSaratin from Hirudo nipponia

In order to finish a bloodmeal successfully, hematophagous organisms often stored a variety of anticoagulant proteins in their salivary glands, such as proteins that inhibit platelet aggregation. When they ingest a bloodmeal, these proteins are injected into the host to prevent the blood from clotting. As one of the origins of leeches used in traditional Chinese medicine, H. nipponia was proved to be clinically effective in treatment of cardiovascular and cerebrovascular diseases. This study cloned the sequence of HnSaratin cDNA derived from salivary glands of H. nipponia. The sequence contains an open reading frame of 387 bp, encoding a protein of 128 amino acids containing a signal peptide of 21 amino acids. After removal of the signal peptide, the molecular mass of mature HnSaratin was 12.37 kDa, with a theoretical isoelectric point (pI) of 3.89. The N-terminal of mature HnSaratin was folded into a globular structure, in which 3 disulfide bonds, a ββαβββ topology and 2 Glu residues that binds collagenous Lys2 were located, and the C-terminal formed a flexible region. The fusion HnSaratin protein was obtained by a prokaryotic expression system. The protein showed anti-platelet aggregation activity, and was observed to prevent blood clotting in rats. The significant high expression of HnSaratin mRNA in salivary glands was induced by bloodmeal ingestion of H. nipponia. Briefly, our work provides theoretical basis for further development and utilization of H. nipponia.

Effects of topical docosahexaenoic acid on postoperative fibrosis in an animal model of glaucoma filtration surgery

PURPOSE

The aim of this study was to evaluate docosahexaenoic acid (DHA) as a potential antifibrotic agent after glaucoma filtration surgery (GFS) in rats.

METHODS

A total of 36 10-week-old Brown Norway rats underwent GFS. Animals were equally divided into three groups: a control group, a DHA group and a mitomycin C (MMC) group. Intraocular pressure (IOP) was measured using a dynamic rebound tonometer, and a photograph of the surgical site was taken on days 1, 3, 7, 10, 14 and 17. The incorporation of DHA into fibroblasts was evaluated by gas chromatography. The expression of alfa-smooth muscle actin (α-SMA) and Smad proteins was assessed by Western blotting.

RESULTS

IOP decreased after surgery in animals from the three groups on day 1 after surgery. Over time, IOP remained lower in the DHA and MMC groups than in the control group (median [interquartile range] 8.0 [7.0-8.0] and 8.0 [7.3-8.0] mmHg vs. 9.0 [8.0-9.0] mmHg, respectively; p < 0.001). Bleb area in the DHA and MMC groups remained larger than that of the control group from day 7 to day 14 (3.9 [2.9-5.2] and 3.5 [2.3-4.4] mm² vs. 2.3 [2.0-2.8] mm² , respectively; p = 0.0021). We did not observe any change in DHA concentrations in the fibroblasts of the DHA group compared with the other groups.

CONCLUSION

The impact of DHA on IOP and bleb area was similar to that of MMC. The mechanisms of action of DHA in rat eye fibroblasts deserve further investigation.

Animal models and drug candidates for use in glaucoma filtration surgery: A systematic review

Glaucoma, a degenerative disease of the optic nerve, is the leading cause of irreversible blindness worldwide. Currently, there is no curative treatment. The only proven treatment is lowering intraocular pressure (IOP), the most important risk factor. Glaucoma filtration surgery (GFS) can effectively lower IOP. However, approximately 10% of all surgeries fail yearly due to excessive wound healing, leading to fibrosis. GFS animal models are commonly used for the development of novel treatment modalities. The aim of the present review was to provide an overview of available animal models and anti-fibrotic drug candidates. MEDLINE and Embase were systematically searched. Manuscripts until September 1st^, 2021 were included. Studies that used animal models of GFS were included in this review. Additionally, the snowball method was used to identify other publications which had not been identified through the systematic search. Two hundred articles were included in this manuscript. Small rodents (e.g. mice and rats) are often used to study the fibrotic response after GFS and to test drug candidates. Due to their larger eyes, rabbits are better suited to develop medical devices. Novel drugs aim to inhibit specific pathways, e.g. through the use of modulators, monoclonal antibodies, aqueous suppressants or gene therapy. Although most newly studied drugs offer a higher safety profile compared to antimetabolites, their efficacy is in most cases lower when compared to MMC. Current literature on animal models and potential drug candidates for GFS were summarized in this review. Future research should focus on refining current animal models (for example through the induction of glaucoma prior to undertaking GFS) and standardizing animal research to ensure a higher reproducibility and reliability across different research groups. Lastly, novel therapies need to be further optimized, e.g. by conducting more research on the dosage, administration route, application frequency, the option of creating combination therapies, or the development of drug delivery systems for sustained release of anti-fibrotic medication.

The control of conjunctival fibrosis as a paradigm for the prevention of ocular fibrosis-related blindness. "Fibrosis has many friends"

The processes involved in ocular fibrosis after disease or ocular tissue injury, including surgery play an important part in the development or failure of treatment of most blinding diseases. Ocular fibrosis is one of the biggest areas of unmet need in ophthalmology. Effective anti-scarring therapies could potentially revolutionise the management of many diseases like glaucoma worldwide. The response of a quiescent or activated conjunctiva to glaucoma surgery and aqueous flow with different stimulatory components and the response to different interventions and future therapeutics is a paradigm for scarring prevention in other parts of the eye and orbit. Evolution in our understanding of molecular and cellular mechanisms in ocular fibrosis is leading to the introduction of new and re-purposed therapeutic agents, targeting a wide range of key processes. This review provides current and futures perspectives on different approaches to conjunctival fibrosis following glaucoma surgery and highlights the challenges faced in implementing these therapies with maximal effect and minimal side effects.

A Comparison of Subconjunctival Wound Healing between Different Methods of Dissecting Subconjunctival Tissues

OBJECTIVE

To compare different methods for dissecting subconjunctival tissues by developing subconjunctival wound healing models.

METHODS

New Zealand white rabbits were separated into 3 groups based on the method by which the rabbit subconjunctival wound healing model was generated: subconjunctival tissues were dissected episclerally (EPI) or subepithelially (SUB), with a corresponding blank control (CON). All the cases in the experimental groups were surgically prepared with conjunctival flaps, and they were sacrificed on the third postoperative day. At the surgical sites, the protein levels of hypoxia-inducible factor-1 (HIF-1)-α, vascular endothelial growth factor (VEGF)-A, and matrix metalloproteinase (MMP)-2 were detected by Western blot, morphological vascularity was measured by Adobe Photoshop, and subconjunctival fibrosis was assessed by histology.

RESULTS

Compared with the CON group, both the EPI and SUB groups showed significantly upregulated protein levels of HIF-1α, VEGF-A, and MMP-2. In addition, the protein levels of HIF-1α, VEGF-A, and MMP-2 were higher in the EPI group than in the SUB group. Morphological vascularity was significantly elevated in the EPI group compared with the SUB and CON groups. Collagen content was markedly increased in the EPI group compared with the SUB and CON groups.

CONCLUSIONS

Dissecting subconjunctival tissues subepithelially inhibits subconjunctival fibrosis, which may be instructive in tenonectomy in filtration surgery.

Effect of Novel Design Modifications on Fibrotic Encapsulation: An In Vivo Glaucoma Drainage Device Study in a Rabbit Model

Purpose

To quantify the effects of modified Ahmed glaucoma valves^® (AGV) with anti-fibrotic plate coatings or a plate surface micro-pattern on outflow resistance and tissue response.

Methods

Twelve New Zealand rabbits were divided into four groups: commercially available AGV implants (n = 3), AGV with hydrophilic coating (n = 3), AGV with heparin coating (n = 3), and AGV with a plate surface micro-pattern (n = 3). After 6 weeks, the anterior chamber silicone tube was cannulated in situ and perfused with 2.5 μL/min of saline. The pressures were recorded with a perfusion system to measure outflow resistance. The rabbits were then euthanized followed by enucleation of all eyes for bleb histological analyses.

Results

Hydrostatic pressures were significantly lower in AGVs with the hydrophilic plate coating (mean difference −9.6 mm Hg; p < 0.001), heparin-coated plates (mean difference −4.4 mm Hg; p < 0.001), and micro-patterned plates (mean difference −18.6 mm Hg, p < 0.001), indicating lower outflow resistance compared to control AGV models. Fibrotic encapsulation was lower in hydrophilic plate coating (84.2 μm; mean difference −6.2 μm, p = 0.425), micro-patterned surface (63.7 μm; mean difference −26.7 μm, p = 0.003), and heparin plate coating (49.3 μm; mean difference −41.1 μm, p = 0.006) when compared to control AGV models.

Conclusions

Modified AGVs with plate coatings and AGVs with micro-patterned plates both appear to reduce postoperative fibrotic encapsulation and aqueous outflow resistance by altering the tissue response to implanted materials. Further studies are needed to characterize the safety and role of plate surface modifications on glaucoma drainage devices.

Modulating Ocular Scarring in Glaucoma Filtration Surgery Using the Epigenetic Adjunct Suberoylanilide Hydroxamic Acid

AIM

The aim of this study is to assess the effectiveness of suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor (HDI) with a broad spectrum epigenetic activity, in improving filtration bleb survival as an adjunct therapy to glaucoma filtration surgery (GFS) in the rabbit model.

MATERIALS AND METHODS

Eighteen New Zealand White rabbits underwent GFS in the left eye and were randomized to receive either a subconjunctival (SC) injection of 0.1 mL SAHA (9.25 μg/mL) or balanced saline solution (BSS) at the end of surgery, or a 3-minute intraoperative topical application of 0.4 mg/mL mitomycin-C (MMC). Bleb survival and histology were compared.

RESULTS

Blebs of rabbits receiving injections of SAHA survived an average (mean ± SD) of 23.2 ± 2.7 days. SAHA rabbits showed a nonsignificant improvement over rabbits that received an injection of BSS, which had a mean survival time of 19.7 ± 2.7 days (p = 0.38) according to a one-way analysis of variance (ANOVA). Eyes receiving intraoperative topical MMC survived an average of 32.5 ± 3.3 days, which is significantly longer than both the control group treated with BSS (p = 0.01) and the experimental group treated with the SAHA (p = 0.0495). SAHA was well tolerated and showed no significant avascularity, necrosis, or conjunctival thinning.

CONCLUSION

Although it was well tolerated, a single intraoperative injection of SAHA did not significantly prolong bleb survival in the rabbit model.

CLINICAL SIGNIFICANCE

Epigenetic adjuncts hold promise for improving GFS outcome; however, future studies must continue to examine different administration protocols and dosages to substantiate their efficacy.

HOW TO CITE THIS ARTICLE

Rodgers CD, Lukowski ZL, et al. Modulating Ocular Scarring in Glaucoma Filtration Surgery Using the Epigenetic Adjunct Suberoylanilide Hydroxamic Acid. J Curr Glaucoma Pract 2019;13(1):37-41.

The impact of conjunctival flap method and drainage cannula diameter on bleb survival in the rabbit model

PURPOSE

To examine the effect of cannula diameter and conjunctival flap method on bleb survival in rabbits undergoing cannula-based glaucoma filtration surgery (GFS).

METHODS

Twelve New Zealand White rabbits underwent GFS in both eyes. The twenty-four eyes were divided into four groups. Two of the four groups (N = 12) received limbus-based conjunctival flaps (LBCF), and the other two (N = 12) received fornix-based conjunctival flaps (FBCF). Six FBCF rabbit eyes were implanted with 22-gauge drainage tubes, and the other six were implanted with 26-gauge tubes. Likewise, six LBCF rabbits received 22-gauge drainage tubes and six received 26-gauge tubes. Filtration blebs were evaluated every three days by a masked observer. Bleb failure was defined as the primary endpoint in this study and was recorded after two consecutive flat bleb evaluations.

RESULTS

Group 1 (LBCF, 22- gauge cannula) had a mean bleb survival time (Mean ± SD) of 18.7 ± 2.9 days. Group 2 (LBCF, 26-gauge cannula) also had a mean bleb survival time of 18.7 ± 2.9 days. Group 3 (FBCF, 22-gauge cannula) had a mean bleb survival time of 19.2 ± 3.8 days. Group 4 (FBCF, 26-gauge cannula) had a mean bleb survival time of 19.7 ± 4.1 days. A 2-way analysis of variance showed that neither surgical approach nor cannula gauge made a statistically significant difference in bleb survival time (P = 0.634 and P = 0.874). Additionally, there was no significant interaction between cannula gauge and conjunctival flap approach (P = 0.874), suggesting that there was not a combination of drainage gauge and conjunctival flap method that produced superior bleb survival.

CONCLUSION

Limbus and fornix-based conjunctival flaps are equally effective in promoting bleb survival using both 22 and 26-gauge cannulas in the rabbit model. The 26-gauge drainage tube may be preferred because its smaller size facilitates the implantation process, reducing the risk of corneal contact.

Suppression of TGF-β pathway by pirfenidone decreases extracellular matrix deposition in ocular fibroblasts in vitro

In glaucoma surgery, fibrotic processes occur, leading to impairment of liquid outflow. Activated fibroblasts are responsible for postoperative scarring. The transforming growth factor-β (TGF-β) pathway plays a key role in fibroblast function, differentiation and proliferation. The aim of this study was the characterization of the fibrotic potential of two subtypes of primary human ocular fibroblasts and the attempt to inhibit fibrotic processes specifically, without impairing cell viability. For fibrosis inhibition we focused on the small molecule pirfenidone, which has been shown to prevent pulmonary fibrosis by the decrease of the expression of TGF-β1, TGF-β2 and TGF-β3 cytokines. For in vitro examinations, isolated human primary fibroblasts from Tenon capsule and human intraconal orbital fat tissues were used. These fibroblast subpopulations were analyzed in terms of the expression of matrix components responsible for postoperative scarring. We concentrated on the expression of collagen I, III, VI and fibronectin. Additionally, we analyzed the expression of α-smooth muscle actin, which serves as a marker for fibrosis and indicates transformation of fibroblasts into myofibroblasts. Gene expression was analyzed by rtPCR and synthesized proteins were examined by immunofluorescence and Western blot methods. Proliferation of fibroblasts under different culture conditions was assessed using BrdU assay. TGF-β1 induced a significant increase of cell proliferation in both cell types. Also the expression of some fibrotic markers was elevated. In contrast, pirfenidone decreased cell proliferation and matrix synthesis in both fibroblast subpopulations. Pirfenidone slightly attenuated TGF-β1 induced expression of fibronectin and α-smooth muscle actin in fibroblast cultures, without impairing cell viability. To summarize, manipulation of the TGF-β signaling pathway by pirfenidone represents a specific antifibrotic approach with no toxic side effects in two human orbital fibroblast subtypes. We presume that pirfenidone is a promising candidate for the treatment of fibrosis following glaucoma surgery.

Suppression of Human Tenon Fibroblast Cell Proliferation by Lentivirus-Mediated VEGF Small Hairpin RNA

Purpose. The functions of vascular endothelial growth factor (VEGF) in scar formation after trabeculectomy were investigated in a human Tenon fibroblast cell line from glaucoma patients using lentivirus-mediated VEGF shRNA. Methods. Human Tenon fibroblast (HTF) cells were isolated from scar tissue of glaucoma patients during secondary surgery. Lentivirus-VEGF-shRNA was constructed and transfected into HTF cells. Subsequently, VEGF mRNA and protein expression were analyzed using quantitative RT-PCR and western blotting, respectively, and the effects of VEGF knockdown were analyzed. The inhibition of HTF proliferation was monitored according to total cell numbers using ScanArray. Results. Both mRNA and protein levels of VEGF were reduced by lentivirus-mediated VEGF-shRNA, and proliferation of HTF cells was inhibited. Conclusions. Primary cultures of human Tenon fibroblast (HTF) were established, and proliferation was decreased following inhibition of VEGF. VEGF may be a suitable therapeutic target for reducing scar tissue formation in glaucoma patients after filtration surgery.

Current and Future Techniques in Wound Healing Modulation after Glaucoma Filtering Surgeries

Filtering surgeries are frequently used for controlling intraocular pressure in glaucoma patients. The long-term success of operation is intimately influenced by the process of wound healing at the site of surgery. Indeed, if has not been anticipated and managed accordingly, filtering surgery in high-risk patients could end up in bleb failure. Several strategies have been developed so far to overcome excessive scarring after filtering surgery. The principal step involves meticulous tissue handling and modification of surgical technique, which can minimize the severity of wound healing response at the first place. However, this is usually insufficient, especially in those with high-risk criteria. Thus, several adjuvants have been tried to stifle the exuberant scarring after filtration surgery. Conventionally, corticosteroids and anti-fibrotic agents (including 5-fluorouracil and Mitomycin-C) have been used for over three decades with semi-acceptable outcomes. Blebs and bleb associated complications are catastrophic side effects of anti-fibrotic agents, which occasionally are encountered in a subset of patients. Therefore, research continues to find a safer, yet effective adjuvant for filtering surgery. Recent efforts have primarily focused on selective inhibition of growth factors that promote scarring during wound healing process. Currently, only anti-VEGF agents have gained widespread acceptance to be translated into routine clinical practice. Robust evidence for other agents is still lacking and future confirmative studies are warranted. In this review, we explain the importance of wound healing process during filtering surgery, and describe the conventional as well as potential future adjuvants for filtration surgeries.

Sequential Therapy with Saratin, Bevacizumab and Ilomastat to Prolong Bleb Function following Glaucoma Filtration Surgery in a Rabbit Model

To determine if sequential treatment with Bevacizumab (Avastin), a monoclonal, VEGF antibody that blocks angiogenesis; Saratin, a 12 kD polypeptide with anti-inflammatory and anti-thrombotic properties; and Ilomastat, a matrix metalloproteinase (MMP) inhibitor, prolongs bleb life following glaucoma filtration surgery (GFS) in a rabbit model. Thirty-two New Zealand White rabbits (eight rabbits per group) underwent GFS in the left eye. Group 1 received a perioperative injection of both Saratin and Bevacizumab, and later, subconjuctival injections of Ilomastat on days 8 and 15. Group 2 received only Saratin perioperatively, and also received Ilomastat injections on days 8 and 15. Group 3, the negative control, received a single perioperative injection of Balanced Saline Solution (BSS) along with post-operative BSS injections on days 8 and 15. Group 4, the positive control, received topical treatment with Mitomycin-C (MMC) at the time of surgery with no further treatment. Blebs were evaluated by an observer masked to treatment every third day. Histology was obtained on two eyes in each group on post-op day twelve as well as all eyes following bleb failure. Eyes in group 1 had a mean bleb survival time of 29 ± 2.7 days, whereas those in group 2 that received the experimental treatment without Bevacizumab had a mean survival time of 25.5 ± 2.7 days. An ANOVA test showed that the Saratin/Ilomastat/Bevacizumab group demonstrated a significant prolongation of bleb survival compared to the BSS control—mean survival time of 19.7 ±2.7 days—(p = 0.0252) and was not significantly different from the MMC positive control group (p = 0.4238)—mean survival time of 32.5 ± 3.3. From tissue histology at day 12, the four different groups showed marked differences in the cellularity and capsule fibrosis. The MMC eyes showed minimal cellularity, were avascular and had minimal fibrous tissue. BSS group showed high cellularity, moderate to high fibrosis, and thicker and more defined capsules than either of the treatment groups and the positive control. Both the Saratin/Ilomastat/Bevacizumab and Saratin/Ilomastat only eyes showed moderate cellularity with minimal fibrosis, with less cellularity and fibrosis present in the triple treatment group. Sequential therapy with multiple agents, including Bevacizumab, prolonged bleb function following GFS in the rabbit model and were significantly better than the negative BSS control. The experimental group did not show the same surface tissue histological thinning and side effects associated with MMC treatment.

Paclitaxel-Releasing Thin Biodegradable Film for Prevention of Bleb Avascularity Without Compromising Filtration in Rabbits

PURPOSE

A honeycomb-patterned film (HPF) prevents bleb scarring and mitomycin C (MMC)-related bleb avascularity in a rabbit model of filtration surgery. In this study, we examined whether a HPF-releasing paclitaxel (PTX) can prevent bleb avascularity without compromising filtration.

METHODS

Filtration surgery was performed in one eye of rabbits. A 14-μm thick HPF made from poly(L-lactide-co-ε-caprolactone) was placed subconjunctivally over the filtration site with the honeycomb surface turned toward the subconjunctival Tenon tissue. The rabbits were divided into four groups (n = 5 each): 1, HPF with no drug; 2, HPF + PTX 50 μg; 3, HPF + 5 μg; 4, HPF + 0.5 μg. Intraocular pressure (IOP) measurements and bleb evaluations using ultrasound biomicroscopy were performed periodically for 4 weeks followed by histological examination. A longer follow-up study (12 weeks) was performed for group 4 (experiment 2; n = 8).

RESULTS

Among all groups at the 4-week follow up, two blebs failed in group 1. The postoperative IOP decrease was significantly greater in PTX-treated eyes than in group 1. The bleb avascular area persisted for 4 weeks in groups 2 and 3. However, no avascular area was observed in groups 1 and 4 at 4 weeks postoperatively. Histology showed minimal fibrosis at the filtration site in all the PTX groups. In experiment 2, some blebs became flatter starting at 10 weeks after surgery.

CONCLUSIONS

PTX released from HPF promoted bleb survival and IOP decrease. The lowest dose of PTX (0.5 μg) was effective at preventing bleb avascularity without compromising filtration.

Improving patient outcomes following glaucoma surgery: state of the art and future perspectives

Of all the treatments currently used to lower intraocular pressure in glaucoma patients, filtration surgery is known to be the most effective. However, in a significant percentage of cases, the constructed channel closes due to excessive scar formation, resulting in surgical failure. The process of postoperative wound healing is characterized by the coagulative and inflammatory phase, followed by the proliferative and repair phase, and finally the remodeling phase. Perioperative antimitotic agents, such as mitomycin C and 5-fluorouracil, are known to modulate the process of wound healing and to improve surgical outcome, but they carry a risk of vision-threatening complications. New alternative strategies to prevent filtration failure, such as inhibition of transforming growth factor-β, vascular endothelial growth factor, and placental growth factor, have shown promising results in the improvement of surgical success. However, it remains necessary to broaden the therapeutic approach by focusing on combined therapies and on extended drug delivery.

CSM enhances the filtration bleb survival in rabbit model of experimental glaucoma surgery

PURPOSE

The aim of this study is to investigate whether CS-g-MMCs conjugate (CSM) could be a new agent to prevent the post-operative fibrosis in a rabbit model of experimental glaucoma filtration surgery.

MATERIALS AND METHODS

In a randomized, controlled, masked-observer study, 40 New Zealand White rabbits underwent trabeculectomy in the right eyes and randomly received subconjunctival injection of phosphate buffered saline, chitosan (CS), CSM (100 µg/ml), CSM (200 µg/ml) or Mitomycin C (100 µg/ml). Bleb characteristics and anterior chamber depth were evaluated by slit-lamp examination. The animals were killed on day 14 and 28. Histopathology and immunohistochemistry were performed to determine the amount of the scarring and fibrosis. Ocular toxicity was assessed by histopathology and electron microscope.

RESULTS

We found that the five groups were similar with respect to intraocular pressure and anterior chamber depth. The medians for survival days were: 5.5, 8, 17.5, 28 and 16 in the PBS, CS, CSM100, CSM200 and MMC groups, respectively. Both the CSM200 and the MMC group showed a significantly larger bleb area than the CSM100, CS and the PBS group. Less scarring was seen on day 14 and 28 in CSM200 and MMC group than in the PBS, CS and CSM100 group by histology and immunohistochemistry assessment. No damages were found in the rabbit eyes in each group.

CONCLUSIONS

Subconjunctival injection of CSM postoperatively can improve the filtration bleb survival in the rabbit model. It can be a safe and effective antimetabolite in glaucoma surgery.

Wound modulation after filtration surgery

Filtration surgery is the standard invasive procedure for the management of intraocular pressure in advanced glaucoma. The key to a successful outcome is to modulate the normal wound healing cascade that leads to closure of the newly created aqueous outflow pathway. Antifibrotic agents such as mitomycin C and 5-fluorouracil have been increasingly used to modulate the wound healing process and increase surgical success. Although these agents have proven efficacy, they also increase the risk of complications. Efforts have centered on the identification of novel agents and techniques that can influence wound modulation without these complications. We detail new agents and methods under investigation to control wound healing after filtration surgery.