Cyclosporin as an adjunct to glaucoma filtration surgery

PLA-PEG Implant as a Drug Delivery System in Glaucoma Surgery: Experimental Study

Excessive postoperative scarring halts the effectiveness of glaucoma surgery and still remains a challenging problem. The purpose of this study was to develop a PLA-PEG-based drug delivery system with cyclosporine A or everolimus for wound healing modulation. Methods: PLA-PEG implants saturation with cyclosporine A or everolimus as well as their further in vitro release were analyzed. Anti-proliferative activity and cytotoxicity of the immunosuppressants were studied in vitro using human Tenon’s fibroblasts. Thirty-six rabbits underwent glaucoma filtration surgery with the application of sham implants or samples saturated with cyclosporine A or everolimus. The follow-up period was six months. A morphological study of the surgery area was also performed at seven days, one, and six months post-op. Results: PLA-PEG implants revealed a satisfactory ability to cumulate either cyclosporine A or everolimus. The most continuous period of cyclosporine A and everolimus desorption was 7 and 13 days, respectively. Immunosuppressants demonstrated marked anti-proliferative effect regarding human Tenon’s fibroblasts without signs of cytotoxicity at concentrations provided by the implants. Application of PLA-PEG implants saturated with immunosuppressants improved in vivo glaucoma surgery outcomes. Conclusions: Prolonged delivery of either cyclosporine A or everolimus by means of PLA-PEG implants represents a promising strategy of wound healing modulation in glaucoma filtration surgery.

[Pharmacological modulation of wound healing in glaucoma surgery]

Despite the well-known effectiveness of pharmacological glaucoma therapy, surgical approach remains one of the main treatment options for some forms and stages of the disease. The long-term success of glaucoma surgery depends on the intensity of local wound healing processes at the surgical site. The most common way to influence healing processes in surgical treatment of glaucoma is the use of antimetabolites. However, given the high risk of serious complications associated with their use, the search for new drugs devoid of these disadvantages continues. The aim of this review is to describe the efficacy and safety of both currently used and upcoming pharmacological ways to influence the wound healing process after glaucoma surgery in order to improve the stability of hypotensive effect.

The efficacy of preoperative posterior subtenon injection of triamcinolone acetonide in noninfectious uveitic patients with secondary glaucoma undergoing trabeculectomy

Objective

The aim of this study was to evaluate the efficacy and safety of preoperative posterior subtenon injection of triamcinolone acetonide (PSTA) in noninfectious uveitic patients with secondary glaucoma undergoing primary trabeculectomy with mitomycin C.

Design

This was a retrospective study.

Patients and methods

We reviewed the medical records of 10 noninfectious uveitic patients, who had received a single preoperative PSTA 40 mg/1 mL, with secondary glaucoma undergoing primary trabeculectomy with mitomycin C. We collected data before and after surgery on intraocular pressure (IOP), anterior chamber (AC) cells, best-corrected visual acuity (BCVA), morphologic characteristics of the filtering bleb and complications.

Results

The mean time between injection and surgery was 7.8±3.88 days. Postoperative IOP level was significantly lower than preoperative level (31.3±11.44 mmHg) at all visits (P<0.02). Antiglaucoma medications were decreased from preoperative (4.9±0.88) to 12-month postoperative (0.8±1.31; P-value <0.001) and also discontinued in seven eyes (70%). About 12 months after surgery, eight eyes (80%) with qualified success and two eyes (20%) with failed treatment were recorded. AC cells and BCVA did not differ significantly from baseline; however, all inflammations were controlled successfully. Most desirable bleb morphology was shown at 12 months as well. Complications were blepharoptosis and hypotony maculopathy in two eyes (20%).

Conclusion

A preoperative PSTA may be an effective and safe option in controlling intraocular inflammation and maintaining bleb function after trabeculectomy in noninfectious uveitic patients with secondary glaucoma during a 12-month period.

Evaluation of an injectable thermosensitive hydrogel as drug delivery implant for ocular glaucoma surgery

In this study, a biodegradable thermo-sensitive hydrogel from poly(trimethylene carbonate)₁₅-F127-poly(trimethylene carbonate)₁₅ (PTMC₁₅-F127-PTMC₁₅) was designed and evaluated as an injectable implant during ocular glaucoma filtration surgery in vivo and in vitro. Mitomycin C (MMC) was loaded into this hydrogel for controlled released to prolong the efficacy and to reduce the long-term toxicity. The properties of the hydrogel were confirmed using ¹H NMR and gel permeation chromatography (GPC). Compared to the Pluronic F127 hydrogel, the PTMC₁₅-F127-PTMC₁₅ hydrogel showed a good solution-gel transition temperature at 37°C, a lower work concentration of 5% w/v and a longer mass loss time of more than 2 weeks. The in vitro study showed that the drug could be released from PTMC₁₅-F127-PTMC₁₅ (5% w/v) hydrogel for up to 16 days with only 57% of drug released in the first day. Moreover, the cell toxicity, which was tested via LDH and ANNEXIN V/PI, decreased within 72 h in human tenon's fibroblast cells (HTFs). The in vivo behavior in a rabbit glaucoma filtration surgery model indicated that this hydrogel loaded with 0.1 mg/ml MMC led to a better functional bleb with a prolonged mean bleb survival time (25.5±2.9 days). The scar tissue formation, new collagen deposition and myofibroblast generation appeared to be reduced upon histological and immunohistochemistry examinations, with no obvious side effects and inflammatory reactions. The in vitro and in vivo results demonstrated that this novel hydrogel is a safe and effective drug delivery candidate in ocular glaucoma surgery.

P-glycoprotein Blockers Augment the Effect of Mitomycin C on Human Tenon's Fibroblasts

PURPOSE

Mitomycin C (MMC), which induces apoptosis in human Tenon's fibroblasts (HTF), is frequently used to retard wound healing after glaucoma surgery. The aim of this in vitro study was to examine whether adjunctive Verapamil and Cyclosporine could augment the cytotoxic effect of MMC on HTF.

METHODS

Fibroblast cell lines were established by explant culture from human tissue biopsy samples obtained during trabeculectomy procedures. Cells were exposed to MMC at varying concentrations (0.01-0.4 mg/ml) for 3 minutes, prior to washing in the presence or absence of the following drugs: Staurosporine (0.003mg/ml), Verapamil (2.5-0.25 mg/ml), or Cyclosporine (50-0.5 mg/ml). Following exposure, cells were cultured for 6 hours and surviving cells quantitated by haemocytometer counts.

RESULTS

Both Verapamil and Staurosporine exhibited mild toxic effects on their own, but greatly enhanced the apoptotic effect of MMC. Staurosporine is too toxic to be considered clinically, so its augmentive effect on the activity of MMC was not studied further here. Doses as low as 0.25 mg/ml of Verapamil continued to show significant augmentation of the apoptotic effect of MMC Cyclosporine at a clinically used concentration (5 mg/ml) exhibited modest augmentation of the effect of MMC.

CONCLUSIONS

Verapamil and Cyclosporine in clinically acceptable concentrations potentiate the effect of MMC and may obviate the need for high dose antimetabolites in trabeculectomy; however, further preclinical study is required.

TRANSLATIONAL RELEVANCE

Adjunctive Verapamil or Cyclosporine may allow lower dose MMC to be used in glaucoma filtration surgery while maintaining the same antifibrotic effects.

Effects of postoperative cyclosporine ophthalmic emulsion 0.05% (Restasis) following glaucoma surgery

PURPOSE

To determine if postoperative topical cyclosporine 0.05% has any beneficial effect following trabeculectomy.

METHODS

This was an interventional, randomized, prospective, double-masked clinical trial of 44 consecutive patients with uncontrolled glaucoma requiring filtration surgery. Ocular surface disease index questionnaire and comprehensive ocular exam, including Schirmer's tear test 1, were performed. Patients underwent routine trabeculectomy, with or without phacoemulsification. The study group (n = 22) received cyclosporine 0.05%, and the control group (n = 22) received artificial tears. Patients were evaluated at 1 and 6 months post surgery. Outcome measures were intraocular pressure, success rate, bleb appearance, ocular surface disease index, Schirmer's tear test 1 and conjunctival inflammation.

RESULTS

Thirty-nine patients completed the study (19 in the study group, 20 in the control group). The mean baseline intraocular pressure was 23.8 +/- 12.6 mmHg in the study group and 25.9 +/- 10.6 mmHg in the control group (P = 0.513). Mean intraocular pressure at postoperative month 6 was 14.88 +/- 6.2 and 14.62 +/- 5.46 mmHg in the study group and control group, respectively (P = 0.837). There was no statistically significant difference in the mean values of Schirmer's tear test 1 and the level of conjunctival hyperaemia between the two groups at baseline, months 1 and 6 post surgery. The treatment group had a statistically significant decrease in ocular surface disease index score at 6 months (P = 0.003), indicating less severity of dry eye symptoms and significant reduction in ocular pain.

CONCLUSIONS

Topical cyclosporine 0.05% had no effect on postoperative bleb function and intraocular pressure following trabeculectomy, but improved subjective ocular surface symptoms in these patients.

Modulation of wound healing during and after glaucoma surgery

Following all types of glaucoma filtration surgery (GFS), scarring still poses the major threat to long-term success. The healing and scarring determine the percentage of patients achieving low final intraocular pressures (IOPs) that are associated with virtually no glaucoma progression. The use of antifibrotic agents to inhibit scarring of trabeculectomy blebs is now a well-established clinical practice. Unfortunately, severe complications such as leakage, infection, hypotony, and endophthalmitis with complete loss of vision may occur. In addition, surgery still fails in some individuals despite maximal doses of current antifibrotics. Better therapeutic agents are needed. Many promising new agents are being evaluated clinically and in vitro. In this chapter, we will discuss our current understanding of the wound healing process after glaucoma surgery and promising new treatment modalities.