Potential toxicity of mitomycin C

Microfluidics-based PLGA nanoparticles of ratiometric multidrug: From encapsulation and release rates to cytotoxicity in human lens epithelial cells

Multidrug nanomedicine is an effective therapeutic approach for the treatment of chronic diseases and cancers. However, co-encapsulation and release of drug combination at a fixed ratio by nanoparticles, particularly for long acting ocular formulations, remains challenging. Herein, poly (lactic-co-glycolic acid) nanoparticles ratiometrically co-encapsulating hydrophilic dual drugs, mitomycin C and doxorubicin, was obtained (D/M PLGANPs) by combining microfluidics and the Design of Experiments approaches. The formulation variable of lactide-to-glycolide ratios (L/G 50:50, 75:15 and 85:15) was used to achieve fast, medium and slow drug release rates of D/M PLGANPs. The dissolution of D/M PLGANPs in simulated intraocular fluid exhibited sustained release of dual drugs at the fixed ratio over 7 days, and analysis using the Korsmeyer-Peppas model showed mechanism of drug release to be governed by diffusion. More importantly, in human lens epithelial cells, the drug release rate was negatively correlated with drug potency. The slower drug release from D/M PLGANPs led to lower efficacy of drug combination against pathogenesis of cellular migration and proliferation, the key pathogenic processes of capsular opacification after cataract surgery. Compared to fast (L/G 50:50) and medium (L/G 75:15) drug release rate of D/M PLGANPs, the slow release formulation (L/G 85:15) exhibited the least cellular uptake of the dual drugs and the ratio of drug combination was not maintained intracellularly. The present study implicates the potential of using microfluidics for synthesizing polymeric nanoparticles of ratiometric drug combination and highlights the drug release rate as the critical determinant of efficacy for the long-acting nanomedicine design.

[The "Three Cherries Technique" for glaucoma drainage devices]

Small sponges are used to apply antimetabolites in order to reduce the risk of fibrosis in filtering glaucoma surgery. Due to the posterior location of the filtering bleb in glaucoma drainage implants, there is a risk that the sponges can dislocate in this area and cannot be retrieved after the exposure time has elapsed. We use the "three cherries technique" to minimize the risk. The term "three cherries technique" was coined by us and has not been used before in the literature. The three sponges that are used for mitomycin C application are each connected by single button sutures with a 7.0 vicryl thread. At the end of the application time, the sponges can be quickly removed by pulling the thread.

Ologen implant versus mitomycin C in combined trabeculectomy and phacoemulsification

Purpose:

To comparatively evaluate in Indian eyes with coexisting cataract and primary open-angle glaucoma the outcome of mitomycin C (MMC) and Ologen implant as adjunctives in combined phacoemulsification with trabeculectomy.

Methods:

Eyes with primary open-angle glaucoma that underwent trabeculectomy and phacoemulsification with IOL implantation with either MMC application or Ologen implant between June 2019 and February 2020 were followed up for 12 months. Thirty-four eyes of 34 participants were studied. The primary outcome was intraocular pressure (IOP), and the secondary outcomes were the number of ocular hypotensives, best distance visual acuity (BDVA), and bleb morphology.

Results:

In 16 eyes treated with MMC and 18 eyes treated with Ologen implant, it was observed that the mean postoperative IOP (14.62 ± 2.89 mm Hg with MMC and 14.56 ± 4.14 mm Hg with Ologen implant) was not significantly different in both groups (P = 0.47). Number of ocular hypotensives and BDVA were also comparable between the two groups. However, bleb morphology was better with Ologen implantation. One eye in the MMC group developed hypotony which was conservatively managed

Conclusion:

MMC and Ologen are both effective adjunctives in combined phaco-trabeculectomy. However, the Ologen implant provides better bleb health and safety.

The corneal endothelium: clinical review of endothelial cell health and function

The endothelial cell is a critical structure within the cornea and is responsible for maintaining corneal clarity through its pump function. Endothelial cells are lost over time naturally but can be injured medically, surgically, or as a part of various dystrophies. Monitoring of endothelial cells can be performed clinically or more formally with specular microscopy. In cases of significant compromise, endothelial cells can be transplanted by various endothelial keratoplasty techniques. The future pipeline is bright for possible endothelial cell regeneration and rehabilitation. This article reviews these topics in depth to provide a comprehensive look at the structure and function of the endothelial cell, etiologies of endothelial cell damage, detailed review of iatrogenic causes of endothelial cell loss, and management strategies.

Neovascularization of angle following trabeculectomy augmented with mitomycin-C

The purpose of this study was to report a case of neovascularization of angle (NVA) following trabeculectomy with mitomycin-c (MMC) in a patient with primary open-angle glaucoma. This case report describes a 68-year-old woman who developed NVA and hyphema 2 weeks following an uneventful trabeculectomy with MMC. Trabeculectomy may be associated with serious and vision-threatening complications such as hypotony, suprachoroidal hemorrhage, endophthalmitis, and bleb-related complications. However, neovascularization of the anterior segment is not a commonly reported complication. Neovascularization of the anterior segment is a rare postoperative complication that usually occurs following strabismus or retinal detachment surgeries. The underlying ischemic trigger for anterior segment neovascularization is usually a posterior segment pathology or carotid artery insufficiency. These causative factors were excluded in our patient by lack of any abnormal finding in fundus fluorescein angiography and carotid Doppler ultrasonography. The patient received three subconjunctival bevacizumab injections (1.25 mg/0.1 ml) with frequent topical steroids and showed marked regression of the neovessels. The bleb was functional, and intraocular pressure remained at low teen afterward. NVA following trabeculectomy without any posterior segment or carotid pathologies responded well to subconjunctival bevacizumab and topical steroids.

A Review of Corneal Endotheliitis and Endotheliopathy: Differential Diagnosis, Evaluation, and Treatment

The corneal endothelium plays an integral role in regulating corneal hydration and clarity. Endotheliitis, defined as inflammation of the corneal endothelium, may disrupt endothelial function and cause subsequent visual changes. Corneal endotheliitis is characterized by corneal edema, the presence of keratic precipitates, anterior chamber inflammation, and occasionally limbal injection, neovascularization, and co-existing or superimposed uveitis. The disorder is classified into four subgroups: linear, sectoral, disciform, and diffuse. Its etiology is extensive and, although commonly viral, may be medication-related, procedural, fungal, zoological, environmental, or systemic. Not all cases of endothelial dysfunction leading to corneal edema are inflammatory in nature. Therefore, it is imperative that practitioners consider a broad differential for patients presenting with possible endotheliitis, as well as familiarize themselves with appropriate diagnostic and therapeutic modalities.

Periocular Amyloidosis Manifesting as Pseudopemphigoid Treated With Mitomycin C

PURPOSE

To describe an unusual cicatrizing manifestation of periocular amyloid and the utility of adjuvant antimetabolite therapy.

METHODS

This is a case report of a 49-year old woman with progressive bilateral upper lid ptosis, who was found to have bilateral inferior forniceal masses with thickening of the conjunctiva. Conjunctival and eyelid biopsies showed evidence of amyloid deposition. Systemic evaluation did not reveal any evidence of systemic amyloidosis. Her blepharoptosis continued to deteriorate, and she underwent bilateral sequential upper lid ptosis correction surgery and debulking procedures. Subsequently, she developed severe and progressive cicatricial conjunctivitis with extensive symblepharon formation in all 4 fornices and restriction of ocular motility, simulating a clinical picture of ocular mucous membrane pemphigoid.

RESULTS

She was treated surgically by division of symblepharon augmented with application of topical mitomycin C intraoperatively. This has been partially successful in freeing up differential movement between her lid and her eye and consequently improving eye protection and lubrication.

CONCLUSIONS

Pseudopemphigoid represents a rare manifestation of periocular amyloid. Risks and benefits of surgical procedures in this context need to be carefully weighed to minimize the risk of secondary complications. Topical mitomycin C may be considered as a relatively safe adjunct in managing the cicatricial component of the disease.

Effect of Mitomycin-C Augmented Trabeculectomy on Corneal Endothelial Cells

Purpose:

To evaluate the effect of mitomycin-C (MMC) on corneal endothelial cell density (ECD) and morphology after trabeculectomy.

Methods:

In this prospective comparative case series, 31 eyes with glaucoma underwent trabeculectomy with (group I), or without (group II) MMC. Specular microscopy was performed pre-, and postoperatively at months 1 and 3. Outcome measures included central corneal endothelial cell count and coefficient of variation (CV) of cell size.

Results:

Overall, mean preoperative ECD was 2,135.8 ± 397.6 cells/mm²; corresponding values at postoperative months 1 and 3 were 2,019.6 ± 447.2 cells/mm², and 1,991.4 ± 425.5 cells/mm², respectively (P > 0.05). Cell loss from month 1 to 3 was 1.3 % (P > 0.05). Subgroup analysis showed significant differences in endothelial cell loss at month 1 (P = 0.048) and month 3 (P = 0.014) between the MMC and control groups with no significant difference between the two groups in terms of cell loss from months 1 to 3, postoperatively (P = 0.968). Overall, mean pre-and postoperative CVs at months 1 and 3 were 27.38 ± 4.55, 27.96 ± 4.26, and 28.35 ± 4.47, respectively, with no significant difference between the two groups (P > 0.05). There was no correlation between preoperative central endothelial cell density (CECD) and MMC related cell loss.

Conclusion:

MMC application in trabeculectomy seems to cause a small but significant corneal endothelial loss. Most of the damage occurs intraoperatively, or in the early postoperative period, however progressive endothelial cell loss is not a major concern.

Prospective study comparing mitomycin C or bevacizumab as adjuvant in trabeculectomy revision by needling

PURPOSE

To compare the use of mitomycin C (MMC) or bevacizumab (BEV) as adjunctive in the needling revision of failed trabeculectomy blebs.

METHODS

Glaucoma patients with failed trabeculectomy were included. Cystic blebs were excluded. All procedures were performed by the same surgeon at the operating room under peribulbar blockade. Rate of success, intraocular pressure (IOP), and number of antiglaucoma drugs in use were compared before and after the procedures. The IOP was measured postoperatively at days 1, 30, 90, and 180. Absolute success was defined as IOP ≤18 mm Hg, without any complication or use of any antiglaucomatous drugs. Qualified success was the same criteria, but with the use of any antiglaucomatous drugs.

RESULTS

Twenty-nine eyes of 29 patients were included: 15 eyes with MMC and 14 eyes with BEV. There was no statistical difference in the IOP reduction between the groups (MMC 32.6 ± 16.1% vs BEV 30.1 ± 12.0%, p = 0.6). The BEV group showed similar reduction in the number of antiglaucoma drugs compared to the MMC group (p = 0.6). Absolute success was found in 28.5% of the BEV group and in 6.6% of patients with MMC. Qualified success was found in 64.3% and 73.4%, respectively, both limited to 180 days.

CONCLUSIONS

In this selected and limited group of patients, bevacizumab can be considered as an alternative to MMC in the needling revision of failed trabeculectomy. Studies with a larger number of patients and longer follow-up are needed to confirm the hypothesis suggested here.

Combined Baerveldt glaucoma drainage implant surgery and surgical bleb revision for preventing a postoperative hypertensive phase

BACKGROUND

In patients with severe optic nerve damage, it is crucial to prevent the hypertensive phase that can develop after Baerveldt glaucoma drainage implant (BGI) surgery. We describe the combination of BGI surgery with surgical bleb revision to prevent the postoperative hypertensive phase.

CASE REPORTS

We report two patients who underwent BGI surgery combined with surgical bleb revision. The combined surgery was performed in a 62-year-old man with open-angle glaucoma (patient 1) and a 37-year-old man with neovascular glaucoma (patient 2) at Asahikawa Medical University in 2013. Each patient had undergone a previous failed trabeculectomy and another trabeculectomy was expected to be unsuccessful. In patient 1, the early postoperative intraocular pressure (IOP) was well controlled due to a well-functioning bleb, despite development of a small amount of hyphema. In contrast, in patient 2 the postoperative IOP was higher with poor bleb formation; however, after bleb needling, the IOP was well controlled. Thus, the usual techniques used after trabeculectomy were also applicable in this combined surgery. For comparison, we also report the case of a 54-year-old woman with secondary glaucoma who underwent BGI surgery alone (patient 3). The postoperative IOP remained relatively high compared to patients 1 and 2.

CONCLUSION

Combining BGI surgery with surgical bleb revision might be effective to prevent the hypertensive phase that can occur after BGI surgery.

Local chemotherapeutic agents for the treatment of ocular malignancies

We critically analyze available peer-reviewed literature, including clinical trials and case reports, on local ocular cancer treatments. Recent innovations in many areas of ocular oncology have introduced promising new therapies, but, for the most part, the optimal treatment of ocular malignancies remains elusive.

Co-treatment of suberoylanilide hydroxamic acid and mitomycin-C induces the apoptosis of rabbit tenon's capsule fibroblast and improves the outcome of glaucoma filtration surgery

PURPOSE

This study was undertaken to develop a new treatment modality that would be able to minimize fibrosis and provide better outcome with glaucoma filtration surgery (GFS).

METHODS

We examined whether co-treatment with mitomycin-C (MMC) and histone deacetylase inhibitor (HDACi) suberoylanilide hydroxamic acid (SAHA) efficiently induces apoptosis on rabbit Tenon's capsule fibroblasts (TCF) in vitro. We further examined the effect of co-treatment with SAHA and MMC on the alteration of IOP and the bleb survival in rabbits following GFS.

RESULTS

Co-treatment of MMC and SAHA efficiently induces apoptosis in TCFs via the up-regulation of p53 and increased phosphorylation of p53 on serine 15 and 392. Also, co-treatment of SAHA and low-dose MMC decreases IOP, prolongs bleb survival, and induces apoptosis of cells under the bleb area following GFS.

CONCLUSION

This study shows that a co-treatment of SAHA and MMC could improve the outcome of GFS.

Intraoperative mitomycin and corneal endothelium after photorefractive keratectomy

PURPOSE

To determine whether there is an increased risk to the corneal endothelium when mitomycin C (MMC) is administered after photorefractive keratectomy (PRK).

DESIGN

Prospective, randomized, double-blind, placebo-controlled crossover trial.

METHODS

Corneal endothelium was analyzed preoperatively and postoperatively in 18 eyes of nine patients who were administered either MMC- or balanced salt solution (BSS)-supplemented PRK at Codet Aris Vision, Tijuana, Mexico. After laser ablation, one eye was randomly assigned to intraoperative topical MMC 0.02% treatment for 30 seconds, and the fellow eye (the control eye) was treated in a standard fashion with topical BSS. Preoperative pachymetry and endothelial cell count were performed and compared with postoperative measurements after one month and three months. Main outcome measure studied was endothelial cell loss.

RESULTS

There was no significant difference in the preoperative endothelial cell count between the 2 groups: MMC group 2835 +/- 395, control group 2779 +/- 492, P = .62. In the control group, at one month and three months the difference in the endothelial cell count was not statistically significant (P = .27, P = .14, respectively). However, in the MMC group the endothelial cell loss was statistically significant: at one month 14.7 +/- 5.1%, and at three months 18.2 +/- 9.0% (P = .0006, P = .002, respectively).

CONCLUSIONS

The use of intraoperative topical MMC 0.02% for 30 seconds after PRK may affect the endothelial cell count.

Characterization of CD95 ligand (CD95L)-induced apoptosis in human tenon fibroblasts

Toxic side effects of cytotoxic agents such as 5-fluorouracil or mitomycin-C in glaucomatous filtering procedures call for alternative approaches to control fibroblast proliferation. CD95L is a death ligand that triggers apoptosis in susceptible target cells. Apoptosis allows for the safe disposal of cells without damaging the surrounding tissue. The goal of this study was to characterize and to evaluate the CD95L induced cell death in cultured Tenon fibroblasts. Human Tenon fibroblasts were treated with different concentrations of CD95L. For comparison, murine NIH 3T3 fibroblasts were used. Immunohistochemistry and Western blot were used to investigate the CD95 and CD95L expression. Cytotoxicity was measured by crystal violet assay. Apoptosis was investigated using in situ DNA end labelling (TUNEL). DEVD-AMC caspase 3 like activity was measured and caspase 3 processing was studied by immunoblot and the use of the caspase inhibitor DEVD-CHO in cell culture assays. Tenon and NIH 3T3 fibroblasts express CD95 and CD95L. The authors found concentration dependent inhibition of proliferation after CD95L treatment. Tenon fibroblasts, but not NIH 3T3 fibroblasts, show synergy when combined with actinomycin D or cyclohexamide. CD95L treatment did not alter total protein or RNA synthesis. Cell death induced by CD95L was apoptotic and activated caspase 3, as TUNEL positive cells and the active fragment of caspase 3 were found. CD95L induced cell death could be inhibited by the caspase-inhibitor.Here, it is demonstrated that the CD95L induced cell death in cultured human Tenon fibroblasts is apoptotic and possibly mediated by the caspase 3 pathway. These results suggest that it may be possible to use CD95L in glaucomatous filtering procedures. In vivo studies are necessary for further evaluation.

Corneal endothelial damage after trabeculectomy with mitomycin C in two patients with glaucoma with cornea guttata

PURPOSE

To report two patients with glaucoma who exhibited severe damage to the corneal endothelium after a trabeculectomy with mitomycin C (MMC).

METHODS

This study includes clinical histories and specular microscopic pictures of the cases.

RESULTS

Both patients were middle-aged women, underwent trabeculectomy with MMC, had moderate to severe cornea guttata preoperatively, and developed a shallow to flat anterior chamber, classified as grade 2 according to Spaeth early in the postoperative period. Stromal opacity caused by corneal edema associated with severe Descemet's membrane folds appeared within 2 to 5 days in both cases. The density of the corneal endothelium was decreased on specular microscopic examination. The severe corneal endothelial damage seen after the trabeculectomy with MMC was likely owing to a combination of the preexisting cornea guttata, the flat anterior chamber, and possibly the administration of MMC.

CONCLUSION

Severe endothelial damage after trabeculectomy with MMC may occur in patients with glaucoma and associated cornea guttata. The use of tight sutures on the scleral flap or a modified operative method, nonpenetrating trabeculectomy, may be effective in preventing a shallow to flat anterior chamber postoperatively.

Toxic effects of mitomycin-C on cultured ciliary process cells and trabecular meshwork cells

Mitomycin-C has recently become an adjunct medication for inhibition of fibroblast proliferation in glaucoma filtering procedures. Prolonged postoperative ocular hypotony has been a frequent complication of trabeculectomy with mitomycin-C. In order to characterize the hypotony mechanism, we compared the toxic effects of mitomycin-C on cultured rabbit ciliary process cells and trabecular meshwork cells. The results indicate that mitomycin-C has a more marked effect on ciliary process cells on 3H-thymidine uptake than on trabecular meshwork cells at concentrations ranging from 10(-1) to 10(-5) mg/ml after 3-, 5- and 60-min treatment, respectively. The living cells after mitomycin-C treatment were estimated with MTT assay that was converted tetrazolium dye of living cells only into insoluble purple formazan crystals within mitochondria. In the presence of mitomycin-C for 3, 5, and 60 min, the cellular MTT values in ciliary process cells were more decreased than in trabecular meshwork cells. Depolarization of the trabecular meshwork cells with 50 mM KCl led to an increase in intracellular calcium concentration, whereas application of mitomycin-C at 10(-3) mg/ml resulted in decrease of KCl-induced intracellular calcium increase. Mitomycin-C (10(-3) mg/ml) decreased cAMP concentration in ciliary process cells following 3- and 5-min treatment; however, it did not significantly affect the cellular cAMP concentration after only a 1-min exposure. Mitomycin-induced marked ladder pattern of DNA fragmentation was observed in ciliary process tissues after treatment with 10(-1) mg/ml of mitomycin-C for 3 and 5 min. However, the DNA pattern in trabecular meshwork tissues was not obviously affected by mitomycin-C. These findings from our results indicate that mitomycin-induced ocular hypotony may result from damage to both ciliary process and trabecular meshwork tissues.

Toxic effects of mitomycin-C on cultured corneal keratocytes and endothelial cells

Improper use of mitomycin-C in ocular medication may result in damage to corneal cells. In this study, the toxic effects of mitomycin-C on cultured porcine keratocytes and endothelial cells were estimated by MTT, 3H-thymidine uptake and cellular counting assay methods. It was found that mitomycin-C caused a dose-dependent toxic effect to keratocytes and endothelial cells. Both cells were treated with mitomycin-C at the concentration ranging from 100, 10, 1, 0.1 to 0.01 microg/ml for 3 min, 5 min or 100 min. The 50% inhibitory dose (ID50) of mitomycin-C to keratocytes and endothelial cells as measured by MTT assay was 0.40, 0.18, 0.16 mg/ml and 0.27, 0.15, 0.14 mg/ml, respectively, after 3, 5 and 100 minutes drug treatment. The ID50 for keratocytes and endothelial cells as measured by 3H-thymidine uptake immediately, 1 day and 7 days after 100 minutes mitomycin-C treatment was 0.3, 0.0002, 143.2 microg/ml and 45.1, 101.1, 450.2 microg/ml, respectively. The ID50 for keratocytes and endothelial cells as measured by cellular counting 1 day and 7 days after mitomycin-C treatment was 232.5, 109.7 microg/ml and 239.9, 367.5 microg/ml, respectively. It is concluded that mitomycin-C is more toxic to cellular proliferation in cultured corneal keratocytes than in endothelial cells.

Subconjunctival mitomycin C for the treatment of ocular cicatricial pemphigoid

PURPOSE

The authors performed a prospective evaluation of the efficacy of treating ocular cicatricial pemphigoid (OCP) with subconjunctival mitomycin C.

DESIGN

Unmasked, prospective, internally controlled case series.

METHODS

Patients were eligible for treatment with subconjunctival mitomycin C under three criteria: (1) significant complications of systemic immunosuppressant therapy; (2) markedly asymmetric conjunctival disease; and (3) end-stage OCP. All patients received monocular subconjunctival injections of 0.25 ml of 0.2 mg/ml mitomycin C to both the superior and inferior bulbar conjunctivae in the eye with the more severe disease.

RESULTS

Nine eyes of nine patients (mean age, 74 years) were treated with subconjunctival mitomycin C to the more-involved eye and were followed for a mean of 23.5 months (range, 12-40 months). Eight of nine patients showed quiescence of their OCP in the treated eye based on serial evaluation of conjunctival cicatrization and grading of conjunctival erythema. Five of the nine untreated eyes showed progression of the conjunctival disease. One patient required concomitant systemic immunosuppressive therapy after subconjunctival mitomycin C. Two patients underwent successful visual rehabilitative surgery in the mitomycin C-treated eye.

CONCLUSION

The use of subconjunctival mitomycin C may be effective in preventing progression of conjunctival cicatrization and erythema in patients with OCP. No complications of mitomycin C treatment were noted. Long-term follow-up and further investigation into the efficacy of subconjunctival mitomycin C in the management of OCP is warranted.

Topical mitomycin C chemotherapy for conjunctival melanoma and PAM with atypia

AIM

To evaluate topical mitomycin C (MMC) chemotherapy in the treatment of conjunctival melanoma and primary acquired melanosis with atypia.

METHODS

In a phase I clinical trial, 10 patients with conjunctival melanoma and/or primary acquired melanosis with atypia were treated with topical MMC 0.04% four times daily. Four patients were given MMC for 28 days as a primary treatment. Six patients were treated with MMC for 7 days after excision and cryotherapy in an effort to improve local control. In this series, 10 patients have been followed for an average of 29 months.

RESULTS

All patients were noted to develop transient keratoconjunctivitis during treatment. One patient also developed a transient corneal epithelial defect. Decreased conjunctival pigmentation was noted in the four patients where topical chemotherapy was used as a primary treatment. Nodular tumours were resistant to topical MMC chemotherapy. Of the six patients treated within 2 weeks after primary excision and cryotherapy, there has been no tumour recurrence or symblepharon formation. Nine of the 10 study patients have maintained within one line of their pretreatment visual acuity. No retinal or optic nerve toxicity was noted.

CONCLUSION

Since no complications which might preclude further investigation of topical MMC chemotherapy occurred, it was concluded that topical MMC chemotherapy was tolerated as a treatment for conjunctival melanoma and primary acquired melanosis with atypia.

Mitomycin C reduces scar formation after excimer laser (193 nm) photorefractive keratectomy in rabbits

Sixteen eyes of eight rabbits were randomised to either mitomycin C or Balanced Salt Solution (BSS) application after photorefractive keratectomy (PRK). Regular examinations of wound healing and haze were performed with the slit lamp. The animals were killed between 1 and 26 weeks after treatment, and the corneas examined by light and electron microscopy. While the grade of haze showed no relevant differences between the two groups, scar tissue was found histologically in the mitomycin group in only 1 of 8 corneas compared with 5 of 8 in the BSS group. A marked reduction in keratocytes in all mitomycin-treated corneas and a normal density of keratocytes in the BSS group was observed. Mitomycin reduced the number of keratocytes in the treated corneas, leading to less scar formation but not to a reduction in haze. Since no morphological correlate has been found, haze remains unexplained in the mitomycin-treated corneas.

Mitomycin against posterior capsular opacification: an experimental study in rabbits

AIMS/BACKGROUND

Posterior capsular opacification is the most common postoperative complication of extracapsular cataract surgery. The purpose of this study was to attempt to inhibit this secondary cataract formation by using mitomycin (an antimitotic drug).

METHODS

A solution containing mitomycin was used to perform hydrodissection (with a 5 minute pause) during extracapsular lens extraction in rabbits. This way of administration was chosen to reduce as much as possible drug diffusion into the anterior chamber. Heparin was added to the irrigating solution to avoid fibrin formation. Its ability to prevent posterior cataract opacification was also evaluated at the end of the study. The animals were sacrificed 4 or 6 months after surgery. Grading concerning two aspects of secondary cataract (proliferation and fibrosis) was obtained on gross examination. Histological analysis was subsequently performed.

RESULTS

This study demonstrated that mitomycin has a significant inhibitory effect on secondary cataract formation (proliferation as well as fibrosis) in rabbits whereas heparin does not seem to have the same effectiveness.

CONCLUSION

This work is a preliminary study concerning the use of mitomycin for prevention of posterior capsular opacification. It has proved its effectiveness in rabbits but more in depth studies are still necessary before its application in humans.

Effects of mitomycin C on the rat retina

To evaluate the retinal toxicity of mitomycin C injection in the rat eye, we conducted an electroretinographic study and a histopathologic study. Three different concentrations of mitomycin C (0.2, 0.3 and 0.4 mg/ml) were injected into either the vitreous cavity or the anterior chamber of the experimental eyes. A full-field electroretinogram was recorded before injection and 2, 4 and 7 days after injection. The retinas of all eyes were examined by light and electron microscopy. We found no evidence of electroretinographic and histologic changes 2 and 7 days after injection of 0.4 mg/ml of mitomycin C into the anterior chamber. However, profound electroretinographic changes did follow injection of the drug into the vitreous. These were absent with the 0.2-mg/ml solution at 7 days, mild with the 0.3-mg/ml solution at 7 days and profound with the 0.4-mg/ml solution as early as 2 days. Intravitreal injection of 0.4 mg/ml, however, showed selective degeneration of Müller cell process at day 2, retinal pigment epithelium changes at day 4 and irregular arrangement of the outer nuclear layer and photoreceptors at day 7. Intravitreal injection of mitomycin C in a concentration comparable to the one used clinically could cause retinal disorders, both functionally and histologically.

Scleral free auto-implant plug with mitomycin as limitation of trepanosclerectomy flow in glaucoma filtering surgery

The purpose of this study is to evaluate the effect of trephination with free scleral auto-implant plug exposed to Mitomycin-C out of the eye, in surgical treatment of primary open-angle glaucoma (POAG), in comparison with efficacy of trabeculectomy with MMC (32 eyes with POAG of patients, younger than 55 years-group 1). Trephination with scleral auto-implant plug with MMC was done on 35 eyes of patients, younger than 55 years, with POAG (group 2). The postoperative follow-up was 28.52 +/- 8.78 months.

SURGICAL PROCEDURE

A limbal 1.0 mm diameter trephination is made beneath the limbus-based conjunctival flap, a small iridectomy is performed. From the external layers of the trephine button one third of the corneoscleral thickness, in the form of a thin disc, is excised. The scleral disc, a free auto-implant, is dipped into liquid containing MMC with concentration 0.2 mg/ml for 5 minutes, outside the eye. Afterwards the scleral disc soaked with MMC is carefully irrigated with 150 ml of BSS and placed in the external part of the trephine fistula in primary position and stabilized with two interrupted 10-0 nylon sutures. The operation is ended as a typical trabeculectomy. The final success rate in terms of IOP (IOP < 14 mmHg) was 100%, without or with antiglaucoma medication, in both groups, but the number of postoperative complications was significantly lower in group 2. Trephination with free scleral auto-implant plug soaked with MMC may represent a viable alternative to trabeculectomy with MMC; the scleral plug may be taken out of the eye and exposed to antimetabolite outside the eye to minimize toxicity.

A fluorophotometric study of corneal endothelium after trabeculectomy using different concentrations of Mitomycin-C

The aim of the study was to determine the corneal endothelial permeability coefficient (Pac) in subjects after trabeculectomies using different concentrations of Mitomycin-C (MMC). MMC, a highly toxic drug, is not without drawbacks and complications such as corneal damage. To ascertain a possible relationship between a level of endothelial permeability (Pac) and concentrations of MMC used, we performed, in a prospective study, trabeculectomies in cases of primary open-angle glaucoma (POAG), younger than 50 years, with either concentrations of 0.5 mg/ml of MMC (group 1: 11 eyes) or 0.2 mg/ml of MMC (group 2: 10 eyes). Group 3 consisted of 8 patients after a typical trabeculectomy without MMC and served as a control group (8 eyes). In all groups, before surgery and again 1, 3 and 6 months after surgery, corneal endothelial permeability (Pac) was determined by using anterior segment fluorophotometry (Fluorotron Master). The thickness of the cornea (CT) was measured with a DGH Technology ultrasonic pachymeter. One month after surgery the mean values of Pac were statistically significantly higher in groups 1 and 2 (group 1: 4.78 x 10(-4) cm/min, group 2: 4.67 x 10(-4) cm/min) in comparison with the control group (group 3: 3.37 x 10(-4) cm/min), but the differences between groups 1 and 2 were not statistically significant (p = 0.05). Six months after operation the mean values of Pac in all groups were normalized. In eyes that underwent trabeculectomy with MMC, higher concentrations of MMC were likely to have a transient adverse effect on corneal endothelial permeability. In light of the resulting toxic intraocular effect of MMC, the damage in the function of the corneal endothelial barrier is greater with greater concentrations of MMC.

Success rate and complications of intraoperative 0.2 mg/ml mitomycin C in trabeculectomy surgery

Adjunctive chemotherapy with Mitomycin C (MMC) has been used in an attempt to modulate the wound healing response in glaucoma filtration surgery. A consecutive series of 20 eyes from 18 patients undergoing trabeculectomy with MMC intraoperatively was studied. Sixteen cases were considered high risk regarding surgical success and 4 patients with low tension glaucoma (LTG) required lower intraocular pressure (IOP) to prevent further visual field loss. Surgical technique involved the use of a limbal-based conjunctival flap and MMC 0.2 mg/ml applied via a sponge (under the scleral flap) to both scleral and conjunctival surfaces for 5 minutes. The mean follow-up period was 12.7 months (range 3-24). There were 17 successful eyes. Of these, 14 are high pressure glaucoma eyes with a mean pre-operative IOP of 30.9 +/- 10.9 mmHg and a mean postoperative IOP of 15.3 +/- 5.2 mmHg (p = 0.001). The remainder of the successful cases include 4 patients with LTG with a mean preoperative IOP of 17.8 +/- 0.5 mmHg and a mean postoperative IOP of 6.8 +/- 0.7 mmHg (p = 0.001). Serious complications included chronic repeated bleb leaks (n = 2) and scleral necrosis (n = 2). There was one case of hypotonous maculopathy. These results are comparable with those of other studies. Despite a relatively low dose of MMC serious side-effects were encountered. Management of these complications is described, and how these effects may be prevented by altering scleral exposure to MMC. In addition a possible explanation for the serious side-effects of MMC-treated trabeculectomies is presented.

Results of treatment with topical mitomycin C 0.02% following excision of primary pterygium

AIMS

The effectiveness of instillation of mitomycin C eyedrops on the recurrence rate of pterygium was assessed in patients undergoing primary pterygium surgery. Any side effects were also noted.

METHODS

Primary pterygia in 38 consecutive patients were surgically excised during July to December 1992. After surgery, mitomycin C 0.02% eyedrops twice daily for 5 days as well as dexamethasone 0.1% four times tapered for the next 6 weeks were instilled. Postoperative follow up ranged from 6 to 11 months.

RESULTS

In one patient the pterygium recurred after 3 months (recurrence rate 2.6%). The side effects encountered were: avascularised sclera in 13 cases between 1-10 months postoperatively; ocular discomfort and lacrimation in five cases; superficial punctate keratitis during the first month in three cases; pyogenic granuloma in two cases. In one patient steroid induced increased intraocular pressure was found 4 weeks after surgery. The adverse side effects were all mild, self limiting, and easily treated.

CONCLUSION

This study suggests that postoperative instillation of mitomycin C 0.02% eyedrops twice daily for 5 days following excision of primary pterygium is an effective and safe treatment to obviate pterygium recurrence.

One-year follow-up results of combined mitomycin C trabeculectomy and extracapsular cataract extraction

PURPOSE

When patients with glaucoma require cataract surgery, combined procedures offer important advantages over cataract surgery alone. Because mitomycin C has improved the success rate of a trabeculectomy in patients at high risk for filtration failure, the authors investigated whether it also would increase the survival rate of functioning filters in combined procedures.

METHODS

Patients with both cataract and glaucoma underwent combined mitomycin C trabeculectomy, extracapsular cataract extraction, and intraocular lens implantation. Mitomycin C (0.5 mg/ml) was applied topically to the trabeculectomy site for 5 minutes before the cataract extraction. Intraocular pressure (IOP), visual acuity, and astigmatism were measured preoperatively and postoperatively. One-year results are available for 74 patients.

RESULTS

At 1 year, 54 (73%) of 74 patients had IOPs of 15 mmHg or less without glaucoma medications. Visual acuity was 20/40 or better in 44 (60%) of 74 patients. Ten (15%) patients had a shift of more than 2 diopters of astigmatism against the rule compared with preoperative values. No notable corneal epithelial toxicity was present. Postoperative symptomatic hypotony with the wound construction occurred in 3 (4%) of 74 patients, with 1 patient requiring surgical revision. Other potential complications of mitomycin C include endothelial toxicity (1 patient had decreased vision due to endothelial folds) and wound stability (1 patient had wound rupture after direct ocular trauma).

CONCLUSION

The 1-year survival rate of a functioning trabeculectomy using mitomycin C in combined glaucoma and cataract surgery is encouraging. The longer-term benefits and possible adverse effects of mitomycin C in combined procedures are unknown and continue to be investigated.

Intraocular toxicity to ciliary nerves after extraocular application of mitomycin C in rabbits

Prolonged postoperative hypotony is a severe complication frequently associated with trabeculectomies performed with a single perioperative application of Mitomycin C. We performed an animal experiment using 8 pigmented rabbits applying different concentrations of Mitomycin C, ranging from 0.05 to 1.0 mg/ml, under the conjunctiva on the intact sclera for 5 minutes. The eyes were examined by light and electron microscopy after 4 weeks. The nerves within the ciliary body in areas adjacent to the region of treatment showed toxic effects related to the concentrations of Mitomycin C applied. In cases where small concentrations were used, only the unmyelinated nerves were damaged with the myelinated remaining intact. In eyes treated with high concentrations, both groups of nerves exhibited severe signs of destruction. This effect is likely to compromise the production of aqueous humor in rabbits, and possibly also in humans.

The effect of brief intrascleral or episcleral application of mitomycin C on the ciliary epithelium and pressure in the rabbit eye

Ten albino rabbits underwent bilateral Cairns' trabeculectomy (group 1). A sponge soaked with 0.5 mg/ml mitomycin C solution was applied under the scleral flap for 5 min followed by irrigation with 20 ml 0.9% sodium chloride solution in the left eyes. In the right eyes a sponge soaked with 0.9% sodium chloride solutions was applied. In 9 albino rabbits a 3 x 2 mm episcleral area at 12 o'clock position was exposed to 0.5 mg/ml mitomycin C solution on one side and to 0.9% sodium chloride solution in the contralateral eye (group 2). Five, 10 and 30 days (group 1 and 2) and 3 months (group 1) following surgery specimens of the ciliary body adjacent, beside and opposite to the site of the operation were excised and studied with light and electron microscopy. No stromal or epithelial morphological changes of toxic origin have been revealed in the ciliary processes, even in specimens adjacent to the surgical area. In 5 albino rabbits (group 3) intraocular pressure was recorded before surgery and 5, 10 and 30 days after unilateral, episcleral mitomycin C application described in group 2. No significant changes or interocular difference has been recorded. The results suggest that long-term postoperative hypotony following trabeculectomy with mitomycin C is not caused by reduced aqueous humour secretion of toxic origin.