Use of bioerodible polymers impregnated with mitomycin in glaucoma filtration surgery in rabbits

Biosafety, Functionalities, and Applications of Biomedical Micro/nanomotors

Due to their unique ability to actively move, micro/nanomotors offer the possibility of breaking through the limitations of traditional passive drug delivery systems for the treatment of many diseases, and have attracted the increasing attention of researchers. However, at present, the realization of many advantages of micro/nanomotors in disease treatment in vivo is still in its infancy, because of the complexity and particularity of diseases in different parts of human body. In this Minireview, we first focus on the biosafety and functionality of micro/nanomotors as a biomedical treatment system. Then, we address the treatment difficulties of various diseases in vivo (such as ophthalmic disease, orthopedic disease, gastrointestinal disease, cardiovascular disease, and cancer), and then review the research progress of biomedical micro/nanomotors in the past 20 years, Finally, we propose the challenges in this field and possible future development directions.

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.

A review of implantable intravitreal drug delivery technologies for the treatment of posterior segment eye diseases

Intravitreal implantable device technology utilizes engineered materials or devices that could revolutionize the treatment of posterior segment eye diseases by affording localized drug delivery, responding to and interacting with target sites to induce physiological responses while minimizing side-effects. Conventional ophthalmic drug delivery systems such as topical eye-drops, systemic drug administration or direct intravitreal injections do not provide adequate therapeutic drug concentrations that are essential for efficient recovery in posterior segment eye disease, due to limitations posed by the restrictive blood-ocular barriers. This review focuses on various aspects of intravitreal drug delivery such as the impediment of the blood-ocular barriers, the potential sites or intraocular drug delivery device implantation, the various approaches employed for ophthalmic drug delivery and includes a concise critical incursion into specialized intravitreal implantable technologies for the treatment of anterior and posterior segment eye disease. In addition, pertinent future challenges and opportunities in the development of intravitreal implantable devices is discussed and explores their application in clinical ophthalmic science to develop innovative therapeutic modalities for the treatment of various posterior segment eye diseases. The inherent structural and functional properties, the potential for providing rate-modulated drug delivery to the posterior segment of the eye and specific development issues relating to various intravitreal implantable drug delivery devices are also expressed in this review.

Intraocular implants for extended drug delivery: therapeutic applications

An overview of ocular implants with therapeutic application potentials is provided. Various types of implants can be used as slow release devices delivering locally the needed drug for an extended period of time. Thus, multiple periocular or intraocular injections of the drug can be circumvented and secondary complications minimized. The various compositions of polymers fulfilling specific delivery goals are described. Several of these implants are undergoing clinical trials while a few are already commercialized. Despite the paramount progress in design, safety and efficacy, the place of these implants in our clinical therapeutic arsenal remains limited. Miniaturization of the implants allowing for their direct injection without the need for a complicated surgery is a necessary development avenue. Particulate systems which can be engineered to target specifically certain cells or tissues are another promising alternative. For ocular diseases affecting the choroid and outer retina, transscleral or intrasscleral implants are gaining momentum.

Formulation factors for preparing ocular biodegradable delivery system of 5-fluorouracil microparticles

Microparticles containing 5-fluorouracil (5-FU) were prepared using poly(DL-lactide-co-glycolide) with an oil-in-oil emulsion/solvent extraction technique. Particle characteristics including size distribution, 5-FU loading efficiencies, in vitro release and degradation were investigated. The dispersed phase was composed of PLG dissolved in dichloromethane, and the continuous phase was paraffin oil containing lecithin. 5-FU was successfully entrapped in the microparticles with trapping efficiencies up to 76%, loading level 10% w/v, and particle size 3 microm. Release profiles of 5-FU loaded microparticles were determined to follow a first-order-time relationship. An optimized preparation of 5-FU microparticles was achieved and was capable of controlling the release of 5-FU over 21 days with an in vitro delivery rate of 0.4 microg 5-FU/mg particles/day in the study. Preliminary animal studies indicated that the 5-FU loaded microparticles as an ocular delivery system showed no ocular toxicity and no significant inflammatory response in rabbits for 2 months. The 5-FU loaded microparticles approach, with PLG, might be a potential for the application of long-term delivery of hydrophilic drugs in the eye.

Mitomycin C Reduces Haze Formation in Rabbits After Excimer Laser Photorefractive Keratectomy

PURPOSE

To investigate the effects of mitomycin C on haze after photorefractive keratectomy (PRK).

METHODS

Twenty of 24 rabbits underwent bilateral 193-nm excimer laser PRK to correct -10.00 D of myopia; the remaining four rabbits were not operated (no PRK group). The right eyes of the 20 rabbits were treated with 0.02% mitomycin C during surgery (PRK+MMC group) and the left eyes did not receive 0.02% mitomycin C (PRK alone group). Clinical and histopathologic examinations were performed.

RESULTS

The most severe haze in the PRK alone group after PRK reached grade 3; the PRK+MMC group did not exceed grade 1 haze. Statistically significant differences were found between the PRK+MMC and PRK alone groups from week 2 to week 26 after treatment (P<.01). Epithelial thickening appeared for 26 weeks in both PRK groups; no statistically significant differences were found between the two PRK groups (P>.05). A marked reduction of keratocytes in the anterior stroma of the PRK+MMC group was observed. At week 1, 2, and 4 after PRK, keratocytes of the PRK+MMC group were only 3.1+/-2.6, 6.8+/-4.7, and 12.4+/-5.7 keratocytes x 10(4)/microm2, respectively, while those of the PRK alone group were 41.2+/-80, 42.3+/-7.8, and 40.0+/-3.3 keratocytes x 10(4)/microm2, respectively. There were statistically significant differences between the two groups (P<.001).

CONCLUSION

A single intraoperative application of topical mitomycin C during PRK in rabbits reduced corneal haze by inhibiting the proliferation of keratocytes.

Beta radiation as an adjunct to low-risk trabeculectomy

PURPOSE

To assess a single dose of intraoperative beta radiation used to enhance the success rate of trabeculectomy in a population of low-risk glaucoma patients in whom antimetabolites might not be indicated.

METHODS

A prospective randomized trial of 65 eyes was designed, with 31 eyes receiving 750 rads of intraoperative beta radiation (group 1), and 34 eyes receiving no supplementation (group 2).

RESULTS

Mean follow-up time was 24 months. Mean postoperative intraocular pressure was 12.2 mmHg in group 1, and 13.7 mmHg in group 2 (P = 0.16). Mean decrease in intraocular pressure was 10.3 mmHg in group 1, and 9.3 mmHg in group 2 (P = 0.49). The two groups were not significantly different in terms of surgical complications.

CONCLUSION

For this population of low-risk patients, there was no significant difference in outcome after applications of a single intraoperative dose of beta radiation.

Intrascleral concentration vs depth profile of mitomycin-C after episcleral application: impact of irrigation

Mitomycin-C has been reported to cause toxic effects on the ciliary body after episcleral application during glaucoma surgery. We investigated the intrascleral diffusion of mitomycin-C in an experimental model. The episcleral sides of scleral quadrants of 14 human donor eyes were exposed for 5 min to sponges (corneal light shield, Merocel corp., Mystic, CT, U.S.A.) soaked with 200 microg ml(-1)mitomycin-C. After the exposure one of four quadrants was not irrigated and the episcleral sides of three quadrants were irrigated with 40, 100 and 200 ml saline. A 9 mm scleral disk was punched out with a trephine and frozen on a kryotome plate 2 min after the end of mitomycin-C exposure. An 8 mm diameter scleral disk was then cut with a trephine, again frozen on a kryotome plate and then horizontally dissected with a kryotome. For analysis purposes seven cuts of 20 microm thickness were combined to one layer of 140 microm. Six layers could be reproduced and were analysed. The mitomycin-C concentrations of these layers were analysed by high-performance liquid chromatography. A concentration vs depth profile was calculated for each group, and the half-width of concentration was calculated by log-linear regression. The mitomycin-C concentration of layer 1 was 24.51 microg g(-1)(+/-7.52) without irrigation, 13.15 microg g(-1)(+/-4.38) after 40 ml irrigation, 10.29 (+/-3.53) after 100 ml irrigation and 8.4 microg g(-1)(+/-1.62) after 200 ml irrigation. In layers 1-3 the concentration of mitomycin-C was significantly reduced by irrigation (ANOVA). In the deeper intrascleral layers irrigation had no effect on the mitomycin-C concentrations. Between layers 2 and 6 the half-width of the mitomycin-C concentration was 101 microm (no-irrigation group), 141 microm (40 ml irrigation group), 153 microm (100 ml irrigation group), and 164 microm (200 ml irrigation group). Irrigation reduced the mitomycin-C concentration only down to half of the scleral thickness, leaving the deep intrascleral concentrations unchanged.

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.

Basic science and clinical aspects of wound healing in glaucoma filtering surgery

Success of glaucoma filtration surgery is influenced by the wound healing response. Attention has been focused on pharmacological agents to control a process that leads to excessive scarring and eventual failure of glaucoma filtration surgery. Several agents, including 5-fluorouracil and mitomycin C, as well as other antiproliferative drugs will be discussed. Newer antifibrotic agents and novel drug delivery systems are under development in tissue culture and animal models in an effort to improve efficacy and safety. This article summarizes current treatment modalities and future prospects to prevent excessive wound healing and improve the success of glaucoma filtration surgery.

Effect of topical aclacinomycin on glaucoma filtration surgery in rabbits

A prospective, randomized, double-masked and placebo-controlled study was performed to compare the effects of a single 5-minute intraoperative exposure to aclacinomycin (AMC) 0.4 mg/ml or 0.8 mg/ml with control eyes treated with saline solution on the success of glaucoma filtration surgery in 26 rabbits. Intraocular pressure (IOP), bleb survival, fistula patency and complications were evaluated. The results showed that IOP in the eyes treated with AMC was significantly lower than that in the control eyes from days 5-40 in the 0.4 mg/ml group and from days 5-20 in the 0.8 mg/ml group. The bleb survival lasted significantly longer in the two treated groups than in the control group and in the AMC 0.4 mg/ml group than in the AMC 0.8 mg/ml group. At 40 days, the rate of sclera fistula occlusion was 0% in the AMC 0.4 mg/ml eyes, 43.8% in the AMC 0.8 mg/ml eyes, and 100% in the control eyes. Significant complications, such as anterior chamber inflammation, hyphema, moderate and severe corneal haze, dense corneal neovascularization and mild cataract occurred only in the eyes treated with AMC 0.8 mg/ml. The results indicated that intraocular treatment with AMC at a dose of 0.4 mg/ml had a markedly beneficial effect on IOP, bleb appearance and fistula patency after experimental filtration surgery in rabbits.

Effects of mitomycin C on the expression of proliferating cell nuclear antigen after filtering surgery in rabbits

BACKGROUND

The aim of the study was to evaluate the effects of mitomycin C on the cell replication activity in wound healing following experimental filtration surgery.

METHODS

Trabeculectomy with or without application of mitomycin C was performed on albino rabbit eyes. At 1, 4, 7, 14, and 28 days after surgery, the expression of proliferating cell nuclear antigen, a marker of cell proliferation, in the filtering site was examined immunohistochemically using a streptavidin-biotin complex method.

RESULTS

In control eyes that underwent trabeculectomy but did not receive mitomycin C, the number of immunoreactive cells increased 4-7 days after operation and decreased markedly at around 14 days. The filtering site was obstructed histologically at 4-7 days after operation. In the mitomycin C-treated eyes, immunoreactive cells appeared 4 days after surgery but disappeared by 7 days at the surgical site. The number of immunoreactive cells in the treated eyes was much lower than that in control eyes.

CONCLUSION

The cell replication activity was markedly inhibited by administration of mitomycin C. The filtering site remained open for 28 days after surgery, whereas it was completely obstructed within 7 days in control eyes. Immunocytochemistry for proliferating cell nuclear antigen, as used in this study, is a simple and reliable method for detection of cell replication activity.

The use of bioerodible polymers and daunorubicin in glaucoma filtration surgery

PURPOSE

Glaucoma filtering surgery usually fails from postoperative fibroblast proliferation, collagen deposition, and subsequent sclerostomy or bleb scarring. Daunorubicin inhibits fibroblast proliferation in vivo and in vitro. The authors studied the effect of a sustained subconjunctival release of daunorubicin by way of a bioerodible polymer on the success of glaucoma filtration surgery in a rabbit model.

METHODS

Daunorubicin was incorporated into the copolymer by compression molding. The resultant implant measured 3.0 mm in diameter, 1.0 mm in thickness, and 8.0 mg in weight. A posterior lip sclerectomy was performed in both eyes of 23 rabbits by the same surgeon. One eye was randomized to receive the disc with daunorubicin, whereas the fellow eye received a blank disk as a control. The appropriate polymer disk then was placed on the scleral surface immediately posterior to the sclerostomy site and the conjunctiva was closed. Intraocular pressures and slit-lamp biomicroscopy were recorded preoperatively, then every other day after surgery for 31 days. Intraocular pressure, bleb survival, and complications were evaluated.

RESULTS

The decrease in intraocular pressure from baseline was significantly greater in the daunorubicin eyes than in the control eyes during postoperative days 5 through 25. Bleb survival was significantly longer in the daunorubicin eyes than in the control eyes (bleb failure in 91% of control eyes versus 22% of treatment eyes by day 13). There were no statistically significant differences between the daunorubicin-treated and control eyes regarding corneal clouding, lens clarity, cataract formation, or conjunctival injection. However, conjunctival erosions occurred in four daunorubicin-treated eyes. Histopathologic examination was performed 2 weeks after surgery on the eyes of three randomly selected rabbits.

CONCLUSION

Daunorubicin in a bioerodible delivery system may potentially be a useful adjunct to glaucoma filtering surgery and requires further evaluation.

Purity and stability assessment of a semi-solid poly(ortho ester) used in drug delivery systems

The research work carried out for developing bioerodible drug delivery devices in which the erosion process was to be confined to the polymer-water interface is at the origin of the discovery of a class of polymers known as poly(ortho esters) (POEs). Thus far, three POE systems have been described. The latest POE was prepared by a transesterification reaction between a triol and an ortho ester, followed by a self-condensation of the reaction product. This polymer, which exhibits viscous characteristics at room temperature, was investigated for use as a drug delivery system in glaucoma filtering surgery. The assessment of POE purity and stability was carried out by a detailed analysis of the influence of the purification procedure and storage conditions. This bioerodible semi-solid POE was purified by a repeated precipitation procedure. Elimination of the small molecular weight oligomers and monomers and of the catalysts and stabilizers used in the synthesis, as well as a decrease of the polydispersity, were obtained with this method. Fourier transform infrared analysis also verified the disappearance of degradation products after the first precipitation. Drying of the precipitated polymer was performed at 40 degrees C in order to avoid thermal degradation of the POE at higher temperatures and to facilitate solvent evaporation through the polymer network by a reduction of polymer viscosity. Water vapour uptake of the polymers stored at different relative humidities has demonstrated the high moisture sensitivity of these semi-solid POEs. The average molecular weight of the polymer and hence its viscosity, as well as the solubility characteristics of the incorporated drug, were found to have a considerable influence on the rate of water vapour absorption and on polymer degradation. The use of inert gas or vacuum to maintain the polymer under anhydrous conditions has been studied. Storage of the semi-solid POE under argon in sealed glass bottles provides good protection of the polymer over time.

In vivo versus in vitro degradation of controlled release polymers for intracranial surgical therapy

Intracranial studies to analyze the degradation kinetics of the bioerodible polymer poly[bis(p-carboxyphenoxy)propane-sebacic acid] [p(CPP-SA) 20:80] copolymer wafers were conducted in a rat model. Rats were separated into four groups: those receiving 1) polymer, 2) polymer loaded with the chemotherapeutic agent BCNU, 3) drug-loaded polymer with previous tumor implantation, and 4) polymer and an absorbable hemostatic material. A polymer wafer was surgically implanted into the brain of each animal. Residual polymer was harvested at varying times for chromatographic analysis. In vitro effects of pH, mixing, and water availability on degradation were also studied. The results of in vitro and in vivo studies were compared to understand the behavior of polymers in a clinical setting. We found that degradation of p(CPP-SA) initially occurred more slowly in vivo than in vitro. The presence of BCNU, tumor, and absorbable hemostatic material did not affect the ultimate time of polymer degradation in vivo, and the intrinsic polymer degradation time of 1 mm thick p(CPP-SA) 20:80 disks in vivo was 6-8 weeks.

Pharmacokinetics of etoposide delivery by a bioerodible drug carrier implanted at glaucoma surgery

PURPOSE

Pharmacological modulation of wound healing after glaucoma filtration surgery is of great clinical interest, but there are only limited data available on drug pharmacokinetics following glaucoma filtration surgery. Therefore we have studied the in vivo release and tissue distribution of etoposide (VP-16) delivered subconjunctivally by a bioerodible drug-carrier during filtration surgery in rabbits.

METHODS

Disks composed of the polyanhydride 1,3-bis(p-carboxyphenoxy) propane and sebacic acid (PCPP:SA) in a weight ratio of 25:75 and containing 1 mg of 3H-etoposide were placed subconjunctivally during posterior lip sclerectomy in one eye of albino rabbits. Animals were euthanized at various times after surgery and etoposide concentrations in fluids and tissues were determined using liquid scintillation counting.

RESULTS

Release of etoposide from the implant was nearly linear over time, at 30 ug/day, except for a burst between days 6 and 7. By the twelfth postoperative day, 92% of the etoposide had been released. Steady state levels averaged 89 ng/mg in the conjunctiva and sclera, 195 ng/ml in the vitreous, and 29 ng/ml in serum. Drug levels in the aqueous humor, other ocular tissues, and in the contralateral eye were negligible.

CONCLUSIONS

The concentration of etoposide delivered by a polyanhydride controlled release device on the ocular surface is sufficient to reduce fibroblast proliferation for at least 12 days after filtration surgery.

Clinical and histopathologic observations concerning hypotony after trabeculectomy with adjunctive mitomycin C

Prolonged hypotony-induced maculopathy is a serious complication of trabeculectomy with adjunctive mitomycin C. We performed trabeculectomies with intraoperative mitomycin C on 59 eyes of 52 consecutive patients. Exposure time to mitomycin C was five minutes in the first seven patients, two of whom had prolonged hypotony-induced maculopathy. One of these required surgical revision of the filtering procedure. Light and electron microscopic study of the excised, avascular bleb disclosed an irregular epithelium and largely acellular subepithelium of loosely arranged connective tissue. In the remaining 52 eyes, the exposure time to mitomycin C was titrated between two and five minutes according to each patient's risk for failure of filtration from excessive fibrosis. Four additional cases of prolonged hypotony-induced maculopathy occurred among these 52 cases (7.7%), all of which were in the lower risk groups that received two- or three-minute exposure to mitomycin C. Four procedures failed, requiring further glaucoma surgery, and all of the patients were in the higher risk groups, receiving three- to five-minute exposures. Our titration of the exposure time to mitomycin C may have reduced, but did not eliminate, the risk fo prolonged hypotony-induced maculopathy, and further study is needed to establish the optimum protocol for the use of this drug as an adjunct to trabeculectomy.

Effects of topical mitomycin C on primary trabeculectomies and combined procedures

The charts were reviewed of all patients who underwent primary trabeculectomies (group 1) or combined procedures (phacoemulsification + intraocular lens implantation + trabeculectomy--group 2) and received intraoperative mitomycin C (0.4 mg/ml) between 1991 and 1992 at Wills Eye Hospital. A total of 54 eyes of 54 patients were included: 39 in group 1 and 15 in group 2. Intraocular pressure was controlled successfully in 97.4% of eyes in group 1 (mean follow up 6.7 months), and in 93.3% in group 2 (mean follow up 6.8 months). Main complications included choroidal detachment (n = 15), shallow anterior chamber (n = 9), cataract formation (n = 8), and hypotony maculopathy (n = 3). The use of mitomycin C in primary trabeculectomies and combined procedures is associated with high success rates. However, it may be associated with unacceptable risks of vision threatening complications related to excessive filtration.

Effects of intraoperative 5-fluorouracil or mitomycin C on glaucoma filtration surgery in the rabbit

PURPOSE

To establish the effects of single intraoperative exposures to either 5-fluorouracil (5-FU) or two different concentrations of mitomycin C (MMC) on filtration surgery in the rabbit.

METHODS

A prospective, randomized, masked-observer, placebo-controlled study was performed to compare the effects on filtration surgery in rabbits of a single 5-minute intraoperative exposure to 5-FU (50 mg/ml), MMC (0.2 mg/ml), or MMC (0.4 mg/ml) with control eyes treated with distilled water.

RESULTS

Intraocular pressures (IOPs) remained lower for longer and bleb survival was increased (P < 0.05) with all three treatments compared with control eyes. The effect of 5-FU was more transient than MMC. Bleb survival was prolonged in the following order: MMC 0.4 > MMC 0.2 > 5-FU 50 mg/ml. At 30 days, blebs were present in 100% of eyes treated with MMC 0.4 mg/ml, 60% of eyes treated with MMC 0.2 mg/ml, and 0% of eyes treated with 5-FU 50 mg/ml or distilled water. The blebs in the eyes treated with MMC were thinner, and significant complications (endophthalmitis, transient corneal opacification and neovascularization, and a presumed bleb leak) only occurred in the eyes treated with MMC 0.4 mg/ml.

CONCLUSIONS

The authors' results suggest that 5-FU and MMC at these concentrations, delivered as a single intraoperative dose, prolong the survival of filtration surgery for different lengths of time in the rabbit, which is a model that normally exhibits aggressive healing and rapid failure of filtration surgery. The implications of these potentially titratable effects for filtration surgery in different categories of patients are discussed.

Results of intraoperative 5-fluorouracil supplementation on trabeculectomy for open-angle glaucoma

The success rate of filtration surgery has been increased by the postoperative subconjunctival injection of 5-fluorouracil, a potent antimetabolite. However, the optimal route of administration has not been determined. Trabeculectomy was performed on one eye each of 14 patients. Topical 5-fluorouracil was applied intraoperatively (50 mg/ml for five minutes) and subconjunctival 5-fluorouracil was injected postoperatively (an average of 5.8 injections) (mean total dose, 29 mg). Seven of the 14 eyes had primary open-angle glaucoma, and seven eyes had open-angle glaucoma with either uveitis, aphakia, or previous failed trabeculectomy. Mean preoperative intraocular pressure was 24.7 mm Hg during treatment with an average of three antiglaucoma medications, and mean final intraocular pressure was 11.9 mm Hg during treatment with an average of 0.2 medication. Thirteen of 14 eyes (93%) had final intraocular pressure of 18 mm Hg or less. Mean follow-up was 6.4 months (range, four to nine months). No remarkable complications occurred. Visual acuity remained stable in 13 of 14 eyes (93%). Intraoperative 5-fluorouracil may be a helpful adjunct in achieving low final intraocular pressure after trabeculectomy.

Intraoperative mitomycin versus postoperative 5-fluorouracil in high-risk glaucoma filtering surgery

In a randomized clinical trial, the authors compared the use of postoperative subconjunctival injections of 5-fluorouracil (5-FU) in 19 eyes with a single intraoperative application of subconjunctival mitomycin (MMC) at the filtering site in 20 eyes at high risk for failure of glaucoma filtering surgery. Six months after surgery, intraocular pressures averaged 10.9 +/- 5.3 mmHg (mean +/- standard deviation) in the MMC-treated eyes versus 14.2 +/- 5.5 mmHg in the 5-FU-treated eyes (P = 0.08) and were less than or equal to 12 mmHg in 60.0% of MMC-treated eyes and 21.1% of 5-FU-treated eyes (P = 0.03). Mitomycin-treated eyes were receiving an average of 0.3 +/- 0.5 medications for intraocular pressure control, and 5-FU-treated eyes were receiving an average of 1.1 +/- 1.1 medications (P = 0.01). Drug-induced corneal epithelial defects were seen in nine 5-FU-treated eyes and in no MMC-treated eyes (P = 0.0004). These results suggest that intraoperative MMC may be a viable alternative to postoperative 5-FU, with lower overall intraocular pressures, decreased dependence on postoperative ocular antihypertensive medications, and decreased corneal toxicity.

Mitomycin concentration in rabbit and human ocular tissues after topical administration

The authors measured mitomycin C (MMC) concentrations in ocular tissues with high-performance liquid chromatography. Mitomycin C concentration after a single subconjunctival injection of the drug in rabbit eyes showed a rapid decrease with a half-life of 0.18 to 0.30 hours for the conjunctiva and 0.20 to 0.45 hours for the sclera at the injection site. Irrigating the ocular surface with 200 ml of saline after MMC application reduced the initial drug concentration to one fifth in the sclera and to one fifteenth in the conjunctiva but did not change the half-life. The MMC concentration in human trabeculectomy specimens obtained immediately after MMC application (0.2 mg/0.5 ml) and irrigation was 5.4 to 12.0 micrograms/g with a mean of 8.4 micrograms/g, a level similar to that in the rabbit sclera immediately after the irrigation after administration of the same MMC dose. These results indicate that MMC disappears rapidly from the ocular tissues and that irrigating the tissues significantly reduces the tissue concentration of MMC.