Sponge delivery variables and tissue levels of 5-fluorouracil

Long-term Results of the PRESERFLO MicroShunt in Patients With Primary Open-angle Glaucoma From a Single-center Nonrandomized Study

PRECIS

The MicroShunt was implanted in 23 patients with primary open-angle glaucoma (POAG) in a feasibility study. Reductions in intraocular pressure (IOP) and medications were sustained for up to 5 years with no long-term sight-threatening adverse events (AEs).

PURPOSE

The purpose of this study was to assess the long-term effectiveness and safety of the PRESERFLO MicroShunt (8.5 mm long, 70 µm lumen surgical device, formerly known as the InnFocus MicroShunt) in POAG.

PATIENTS AND METHODS

In a feasibility study (NCT00772330), patients with POAG inadequately controlled on maximum tolerated therapy with IOP ≥18 to ≤40 mm Hg underwent MicroShunt implantation with adjunctive mitomycin C (0.4 mg/mL), alone or in combination with cataract surgery. Years 1 to 3 findings have previously been reported. Endpoints of this extension study included IOP reduction and success at years 4 and 5 (primary), incidence of AEs, medication use, and reoperations.

RESULTS

Mean IOP was reduced from 23.8±5.3 mm Hg at baseline to 12.8±5.6 mm Hg (year 4; n=21) and 12.4±6.5 mm Hg (year 5; n=21). Overall success (with/without medication use) was 87.0% (year 4) and 82.6% (year 5). The mean number of medications reduced from 2.4±1.0 at baseline to 0.8±1.3 (year 5). Common (≥5% of patients) AEs included corneal edema (n=4), transient hypotony (n=4), bleb-related complications (n=3), and device touching the iris (n=3). There were 4 reports of serious AEs and 2 reoperations.

CONCLUSIONS

In this extension study, sustained reductions in mean IOP and medications were observed up to 5 years post-MicroShunt implantation. There were no reports of long-term sight-threatening AEs and a low rate of postoperative interventions.

Current variations of glaucoma filtration surgery

PURPOSE OF REVIEW

Trabeculectomy continues to be the most effective incisional surgery for uncontrolled glaucoma. Since its introduction by Cairns in 1968, the procedure has undergone numerous modifications. This article will summarize the current variations of glaucoma filtration surgery and evidence-based review of their potential advantages and disadvantages.

RECENT FINDINGS

Recent innovations in glaucoma filtration surgery have focused on wound modulation to enhance long-term surgical outcomes and the search for a small incision surgery with more predictable outcomes, lower complication rates, and rapid visual recovery. Amniotic membranes, antivascular endothelial growth factor agents, and tissue-engineered biodegradable implants are currently being investigated as alternatives to mitomycin C and 5-fluorouracil to reduce inflammation and subsequent bleb failure with fewer complications. The Ex-PRESS glaucoma filtration device appears promising with its unique feature of small-incision surgery, fewer intraoperative and postoperative complications, and its ability to lower intraocular pressure significantly, which appears to be comparable with standard trabeculectomy.

SUMMARY

Knowledge and surgical expertise in handling current variations of glaucoma filtration surgery are essential to offer an individualized approach with the overall goal of optimizing surgical outcomes and minimizing complications.

Comparison of ophthalmic sponges and extraction buffers for quantifying cytokine profiles in tears using Luminex technology

PURPOSE

Evaluating cytokine profiles in tears could shed light on the pathogenesis of various ocular surface diseases. When collecting tears with the methods currently available, it is often not possible to avoid the tear reflex, which may give a different cytokine profile compared to basal tears. More importantly, tear collection with glass capillaries, the most widely used method for taking samples and the best method for avoiding tear reflex, is impractical for remote area field studies because it is tedious and time-consuming for health workers, who cannot collect tears from a large number of patients with this method in one day. Furthermore, this method is uncomfortable for anxious patients and children. Thus, tears are frequently collected using ophthalmic sponges. These sponges have the advantage that they are well tolerated by the patient, especially children, and enable standardization of the tear collection volume. The aim of this study was to compare various ophthalmic sponges and extraction buffers to optimize the tear collection method for field studies for subsequent quantification of cytokines in tears using the Luminex technology.

METHODS

Three ophthalmic sponges, Merocel, Pro-ophta, and Weck-Cel, were tested. Sponges were presoaked with 25 cytokines/chemokines of known concentrations and eluted with seven different extraction buffers (EX1-EX7). To assess possible interference in the assay from the sponges, two standard curves were prepared in parallel: 1) cytokines of known concentrations with the extraction buffers and 2) cytokines of known concentrations loaded onto the sponges with the extraction buffers. Subsequently, a clinical assessment of the chosen sponge-buffer combination was performed with tears collected from four healthy subjects using 1) aspiration and 2) sponges. To quantify cytokine/chemokine recovery and the concentration in the tears, a 25-plex Cytokine Panel and the Luminex xMap were used. This platform enables simultaneous measurement of proinflammatory cytokines, Th1/Th2 distinguishing cytokines, nonspecific acting cytokines, and chemokines.

RESULTS

WE DEMONSTRATED THE FOLLOWING: (i) 25 cytokines/chemokines expressed highly variable interactions with buffers and matrices. Several buffers enabled recovery of similar cytokine values (regulated and normal T cell expressed and secreted [RANTES], interleukin [IL]-13, IL-6, IL-8, IL-2R, and granulocyte-macrophage colony-stimulating factor [GM-CSF]); others were highly variable (monocyte chemotactic protein-1 [MCP-1], monokine induced by interferon-gamma [MIG], IL-1β, IL-4, IL-7, and eotaxin). (ii) Various extraction buffers displayed significantly different recovery rates on the same sponge for the same cytokine/chemokine. (iii) The highest recovery rates were obtained with the Merocel ophthalmic sponge except for tumor necrosis factor-α: the Weck-Cel ophthalmic sponge showed the best results, either with cytokine standards loaded onto sponges or with tears collected from the inner canthus of the eye, using the sponge. (iv) IL-5, IL-10, and interferon-α were not detected in any tear sample from four normal human subjects. Twenty-two cytokines/chemokines that we detected were extracted from the Merocel sponge to a satisfactory recovery percentage. The recovery of IL-7 was significantly lower in the extracted Merocel sponge compared to the diluted tear samples. The cytokine/chemokine extraction from tears showed the same pattern of extraction that we observed for extracting the standards.

CONCLUSIONS

Simultaneous measurement of various cytokines using ophthalmic sponges yielded diverse results for various cytokines as the level of extraction differs noticeably for certain cytokines. A second set of controls (standard curves "with sponges") should be used to delineate the extent of extraction for each cytokine to be analyzed. Many cytokines/chemokines were detected in tear samples collected with the Merocel sponge, including many that have been implicated in ocular surface disease. Luminex detection of cytokine/chemokine profiles of tears collected with Merocel sponges and extracted with buffer EX1 may be useful in clinical studies, for example, to assess cytokine profiles evaluation in ocular surface diseases.

Anti--vascular endothelial growth factor therapy in glaucoma filtration surgery

PURPOSE

To examine evidence supporting the use of vascular endothelial growth factor (VEGF) inhibition in controlling wound healing after glaucoma filtration surgery in primary open-angle glaucoma, to identify the optimum method of administration, and to clarify the potential position of anti-VEGF monoclonal antibodies in comparison with 5-fluorouracil and mitomycin C.

DESIGN

Perspective based on an overview of evidence from current peer-reviewed literature.

METHODS

Analysis of evidence from animal studies, in vitro studies, human studies, and from the use of anti-VEGF monoclonal antibodies in systemic disease.

RESULTS

There is evidence that glaucoma patients have elevated levels of VEGF in the aqueous before filtration surgery, that this increases in animals after filtration surgery, and that both can be suppressed in animals by intraocular injection of bevacizumab. VEGF not only has a role in angiogenesis, but also has a direct action on fibroblast activity that may be modified directly at the time of filtration surgery.

CONCLUSIONS

There is evidence for a role for VEGF in wound healing after glaucoma filtration surgery. The optimum route of administration and dosing regimen of anti-VEGF antibodies and their positioning in comparison with 5-fluorouracil and mitomycin C are uncertain. There is some evidence that subconjunctival injection may produce sustained intraocular tissue levels. There is also evidence that bevacizumab may act in synergy with 5-fluorouracil. Although there are no direct comparative studies, it seems unlikely that bevacizumab alone will be as effective as mitomycin C, although bleb morphologic features may be better.

The moorfields safer surgery system

This review presents the 'Moorfields Safer Surgery System', which is designed to improve the consistency and outcomes of trabeculectomy surgery. Evidence-based recommendations are made for each step of the surgery. This system requires a minimum of equipment and can be easily implemented by most surgeons. The system is ultimately designed to preserve the vision in our patients by minimising complications while maintaining a desired intraocular pressure.

Subconjunctival sustained release 5-fluorouracil for glaucoma filtration surgery

AIM

To determine the release characteristics of a 5-fluorouracil-loaded poly (lactic acid) disc (5-FU-PLA-DS) and the effect of sustained drug delivery on the success of glaucoma filtration surgery in rabbit eyes.

METHODS

A method of microspheres accumulated by excessive carriers was used in the preparation of the 5-FU-PLA-DS. The disc was characterized for drug loading, entrapment efficiency, in vitro release, and external morphology. It was then implanted subconjunctivally into rabbit eyes with trabeculectomy. Intraocular pressure, ocular inflammatory reaction, filtration bleb appearance, and persistence were evaluated up to postoperative d 90. A quantitative analysis of 5-fluorouracil (5-FU) was performed in the aqueous humor. Ultrasound biomicroscopy was used to assess the appearance of the filtering fistula.

RESULTS

The 5-FU-PLA-DS was produced with the drug-loading of 3.07+/-0.08 mg (mean+/-SD). 5-FU was released for 91 d with suppressive concentrations. The decrease in intraocular pressure from baseline was significantly more marked in the 5-FU-PLA-DSimplanted eyes during postoperative d 3-90, and the persistence of bleb and filtration fistula was longer than the control eyes (P<0.05). Corneal toxicity and hyperemia triggered by 5-FU was lower in the 5-FU-PLA-DS-implanted eyes than those exposed to 5-FU intraoperatively. The 5-FU concentration in the aqueous humor was insufficient for corneal endothelial damage. No evidence of toxic reaction was found in the conjunctival biopsy.

CONCLUSION

5-FU-PLADS displaying sustained intraocular release of 5-FU, reduced intraocular pressure, and prolonged bleb persistence, while significantly reducing 5-FU toxicity.

Presence of mitomycin-C in the anterior chamber after photorefractive keratectomy

PURPOSE

To assess the presence of mitomycin-C (MMC) in hen aqueous humor after photorefractive keratectomy (PRK).

SETTING

Instituto Universitario de Oftalmobiología Aplicada, Faculty of Medicine, University of Valladolid, and Department of Analytical Chemistry, Faculty of Sciences, University of Valladolid, Valladolid, Spain.

METHODS

Mitomycin-C 0.02% was applied topically for 2 minutes to a right hen's eye after PRK (Group A) and to the left eye with intact epithelium (Group B). At different time points (10, 30, 60, 360, and 720 minutes), aqueous humor was extracted and high-performance liquid chromatography was performed to detect and quantify MMC levels.

RESULTS

The mean maximum drug concentration of MMC measured in the aqueous humor was 187.250 microg/L +/- 4.349 (SD) in Group A and 93.000 +/- 4.899 microg/L in Group B, both detected 10 minutes after topical application. Statistically significant differences were found between Groups A and B at 10, 30, and 60 minutes, with decreasing MMC levels in both groups but a higher concentration in Group A. After 360 minutes, MMC levels were undetectable in Group B and after 720 minutes in Group A.

CONCLUSIONS

Mitomycin-C was detectable in the aqueous humor of the hen eye after topical application in PRK-treated eyes and in eyes with intact epithelium. The presence of MMC is of concern as it may lead to ocular toxicity in the long term.

Intra-operative mitomycin C for glaucoma surgery

BACKGROUND

Trabeculectomy is performed as a treatment for glaucoma to lower the intraocular pressure (IOP). Mitomycin C (MMC) is an antimetabolite used during the initial stages of a trabeculectomy to prevent excessive postoperative scarring and thus reduce the risk of failure.

OBJECTIVES

To assess the effects of intraoperative MMC compared to placebo in trabeculectomy.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) on The Cochrane Library (Issue 1, 2005), MEDLINE (1966 to March 2005), EMBASE (1985 to 20 March 2005), SIGLE (1980 to December 2004), the National Research Register (Issue 1, 2005), LILACS (29 March 2005) and reference lists of articles. We also contacted researchers in the field.

SELECTION CRITERIA

We included randomised trials of intraoperative MMC compared to placebo in trabeculectomy surgery.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. We contacted trial investigators for missing information.

MAIN RESULTS

Eleven trials, involving a total of 698 participants, were included. The trials enrolled three types of participants (high risk of failure, trabeculectomy combined with cataract surgery, no previous surgical intervention). Mitomycin C appears to reduce the relative risk of failure of trabeculectomy both in eyes at high risk of failure (relative risk 0.32, 95% confidence interval 0.20 to 0.53) and those undergoing surgery for the first time (relative risk 0.29, 95% confidence interval 0.16 to 0.53). No significant effect on failure was noted in the group undergoing trabeculectomy combined with cataract extraction. Mean IOP was significantly reduced at 12 months in all three participant groups receiving MMC compared to placebo. No significant increase in permanent sight-threatening complications was detected. However, none of the trials were large enough or of sufficient duration to address the long-term risk of bleb infection and endophthalmitis which has been reported in observational studies. Some evidence exists that MMC increases the risk of cataract.

AUTHORS' CONCLUSIONS

Intraoperative MMC reduces the risk of surgical failure in eyes that have undergone no previous surgery and in eyes at high risk of failure. Compared to placebo it reduces mean IOP at 12 months in all groups of participants in this review. Apart from an increase in cataract formation following MMC, there was insufficient power to detect any increase in other serious side effects such as endophthalmitis.

Recent advances in trabeculectomy technique

PURPOSE OF REVIEW

Trabeculectomy is an effective operation for lowering intraocular pressure. However, success is limited by complications such as infection, hypotony, and scarring.

RECENT FINDINGS

These complications, which are increased by antifibrotic use, can be reduced with attention to surgical technique. We highlight the benefit of sub-Tenon anaesthesia, careful choice of the surgical site, fashioning of the scleral flap to produce diffuse aqueous flow, and better intraocular pressure control, maintenance of intraocular pressure, a formed anterior chamber, with outflow control during surgery using an infusion, optimal method of antimetabolites application, new adjustable sutures, and corneal-conjunctival closure techniques.

SUMMARY

These techniques reduce hypotony, producing a diffuse noncystic bleb with long-term pressure control.

National survey of antimetabolite use in glaucoma surgery in the United Kingdom

AIMS

To assess the pattern of use of antimetabolites in trabeculectomy surgery by all consultant ophthalmologists in the United Kingdom.

METHODS

A postal questionnaire of 12 questions regarding antimetabolite use in trabeculectomy surgery was sent to all 749 consultant ophthalmologists in the United Kingdom. The consultants were asked to estimate the number of trabeculectomies they performed per year, how often they used 5-fluorouracil (5-FU) in primary and redo surgery, their usual method of administration of 5-FU, how often they used mitomycin (MMC) in primary and redo surgery, and their usual dosage regimen of MMC. Factors that influenced the decision to use or not use antimetabolites were also assessed.

RESULTS

The response rate of consultants returning the questionnaire was 82% (615 out of 749); 87% (533) of these consultants perform trabeculectomy surgery. Of these 533 consultants, 98 (18%) never use an antimetabolite. Most consultants (82%) use antimetabolites, but use them infrequently (only 9% using antimetabolites in more than half their cases). The preferred antimetabolite is 5-FU rather than MMC. Of the 435 consultants performing trabeculectomy surgery and using antimetabolites, 402 (93%) use 5-FU and 179 (41%) use MMC. Various factors influenced the decision to use or not use an antimetabolite, but experience of complications associated with their use was a factor for 34% of consultants.

CONCLUSION

The use of antimetabolites, particularly MMC, in the United Kingdom is much less than in America or Japan, where trabeculectomy with MMC is the surgical procedure preferred by glaucoma specialists.

Problem of dural scarring in recording from awake, behaving monkeys: a solution using 5-fluorouracil

In studies using single neuron recordings from awake, behaving monkeys, it is necessary to make repeated transdural penetrations using fragile microelectrodes. The tough connective tissue that accumulates after the dura mater is first exposed is often problematic because of electrode breakage and the mechanical stress to the underlying brain tissue caused by excessive dimpling during penetration. We describe the use of an antimitotic compound, 5-fluorouracil (5FU) to control the growth of this connective tissue. 5FU can be safely applied for short periods to the exposed dural tissue on a regular basis provided that it is thoroughly rinsed after application. The advantages of using 5FU are fourfold: first, it depresses fibroblast division and minimizes dural growth and scar tissue formation so that penetrations are easier with less electrode damage or breakage. Second, the frequency of surgical procedures required to remove this tissue are greatly reduced, which benefits both the experiment animal and the experiment. Third, 5FU reduces vascularization of the tissue so that its removal is far easier and without significant blood loss. Finally, 5FU seems to inhibit bacterial infections within the recording chamber. In macaque motor cortex, we performed a quantitative study of electrophysiological data recorded from monkeys with and without 5FU treatment. No significant deleterious side effects produced by 5FU could be detected. Likewise, histological examination of cortical tissue underlying treated dura did not reveal any obvious signs of damage by 5FU. We recommend this approach, with the appropriate safety precautions, to all those neurophysiologists using transdural microelectrode methods in chronically prepared experimental animals. It is also possible that this technique may be useful in other situations where there is dural scarring after surgical intervention or injury.

Beta irradiation: new uses for an old treatment: a review

Beta radiation has a long history as a treatment modality in ophthalmology. It is a convenient and practical method of applying radiation and has the advantage of minimal tissue penetration. There has been a recent resurgence in the use of beta radiation in other areas in medicine, such as the prevention of restenosis after coronary artery stenting. Beta radiation has been shown in vitro and in vivo to inhibit proliferation of human Tenon's fibroblasts, which enter a period of growth arrest but do not die. Effects on the cell cycle controller p53 have been shown to be important in this process. In ophthalmology, beta radiation has been used widely for the treatment of pterygium and is under evaluation for treatment of age-related macular degeneration and for controlling wound healing after glaucoma drainage surgery. In this latter role, beta radiation may be particularly appropriate for use in developing countries to improve the results of trabeculectomy while potentially avoiding some of the side effects of other antimetabolites.

Long term results and complications of trabeculectomy augmented with low dose mitomycin C in patients at risk for filtration failure

AIM

To determine the results and complications up to 5 years after trabeculectomy with 0.02% mitomycin C (MMC) in glaucoma patients at risk for failure of filtration surgery.

METHODS

A consecutive series of 21 eyes from 20 patients who underwent trabeculectomy with MMC 0.02%, with an exposure time of 2 minutes, was retrospectively analysed and the results were compared with previously published data.

RESULTS

The mean preoperative intraocular pressure (IOP) was 28 mm Hg on an average of 2.8 glaucoma medications, and the mean postoperative IOP after 3 years was 14 mm Hg on an average of 0.4 medications. Three years after trabeculectomy, 17 of 21 (80.9%) eyes had an IOP of less than 21 mm Hg without medical treatment. Using Kaplan-Meier life table analysis the 5 year probability of an IOP less than 21 mm Hg without medication was 67% and with medication was 90%. Two patients required further glaucoma surgery during the first postoperative year, and another developed hypotonous maculopathy which was reversed after bleb revision. Seven patients developed visually significant cataract as a late consequence of the surgery. There were no bleb related infections.

CONCLUSION

In the long term MMC 0.02% used for 2 minutes intraoperatively is an effective adjunctive treatment in glaucoma patients at risk for bleb failure and in this dose is associated with few complications.

Modulation of wound healing after glaucoma surgery

The healing process after glaucoma filtration is the main determinant of surgical failure and, even more important, the final intraocular pressure. The ability to fully control wound healing may ultimately give us the ability to set the intraocular pressure in the low teens for all patients undergoing glaucoma filtration surgery. The authors review the changes in how to use antimetabolites to improve safety, and many of the exciting new areas of progress, including growth factor neutralization and future molecular therapies to control wound healing.

Intra-operative mitomycin C for glaucoma surgery

BACKGROUND

Trabeculectomy is performed as a treatment for many types of glaucoma in an attempt to lower the intra-ocular pressure. Mitomycin C is an antimetabolite applied between the sclera and conjunctiva during the initial stages of a trabeculectomy to prevent excessive post-operative scarring and thus reduce the risk of failure.

OBJECTIVES

The objective of this review is to assess the effects of intra-operative application of mitomycin C in eyes of people undergoing trabeculectomy.

SEARCH STRATEGY

We searched the Cochrane Eyes and Vision Group specialised register, The Cochrane Controlled Trials Register - CENTRAL, MEDLINE, EMBASE and the reference lists of relevant articles. We used the Science Citation Index to search for articles that cited the included studies. We contacted investigators and experts for details of additional relevant trials.

SELECTION CRITERIA

We included randomised trials of intra-operative mitomycin C compared to placebo in trabeculectomy.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data. We contacted trial investigators for missing information. Data were summarised using relative risk, odds ratio and weighted mean difference.

MAIN RESULTS

This review includes 11 trials involving a total of 698 participants. The trials included three types of participants (those at high risk of failure, those undergoing trabeculectomy combined with cataract surgery, and those with no previous surgical intervention). Mitomycin C appears to be effective in reducing the relative risk of failure of trabeculectomy both in eyes at high risk of failure (relative risk 0.32, 95% confidence interval 0.20 to 0.53) and those undergoing surgery for the first time (relative risk 0.29, 95% confidence interval 0.16 to 0.53). No significant effect on failure was noted in the group undergoing trabeculectomy combined with cataract extraction. Mean intra-ocular pressure was significantly reduced at 12 months in all three participant groups receiving mitomycin C compared to placebo. No significant increase in permanent sight threatening complications was detected. Some evidence exists that mitomycin C increases the risk of cataract. The quality of trial reporting is poor in eight trials. Repeat analysis with three trials rated as low risk of bias did not yield different results.

REVIEWER'S CONCLUSIONS

Intra-operative mitomycin C reduces the risk of surgical failure in eyes that have undergone no previous surgery and in eyes at high risk of failure. Compared to placebo it reduces mean intra-ocular pressure at 12 months in all groups of participants in this review. Apart from an increase in cataract formation following mitomycin C, no demonstrable significant increase in other side effects was detected.

Modulating conjunctival wound healing

Advances in molecular and cell biology have led to an expansion in our knowledge and understanding of the processes involved in wound healing. We review existing and potential therapies modulating the conjunctival scarring response, with particular reference to glaucoma filtration surgery. We discuss how the refinement of present antimetabolite regimens can minimise complications and improve surgical results, and advocate their use in carefully selected patient groups. Perhaps the most promising approach is targeting biological molecules. Hence, use of fully human neutralising monoclonal antibodies to the growth factor TGF beta has potential as a useful strategy for modifying conjunctival scarring. Combination therapies may also afford an improved therapeutic index. It is hoped that future therapies can offer safer, more specific, focal and titratable treatment, with far-reaching clinical applications.

Wound healing modulation after glaucoma surgery

Recent developments in molecular and cell biology have made a major impact on our understanding of the wound healing process and its modification. In this article, the spectrum of therapies that are either currently available or have potential application as modulators of the scarring response following glaucoma surgery are reviewed. Refinement of existing antimetabolite regimens can improve surgical results, especially in carefully selected patient groups. However, the most promising new approach appears to be using molecular-based therapies, such as fully human neutralizing monoclonal antibodies, designed to target specific molecules in the scarring response. Such strategies ultimately offer the potential of safer, more specific, focal, and titratable treatment, with far-reaching clinical applications.