Holger Mietz

The effect of preservatives and antiglaucomatous medication on the histopathology of the conjunctiva

Abstract• Background: Topical medication applied chronically for the treatment of glaucoma changes the cellular profile of the conjunctiva. We wanted to determine the role of preservatives, which are usually combined with the drugs, on this effect • Methods: We applied metipranolol 0.3 % and pilocarpine 2 % with and without benzalkonium chloride 0.01 % and cetrimonium chloride 0.004 %, respectively. Twenty-four rabbits, divided into four groups, were treated for 3 months. The complete globes and the adherent bulbar conjunctiva were examined histopathologically and immunohistochemically • Results: With special stains for collagen, a slight increase of the thickness of subepithelial collagen of the conjunctiva was present in both groups treated with medication and preservative compared with eyes treated with medication alone. This effect was also true for special antibodies for collagen type IV and α -smooth muscle actin in the eyes treated with pilocarpine, but not in the eyes treated with metipranolol • Conclusion: The results suggest that preservatives may have an additional adverse effect on the conjunctiva in addition to the effects of the medications alone.

Extraocular application of mitomycin C in a rabbit model: cytotoxic effects on the ciliary body and epithelium

Since prolonged postoperative hypotony has been a frequent complication of glaucomatous filtration surgery in which mitomycin C (MMC) was used, it is important to determine the intraocular toxic effects of the drug. We placed MMC, in concentrations of 0.05, 0.2, and 1.0 mg/mL on the intact sclera of rabbits and obtained the eyes after 1, 7, and 28 days. Examination of the ciliary epithelium by transmission electron microscopy revealed an electron-dense material near the endoplasmic reticulum. Large intracellular vacuoles were present, and the mitochondria appeared swollen. These findings suggest a toxic effect of MMC on the ciliary epithelium in rabbits after extraocular application, possibly decreasing aqueous production.

Risk factors for failures of trabeculectomies performed without antimetabolites

AIMS To assess the risk profile for the failure of trabeculectomies in a large group of patients who were selected to be operated on without the use of antimetabolites. This was done in an effort to find subgroups of patients who may not need antimetabolites for primary procedures. METHODS Consecutive patients scheduled for routine trabeculectomies were operated during a 4 year period and were followed up for at least 6 months postoperatively. Patients were regularly examined in the glaucoma unit and by their local ophthalmologists. Pre- and postoperative data were evaluated and success rates determined. RESULTS 709 eyes of 566 patients were operated on; 534 eyes of 534 patients (94.4%) were finally evaluated. The mean follow up was 27.9 (SD 13.6) months with a range of 6–62 months. Success rates for complete surgical success ranged from 59% in the best group with pigmentary dispersion syndrome to 0% in the worst group with neovascular glaucoma. Success rates of patients with POAG, pseudoexfoliation, chronic angle closure, pigmentary dispersion syndrome, and dysgenetic glaucoma were similar. Failure rates ranged from 11% in the best group (pseudoexfoliation) to 80% in the worst group (neovascular glaucoma). Failure rates were high in complicated forms of glaucoma such as traumatic (30%), buphthalmus (40%), and uveitic (50%). For repeat trabeculectomies, the failure rate was 49% (20 of 41 eyes). The mean time until failure ranged from 2.7 months (traumatic) to 15.5 months (pigmentary dispersion syndrome) and was 4.9 months for repeat trabeculectomies. CONCLUSION Trabeculectomy performed in selected groups of patients has a favourable outcome without the use of antimetabolites. It may be possible to avoid antimetabolites in these groups of patients for primary procedures.

Suramin inhibits wound healing following filtering procedures for glaucoma.

BACKGROUND Trabeculectomies are the most frequently performed procedures in surgically treating eyes with glaucoma. Failures are caused by fibrosis in the external ostium of the filtering procedure. In order to inhibit the fibrotic wound healing reaction, a new pharmacological approach using suramin, which inhibits a variety of important growth factors was used. METHODS Pigmented rabbits were used and filtering procedures performed. Suramin was applied with concentrations ranging from 10 mg/ml to 333 mg/ml once during surgery and four times following surgery. The success of the filtering procedure was assessed by intraocular pressure measurements. To evaluate possible intraocular toxic effects, treated eyes were histopathologically evaluated after 4 weeks, and the ciliary body adjacent to the site of application was examined using electron microscopy. RESULTS With concentrations of suramin of 200 mg/ml and 333 mg/ml, the trabeculectomies were patent longer than in the controls and in eyes operated with mitomycin C, which currently is the most frequently used antiproliferative drug to enhance the outcome of surgery in humans. No severe toxic effects to the ciliary epithelium were seen in suramin treated eyes. CONCLUSIONS This study demonstrates for the first time the efficiency of a substance that broadly inhibits the action of growth factors on target cells in the setting of ocular wound healing. In this in vivo model, suramin has been shown to be highly effective in preventing scarring and in having fewer toxic side effects than usually used antimetabolites. These results therefore may suggest a new approach to the surgical treatment of glaucoma.

Three-Year Follow-up of Trabeculectomies Performed With Different Concentrations of Mitomycin-C

BACKGROUND AND OBJECTIVE Mitomycin-C is effective for improving success rates of trabeculectomies. The authors sought to determine longterm success rates and complications by studying two widely used concentrations. PATIENTS AND METHODS Trabeculectomies were performed with mitomycin-C (MMC) in concentrations of 0.5 mg/ml (group 1) and 0.2 mg/ml (group 2) in a prospective, nonrandomized fashion. Patients were observed for at least 3 years, and all follow-up data were analyzed in addition to the preoperative and postoperative conditions and complications. RESULTS A total of 51 and 40 eyes (groups 1 and 2, respectively) were observed for 3 years. The majority of the eyes had repeat trabeculectomy. Complete surgical success was reached in 76% and 63%, respectively. The mean intraocular pressure (IOP) in the two groups decreased significantly, and the decrease was larger in the MMC 0.5 mg/ml group (P < .015). The mean visual acuity did decrease in the two groups, but this was not significant. Complications included short-term and long-term hypotony, conjunctival dehiscence, choroidal detachments, and endophthalmitis. Trabeculectomies failed both within the first 3 months (n = 4; 4%) and later (n = 11; 12%). CONCLUSION Three-year results of trabeculectomies performed with MMC are promising. A dose-response effect of the concentration of MMC and IOP levels is present, suggesting that the higher concentration leads to lower IOP values. Despite the antimetabolic effect of MMC, trabeculectomies fail in both the short-term and the long-term.

Long-term Intraocular Toxic Effects of Topical Mitomycin C in Rabbits

PurposeTo detect whether toxic intraocular effects of mitomycin C (MMC) after extraocular application are long-standing or are reversible over time. MethodsWe placed sponges soaked with MMC on the intact sclera of rabbit eyes after incision of the conjunctiva. Controls received sponges soaked with balanced salt solution. Concentrations of MMC were 0.1 and 0.2 mg/ml. The eyes were examined histologically after 6 and 12 months. ResultsIn all MMC-treated eyes, pathologic changes of the ciliary epithelium were present, which included irregular cell surfaces, intracytoplasmatic vacuoles, swelling of mitochondria, and disorganization of the endoplasmic reticulum. Nerves within the ciliary body also exhibited mild-to-moderate loss of axons in nonmyelinated nerves and increase of interstitial collagen deposition. Capillaries within the ciliary body consistently had a thickened basement membrane, which was arranged in two to three layers in multiple areas. The changes seen were similar in eyes examined at 6 and 12 months after application of MMC. ConclusionsThese results suggest that toxic intraocular changes are dose dependent and do not recover over time. The impact of these findings on humans is unclear, but may further emphasize the high toxic potential of MMC.

Histopathology of an Avascular Filtering Bleb After Trabeculectomy With Mitomycin-c

SummaryThe development of an avascular filtering bleb following trabeculectomy with mitomycin-C is a frequently encountered clinical phenomenon. We studied a small portion of conjunctiva from such a filtering bleb with light and electron microscopy. Examination revealed markedly irregular epithelium. The substantia propria contained only a few cells and no vessels. The basement membrane of the basal layer of the conjunctival epithelial cells was irregular with areas of variable thickness, breaks, and complete absence. These factors may contribute to the long-standing hypotony following trabeculectomy with mitomycin-C seen in a considerable number of patients.

Decorin and suramin inhibit ocular fibroblast collagen production

Abstract• Background: The process of ocular wound healing with respect to glaucomatous filtering procedures is of current interest. Delaying this response in patients could possibly lead to more favorable surgical results. So far, only highly toxic antimetabolites have come into frequent clinical use. The possible efficacy of other groups of substances such as growth factor inhibitors has not yet been examined in vitro. • Methods: We exposed Tenons capsule fibroblasts in tissue culture to various concentrations of decorin and suramin. The dose responses of type I and type III collagen to these inhibitors were measured using an ELISA-type dot blot assay. Total cellular protein production was assayed by measuring the incorporation of tritiated leucine. • Results: At a concentration of 10 μg/ml, suramin reduced the collagen production by more than 80%. Decorin, at a concentration of 100 μg/ml, reduced type I collagen production by about 50% while type III collagen was reduced by 80%. At these concentrations, the total cellular protein production was not inhibited. • Conclusions: Both suramin and decorin, which specifically inhibit the action of growth factors on target cells, reduce the production of collagen synthesis by Tenons capsule fibroblasts. This is a specific effect, because total protein production is not influenced. This sets these substances apart from antimetabolites. Decorin and suramin may have clinical relevance in that they appear to interfere with ocular wound healing more specifically than the substances so far frequently used.

A mouse model to study the wound healing response following filtration surgery.

Abstract · Background: Failure of trabeculectomy is attributed to an exaggerated wound healing response at the episcleral level. We have developed a simple technique in mice that creates corneoscleral wounds and used it to study the role of growth factors in wound healing associated with loss of fistular patency. In addition, the effect of suramin on the wound healing response has been investigated. · Materials and methods: Using black C57B1/6 mice, we created a fistula from the subconjunctival space to the anterior chamber by external penetration with a 25-gauge needle through the bulbur conjunctiva. Eyes were examined by light microscopy at different times following surgery and evaluated for the presence of growth factors in the sclerosing wound by immunohistochemistry. In an additional group, suramin (1.0 mg/ml) was applied topically five times. · Results: The limbal/scleral wounds closed rapidly. Granulation tissue consisting mostly of fibroblasts developed within the first 2 days, and the collagen component increased over time. By 4 weeks, the wound was completely healed. We found that within 1 day after surgery GF β2 reached high intensity. TGF β1 and PDGF A reached maximal intensity by day 2 and remained elevated for about a week. PDGF B was present at moderate intensity even before surgery. Myofibroblastic differentiation was observed from days 2 to 7. Suramin-treated wounds showed a decrease of cells and delay in fibroblast maturation. TGF β1 and TGF β2 levels persisted longer than in the controls, while PDGF A and PDGF B levels were lower than in the controls at all time points. · Conclusions: The mouse corneoscleral wound model that we have developed mimics the process of wound healing and fistulizing surgery that takes place in other animal models and in human eyes in which the outcome of the surgery is poor. Our analysis of the appearance of growth factors associated with wound healing demonstrates that PDGF A as well as TGF β1 and TGF β2 appear early in the process at high levels and are potential targets for interventive strategies to ensure channel patency. Suramin has a distinct effect on the wound healing process and expression of growth factors and may be a promising substance for clinical use.

Unilateral retinoblastoma in an adult: report of a case and review of the literature.

PURPOSE The authors report the clinical, cytologic, and histopathologic findings of a unilateral retinoblastoma occurring in a 26-year-old woman. This tumor usually affects young children; the mean age at the time of diagnosis usually ranges from 10 to 25 months. METHODS Histopathologic examination of the enucleated right eye included using standard techniques, as well as immunohistochemical stains of formalin-fixed, paraffin-embedded tissues. RESULTS Histologic examination of sections of the eye showed a retinal tumor that was centered in the equatorial region and had the typical features of a poorly differentiated retinoblastoma. Focal choroidal invasion and seeding of the anterior and posterior chambers were observed. Immunoreactivity of the tumor cells for neuron-specific enolase confirmed that the tumor is a neuronal neoplasm consistent with retinoblastoma. CONCLUSION Retinoblastoma occurring in adults is a rare finding. In most large series of retinoblastomas, no adults are included. Only eight patients 20 years of age or older with retinoblastomas have been documented previously. In the current case, the patient had no evidence of orbital recurrence or metastasis 6 years after enucleation of the eye. It may be important for clinicians to consider this diagnosis when confronted with a retinal mass of unknown etiology in adults.