Morphometric Study of Wound Healing in a Model of Filtering Surgery with Mitomycin-C

Long-Term Effects of Postoperative Subconjunctival Injections of Mitomycin-C in the Rabbit Eye

Aim

Single or multiple subconjunctival injections of mitomycin-C (MMC) may offer one way of establishing the total dosage of MMC more accurately. The method also allows re-applications later postoperatively. In this experimental, randomized prospective study we compared the effects of a single intraoperative application of MMC at the filtering site and a single postoperative subconjunctival injection of the drug.

Methods

The left eyes of 32 pigmented rabbits were divided into two groups. In the first group we applied MMC intraoperatively (10) with a 4×1 mm surgical sponge soaked in a MMC solution (0.5 mg/ml). In the second group we injected 0.4 ml of the same solution subconjunctivally (SC) immediately after (conjunctival) suture. Post-operative evaluation was carried out every day during the first week, then every three days until day 58. Survival analyses were done for intraocular pressure (IOP) and bleb failure. Log-rank tests were used to compare survival differences between the groups.

Results

The IO group showed longer survival parameters than the SC group (p<0.05), both in the control of IOP and as regards blebs. The histological persistence of fistulas was similar. The IO group, however, had a higher incidence of undesirable side effects.

Conclusions

Our findings suggest IO application of MMC is more effective in reducing fibroblast ingrowth. However, subconjunctival application offers certain advantages such as the possibility of repeating the treatment postoperatively and, therefore, using a smaller initial dose.

Effect of human RAD50 gene therapy on glaucoma filtering surgery in rabbit eye

PURPOSE

To investigate the antiproliferative effects of the subconjunctival injection of human RAD50 (hRAD50) on fibroblasts after glaucoma filtering surgery.

METHODS

After glaucoma filtering surgery in normal rabbit eye, the subconjunctival injection of hRAD50 was performed. Morphologic changes in the subconjunctival area of hRAD50-treated eyes were compared with those of mitomycin C (MMC)-treated and control eyes using light and electron microscopy. Results. Two weeks after hRAD50 treatment (2 microg), the conjunctival epithelium increased in thickness and had many tonofilaments, but the basal lamina was intact. The subconjunctival fibroblasts exhibited a granular endoplasmic reticulum without distension. Most of the collagen bundles and fibers around the fibroblasts disappeared, and apoptotic cells with many fragmented nuclei and condensed chromatin were observed. Four weeks after hRAD50 treatment, the findings were similar with those of 2 weeks except for a slight increase in the number of collagen bundles and fibers and the appearance of macrophages. In MMC-treated eyes, the conjunctival epithelium also increased in thickness and had many tonofilaments. However, intercellular spaces were widened and the basal lamina was interrupted in some areas. Most of the collagen bundles and fibers were shortened, and apoptotic cells were also observed.

CONCLUSIONS

These results demonstrate that the histologic antiproliferative effects of local hRAD50 on the conjunctival fibroblasts are similar to those of MMC, but without damage to the basal lamina of the conjunctival epithelium, and suggest that hRAD50 may be useful as a possible antifibroblastic agent for glaucoma filtering surgery. However, further investigations are needed to test for possible systemic complications, which so far have not been reported.

Systemic anti-inflammatory fibrosis suppression in threatened trabeculectomy failure

PURPOSE

To provide a rationale for the use of systemic anti-inflammatory fibrosis suppression in the postoperative management of threatened early trabeculectomy bleb failure.

METHODS

A review of the literature and of the authors' own experiences was conducted.

RESULTS

The most important cause of persistent elevation of intraocular pressure after trabeculectomy is unduly marked or persistent inflammation with deposition of fibrous tissue, which prevents the formation of an adequately draining bleb. It was found that a clinically useful degree of suppression of bleb inflammation and fibrosis can be obtained with a 4-6 week course of the combined systemic administration of prednisone (10 mg t.i.d.), a non-steroidal anti-inflammatory agent (e.g. diclofenac 100 mg SR daily) and colchicine (0.25 mg or 0.3 mg t.i.d.), which was termed anti-inflammatory fibrosis suppression. Topical atropine 1% t.i.d. and adrenaline 1% t.i.d. eye drops can also be considered in addition to routine postoperative topical steroids.

CONCLUSIONS

Despite advances in surgical techniques and methods to control fibrosis, anti-inflammatory fibrosis suppression is a valuable tool to have available in the post-operative period for management of trabeculectomies that threaten failure. This regime produces a diffuse bleb, which has a very low risk of late infection or bleb perforation. It is recommend that this regime be added to the list of therapies that are considered when clinical features suggestive of a failing bleb are confronted early in the post-operative course.