| Purpose: Based on experience learned from earlier animal study, we describe a short-term pilot study that evaluates the safety and efficacy of trabeculectomy with implantation of OculusGen in refractory glaucoma patients. OculusGen, by its characteristics, improves the regenerating tissue-remodeling and reduces scar formation by guiding fibroblast to grow through the matrix pores randomly.
Methods: In this prospective and non-randomized study, twelve patients underwent trabeculectomy with new device in one eye for refractory glaucoma, which is defined as having previously failed medical, laser or surgical treatment, or some combination thereof. The OculusGen was implanted on the top of the scleral flap at the limbus before closing the conjunctival wound during trabeculectomy operations. Intraocular pressure (IOP), number of medications and complication were assessed before and after surgery.
Results: The mean preoperative IOP was 45.67±7.45mmHg with 2.07±0.84 antiglaucoma medications. Postoperatively, the mean IOP at last follow up (6 months) for all eyes was 16.11±3.17mmHg (64.50% reduction) with 0.33±0.18 antiglaucoma medications. There were no significant intra-operative complications in any patients. Transient postoperative shallow anterior chamber, hyphema and hypotony occurred in one patient.
Discussion: The goal of glaucoma surgery is to preserve the optic nerve function and to enhance the patient’s quality of life. Recently several large clinical trials have shown that an IOP in the low teens best prevents the risk of glaucoma progression and this usually can be achieved by filtering surgery. Trabeculectomy is the current operating process and remains the gold-standard surgical procedure for reduction of intraocular pressure (IOP) after maximal medical treatment has failed. The most critical factor of the final IOP after filtering surgery is the wound healing process of the eye. If the healing could be well modulated then most patients could achieve a low target IOP after surgery. However, scar formation over the trabecular door and subconjunctival space is the most common cause of bleb failure.
Clinically, mitomycin-C, 5-fluorouracil, tissue plasminogen activator and corticosteroid are used for the inhibition of fibroblast proliferation to prevent scar development after glaucoma surgery. Unfortunately, The application of antifibrotics to inhibit fibroblasts during or after trabeculectomy usually increases the success rate but induces some severe early and late complications, including wound leakage, corneal toxicity and hypotony maculopathy. Moreover, histopathological examination of blebs after filtering surgery with anti-metabolic agents reveals irregularities in the conjunctival epithelium, breaks in the basement membrane, and hypocellularity of conjunctiva and subconjunctival tissue, each of which may predispose to bleb leaks. Resultant avascular thinning layers of the conjunctiva decrease the defense mechanism and bring the risk of bleb infection and endophthalmitis.
On the other hand, wound contraction and dense, linear collagen deposition, as experienced in scar formation, decreases outflow of the aqueous from the anterior chamber. The structural patterns of the conjunctiva, especially the patterns of collagen deposition and its density, determine the reservoir function of the bleb. Tenon’s capsule cysts, consisting of compressed collagen lamellae with few cells and no epithelial lining, are another complication of filtering surgery related to uncontrolled IOP. An ideal result after surgery would require a normalized bleb structure, a maintained dynamic balance between aqueous production and drainage (from conjunctival vessels) and a sufficiently preserved subconjunctival space during the process of wound healing.
Some pump- or tube-like devices made with artificial materials have been implanted into the subconjunctival space or the anterior chamber surroundings as an alternative to the filtering bleb or drainage fistula in order to lower the IOP. The complications of tube-shunt surgery include excessive aqueous outflow, tube obstruction or migration, corneal damage, strabismus, and long term foreign body reaction may happen usually because of the characteristics of non-biodegradable devices. For these reasons, such implants are not a general therapeutic consideration.
In recent years, tissue-engineering studies achieved great progress in scar prevention. The application of 3D collagen-glycosaminoglycan copolymers can lead to a random reorganization of regenerating myofibroblasts , fibroblasts and the secreted extra-cellular matrix ( i.e. collagen), resulting in a reduction of scar formation. This matrix has an advantage over the previously mentioned implants due to the fact that it is fully biodegradable after a certain period of time, depending on the inflammatory condition of the subconjuctival space. The 3D porous structure reduces intraocular pressure by leading a non-scarring physiologic regeneration of the extra-cellular matrix, and by providing a mature physiological aqueous reservoir system after glaucoma filtering surgery.
Conclusions: The preliminary results of this study indicate that the OculusGen implantation in trabeculectomy represents a new, safe, simple and effective therapeutic approach for treating refractory glaucoma. Normalization of subconjunctival wound healing by tissue engineering is applied to traditional filtering surgery, bringing a novel approach to anti-scarring. A larger-scale study with a longer follow-up period is required to confirm these observation.
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