Adhesives in retinal detachment surgery

RE-INVENTING CYANOACRYLATE RETINOPEXY IN THE 21ST CENTURY: LITERATURE REVIEW AND CASE SERIES

PURPOSE

We report use of cyanoacrylate (N-butyl-Cyanoacrylate) in previously failed retinal reattachment surgeries for chorio-retinal colobomas. We report the surgical technique, its challenges, and long-term outcomes in three patients who underwent the surgery.

METHODS

A chart review of patients with chorio-retinal colobomas and retinal detachment repair with cyanoacrylate at a tertiary eye care center in Nepal. Cyanoacrylate was used to seal colobomatous retinal breaks in eyes which had undergone multiple retinal surgeries with failed outcome.

RESULTS

Three eyes that were operated using cyanoacrylate were included. All three patients had attached retina and none of the patients required a long-term tamponading agent. None of the patients underwent head positioning following the surgery. All of the patients had a visual acuity gain of 3/60 or more at the end of 8 months. No adverse or inflammatory reactions were noted.

CONCLUSION

We demonstrate that cyanoacrylate is safe and less resource-demanding without a requirement of second surgery to remove a tamponading agent. It could be helpful in eyes with persistent retinal detachment in colobomatous eyes. Because we were able to achieve favorable outcomes without head positioning, we believe it may also be helpful in patients who are not suitable for positioning because of bodily or bony deformities and in retinal detachment with other coexisting trauma.

Ocular Biocompatibility of Poly-N-Isopropylacrylamide (pNIPAM)

Purpose. To study the safety of intravitreal injections of poly-N-isopropylacrylamide (pNIPAM) tissue adhesive in rabbit eyes. Methods. Twelve study rabbits received an intravitreal injection of 0.1 mL 50% pNIPAM in the right eye. Follow-up examinations included color fundus photography, fundus fluorescein angiography (FA), optical coherence tomography (OCT), and electroretinography (ERG). Subsequent to the last follow-up assessment, the rabbits were sacrificed and histopathological study on the scleral incision sites was performed. Results. All study animals developed mild to moderate levels of inflammatory reaction in the conjunctiva, anterior chamber, and the anterior vitreous during the first month of follow-up. After this period, the level of the inflammatory reaction progressively decreased and completely disappeared after the third month of follow-up. The lens and cornea remained clear during the entire follow-up period. OCT and FA did not show areas of retinal damage or neovascularization. Histological and ERG studies of eyes injected with pNIPAM demonstrated absence of retinal toxicity. Conclusion. Intravitreal injections of pNIPAM were nontoxic in this animal study, and pNIPAM may be safe to be used as a bioadhesive in certain retinal diseases.

Intraocular Use of Hydrogel Tissue Adhesive in Rabbit Eyes

PURPOSE

To evaluate the safety and efficacy of newly developed hydrogel glue to treat rhegmatogenous retinal detachments in in vitro and in vivo studies.

METHODS

In the in vitro study, the solid hydrogel glue was soaked in a balanced salt solution (BSS). The pH was measured periodically, and the dissolution time was recorded. In the in vivo study in six albino rabbits, 0.1 ml of hydrogel glue was injected into the right vitreous cavity, and 0.1 ml BSS was injected into the left vitreous, as the control. Clinical, electroretinography (ERG) and histological examinations were performed. Retinal detachment with a retinal hole was created in 12 albino rabbits after vitrectomy. After fluid-air exchange, the hydrogel glue was applied to the hole in nine rabbits; three other rabbits were used as controls. Clinical and histological examinations were performed.

RESULTS

The pH ranged from 6.65 to 8.14. The glue remained solid in BSS for 7 weeks. The glue injection did not induce inflammation. There was no significant difference between the study and control eyes in the ERG amplitude or the implicit times of the a and b waves. No significant histological abnormality was detected. The retina was reattached with glue in three of nine eyes. The histological examination showed glue under the retina.

CONCLUSIONS

Hydrogel glue, which seemed to be minimally toxic to the eye, can be used to patch retinal breaks. However, methods to mix a small amount of each solution completely and a more effective intraocular delivery system for the glue are needed.

Advances in the use of adhesives in ophthalmology

PURPOSE OF REVIEW

To summarize the known uses of available medical tissue adhesives in the management of diseases of the anterior segment, highlighting recent developments in the field.

RECENT FINDINGS

Human fibrin glues may be used in place of cyanoacrylate tissue adhesives in the treatment of progressive corneal thinning and small perforations, potentially resulting in less corneal and conjunctival inflammatory reaction. Additional currently proposed uses of fibrin glues in ophthalmic surgery include minimizing sutures in recurrent pterygium surgery, forniceal reconstruction, amniotic membrane transplantation, and lamellar corneal grafting.

SUMMARY

After reviewing the literature pertaining to the current use of tissue adhesives in ophthalmic surgery, the authors conclude that the main indication for cyanoacrylate tissue adhesives is for the treatment of progressive corneal thinning and small, uncomplicated corneal perforations. Human fibrin glues appear to be equally effective in such cases and have the advantage of biocompatibility, allowing application over a larger surface area and the use of a superficial covering layer such as amniotic membrane or conjunctiva for further reinforcement and promotion of rapid re-epithelialization. Other applications of human fibrin glues in ophthalmic surgery are evolving, but their widespread use is limited by concern over the theoretic risk of viral transmission and the complexity of their preparation and application in comparison with traditional sutures.

Intraoperative adjunctive agents in vitrectomy: serum, cytokines, and glue

The surgical goal in the treatment of retinal breaks is to seal the edges of the break, and traditionally, photocoagulation and cryocoagulation have been used to accomplish this. However, it is sometimes difficult in complicated retinal detachments to maintain the seal against tractional forces. Adhesion is achieved through a process of cell necrosis, inflammation and subsequent fibrovascular proliferation. This strategy, however, may not be appropriate in vision-sensitive areas such as macular holes. To improve the success rate of macular hole surgery, a number of authors have advocated the use of biological modifiers, such as transforming growth factor beta, human autologous serum, tissue glue, or platelet concentrates. These materials may enhance the adhesion of the detached retina and therefore lead to a better anatomical and functional success. We have reviewed the advances of intraoperative application of synthetic or biological adhesives. However, through the improvement of surgical techniques and surgeons' skills in recent years, the anatomical success rate of macular hole surgery has increased in most institutions without adjunctive additives. Thus, many surgeons believe that adjunctive additives may not be necessary for most idiopathic macular holes.

Proliferative vitreoretinopathy: an overview

Proliferative vitreoretinopathy (PVR) is still the most common cause of failure of surgery for rhegmatogenous retinal detachment, despite the substantial effort that has been devoted to better understanding and managing this condition during the past 25 years. Basic research has indicated that PVR represents scarring, the end stage of the wound-healing process that occurs after retinal detachment surgery. Medical treatment has been directed toward preventing inflammation, the first phase of the wound healing process, and inhibiting cell proliferation, the second phase. The 1983 Retina Society classification was modified in 1989 by the Silicone Study Group, whose classification differentiates between posterior and anterior forms of PVR and recognizes three patterns of proliferation: diffuse, focal, and subretinal. The anterior form has a worse prognosis than the posterior form, and its treatment requires more complex surgical procedures. In this review, risk factors and pathobiology of PVR are discussed, and management of PVR of various degrees of severity are considered.

Treatment of retinal breaks with autologous serum in an experimental model

PURPOSE

The standard treatment for retinal breaks is thermal adhesion. Breaks in the posterior pole (i.e., macular holes) recently have been treated using vitrectomy and the recombinant cytokine transforming growth factor-beta. This has been shown to achieve closure of the retinal breaks by stimulating localized fibrocellular proliferation. Serum has been shown to contain chemoattractants and mitogens for many types of cells. The authors studied the clinical and histologic effect of autologous serum application to retinal breaks in an experimental model.

METHOD

Twenty-four rabbits underwent pars plana lensectomy, vitrectomy, retinectomy, fluid-air exchange, application of test solution (12 with Hank's buffered salt solution and 12 with autologous serum), and air-gas exchange. Clinical examination with indirect ophthalmoscopy was performed, and animals were killed 5, 14, and 28 days after treatment. Tissue sections through the retinectomy were studied by light microscopy, electron microscopy, and immunocytochemistry.

RESULTS

None of the serum-treated eyes showed retinal detachment at the site of the retinectomy by evaluation with indirect ophthalmoscopy at each of the time points. In contrast, in control eyes retinal detachment developed at the retinectomy site from 0% at day 5 to 50% at day 14 and 75% at day 28. By light microscopy, serum-treated eyes contained multilayers of fibroblast-like cells adhering the retinectomy edges to the underlying retinal pigment epithelium and choroid. The control eyes had nonadherent retinal edges at the retinectomy site with little sign of fibrocellular response. Results were confirmed by electron microscopy. The fibroblast-like cells by immunocytochemistry contained vimentin, cytokeratin 18, and/or glial fibrillary acidic protein.

CONCLUSION

This study suggests that serum induces a localized fibrocellular response at the retinectomy edges compared with control eyes. This response, characterized by light microscopy, electron microscopy, and immunocytochemistry, appears to involve a mixed population of glial, retinal pigment epithelial, and/or fibroblastic cells. These cells seem to enhance adhesion and subsequent reattachment of the edges of the retinectomies at the time points studied when compared with controls.

The treatment of vitreoretinal scar tissue

Methods of treating vitreoretinal scarring have been transformed by the introduction and development of closed intraocular microsurgery. Controlled access to the posterior segment of the eye, under excellent conditions for intraoperative viewing, have increased our understanding of the pathophysiology of epiretinal membranes. The ready ability to harvest tissue specimens for histopathological and immunochemical study, enabled by this type of surgery, has provided the stimulus for much basic research into the nature of fibrocellular (and fibrovascular) proliferative disease. Treatment of retinal conditions characterised by the proliferation of fibrocellular membranes has been improved, but the most important future advances are likely to be made in the fields of molecular biology and pharmacology.