Introduction
Small corneal holes can be treated using tissue adhesives. A penetrating corneal injury or defect needs immediate medical treatment and is frequently efficiently handled in the office using a tissue adhesive solution. Cyanoacrylate adhesives and fibrin glues are two options for treating acute corneal perforations up to 3 mm in diameter or severe corneal thinning caused by microbial keratitis, traumatic or post surgical wound leaks, chemical burns, neurotrophic keratitis, and other non-infectious corneal melts.
This article examines the fundamental preparations and applications of tissue adhesives for treating corneal damage and the two principal adhesives now available: cyanoacrylates and fibrin glue. Nonbiologic (cyanoacrylate) and biologic (fibrin glue) adhesives are now available. It should be emphasized that all commercially available tissue adhesive products are deemed off-label for ocular application.
What Are Corneal Perforations?
Corneal perforation, a potentially fatal consequence, can occur due to various disorders that cause corneal melting. Several causes include microbial keratitis, ocular surface disease, autoimmune illnesses, and trauma with piercing injuries. It is linked with severe ocular morbidity and requires immediate surgery to restore globe integrity and reduce the risk of subsequent problems such as endophthalmitis, choroidal hemorrhage, and glaucoma. Several treatment methods in the literature have been documented, with multi-staged procedures necessary to enable visual restoration. These operations range from temporary remedies like corneal gluing through corneal transplantation, with decision-making influenced by the hole's location, size, and underlying cause.
What Are the Types and Uses of Corneal Sealants?
Small corneal holes may be treated using tissue adhesives. Nonbiologic (cyanoacrylate) and biologic (fibrin glue) adhesives are now available.
Adhesives Based on Cyanoacrylates
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Several cyanoacrylate adhesive preparations are now available for therapeutic usage.
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However, cyanoacrylates with moderate-length alkyl side chains (e.g., Histoacryl, Isodent, Indermil, and Nexacryl) are favored for corneal application.
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These adhesives can be applied when the patient is seated at a slit lamp microscope or lying supine under a microscope.
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A topical anesthetic is administered, then an eyelid speculum is inserted.
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A cotton tip applicator or Weck-cel sponge is utilized to dry the cornea and gently debride the epithelium surrounding the defect.
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If the hole is big or gaping, or if the anterior chamber is flat, an intracameral injection of viscoelastic solution or air may be explored to maintain the anterior chamber and avoid adhesive adherence to the iris or lens.
Application Techniques
A tiny amount of cyanoacrylate glue is then applied to a sterile plastic drape or the inside of clean glove wrapping paper and pulled into a tuberculin syringe through a 30-gauge needle. A little glue is applied directly to the cornea, where it polymerizes, expands, and hardens within seconds. A fluorescein strip should be used to check the incision for a Seidel leak, and a soft bandage contact lens should be inserted. The cyanoacrylate glue and bandage contact lens should ideally be retained until spontaneous sloughing occurs. The duration of adhesive adhesion ranges from a few days to more than two months on average.
Advantage
Cyanoacrylate glue has the benefit of having quick bacteriostatic action against Gram-positive pathogens. As long as the contact lens and adhesive are in place, the patient should be given topical antibiotic medication suited to an identified infectious organism or prophylactic. In the presence of cyanoacrylate glue, stromal neovascularization is a significant and expected component of the corneal healing response.
Complications
The necessity for reapplication of the glue, significant papillary conjunctivitis, and secondary glaucoma are expected consequences of cyanoacrylate application to the cornea. Irido-corneal synechiae, posterior synechiae, and polymerization on the corneal endothelium can all develop due to unintentional glue instillation into the anterior chamber. Finally, additional microbial infiltrates can form, mainly if the contact lens and adhesive are used for over six weeks. Therefore, attention is required.
Fibrin Adhesive
While tissue adhesives were initially utilized in ocular surgery in the 1960s, the Food and Drug Administration (FDA) approved the first commercially available fibrin sealant (Tisseel VH) for hemostasis in 1998. Duchesne described using Tisseel for treating corneal perforations in 2001. Fibrin sealants are human plasma-based biological glues that combine thrombin and fibrinogen to generate active fibrin glue. Although different hospital laboratories can " homemade " fibrin glues, Tisseel VH is the most often utilized commercial product for ophthalmic uses.
Tisseel fibrin glue is available in four color-coded and labeled vials:
(1) sealer protein concentrate (human),
(2) fibrinolysis inhibitor solution (bovine),
(3) thrombin (human), and
(4) calcium chloride solution.
The sealer protein solution is formed by heating and combining the first two components, and the thrombin solution is formed by heating and mixing the third and fourth components. The answers are stable for up to 4 hours after reconstitution and take around 20 minutes to prepare. The manufacturer's specialized injector (Duploject system) must improve for the small quantities of glue utilized in ophthalmic instances. Instead, draw and store the sealer protein and thrombin solutions in separate 3-cc syringes.
Application Techniques
The adhesive should be applied with the patient recumbent and under a microscope. The methods for preparing the eye are the same as those outlined above for using cyanoacrylate glue. Through 27-gauge needles, the sealer protein and thrombin solutions are separately administered to the corneal defect. The bond will harden in about 30 seconds, but it should let it settle for several minutes before Seidel testing and applying a bandage contact lens. Fibrin glue can keep the amniotic membrane in place while the corneal incision heals. Ocular tissue adhesive research aims to produce more effective sealants with improved tissue compatibility, clarity, and durability.
ReSure Sealant
ReSure is a polyethylene glycol hydrogel that is not cyanoacrylate or fibrin glue and is authorized to close clean corneal incisions used in cataract removal/IOL installation. It comes in two parts: a polyethylene glycol solution and a trilysine amine solution, which the user must mix to make the sealant. The mixture is applied to the eye using an applicator included with the ReSure kit. This product is a sealant and a derivative of DuraSeal, which neurosurgeons use to seal the dura during CSF leaks. The primary distinction between a sealant and a glue is that the former is intended to penetrate and seal a crack, while the latter is designed to fill it.
Conclusion
Many surgeons' lives have been made more accessible by using synthetic glues and bioadhesives, which allow them to attach ocular tissues or prevent tissues from additional harm caused by diseases such as corneal perforations. With the clearance of ReSure Sealant (Ocular Therapeutix), ophthalmologists now have another sealant alternative. This article summarized the available glues and sealants, usage advice, and some novel applications that surgeons have been experimenting with. When the adhesive is cured in place, it takes on a rubber consistency and becomes highly durable. It will remain for at least a few days, and its advantage is that it reduces the need for sutures.
