Anti-Inflammatory Effect of Heparin in Pediatric Cataract Surgery
Viraj A. Vasavada
Sajani K. Shah
Mamidipudi R. Praveen
Abhay R. Vasavada
Surgical management of pediatric cataract has shown marked development. The higher risk of postoperative complications after pediatric cataract surgery is attributed mainly to the greater inflammatory response after surgery. This reaction is associated with younger age and may be influenced by the surgical technique, intraoperative injury to adjacent structures such as the iris, and presence of antecedent ocular infection (e.g., rubella). Although cataract surgical techniques have seen a plethora of improvements, postoperative inflammation continues to be a significant factor compromising the outcome of pediatric cataract surgery.1,2,3,4 Certain discernible signs of intraocular inflammation are increased number of cells and flare, inflammatory precipitates on the intraocular lens (IOL), formation of synechia, and inflammatory cyclitic membranes. Some authors have also suggested that increased postoperative inflammation may contribute to posterior capsule opacification (PCO).4 Therefore, techniques that might prevent or at least lower the inflammatory response may prove to be beneficial.
HEPARIN AND ITS ANTIINFLAMMATORY PROPERTIES
Proteoglycan heparin is a long-chain polysaccharide composed of repeating units of hexosamine and either iduronic acid or glucuronic acid. It is an intracellular component of mast cells.
The effects of heparin as an anticoagulative agent are well known. It acts indirectly at multiple sites in both the intrinsic and extrinsic blood-clotting systems, where it potentiates the inhibitory action of antithrombin II on several activated coagulation factors, such as IX, XI, and XII. Through these mechanisms, heparin acts to inhibit formation of a fibrin scaffold. Storage of heparin in mast cell granules, which are released by several inflammatory effect or mechanisms, suggests that endogenous heparin has a role in inflammation.5 Experimental studies have demonstrated anti-inflammatory and antiproliferative properties of heparin.5,6,7 It may decrease the postoperative intraocular inflammatory response by deactivation of the coagulation pathways and the formation of fibrin. Other mechanisms through which heparin may inhibit inflammation include inhibition of fibroblast proliferation,6 interference with lymphocyte recirculation,7 induction of apoptosis in human peripheral blood neutrophils,8 and inhibition of complementary activation.
The use of heparin in ophthalmic surgery was first described by Johnson and colleagues,9 who found that supplementing heparin in the infusion solution or giving a single intravenous injection resulted in a significant reduction in postoperative intraocular fibrin formation after vitrectomy and cyclocryotherapy in rabbits. Subsequently, experimental studies10,11 showed that infusion of heparin or low molecular weight heparin inhibits the formation of fibrin during lensectomy and vitrectomy. The anti-inflammatory properties of heparin have been used during or following cataract surgery in the following forms:
1. Surface coating of IOLs with heparin—Heparin Surface-modified IOLs:
With polymethyl methacrylate (PMMA) IOLs, there were concerns of a greater inflammatory response, particularly in children. Heparin surface-modified (HSM) IOLs were designed to improve the biocompatibility of IOLs. It has been suggested that an HSM IOL may reduce the incidence of inflammatory precipitates on its surface.12 The use of HSM IOL in conjunction with posterior capsulorhexis and intracameral heparin decreased PCO in pediatric cataract surgery without significant side effects.13 However, heparin-coated IOLs did not gain widespread popularity because of their cost and the need for a large incision. Subsequently, PMMA was replaced by newer IOL materials with enhanced biocompatibility. The current day foldable acrylic lenses might result in less
IOL precipitation as a result of lens hydrophobicity and smaller surgical wound.14
IOL precipitation as a result of lens hydrophobicity and smaller surgical wound.14
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