Cataract surgery is an invasive procedure involving an incision and manipulation of ocular tissue, leading to intraocular inflammation. The latter is characterised by redness, swelling, and/or pain. Inflammation arises from the release of prostaglandins (PGs). Activation of phospholipase A2, following tissue injury during surgery, breaks down cell membrane phospholipids to arachidonic acid. This is then converted to PGs by activation of cyclo-oxygenase (COX) enzymes via the COX-1 and COX-2 pathways. Production of PGs causes local vasodilation and increased vascular permeability resulting in a number of symptoms including hyperaemia, miosis, pain, photophobia and diminished visual acuity secondary to cystoid macular oedema (CMO) – the most common complication of cataract surgery and potentially the most adverse ocular outcome of PG production.1
Two agents are primarily employed for the reduction of intraocular inflammation: non-steroidal anti-inflammatory drugs (NSAIDs) and corticosteroids. NSAIDs are potent inhibitors of cyclo-oxygenase enzymes and hence of PG synthesis. Together with corticosteroids, they act on the COX-1 and COX-2 pathways. While corticosteroids inhibit phospholipase A2, preventing arachidonic acid release from phospholipids, NSAIDs act downstream and more specifically in the cascade by direct inhibition of COX-1 and COX-2 enzymes (see Figure 1).2 Post-operative ocular inflammation is a complex condition owing to the diverse types of tissues that may be affected, including the conjunctiva, retina, sclera, aqueous and vitreous humour, cornea, iris, ciliary body, choroid and retina.3
Corticosteroids have a long history of use in the management of ocular inflammation but their efficacy is tempered by serious adverse effects including impairment of wound healing, elevation of intraocular pressure (IOP), progression of cataracts, increased susceptibility to microbial infections owing to a suppressed host immune response, delayed corneal epithelial and stromal wound healing, and safety issues associated with long-term use including glaucoma.1
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