Management of Primary Open-Angle Glaucoma and Ocular Hypertension: The Potential Role of Latanoprost

Abstract

Primary open-angle glaucoma (POAG) is a chronic progressive disease characterised by damage to the optic nervehead (optic disc) which leads to visual field loss and may eventually result in blindness if left untreated. Intraocular pressure (IOP) is elevated in the majority of patients. Early intervention, based on reduction of IOP, can prevent or delay visual impairment and topical ocular hypotensive therapy is the mainstay of management. Argon laser trabeculoplasty or filtration surgery are most often used after failure of topical therapy but are also used as the initial intervention in some cases. Latanoprost is an ester prodrug analogue of prostaglandin F2a available for the topical management of open-angle glaucoma and ocular hypertension. It lowers diurnal IOP by approximately 25 to 35%, by enhancing uveoscleral outflow of aqueous humour. This mechanism differs from that of other ocular hypotensive agents. Because its ocular hypotensive effects last for at least 24 hours after a single dose, latanoprost is administered once daily. Comparative studies have shown that latanoprost 0.005% once daily is more effective than timolol 0.5% twice daily in lowering IOP. Additional reductions in IOP are achieved when latanoprost is used in combination with topical timolol or dipivefrin, or with oral acetazolamide. The most common local adverse effects associated with latanoprost are eye irritation (burning, stinging, tearing and/or itching), mild conjunctival hyperaemia, superficial punctate keratopathy and foreign body sensation. Increased pigmentation of the iris occurs in a variable proportion of patients treated with latanoprost. This phenomenon appears to be permanent, is most likely to occur in eyes with mixed iris colour and its long term clinical significance is unknown. In contrast with timolol, latanoprost is not associated with systemic adverse effects, having essentially no effect on heart rate or systemic blood pressure. Latanoprost is currently recommended for use in patients who respond inadequately to, or are unable to tolerate, other ocular hypotensive agents, or as firstline therapy, depending on the market. However, it has a number of favourable properties, which suggests that it has considerable potential for much wider use. Although further long term tolerability data are required, it appears possible that latanoprost and other topical prostaglandin analogues might largely replace β-adrenergic antagonists as first-line therapy for management of POAG and ocular hypertension in the future.