REVIEW - IMPLANTS

An implantable sustained release device has been developed to treat ch ronic disorders of the eye. The device, consisting of a central core o f drug encased in layers of permeable and impermeable polymers, can be implanted subconjunctivally or intravitreally. This technique was use d to develop a ganciclovir device which, when implanted into the vitre ous, maintains therapeutic vitreous levels of drug for 8 months. Initi al studies in patients with cytomegalovirus (CMV) retinitis indicate t hat this treatment may offer better control of the disease and fewer s ide effects than existing therapies. Cyclosporine A devices were prepa red for the treatment of uveitis. Early data suggests that these devic es maintain therapeutic levels in the vitreous for approximately 3 yea rs. Work on efficacy and toxicity is continuing. Although clinical app lications of these devices are likely to be restricted to diseases req uiring chronic drug therapy, they can be used to investigate optimal d elivery rates. Subconjunctivally implanted devices releasing 5-FU for 12 days maintained filters in cynomolgus monkeys for 3 months. Similar devices maintained low intraocular pressure in 75% of high risk filte r patients.