Glaucoma is one of the leading causes of
blindness in developed countries and is mainly attributable to the apoptosis of retinal ganglion cells (RGCs). Although several diagnostic tools have been developed to detect and monitor this disease, none has the requisite sensitivity to identify it at a preclinical stage or to perceive small changes in
retinal health over short periods. Specifically, irreversible visual changes occur before neuronal damage is discovered. The most widely accepted in vitro assay for apoptotic cells involves the use of fluorescent
annexin A5. The radiolabelling of this marker makes it possible to assess, in vivo and non-invasively, various diseases in which the apoptotic process is pivotal, such as
myocardial infarction or tumour response to
chemotherapy. Recently, a new technique has been developed to visualise directly individual RGCs undergoing apoptosis in the living eye. This DARC (detection of apoptosing
retinal cells) technology uses fluorescently labelled
annexin A5 to bind apoptosing retinal neurons and confocal scanning
laser ophthalmoscopy to detect the marked dying cells. Based on experimental models, DARC has been suggested to offer a direct and quantitative assessment of the
retinal condition of patients. A Phase I clinical trial in
glaucoma patients is scheduled to start shortly. This technology has the potential to pre-empt the diagnosis of
glaucoma prior to visual deterioration, to provide an accurate numeric evaluation highlighting even small
retinal changes and to allow the rapid judgement of the efficacy of both current and new therapeutic strategies.