Geographic atrophy: clinical features and potential therapeutic approaches

In contrast to wet age-related macular degeneration (AMD), where loss of vision is typically acute and treatment leads to a relatively rapid reduction in retinal fluid and subsequent improvements in visual acuity (VA), disease progression and vision loss in geographic atrophy (GA) owing to AMD are gradual processes. Although GA can result in significant visual function deficits in reading, night vision, and dark adaptation, and produce dense, irreversible scotomas in the visual field, the initial decline in VA may be relatively minor if the fovea is spared. Because best-corrected VA does not correlate well with GA lesions or progression, alternative clinical endpoints are being sought. These include reduction in drusen burden, slowing the enlargement rate of GA lesion area, and slowing or eliminating the progression of intermediate to advanced AMD. Among these considerations, slowing the expansion of the GA lesion area seems to be a clinically suitable primary efficacy endpoint. Because GA lesion growth is characterized by loss of photoreceptors, it is considered a surrogate endpoint for vision loss. Detection of GA can be achieved with a number of different imaging techniques, including color fundus photography, fluorescein angiography, fundus autofluorescence (FAF), near-infrared reflectance, and spectral-domain optical coherence tomography. Previous studies have identified predictive characteristics for progression rates including abnormal patterns of FAF in the perilesional retina. Although there is currently no approved or effective treatment to prevent the onset and progression of GA, potential therapies are being evaluated in clinical studies.