Retinal Sensitivity Loss Extends Past Lesion Borders in GA

The reduced sensitivity around GA lesions noted in this study appeared to be a combination of global macular sensitivity loss from AMD and additional losses specifically associated with GA, closely tied to the distance from the GA border. These images from the study show the overlaying of retinal sensitivity measurements on fundus autofluorescence images and calculation of distances between test points and atrophic regions. Photo: Mukherjee S, et al.Ophthalmol Sci. July 8, 2025. Click image to enlarge. As geographic atrophy (GA) progresses, it typically starts in the parafoveal region and gradually expands, leading to severely diminished vision, particularly when it affects the fovea. However, conventional visual acuity tests may not reliably track GA progression due to periods of stability in acuity. Microperimetry is a promising tool for assessing retinal sensitivity at specific locations, which was used in a study published earlier this week in Ophthalmology Science to determine how sensitivity varies with distance from lesions. The main conclusions underscore the existence of a critical perilesional zone around GA borders, where retinal sensitivity decreases steeply, a discovery that could inform future therapeutic strategies.To perform the study, researchers collected data from a longitudinal microperimetry dataset derived from a Phase II trial evaluating the safety and efficacy of oral minocycline for GA progression. This multicenter trial included 26 participants aged 55 and older who had GA secondary to AMD in at least one eye. Mesopic retinal sensitivity was measured at baseline, three months and every six months thereafter using a T-shaped test pattern centered on the fovea. This method allowed precise testing of retinal function at various distances from GA lesions, enabling a detailed analysis of sensitivity changes.The results revealed dramatic differences in retinal sensitivity based on proximity to GA lesions. Notably, retinal sensitivity increased sharply within 0 to 2.05° (approximately 580µm) from the GA borders. In particular, the study found that for distances less than 2.05°, sensitivity increased by about 1.9 dB per degree. Beyond this distance, the increase continued at a slower linear rate of 0.56 dB per degree.Furthermore, the analysis indicated that retinal sensitivity declines over time, with an average decrease of -0.07 dB per month. This longitudinal assessment highlighted that diminished retinal sensitivity expands ahead of the GA expansion itself, acting as an advancing wave of visual function decline.“The data support both the idea of a very steep, if not quite precipitous, change in visual function close to GA borders, as well as the idea of a gradual change, though only at greater distances from GA borders,” the researchers explained in their study. They also made an interesting observation: even the highest average retinal sensitivity measured at the farthest distances from the GA border was still below the expected values for these macular areas—around 18 dB—based on data from individuals of similar ages without retinal disease using the same microperimetry device; this several-decibal deficit was also noted in a prior cross-sectional study. Hence, the study authors propose that “the depressed retinal sensitivity values surrounding GA lesions appear to represent the combination of global macular sensitivity losses attributable to AMD and additional losses related specifically to GA, with the latter being highly spatially determined according to distance from the GA border.”They concluded, “Overall, the findings highlight that substantial impairment in visual function extends a long distance from GA borders themselves,” which they note “has important implications both for the design of interventional trials, for decision-making in clinical practice, and for understanding the sequence of events in AMD pathophysiology.” Click here for the journal source. Mukherjee S, Vance E, von der Emde L, et al. Variation in mesopic retinal sensitivity relative to distance from geographic atrophy in age-related macular degeneration. Ophthalmol Sci. July 8, 2025. [Epub ahead of print].