An analysis of a large clinical trial dataset found no clear association between measures of visual function and geographic atrophy (GA) lesion area. The study did find, however, that microperimetry outcomes were moderately correlated with GA lesion area.

The researchers collected data from the largest Phase III studies of GA (known as Chroma and Spectri), which provided a unique data set of functional endpoints in GA. The researchers found that GA area, measured on fundus autofluorescence, enlarged approximately 2mm²/year on average across all treatment groups in each study and was accompanied by overall deterioration in all functional endpoints. They also found there were no statistically significant differences between lampalizumab or control groups for changes from baseline in functional assessment scores.

Regarding visual function tests, only microperimetry outcomes were moderately correlated with GA lesion area when assessed cross-sectionally at baseline and week 48. All other functional parameters had no or weak correlation with GA lesion area.

The study concluded that it was not possible to predict visual function outcomes from GA lesion size. Nevertheless, the researchers believe its results indicate an unmet need for precise and sensitive functional end points that correlate strongly with anatomic features to allow us to understand structure-function relationships in patients with GA.