Development of a conceptual, HOV-inspired spatial weighting model for quantifying geographic atrophy severity

Area of Science:

• Ophthalmology
• Medical Imaging
• Retinal Diseases

Background:

• Geographic atrophy (GA) is an advanced form of age-related macular degeneration.
• Assessing GA progression traditionally relies on lesion area, which may not fully represent functional impact.
• Understanding spatial characteristics of GA is crucial for evaluating disease severity and progression.

Purpose of the Study:

• To develop a novel Hill of Vision (HOV)-inspired severity score for geographic atrophy (GA).
• To evaluate this new score's ability to capture spatial disease progression, including lesion location and proximity to the foveal center.
• To compare the HOV-inspired score with the conventional lesion area (ΔArea) metric.

Main Methods:

• Retrospective analysis of 103 untreated fellow eyes from the MAHALO study using fundus autofluorescence images.
• Delineation and binarization of GA lesions to create mask images.
• Application of a Gaussian weighting function based on distance from the foveal center to develop a unitless severity score.

Main Results:

• Mean changes in lesion area (ΔArea) and severity score (ΔSeverity) over 18 months were 1.02 mm² and 5811, respectively.
• A weak but significant correlation (r=0.36, p<0.01) was found between ΔArea and ΔSeverity.
• Parafoveal GA expansion led to steeper severity increases compared to peripheral expansion, despite similar area growth.

Conclusions:

• The developed HOV-inspired severity score offers a spatially weighted framework for assessing GA progression.
• This score may complement traditional structural metrics by integrating lesion location relative to the fovea.
• The findings highlight the importance of spatial factors in evaluating the functional impact of GA.