Revisiting the Drasdo Model: Implications for Structure-Function Analysis of the Macular Region.

Area of Science:

• Ophthalmology
• Computational Biology
• Medical Imaging

Background:

• Accurate macular structure-function analysis is crucial for diagnosing and monitoring retinal diseases.
• Existing models may not adequately account for individual variations in eye size, such as axial length (AL).
• The Drasdo model offers a framework for understanding retinal ganglion cell (RGC) displacement.

Purpose of the Study:

• To implement and validate the Drasdo RGC displacement model for macular structure-function analysis, incorporating axial length (AL) customization.
• To compare two methods of applying the displacement model to perimetric stimuli.
• To ensure the model's applicability to clinically relevant measurements.

Main Methods:

• Measured the effect of AL on inner retinal shape using 235 optical coherence tomography (OCT) scans from healthy eyes.
• Applied the Drasdo model with two methods: Method 1 (displacing stimulus center) and Method 2 (displacing stimulus edge).
• Validated results using RGC density maps from 28 OCT scans of young healthy subjects.

Main Results:

• Retinal structure size significantly increased with AL, consistent with geometric scaling.
• Method 1 underestimated RGC counts by up to 60%, while Method 2 showed no bias.
• The findings were confirmed on clinically available OCT measurements.

Conclusions:

• The Drasdo model effectively incorporates AL through geometric scaling for RGC displacement.
• Method 2 is recommended for accurate structure-function analyses in the macula.
• A free web application is available for researchers to utilize these findings.