The eye dome lighting radius is a value between 1 and 5 inclusive. Ensure that IsEyeDomeLightingEnabled is true for this value to have effect. The default value is 2 pixels wide. Note, that a larger radius will slow down performance.
// get current EDL settings
bool isEnabled = lasDatasetLayer.IsEyeDomeLightingEnabled;
var radius = lasDatasetLayer.EyeDomeLightingRadius;
var strength = lasDatasetLayer.EyeDomeLightingStrength;
// set EDL values
lasDatasetLayer.SetEyeDomeLightingEnabled(true);
lasDatasetLayer.SetEyeDomeLightingStrength(65.0);
lasDatasetLayer.SetEyeDomeLightingRadius(2.0);