The horizontal raphe (HR) as a demarcation line dividing the retina and choroid into separate vascular hemispheres is well established. but its development has never been discussed in the context of new findings of the last decades. Although factors for axon guidance are established (e. g. https://www.roneverhart.com/Ludwig-P2230B-Imperial-Tension-Lug-for-Snare-Drums-p9792/