Dyslexia is highly familial and heritable, and most likely results from interactions between multiple genetic and environmental risk factors. The data in topic 11.1 Genetic Etiology, suggests there is a direct link between a specific genetic background and a biological mechanism leading to the development of dyslexia.

Could Pressure Phosphenes be one of the "biological mechanism" that causes the extra push for creating Ectopias?

Ectopias are produced before six months of gestation when there is a breach in the pial-glial border which normally prevents neurons from migrating too far. In foetal development, by the end of the sixth month, the eyelids begin to part and the eyes open, and the baby may respond to sounds by moving or increasing the pulse.

A pressure phosphene is caused by pressure, not high intraocular pressure like in glaucoma, but some sort of pressure on the retina. Vitreal traction is a big one...vitreous "tuging" on your retina from the inside, usually not dangerous or fixable. Or pressure from the outside like when you turn your eye a certain way the bones around your eye press on the musculature around your eye which slightly deform the outside of your eye, causing the retina on the inside to also be slightly and temporarily deformed or "pushed in", causing a flash, really common. I can even make myself have pressure phosphenes by closing my eyes and looking in certain directions, it is totally harmless and not fixable. (Source: Medhelp )

It is a visual sensation that is produced by something other than light falling on the retina. When you poke the side of your eyeball with your finger, you see a round dark spot with bright edges. This is a "pressure phosphene", produced by mechanical stimulation of retinal nerve cells. "Electrical phosphenes" can be produced by passing electric current through the eye, or directly into the visual cortex of the brain.