Great questions! Visual impairment in children with CP is very common. The most common cause is your original thought about the location of injury and how it affects the visual pathways, especially in children with periventricular leukomalacia (PVL), intraventricular hemorrhage (IVH), hypoxic-ischemic injury. Damage to the optic radiations, occipital cortex, or dorsal visual stream can result in cerebral visual impairment (CVI). So the eyes are structurally sound, but the brain has a really hard time processing visual input. Another cause of visual impairment can be ocular motor dysfunction like strabismus, nystagmus, or poor tracking due to impaired motor control of the extraocular muscles. A third cause of visual impairment is purely due to conditions related to prematurity, such as retinopathy of prematurity and optic nerve hypoplasia. These conditions are just simply more common in premature infants and therefore can be seen in children with CP.
Fluctuating visual performance is also common, especially in kids with CVI. Since CVI is a problem with the brain processing information (rather than the eye itself) vision can vary depending on fatigue, environmental complexity, cognitive load, posture, or seizure activity. A child do a great job visually attending in a quiet, supported setting but struggle in a busy environment or when working hard to maintain posture. This is why CVI is so tricky!