Found some studies that examined the effect of valsalva maneuver on intraocular pressure or central retinal venous pressure. In most of them the IOP had transient modest increase and the CRVP increased markedly (depending on force of blow) but also temporarily. They basically investigated glaucomatous damage.
The activities under investigation were heavy lifting, coughing, or playing a wind instrument (that has some resistance).
What I haven't found though if doing these activities for an extended period of time (e.g. being a wind instrument player or lifting heavy weights regularly) could lead to damage to the optic nerve or to thinning of the RNFL due to the temporarily increased IOP and CRVP?