what is donating eyes ? idols are made with eyes, but may be you're refering to externally fixed eyes like this in white or silver.
There is no issue with any such donation. Maybe the because of popular belief about sani's vision, people are scared of his eyes.
One thing to keep in mind is that you should never get your name written on any donation that goes to temple. Just make it a silent donation (gupt-daan).
Anyone who gets their name written on temple donations, temple walls, records etc have no liberation and their soul remains stuck there as long as that temple exists.