A sun-reflecting physical block, such as the titanium dioxide/zinc oxide combo you report using, adheres better than do sun-absorbing chemical protectants (e.g., octyl methoxycinnamate) and doesn't run as easily. If such a block does get into the eye, they may be transiently bothersome but shouldn't cause any meaningful irritation and pose no threat to the eye. Just make sure the physical block you are using is high quality and doesn't contain questionable petroleum derivatives.
This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual and should not be construed as such.