My doctor prescribed a lubricating eye drop that also contains vitamin D. Can I use a Sodium Hyaluronate 0.18% w/v Eye Drop without vitamin D instead?

It's a fair question, since not every lubricating drop on the shelf has the exact same additions as what was written on your prescription. Sodium Hyaluronate 0.18% w/v Eye Drop is a lubricant on its own and works well for dryness and irritation, but if your doctor specifically added vitamin D for a reason related to your eye condition, swapping it out isn't something I'd do without checking with them first. A quick call to your doctor or a chat with your pharmacist will tell you whether the plain formulation covers what you need.