An employer has a right to seek information from about your condition to ensure that they are protected by work cover.
You do not have to allow this to happen it is your decision.
Unless you authorise it they cannot get the information.
You have a right to ask your employer to give you a letter with what they want to know and you can then take it to your doctor and have them issue a detailed report.
The issue from your post is that you are going on a cruise but you cannot work. If you can work in a wheelchair the question is why cant you return to work.
You may be on unpaid leave but your employer also has a right to know how the injury will impact on your work on your return. I would not give them the right to talk to the doctor but ask them to give you a detailed letter on what they want and you will speak to your doctor.
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