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Certainly with that long an axis, you are at higher risk for retinal detachment. But even if you didn't have surgery, you are still at higher risk for retinal detachment and myopic degeneration (a form of macular degeneration). If you are to have surgery, you should not have a retrobulbar block (due to the long axis) but should have it done under topical anesthetic.
The way I look at it is that, with a -19 eye, your quality of vision can't be that great anyways. If you can improve that with surgery, I would take it (even with the slight risk).
Hope this helps and good luck.