Keratoconus is a degenerative eye disease with no known cure: https://en.m.wikipedia.org/wiki/Keratoconus
Corneal Cross Linking exists, but only stalls progression and doesn't really work for advanced cases
https://www.livingwithkeratoconus.com/ilink-is-the-only-corneal-cross-linking-that-is-fda-approved/
However, the disease is genetic and has to do with protein formation, so there's some chance that we can develop a gene-based therapy that totally stops and potentially reverses progression.
Will we get some effective long-term treatment by 2040? I'll accept any cure, gene-based or not.
@Mqrius "a gene-based therapy that totally stops and potentially reverses progression"
So CXL doesn't count because the efficacy rate is too low. I'll use my judgement if a therapy seems to be fuzzily on that boundary, but I'd say I'd want it to be at least 5x more effective than CXL