The risk is also mitigated because if the gene manipulation causes cancer, it should be relatively restricted to the eye, which can be removed in the worst case.
For a long time, gene therapy was shied away from because of an early case of oncogenesis with a lentiviral vector: https://pdfs.semanticscholar.org/cba7/d43412c1709861aea218e4...
It’s like neither of you read the article.
At least this requirement is much less nasty in a treatment for blindness than it would be in anything else.
Done before every lasix procedure, for instance. I don’t think it’s supposed to be that painful (there aren’t many nerves in the eye), just freaky. I believe oral sedatives are common.
Your eyeball is filled with vitreous humour which although technically a fluid is really like a thick layer of gelatine, surgical instruments can't navigate that.
Before a needle is able to reach that retinal area, the surgeon must perform what is known as a Vitrectomy which is basically a chop and suction of that gelatine in order to have a good visual and be able to accurately manipulate surgical instruments.
Source: worked in embedded software for ophthalmic surgery equipment.
There is already an FDA approved treatment for one heritable form of retinitis pigmentosa.
https://www.nature.com/articles/s41591-020-0763-1
There are currently active stage 2 trials for multiple forms of achromatopsia.