What is the ruling on the a marriage of a young man afflicted with a hereditary birth defect in the eyes, knowing that his father is afflicted with the same defect, but his grandfather was not?

The aforementioned deformity does not invalidate the marriage, especially since the woman will be aware of it due to its apparent nature. Even if it is not apparent to her, it will not affect the validity of the marriage, nor does it grant her the option to annul the marriage, as it is not among the diseases that establish this option.