Your boyfriend has pathologic high myopia. No one can tell you what will happen to his eyes as he gets older. High myopes have higher rates of glaucoma, retinal detachment, and myopic macular degeneration. No one knows the future. The best he can do is live a healthy lifestyle, avoid trauma and contact sports and have a team of capable ophthalmologists. he needs a retina surgeon and a comprehensive ophthalmologist or anterior segment/cornea/ specialist. You might ask his ophthalmology team about surface cornea surgery (PPK) or femtosecond laser surgery. This would not help the health of his eye only reduce the strength of glasses or contact lens he wears.