Beethoven started going deaf in his late 20s. Already famous by age 25 for his piano sonatas, at 31 he was traumatized by losing his hearing. But he kept on composing: the “Moonlight” Sonata during the onset of deafness; the dramatic “Waldstein” Sonata at 32; piano sonatas kept on coming until he was 50. In his deaf period came the revolutionary sounds of his 3rd through 8th symphonies, piano and violin concertos (age 32-40). After 44 he became less productive, with intermittent flashes (Missa Solemnis, Diabelli Variations, Ninth Symphony) composed at 47-53, dying at 56. His last string quartets were composed entirely in his head, left unperformed in his lifetime.
Handel went blind in one eye at age 66; laboriously finished the oratorio he was working on; went completely blind at 68. He never produced another significant work. But he kept on playing organ concertos, “performing from memory, or extemporizing while the players waited for their cue” almost to the day he died, aged 74.
