Complex sentence: In 1923, he underwent two operations to remove his cataracts: the paintings done while the cataracts affected his vision have a general reddish tone, which is characteristic of the vision of cataract victims.
Split into simpler sentences: In 1923, he underwent two operations to remove his cataracts. The paintings done while the cataracts affected his vision have a general reddish tone, which is characteristic of the vision of cataract victims.