Due to old age, my eyesight has been getting worse.
Literal
Old-age [cause-で] eyes [subject-が] well see-can-not become-coming.
~なくなってきている stacks three auxiliaries: ~なくなる (become unable to) + ~てくる (gradual change) + ~ている (ongoing state). Together they express 'has been gradually becoming unable to see well.' で marks old age as the cause.