The correlation I see is that many pets with food allergies are put on a lamb and rice diet –once upon a time, lamb was a novel protein so it really helped allergy dogs. Now, lamb is a very common ingredient in pet foods so it doesn’t work as well for allergies.
Dogs with a life-time of food allergies are highly at risk for developing SARDS – Sudden Acquired Retinal Degeneration Syndrome. SARDS dogs have normally functioning eyes but the brain cannot see the picture coming in the eyeball. There are some experimental treatments, but nothing is definitive for fixing/treating SARDS. SARDS dogs become blind. That is the correlation I see (no pun intended): food allergies – lamb diet – SARDS blindness.