Ask for the scientific peer reviewed study that supports the claim made of the inactive ingredient, frankly their explanation sounds like the stuff you hear from naturopath quackery when selling their unproven "cures".
How much does sorbitol cost? Does it justify the price difference?

Edgar replies: Bob, the PR person from Alcon provided these research studies as part of the their response:

* Systane(r) lubricant eye drops in the management of ocular dryness Umberto Benelli Clin Ophthalmol. 2011; 5: 783-790.

** Torkildeson G, Abelson MB et al. Evaluation of functional visual performance using the IVAD method with currently marketed artificial tear products. Invest Ophthamol. Vis. Sci. 2009 50: E-Abstract 4649.