The estimated number of contact lens wearers worldwide exceeds 140 million people: contact lenses are indeed commonly used for corrective, therapeutic and esthetics purposes. Ocular dryness is acknowledged as the most common complaint of the contact lens wearer. Over 70% of wearers report dryness symptoms late in the day, and up to 35% of these suffer enough discomfort to cause permanent cessation of wear. The ocular dryness is strictly connected to the lenses dehydration. To avoid this problem, companies are studying new materials, based on different copolymers or addition of specific moistening agents, either directly linked to the lenses or solvated in their conservation solutions. We propose to study by neutron radiography the dehydration process of the most common materials used for soft optical lenses, with and without addition of hyaluronic acid.