RESEARCH Impact of contact lens material and design on the ocular surface Clin Exp Optom 2017 DOI:10.1111/cxo.12622 Javier Ruiz-Alcocer* PhD Daniel Monsálvez-Romín † MSc Santiago García-Lázaro † PhD César Albarrán-Diego † MSc José Luis Hernández-Verdejo ‡ PhD David Madrid-Costa ‡ PhD *Biotechnology Department, Universidad Europea, Madrid, Spain † Research Group (GIO), Optics Department, University of Valencia, Valencia, Spain ‡ Optics Department, Complutense University of Madrid, Madrid, Spain E-mail: j.ruizalcocer@hotmail.com Submitted: 18 July 2016 Revised: 29 May 2017 Accepted for publication: 29 May 2017 Background: To evaluate the impact on the ocular surface of a daily disposable hydrogel contact lens with high water content compared with two silicone hydrogel daily disposable lenses of lower water content. Methods: The hydrogel lens assessed was made from nesofilcon A and the silicone hydro- gel lenses were made of delefilcon A and stenfilcon A. Contact lens thickness was mea- sured to assess material stability during daily wear, and ocular surface parameters such as tear film osmolarity, tear meniscus area and central corneal thickness were also assessed. Optical quality was analysed for all cases by means of wavefront aberrometry. Results: The nesofilcon A was shown to be the thinnest lens (p < 0.001), while no differ- ences in lens thickness were found between the two silicone hydrogel lenses (p = 0.495). No significant differences were found in tear film osmolarity, tear meniscus area, central corneal thickness or corneal aberrations, either as a function of the lens measured or time of use (p > 0.05). Conclusion: In spite of having the thinnest lens and the highest water content, the hydro- gel does not significantly impact on tear film and corneal swelling after one day of use in first-time wearers. Key words: dehydration, soft contact lenses, stability, water content In spite of the improvement of contact lens materials over the last few decades, the major challenge for contact lens manufac- turers and clinicians remains the reduction of ‘dropouts’ among contact lens wearers. The comfort and behaviour of lenses and their impact on the ocular surface have been closely linked to contact lens wear discontinuation. 1 Among the most important issues related to contact lens wear, oxygen transmission and mechanical interaction of the lens have been the focus of the vast majority of studies conducted in this field. It is well known that conventional hydrogels have always incorporated higher water content in order to achieve higher oxygen perme- ability. However, high water content con- tact lenses tended to dehydrate to a higher degree, thereby causing certain physiologi- cal disorders. 2 Therefore, in order to avoid physiological complications, manufacturers designed thicker contact lenses, which led to a reduction of oxygen transmission and an increase in potential mechanical complications. The emergence of silicone hydrogel materials changed this scenario. These materials provided a significant increase in corneal oxygenation without needing to increase the water content of the lenses. With the use of these contact lenses, hyp- oxic complications have been largely elimi- nated. 3 However, both the intrinsic higher modulus 4 and hydrophobic behaviour 5,6 caused related complications, inducing cli- nicians to refit conventional hydrogel lenses. Another important issue relating to con- tact lens performance concerns the associ- ated complications due to prolonged or continuous wear. Manufacturers have addressed these problems successfully by increasing the frequency of lens replace- ment. With the increased use of daily dis- posable soft contact lenses, the frequency of such complications has reduced. This advance has been widely welcomed by man- ufacturers and clinicians alike; in fact, in 2015 daily disposables already represented 30 per cent of all contact lenses fitted worldwide, continuing a global upward trend over the last 15 years. 7 Seeking to improve the behaviour of materials and reduce discontinuation rates, contact lens manufacturers continually introduce innovations into the market. Of particular interest is a daily disposable con- tact lens made of a conventional hydrogel with high water content and an internal surfactant that aims to prevent dehydra- tion. This raises the question as to whether this lens will offer benefits in contact lens performance. To date no studies have assessed the integrity of the lenses and the ocular sur- face during and after lens use. 8–13 There- fore, this study sought to assess in vivo changes in contact lens thickness of a high water content hydrogel lens, compared with two other silicone hydrogel daily dis- posable contact lenses. Tear film osmolar- ity, tear meniscus area and central corneal thickness variations were also assessed. The optical quality of the ocular surface-lens sys- tem was analysed while these lenses were being used. METHODS A three-week crossover study was carried out with a sample of 20 eyes of 20 patients. The age of the subjects who underwent the study ranged from 20 to 35 years © 2017 Optometry Australia Clinical and Experimental Optometry 2017 1 CLINICAL AND EXPERIMENTAL