Purpose: To evaluate the impact of contact lens (CL)-induced corneal swelling on the optical quality of the eye by means of the double-pass technique.; Methods: Measurements of 6 healthy subjects were obtained in 5 visits over 1 week, at baseline and after sleeping with 4 different CLs of +0.50 D, +2.00 D, +5.00 D and +8.00 D (Acuvue2), randomly fitted on 4 different days. The control eye wore no CL Corneal pachymetry and optical quality of the eye (OQAS, Visiometrics) were measured once at baseline and at three interval times in the follow-up.visits: immediately after CL removal, and 1 and 2 h after CL removal. Optical quality was evaluated by means of the Strehl ratio and OQAS values at 100%, 20% and 9% contrasts. Intraocular scattering was evaluated with the objective scatter index (OSI).; Results: Mean overnight swelling was 5.98 4.29% in CL-eyes versus 0.30 0.78% in control eyes (p <0.01). Corneal swelling was maximal immediately after CL removal and decreased with time (p <0.01). A significant worsening in all optical quality parameters and a significant increase of the OSI were found in eyes with corneal swelling (p < 0.05). Two hours after CL removal there were no statistically significant differences (p >0.05) between CL-eyes and control eyes in any of the measured parameters.; Conclusions: Corneal swelling has a significant impact on the optical quality of the eye and on intraocular scattering as assessed with the double-pass technique. (C) 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.