Structural and optical changes in the eye after short-term soft contact lens wear Marco A Miranda, Clare O’Donnell, Hema Radhakrishnan Faculty of Life Sciences, The University of Manchester, UK
Purpose: To investigate the magnitude and aetiology of structural and optical changes in the cornea after short-term hydrogel contact lens wear and to explore the effect of these changes on visual performance. Methods:In the first part of the study, 16 subjects were fitted with a low-Dk hydrogel contact lens (CH) in one eye and a silicone hydrogel (SH) lens in the contralateral eye. In the second part of the study, subjects were fitted with a low modulus silicone hydrogel lens in one eye and a high modulus silicone hydrogel lens in the contralateral eye. Both lenses were manufactured in two different thicknesses (100μm and 200μm). In both studies, the lenses were worn for 1 month in daily wear (DW) and 1 week in extended wear (EW), with at least 1 week ‘wash out’ in between. For the second part of the study, after at least one week without lenses, these wear-schedules were repeated for a different combination of lens modulus/lens design. All lenses were plano-powered and were manufactured in matched designs with the same specifications. Measurements of corneal topography, corneal pachymetry (apical and peripheral), and corneal and ocular aberrations were performed at baseline and after lens wear using a Scheimpflug imaging system (Oculus Pentacam) and a Hartmann-Shack aberrometer (IRX3). Best corrected visual acuity (BCVA, logMAR) and contrast sensitivity measurements (CS, Pelli-Robson) were also performed. Results: The optical and structural changes in the cornea after 1 month of DW and 1 week of EW for both the CH and SH materials were of low magnitude. The topographic and pachymetric changes observed were not found to be significant (p>0.05, RMANOVA). The change in aberrations from baseline with both materials and both regimens of wear was also not statistically significant (p>0.05, RMANOVA). No relationship was found between the amount of change in refractive error after lens wear and the baseline refractive error. Conclusion: Our data showed that the CH and SH lenses tested do not significantly alter the structure or the optical performance of the cornea after one month of daily wear and 1 week of extended contact lens wear. The effect of lens thickness on changes in refraction, corneal aberrations, and topographic and pachymetric parameters will also be discussed. Acknowledgements: This study was supported by a research grant from Ciba Vision.