Low Water Content Hydrogel Contact Lenses (HCL) Induce Corneal Irregularity

Abstract

Abstract: : Purpose: Although it is known that contact lenses (CL) can cause corneal irregularity, there is scarce information gained from prospective studies evaluating this alteration before and after the use of two types of hydrogel contact lenses (HCL) Methods: Thirty healthy myopic subjects (60 eyes) between 18 and 35 years of age who had never worn CL before were randomised into two groups: Group 1 (15 patients, 30 eyes) were fitted with non ionic low water content frequent replacement (38%) HCL (Polymacon G); Group 2 (15 patients, 30 eyes) were fitted with non ionic high water content frequent replacement (66%) HCL (Alphafilcon A). Subjects were asked to wear CL a minimum of five days per week and six hours per day. Evaluations were always made after a wearing time >4 hr.. Corneal irregularity was measured by corneal topography instrument (Humphrey Atlas Corneal Topographer) using the Corneal Irregularity Measure (CIM) coefficient Data were collected before HCL fitting (Visit 0), after 12 months (Visit 1), and after 15 days of discontinuation of CL use (Visit 2). Results: Group 1 showed a significant (p<0.01) increase in CIM coefficient (0.085±0.124) after 12 months of HCL use; a tendency (0.023±0.204; p=0.537) to recover regularity after 15 days of discontinuation of CL use was observed. Group 2 showed no significant differences at any time-point. Conclusion: The water content of a CL seems to be relevant to the maintenance of corneal regularity. These results, in addition to the already proven higher oxygen transmissibility, may further support the use of high water content HCL.

Keywords: contact lens • cornea: clinical science • clinical (human) or epidemiologic studies: out