Azeredo, Joana

Lira, Madalena

Oliveira, M. Elisabete

Santos, Lívia

Universidade do Minho: RepositoriUM

RefractiveIndex and Hydrophobicityafter Contact Lenses WearM.Lira , L.Santos , M.Elisabete C.D.Real Oliveira , J. Azeredo.1 2 1 21. Physics Department (Optometry), University of Minho, Portugal; 2. Biological Engineering Department, University of Minho, Portugal.Purpose:The hydrophobicity andrefractive index are importantparameters of contact lenses(CL). In this work we studiedthe change in hydrophobicityand refractive index ofdiferent silicone hydrogel CLand a conventional disposablehydrogel lens after wear.Methods:Mean ages:22.1 ± 4.2 years.Interval:Between 16 and 35years.Results:Only conventional hydrogel CL, the one with the greater water content,exhibited alterations in refractive index and hydrophobicity after being weared.The changes in theses properties are probably due to the presence of a biofilmproduced by the tear film(1). Since the refractive index is function of watercontent, it’s increase must be due to dehydration of CL due to the presence ofthe biofilm.(1)Ionnis Tranoudis, Nathan Efron, Contact Lens &Anterior Eye, 27 (2004) 193-208.Conclusions- The hydrophobicity was determined through contactangle measurement using the advancing typetechnique with Milipore water in 34 lenses.-The refractive indexes were measured with anautomated refractometer (CLR 12-70, IndexInstruments),in 72 lenses before and after the CLbeing weared.- The degree of hydrophobicity of theconventional hydrogel increases after wearand there are no significant differences in thehydrophobicity for the silicone hydrogellenses (Figure 1).- The refractive index increases for theconventional hydrogel lens after wear, thedifference being statiscal significant with pTable 1 There are no significant differencesbetween the measurements obtained on therefractive index for the silicone hydrogelcontact lenses, before and after contactlenses wear.<0.01.( )Madalena LiraDepartamento de FisicaUniversidade do MinhoCampus de Gualtar4710-057 BragaPortugal Email. Mlirafisica.uminho.ptTel. + 351 253 604068Fax. + 351 253 604061Poster: A110Figure 1. Plotts of difference for the values of contact angles obtained for new and weared contact lensesTable 1. Refractive index for the different lens materials measured before nn and after nu contact lenses beeing used.( ) ( )- The material of the silicone hydrogel CL used in this work were Balafilcon A,Lotrafilcon A, Lotrafilcon B and the conventional disposable hydrogel was EtafilconA.- The experiments were performed after CL removal of patiens from both sexes.- Every patient used the conventional disposable hydrogel during 15 days and thesilicone hydrogel CL during 1 month, one in each eye, in a daily wear schedule.- The samples were measured at a room temperature of 21ºC.02 04 06 08 01 0 01 2 0A c u vu e A d va n c e P u re vis io n F o c u sN ig h t & D a yO p t ixWatercontactangle(º)U n w o r n C LW o r n C L

Refractive index and hydrophobicity after contact lenses wear

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Universidade do Minho: RepositoriUM