Effect of Multifocal Contact Lenses in Peripheral Refraction and in Accommodation of Young SubjectsContacto Multifocais

Resumo

Myopia is becoming a public health concern, with well documented evidence of rapid increasing prevalence in Asia, Europe and the United States of America. Further concerns arise from the fact that myopia onset takes place at an earlier age and progresses over a superior number of years, resulting in higher degrees of myopia in adulthood thus presenting an increased risk of visual loss related with severe eye disease. Over the past 10 years, contact lenses have become an essential device in the strategies to control myopia progression and there is now evidence that different contact lens designs are effective in slowing-down myopia progression. Considering that such lenses have the potential to change the pattern of peripheral refraction and the depth of focus, the present thesis was developed with the aims of investigating the effect of different contact lens devices in the patter of axial and peripheral refractive error in young adults and their effect in the accommodative function. The methods used included axial and peripheral refractive evaluation with an open field autorefractor; a system linked to autorefractometer to dynamic refractive data collection allowing to measure accommodative response and pupil size; a Hartmann-Shack (H-S) aberrometer was also used to determine axial optical aberrations and also a manufactured system linked to H-S to provide peripheral aberrations measurement. We performed 7 trials involving 308 healthy non-myopic and myopic subjects. Results show myopic shift at peripheral refractive pattern of myopic eyes by wearing dominant design MFCL. Peripheral ocular aberrations in eyes fitted with MFCL also were modified; the trend was to increase, depending of design but mainly spherical aberration and coma. Accommodative function of unaided young eyes revealed LAG, mainly at higher accommodative demand. The accommodative facility and accuracy were not significantly modified by wear of MFCL independently of design. Comparison between methods of measuring peripheral refraction revealed that there were no differences between measurements using eye rotation or head rotation with and without MFCL; also were comparable measurements by using an open-field autorefractometer or an adapted H-S aberrometer. The main conclusions were that peripheral refraction and peripheral aberrations could be modified differently by different design of MFCL. Accuracy and amount of accommodation not changed by wear of neither design of MFCL tested.