Mechanical performance of hydrogel contact lenses with a range of power under parallel plate compression and central load.
J Mech Behav Biomed Mater
; 22: 59-64, 2013 Jun.
Article
en En
| MEDLINE
| ID: mdl-23583634
ABSTRACT
When a contact lens is compressed between two parallel plates (PPC) or under a central load (CLC), the constitutive relation depends not only on the mechanical properties such as elastic modulus, E, of the hydrogel materials, but also the lens power, d, or thickness variation, h(Ï0), along the meridional direction Ï0. Hyperopic lenses (d>0) are thicker at the apex along the optical axis and thin out gradually along the meridian, while myopic lenses (d<0) are thinnest at the apex. Mechanical deformation is quantified by the inter-relationship between applied force, F, vertical displacement of the external load, w0, contact or dimple radius, a, and the deformed profile, w(r). Force responses show that lenses with positive d are apparently stiffer in the initial loading but become more compliant as load increases. Conversely, lenses with negative d are more deformable initially and becomes gradually more resistant to loading. This is consistent with the theoretical shell model using the same E. The mechanical behavior has significant impacts in defining the degree of comfort of contact lenses as well as the lens adhesion to the corneal epithelium.
Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Ensayo de Materiales
/
Lentes de Contacto
/
Fuerza Compresiva
/
Hidrogeles
Idioma:
En
Revista:
J Mech Behav Biomed Mater
Asunto de la revista:
ENGENHARIA BIOMEDICA
Año:
2013
Tipo del documento:
Article
País de afiliación:
Estados Unidos