Expandable Silicone Implants for Scleral Buckling

Refojo, Miguel F.; Banuelos, Antonio

doi:10.1001/archopht.1973.01000050129012

Cited by 4 publications

(1 citation statement)

References 2 publications

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“…They are made up of acrylic polymers with very hydrophilic side chains and agents (ethylene glycol dimethacrylate, EDGMA) linking the polymer molecules in 3D networks. Thus, the hydrophilic groups contribute to the absorption of water into the polymer, whereas the hydrophobic bonds limit it; consequently, the hydration of a hydrogel can be modified by increasing or decreasing the degree of chain cross-linking. − On the contrary, hydrophobic lenses do not allow this control of water content. In this case, their main component is the poly(methyl methacrylate) homopolymer (PMMA) obtained by the polymerization of monomer MMA, which has demonstrated excellent transparency but has a low water content (<10%) that causes an unpleasant sensation of a foreign body in the eye …”

Section: Introductionmentioning

confidence: 99%

Approach to Knowledge of the Interaction between the Constituents of Contact Lenses and Ocular Tears: Mixed Monolayers of Poly(methyl methacrylate) and Dipalmitoyl Phosphatidyl Choline

Conde

Trillo

et al. 2011

Langmuir

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Mixed monolayers of poly(methyl methacrylate) (PMMA), the main component of hard contact lenses, and dipalmitoyl phosphatidyl choline (DPPC), a characteristic phospholipidic constituent of ocular tear films, were selected as an in vitro model in order to observe the behavior of contact lenses on the eye. Using Langmuir monolayer and Brewster angle microscopy (BAM) techniques, the interaction between both components was analyzed from the data of surface pressure-area isotherms, compressional modulus-surface pressure, and relative film thickness versus time elapsed from the beginning of compression, together with BAM images. Regardless of the surface pressure at which the molecular/monomer areas (A(m)) were recorded, the A(m) mole fractions of PMMA (X(PMMA)) plots show that the experimental results match the theoretical values calculated from additivity rule A(m) = X(PMMA)A(PMMA) + X(DPPC)A(DPPC). The application of the Crisp phase rule to the phase diagram of the PMMA-DPPC system can explain the existence of a mixed monolayer made up of miscible components with ideal behavior at surface pressures below 25 mN/m. However, at very high surface pressures, when collapse is reached (at 60 mN/m), the single collapsed components are segregated into two independent phases. These results allows us to argue that PMMA hard contact lenses in the eye do not alter the structural characteristics of the phospholipid (DPPC) in tears.

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