Twenty first century trends in silicone hydrogel contact lens fitting: An international perspective

Morgan, Philip B.; Efron, Nathan; Helland, Magne; Itoi, Motozumi; Jones, Deborah; Nichols, Jason J.; Worp, Eef van der; Woods, Craig A.

doi:10.1016/j.clae.2009.12.011

Cited by 37 publications

(11 citation statements)

References 6 publications

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“…A jelly is a hydrogel of polysaccharides [1]; contact lenses are hydrogels of silicone [2]; and cells in the human body are connected by hydrogels of collagen [3]. These hydrogels have mechanical properties common to both fluids and solids, i.e., they are viscoelastic.…”

Section: Introductionmentioning

confidence: 99%

“…The hydrophobicity of polymers can also be tuned to regulate hydrogel elasticity by changing pH [4] or temperature [5]. In fact, as a result of this tunable elasticity, hydrogels are widely applied in the food industry [1], environment control [6], medical instrumentation [2, 7], and medicine [4, 5, 7]. Thus, an understanding of the physical mechanisms affecting elasticity of hydrogels is useful.…”

Section: Introductionmentioning

confidence: 99%

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Non-affine deformations in polymer hydrogels

et al. 2012

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Most theories of soft matter elasticity assume that the local strain in a sample after deformation is identical everywhere and equal to the macroscopic strain, or equivalently that the deformation is affine. We discuss the elasticity of hydrogels of crosslinked polymers with special attention to affine and non-affine theories of elasticity. Experimental procedures to measure non-affine deformations are also described. Entropic theories, which account for gel elasticity based on stretching out individual polymer chains, predict affine deformations. In contrast, simulations of network deformation that result in bending of the stiff constituent filaments generally predict non-affine behavior. Results from experiments show significant non-affine deformation in hydrogels even when they are formed by flexible polymers for which bending would appear to be negligible compared to stretching. However, this finding is not necessarily an experimental proof of the non-affine model for elasticity. We emphasize the insights gained from experiments using confocal rheoscope and show that, in addition to filament bending, sample micro-inhomogeneity can be a significant alternative source of non-affine deformation.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Non-affine deformations in polymer hydrogels

et al. 2012

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“…17 Originally introduced for overnight and continuous use, it was anticipated that the increased oxygen transmissibility would result in a healthier cornea that was capable of withstanding infections. Although the lenses eliminated hypoxia-related complications, it was not clear if silicone hydrogels used on an overnight wear basis impacted on the rate of microbial keratitis or inflammatory events.…”

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confidence: 99%

Adverse Events during 2 Years of Daily Wear of Silicone Hydrogels in Children

Sankaridurg

Chen

Naduvilath³

et al. 2013

Optometry and Vision Science

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Purpose Type and incidence of adverse events and rate of discontinuations for 2 years of daily wear with silicone hydrogel contact lenses in Chinese children with myopia. Methods Two hundred forty children aged 7 to 14 years were enrolled in a prospective randomized clinical trial from November 2008 to April 2009. Children with myopia of up to −3.50 diopters (D) spherical equivalent with astigmatism less than or equal to −0.75 D were randomized to one commercial and three experimental lens designs of Lotrafilcon B silicone hydrogel lenses (four groups) used bilaterally on a daily wear, monthly replacement schedule. The main outcome measures were incidence per 100 patient-years (incidence, in percentage) of adverse events and rate of discontinuations. Results There were no events of microbial keratitis. Fifty-five adverse events (incidence, 14.2%) were seen. There were also 12 recurrent events. The type and incidence percentage were contact lens papillary conjunctivitis (16 events, 4.1%), superior epithelial arcuate lesions (SEALs, six events, 1.5%), corneal erosions (eight events, 2.1%), infiltrative keratitis (five events, 1.3%), asymptomatic infiltrative keratitis (seven events, 1.8%), and asymptomatic infiltrates (13 events, 3.42%). There were differences in the incidence of SEALs between groups (p = 0.023), with the incidence of SEALs being greater with one of the experimental designs. No event resulted in any vision loss. Seventy participants (29.2%) discontinued, with one-third (26 participants, 10.8%) occurring in the first month of lens wear. Discomfort and non–lens-related reasons such as safety concern and disinterest were frequently cited reasons for discontinuations. Conclusions Adverse events with daily wear of silicone hydrogels in children were mainly mechanical in nature, and significant infiltrative events were few. The large number of dropouts in the early days of lens wear and their reasons for discontinuation suggest that adaptation and patient motivation are critical for survival in lens wear.

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“…Moreover, an increase in oxygen permeability was also allowed by these new lenses, which has a beneficial effect in the prevention of hypoxia-associated pathologies of the eye [3]- [5].…”

Section: Introductionmentioning

confidence: 99%

“…In the recent past, the emergence of hyperpermeable lenses (i.e., with a higher oxygen permeability than water) is being observed in the sector of soft contact lenses [2], [3].…”

Section: Introductionmentioning

confidence: 99%

Oxygen permeability measurements of contact lenses: A proposal for accuracy improvement

D’Avenio¹,

Poli²,

Daniele³

et al. 2013

2013 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)

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Contact lens are a widespread medical device. In view of the importance of a proper oxygenation of the cornea, new materials are continuously being tested, with a high permeability to oxygen. Taking into account the limitations of the methods for testing soft contact lenses, as presented in the relevant international standards, this paper focuses on the polarographic method and on the approach of measuring oxygen permeability of stacked contact lenses. The effect of the interspersed saline solution layers on the measurable permeability of the stack is considered, using Fick's law of diffusive flux, and a proposal for accuracy improvement in oxygen permeability measurements is presented.

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Twenty first century trends in silicone hydrogel contact lens fitting: An international perspective

Cited by 37 publications

References 6 publications

Non-affine deformations in polymer hydrogels

Non-affine deformations in polymer hydrogels

Adverse Events during 2 Years of Daily Wear of Silicone Hydrogels in Children

Oxygen permeability measurements of contact lenses: A proposal for accuracy improvement

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