Thickness of the Pre- and Post–Contact Lens Tear Film Measured In Vivo by Interferometry

Nichols, Jason J.; King‐Smith, P. Ewen

doi:10.1167/iovs.02-0377

Cited by 119 publications

(80 citation statements)

References 20 publications

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“…It is well known that soft lens wear leads to unstable tear film, with studies showing diminished tear break-up time, 37,38 reduced tear meniscus height, 39,40 and pre-lens tear thickness. 4,41 Our results add to this body of evidence, showing that during soft contact lens wear the quality of the tear film is poorer in the inter-blink interval.…”

Section: Discussionsupporting

confidence: 73%

Tear Film Surface Quality with Soft Contact Lenses Using Dynamic Videokeratoscopy

Kopf

Iskander

et al. 2008

Journal of Optometry

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PURPOSE:To investigate changes in tear film surface quality after commencing soft contact lens wear. METHODS: Tear film surface quality (TSQ) was assessed during the interblink period using dynamic videokeratoscopy at 25 Hz. A quantitative value of TSQ is derived for each raw Placido ring image. Eleven young subjects with normal tear characteristics participated in the study. Dynamic videokeratoscopy was taken three times per day; in the morning, at lunchtime, and in the afternoon. This was done on two baseline days (bare eye) and on the first and seventh days of lens wear for a conventional hydrogel lens and following a week of no lens wear, for a further week of silicone hydrogel lens wear. Additionally clinical tests to assess TSQ were conducted and subjects were also asked to rate the subjective dryness of their eyes. RESULTS: All lens wear measurements showed a significant worsening of TSQ compared to bare eye measurements (repeated measures ANOVA, P<0.01). A significant diurnal change was found on the first day of silicone hydrogel contact lens wear, where TSQ improved during the day (P=0.045). However, no diurnal changes were found in TSQ for the other lens wearing days or for the bare eye condition (P>0.05). The subjective rating of dryness correlated with TSQ values (Pearson's r=0.62, P<0.05) for the bare eye condition, but not during contact lens wear. TSQ derived from the right and left bare eyes of the same individuals showed a significant correlation (Pearson's r=0.61, P<0.05). CONCLUSIONS: The measurement of TSQ using dynamic videokeratoscopy differentiates between bare eye and lens wearing conditions. It also shows a small systematic improvement in tear surface quality during the first day of silicone hydrogel lens wear and a significant association with subjective dryness for the bare eye condition. (J Optom 2008;1:14-21 ©2008 Spanish Council of Optometrists) KEY WORDS: high speed videokeratoscopy; tear film; dry eye; contact lens. RESUMEN OBJETIVO:Investigar los cambios en la calidad de la superficie de la película lagrimal tras empezar a utilizar lentes de contacto blandas. MÉTODOS: Se evaluó la calidad de la superficie de la película lagrimal (CSPL) durante el periodo comprendido entre dos parpadeos consecutivos utilizando videoqueratoscopia (topografía corneal estándar) dinámica a 25 Hz. Para cada imagen registrada de los anillos de Plácido se derivó un valor cuantitativo de la CSPL. En el estudio participaron once sujetos jóvenes cuya lágrima presentaba características normales. Se realizaron medidas de videoqueratoscopia dinámica tres veces al día: por la mañana, a la hora de comer y por la tarde. Estas medidas se llevaron a cabo primero, en dos días distintos, para recabar datos de referencia (ojo desnudo, sin lente de contacto); posteriormente, el primer y el séptimo día de uso de una lente de contacto convencional de hidrogel y finalmente, y tras una semana sin utilizar lentes, se realizaron medidas el primer y el séptimo día de uso de una lente de hidrogel de silicona. De maner...

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Section: Discussionsupporting

confidence: 73%

Tear Film Surface Quality with Soft Contact Lenses Using Dynamic Videokeratoscopy

Kopf

Iskander

et al. 2008

Journal of Optometry

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“…They are composed primarily of mucin, 1 and their sizes have been reported to range between 20 and 200 mm in diameter. [2][3][4][5][6][7] Because they can be significantly larger than the thickness of the postlens tear film [8][9][10][11] or the corneal epithelium, it is not surprising that some mucin balls can become deeply embedded into the cornea. They can be blinked away or leave depressions on the corneal epithelium on lens removal.…”

Section: Mucin Ballsmentioning

confidence: 99%

Mechanical Complications Induced by Silicone Hydrogel Contact Lenses

Lin

Yeh

2013

Eye &Amp; Contact Lens: Science &Amp; Clinical Practice

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“…The soft contact lenses examined by Monticelli, Chauhan, and Radke [24] had thickness of 200 μm. If we take as a typical tear film thickness between 1 and 5 μm (e.g., see Bron et al [5] or Nichols and King-Smith [16]) and use a representative contact lens thickness of 100 μm, then typical values for H range between 20 and 100. Measurements of the lens permeability by Monticelli, Chauhan, and Radke [24] indicate that a realistic value for Da for soft contact lenses is Da = 10 −8 (based on their measured permeability of approximately 10 −8 μm 2 and a tear film thickness of 1 μm) or even smaller.…”

Section: Numerical Methods and Parameter Estimationmentioning

confidence: 99%

“…Certainly the introduction of a contact lens further complicates the basic geometry of the tear film and introduces the possibility of multiple layers (mucoaqueous and lipid) in the pre-lens and post-lens films. Recent measurements of pre-and post-lens tear films suggest a value near 2.3 μm for each (Nichols and King-Smith [16]) and, in general, different thinning rates for pre-and post-lens films (Nichols and King-Smith [17] and Nichols, Mitchell, and King-Smith [18]). …”

mentioning

confidence: 99%

Thin Film Evolution over a Thin Porous Layer: Modeling a Tear Film on a Contact Lens

Nong¹,

Anderson²

2010

SIAM J. Appl. Math.

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Abstract.We examine a mathematical model describing the behavior of the precontact lens tear film of a human eye. Our work examines the effect of contact lens thickness and lens permeability on the film dynamics. Also investigated are gravitational effects and the effects of different slip models at the fluid-lens interface. A mathematical model for the evolution of the tear film is derived using a lubrication approximation applied to the hydrodynamic equations of motion in the fluid film and the porous layer. The model is a nonlinear fourth-order partial differential equation subject to boundary conditions and an initial condition for post-blink film evolution. The evolution equation is solved numerically, and the effects of various parameters on the rupture of the thin film are studied. We find that increasing the lens thickness, permeability, and slip all contribute to an increase in the film thinning rate, although for parameter values typical for contact lens wear, these modifications are minor. Gravity plays a role similar to that for tear films in the absence of a contact lens. The presence of the contact lens does, however, fundamentally change the nature of the rupture dynamics as the inclusion of the porous lens leads to rupture in finite time rather than infinite time. [5], and Cher [6]) suggest a somewhat more complex system. In particular, the current view replaces the mucus and aqueous layers with a mucoaqueous layer in which mucins secreted from goblet cells are distributed throughout the bulk of the tear film and epithelial mucins form a complex barrier at the corneal surface. Measurements of the overall thickness of a human tear film range from a few microns to as many as 40 (see the review by Bron et al. [5]). The corneal surface itself has 100-nm-scale microbumps and rod-like mucins of length 200-500 nm that extend into the tear film [4]. These mucins have multiple functions ranging from cleanup and removal of debris from the tear film, stabilization of the tear film, and, with particular attention to the membrane-associated mucins, maintaining wettability at the corneal surface. The lipid layer, whose thickness has been estimated to range between 13-100 nm, serves to further stabilize the film and to slow evaporative mass loss (Bron et al. [5]).Dry eye syndrome is a common disorder of the human tear film that results from decreased tear production, excessive tear evaporation, and/or an abnormality in the

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Thickness of the Pre- and Post–Contact Lens Tear Film Measured In Vivo by Interferometry

Cited by 119 publications

References 20 publications

Tear Film Surface Quality with Soft Contact Lenses Using Dynamic Videokeratoscopy

Tear Film Surface Quality with Soft Contact Lenses Using Dynamic Videokeratoscopy

Mechanical Complications Induced by Silicone Hydrogel Contact Lenses

Thin Film Evolution over a Thin Porous Layer: Modeling a Tear Film on a Contact Lens

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