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Peer-reviewed articles

2016

Walther,H., Subbaraman,L., Jones,L. W. In vitro cholesterol deposition on daily disposable contact lens materials. Optometry and Vision Science 2016;93,1:36-41. [ Show Abstract ]

Purpose. The goal of this study was to analyze how various incubation times affect the uptake of cholesterol on silicone hydrogel (SH) and conventional hydrogel (CH) daily disposable (DD) contact lens materials using an in vitro radiochemical detectionmethod. Methods. Three SH (somofilcon A, delefilcon A, and narafilcon A) and four CH (etafilcon A, nesofilcon A, ocufilcon A, and nelfilcon A) contact lenses were incubated in an artificial tear solution that contained major tear film components and a portion of radioactive 14C-cholesterol. Lenses (N = 4) were incubated for four incubation times (2, 6, 12, or 16 h) to assess the effects on cholesterol deposition. Subsequent to the incubation, the lenses were extracted using 2:1 chloroform:methanol, and the extracts were analyzed in a beta counter and (in nanograms per lens) extrapolated from standard curves. Results. In general, cholesterol deposited statistically significantly more on SH lenses than CHs (p e 0.033), with the exception of somofilcon A and nesolfilcon A materials (p = 0.067). Within the SH materials, narafilcon A accumulated the largest quantity of cholesterol (p G 0.05) and somofilcon A the lowest (p G 0.05). The uptake of cholesterol ranged from 22.63 T 2.98 ng/lens to 97.94 T 4.18 ng/lens for all lens materials. The accumulation of cholesterol was shown to be continuous throughout the 16 h of incubation, without reaching a plateau (p G 0.001). Conclusions. For the periods thatDDlens materials are worn, cholesterol deposits significantlymore ontoSHcontact lenses than CHs. This could have implications for wearers who have higher levels of lipid in their tears that are fitted with SH DD materials. Copyright © American Academy of Optometry.

Phan,C. -M, Walther,H., Gao,H., Rossy,J., Subbaraman,L. N., Jones,L. Development of an in Vitro ocular platform to test contact lenses. Journal of Visualized Experiments 2016;2016,110:e53907. [ Show Abstract ]

Currently, in vitro evaluations of contact lenses (CLs) for drug delivery are typically performed in large volume vials,1-6 which fail to mimic physiological tear volumes.7 The traditional model also lacks the natural tear flow component and the blinking reflex, both of which are defining factors of the ocular environment. The development of a novel model is described in this study, which consists of a unique 2-piece design, eyeball and eyelid piece, capable of mimicking physiological tear volume. The models are created from 3-D printed molds (Polytetrafluoroethylene or Teflon molds), which can be used to generate eye models from various polymers, such as polydimethylsiloxane (PDMS) and agar. Further modifications to the eye pieces, such as the integration of an explanted human or animal cornea or human corneal construct, will permit for more complex in vitro ocular studies. A commercial microfluidic syringe pump is integrated with the platform to emulate physiological tear secretion. Air exposure and mechanical wear are achieved using two mechanical actuators, of which one moves the eyelid piece laterally, and the other moves the eyeballeyepiece circularly. The model has been used to evaluate CLs for drug delivery and deposition of tear components on CLs.

2013

Walther,H., Lorentz,H., Heynen,M., Kay,L., Jones,L. W. Factors that influence in vitro cholesterol deposition on contact lenses. Optometry and Vision Science 2013;90,10:1057-1065. [ Show Abstract ]

PURPOSE: The purpose of this study was to analyze the impact that incubation time, lipid concentration, and solution replenishment have on silicone hydrogel (SiHy) and conventional hydrogel (CH) contact lens cholesterol deposition via in vitro radiochemical experiments. METHODS: Four SiHy (senofilcon A, lotrafilcon B, comfilcon A, balafilcon A) and two CH (etafilcon A and omafilcon A) contact lenses were incubated in an artificial tear solution (ATS) that contained major tear film proteins, lipids, salts, salts, and a trace amount of radioactive C-cholesterol. Lenses were incubated for various incubation times (1, 3, 7, 14, or 28 days), with three concentrations of lipid (0.5×, 1×, 2× tear film concentration) and with or without solution replenishment to assess each variable's impact on cholesterol deposition. After incubation, the lenses were extracted using 2:1 chloroform:methanol, extracts were analyzed in a beta counter and masses (micrograms per lens) were extrapolated from standard curves. RESULTS: Within the SiHy materials, balafilcon A deposited the greatest amount of cholesterol (p replenishing > 1× > 0.5×. CONCLUSIONS: Overall, SiHy lenses deposit significantly more cholesterol than CH lens materials, and the mass of lipid deposited is dependent on the contact lens material, length of incubation, concentration of lipids in the ATS, and the replenishment of ATS. Copyright © 2013 American Academy of Optometry.

Abstracts

2016

Walther H, Phan C, Subbaraman L, Jones L. Cholesterol Penetration into Daily Disposable Contact Lenses Using a Novel In Vitro Eye-Blink Model. Invest Ophthalmol Vis Sci 2016;57: E-abstract 1476. [ PDF ]

Qiao H, Phan C-M, Walther H, Subbaraman L, Jones L. Localizing lysozyme deposition on contact lenses using a novel in vitro eye model. Optom Vis Sci 2016;93: E-abstract 160100.

Walther H, Phan C-M, Qiao H, Liu Y, Subbaraman L, Jones L. In vitro eye model to simulate the impact of blinking on contact lens deposition and drug delivery. Optom Vis Sci 2016;93: E-abstract 160101.

Phan C-M, Walther H, Riederer D, Smith R, Subbaraman L, Jones L. Determination of the release of wetting agents from nelfilcon a using a novel in vitro eye model. Optom Vis Sci 2016;93: E-abstract 165114. [ PDF ]

2015

Walther H, Subbaraman L, Jones L. Novel in vitro method to determine pre-lens tear break up time of hydrogel and silicone hydrogel contact lenses. Invest Ophthalmol Vis Sci 2015;56: E-abstract 6105. [ PDF ]

2014

Walther H, Subbaraman L, Wettig S, Jones L. In vitro surface pressure measurements of various tear film lipids. Invest Ophthalmol Vis Sci 2014;55: E-abstract 43. [ PDF ]

2013

Subbaraman L, Walther H, Kay L, Jones L. In vitro efficiency of contact lens care solutions in removing cholesterol deposits from silicone hydrogel contact lenses. Contact Lens & Anterior Eye 2013;36,S2:e41.

Schulze M, Simpson T, Situ P, Menzies K, Walther H, Jones L. Effects of magnification on tear meniscus parameters using optical coherence tomography (OCT) images. Canadian Optometry Schools Research Conference, Waterloo, Canada, 2013.

Walther H, Subbaraman L, Jones L. Method optimization to quantify oxidative stress in tear film lipids. Canadian Optometry Schools Research Conference, Waterloo, Canada, 2013.

Walther H, Subbaraman L, Jones L. Efficacy of multi-purpose solutions in removing cholesterol desposits from silicone hydrogel contact lenses. Invest Ophthalmol Vis Sci 2013;54: E-Abstract 517.

2012

Walther H, Subbaraman L, Jones L. In Vitro Dehydration of Daily Disposable and Silicone Hydrogel Contact Lens Materials . Invest Ophthalmol Vis Sci 2012;53:ARVO E-Abstract 6121.

2011

Jones L, Lorrentz H, Walther H, Heynen M, Kay L. Impact of lipid concentration, exposure time and tear film components on in vitro model lipid deposition to silicone hydrogel and hydrogel contact lens materials. International Society for Contact Lens Research (Napa Valley, California), 2011.

Muntz A, Lorentz H, Walther H, Heynen M, Joyce E, Sickenberger W, Jones L. Utility of a pulsating contact lens case to aid cholesterol removal from contact lens materials soaked in a no-rub MPS regimen. Contact Lens & Anterior Eye 2011;34,S1:S9.

Walther H, Lorrentz H, Kay L, Heynen M, Jones L. The effect of in vitro lipid concentration on lipid deposition on silicone hydrogel and conventional hydrogel contact lens materials. Contact Lens & Anterior Eye 2011;34,S1:S21.

Schulze M, Simpson T, Situ P, Menzies K, Walther H, Jones L. Effects of magnification on tear meniscus parameters using optical coherence tomography (OCT) images. Optom Vis Sci 2011;88:E-abstract 115482.

Situ P, Simpson T, Schultze M, Menzies K, Walther H, Jones L. Intra- and inter-operator variability of meridional corneal and epithelial thickness measurements obtained using optical coherence tomography (OCT). Optom Vis Sci 2011;87: E-abstract 115021.

Lorentz H, Walther H, Heynen M, Kay L, Jones L. Radiochemical kinetic uptake of three lipids on silicone hydrogel and conventional hydrogel contact lens materials. Invest Ophthalmol Vis Sci 2011;52:E-Abstract 6479.

Walther H, Lorentz H, Heynen M, Kay L, Jones L. The effect of concentration the in vitro radiochemical uptake of three lipids on silicone hydrogel and conventional hydrogel contact lens materials. Contact Lens & Anterior Eye ;34,s21:.