Alisa Sivak, MA, DipEd

Alisa assists the Centre for Contact Lens Research by writing and editing publications, reports, grant applications, and educational communications.

M.D. Willcox and colleagues (Institute for Eye Research, Australia) indentified 68 different proteins deposited on silicone hydrogel contact lenses during one month of daily wear.  They found that senofilcon A (with PHMB solution) had adsorbed the highest number of protein species (31) while protein samples from lotrafilcon B (with peroxide) and galyfilcon A (with polyquad) had the lowest number (4).  Lysozyme, lipocalin and proline rich protein 4 were detected most frequently.
M.C. Coles-Brennan (Brennan Consultants, Australia) and colleagues (Vistakon, Johnson & Johnson Vision Care) reported that a variety of silicone hydrogel lenses induce similar (statistically insignificant) corneal endothelial bleb responses.

There is currently no standard for grading corneal staining or the clinical significance of global corneal staining.  M.B. Albright and colleagues (Ophthalmology and Visual Sciences, University Hospitals Case Medical Centre, Ohio) found significant differences in methods and outcomes in comparing four grading methods with respect to clinical significance of corneal staining in photographs obtained in a longitudinal analysis of silicone hydrogel lenses.  M.M. Hom (private practice, California) reported that fluorescein dye exhibits higher grades of conjunctival staining than lissamine green dye in silicone hydrogel lens wearers.  J. Kuo and colleagues (Case Western Reserve University, Ohio) found no association between asymptomatic corneal staining and other clinical slit lamp signs during extended wear of silicone hydrogel lenses.  J.R. Webb and J.R. Paugh (Centre for Vision Research, Southern California College of Optometry) and colleagues (Alcon Research, Ltd., Texas) evaluated corneal staining and corneal barrier function with respect to lens-solution bio-incompatibility.  Their results suggest that this incompatibility mirrors corneal staining data relative to corneal compromise.

L.N.Subbaraman (Centre for Contact Lens Research, University of Waterloo) and colleagues (Department of Chemical Engineering, McMaster University) reported a gradual increase in lactoferrin deposition on silicone hydrogel and conventional hydrogel materials incubated in a lactoferrin solution.    The kinetics of this deposition varied according to the chemical structure of the lens material:  After 28 days, etafilcon A and balafilcon A adsorbed the most lactoferrin, while lotrafilcon A and B adsorbed the least. 

In a 12-month study, H.D. Cavanagh and D.M. Robertson (Ophthalmology, University of Texas Southwestern Medical Center, Texas) compared Pseudomanas binding rates to shed human corneal epithelial cells following long term daily and extended silicone hydrogel lens wear (lotrafilcon A and B, galyfilcon).  Daily wear had no significant effect on central epithelial thickness.  There was a decrease in central epithelial thickness with extended wear, and all lens wear decreased epithelial surface cell desquamation, with adaptation occurring for both over one year.  There was no significant difference between lenses or wear modality with respect to PA binding.

P. Stauffer and colleagues (Alcon Research, Ltd., Texas) studied the effect of temperature and solution osmolality on the bulk water in different contact lenses in vitro to try to explain why lens dehydration occurs during wear (in vivo).  Results showed that the diameter and water content of contact lenses depends strongly on the temperature and osmolality of the equilibration solution.  The degree of these effects varies with different lens types, particularly silicone hydrogel lens materials. 

D. Tilia (International Clinical Trials Centre, Institute for Eye Research, Australia) and colleagues found that eight days is the median duration of interruption from lens wear due to corneal inflammatory events in participants wearing silicone hydrogel lenses for three months.  The majority of events resolved within two weeks.  Events occurring in the summer and accompanied by illness were associated with a longer interruption, as were factors such as older age and climatic conditions.
Currently there are no standardized methods for evaluating lens care solutions with respect to Acanthamoeba.  S.L. Buck and colleagues (Alcon Laboratories, Texas) evaluated the activity of a contact lens solution against Acanthamoeba using modified methodology based on the FDA, ANSI and ISO Stand Alone and Regimen tests for bacteria and fungi.  They found that these methods are able to reliably and objectively evaluate lens solutions against Acanthamoeba.

M.F. Mowrey-McKee (CIBA Vision) and colleagues (Ophthalmology, Emory University, Georgia) determined the metabolic effects of closed and open eye lid conditions in the rabbit with and without silicone hydrogel contact lenses.  The open eyes (both with and without lenses) had higher aqueous glucose than comparable closed eyes, and the open eyes had lower lactate than closed eyes (with and without lenses). Open eyes (with lenses) had significantly less lactate in the cornea and aqueous humor compared to eyes wearing no lens.

Y. Zhang (Anatomy & Cell Biology, Wayne State University, Michigan) and colleagues (CIBA Vision) used a rat contact lens model to demonstrate that high-Dk contact lenses show no increase in conjunctival Langerhans cell number or risk of infection compared with no contact lens, whereas low-Dk lenses increased conjunctival Langerhans cells and Bcl-2 (anti-apoptotic) expression.