Alisa Sivak, MA, DipEd

Alisa is Communications Coordinator at the Centre for Contact Lens Research, University of Waterloo, Canada

Part two of our synopsis of the 2008 Meeting of the American Academy of Optometry highlights posters and paper presentations focusing on the fitting multifocal lenses, the physiological response to contact lens wear, comfort, and the demographics of prescribing trends, among other topics.  Click here to see part one of the synopsis.

Stefan Bandlitz et al. (Cologne College of Optometry, France) measured corneal hysteresis (the capacity of corneal tissue to absorb and dissipate energy) and corneal resistance (a measurement of the total viscoelastic response of the cornea during applanation) using hydrogel and silicone hydrogel lenses (one lens = modulus of elasticity 1.0, the other = modulus of elasticity 1.5).  Results showed that both measurements increase with increasing modulus and positive dioptric power.

According to Carol Lakkis and Jared Slater (Clinical Vision Research, Victoria College of Optometry, Australia), an upgraded lotrafilcon A lens (with visibility tint, inversion indicator and comfort additive in the package saline) performed comparably to a senofilcon A lens for overnight wear in terms of distance visual acuity, corneal and conjunctival staining, limbal and bulbar redness and palpebral conjunctival papillae in addition to overall comfort and comfort on insertion over a two-week period.  At two weeks, the senofilcon A lens had significantly greater front surface deposits, poorer wettability and reduced movement.  For both lenses, end-of-day comfort scores were significantly lower than scores for comfort on insertion. 

Lenses coated with selenium, a material able to block bacterial colonisation, are comparable to balafilcon A lenses with respect to staining, subjective responses and fitting, reported Jerome Ozkan and colleagues (Institute for Eye Research, Australia). This team observed less conjunctival indentation with the test lens, and all worn selenium-coated lenses showed similar antibacterial activities against S. Aureus or P. aeruginosa compared to unworn lenses.  

Lakshman Subbaraman and colleagues (Centre for Contact Lens Research, Canada; Institute for Eye Research, Australia) reported that lysozyme deposited on balafilcon A, lotrafilcon B and galyfilcon A  lenses contact lens materials does not possess antibacterial activity against certain strains of Gram positive and Gram negative bacteria.

Using an in vitro model including clinical isolates and standard reference stains, Loretta Szczotka-Flynn and colleagues (Case Western Reserve University Dept. of Ophthalmology, USA) assessed the antimicrobial activities of various marketed contact lens care solutions against bacterial biofilms.  Results showed that P. aeruginosa, S. marcescens and S. aureus form biofilm on lotrafilcon A lenses, and are resistant to the antimicrobial activity of most marketed contact lens care products.
According to Nancy Keir and Colleagues (Centre for Contact Lens Research, University of Waterloo, Canada), subjects preferred a peroxide-based lens care system when they compared it with a polyquad-based multipurpose care system formulated for use with silicone hydrogel lenses. This research team found it interesting that subjects reported longer comfortable wearing time with all lenses despite the fact that the research team recorded slightly better wettability and fewer visible deposits with the polyquad-based solution. 

Robin Chalmers, Bill Long and Timothy Giles (Independent, USA) reviewed the clinical records of 872 patients to determine whether the distribution of patient demographics and refractive error are different for a variety of lens types.  Results reveal differences across lens type.  Although silicone hydrogel lenses (536 patients) were prescribed nearly as frequently as conventional hydrogels (595 patients), findings based on patient demographics indicate some “patient selection” in prescribing:  Daily disposable lenses  were prescribed more frequently for teens than any other lens types; more toric lenses were prescribed for males than spherical lenses; daily disposables were prescribed most often for new fits.  Silicone hydrogels (toric and spherical) were prescribed for 12.4% of plus power fits compared to 16.0% hydrogels.

Jill Woods and colleagues (Centre for Contact Lens Research, University of Waterloo, Canada) reported that fitting a first time presbyopic correction with the lotrafilcon B aspheric multifocal lens required the same chair time as fitting a monovision correction. These results came from a study investigating the number of multifocal lenses required to fit 26 presbyopes who had never before been prescribed any form of presbyopic correction. 

Hayes Powell and colleagues (Advanced Medical Optics, USA) reported that PHMB uptake is highest with ionic and non-silicone hydrogel lenses, while Aldox uptake is highest with all silicone hydrogels.