Introduction

Picture of Fort Lauderdale, Florida, USA

Focusing on the latest eye and vision research, ARVO 2002 has been, as always, one of the most scientifically interesting meetings. The numbers of abstract submissions did not decline much despite the difficult time following September 11, with over 5,000 abstracts reviewed. The meeting encompassed exciting symposia, minisymposia, special interest group meetings, and session presentations, providing updates on all aspects of eye and vision research. The Award Ceremonies honored outstanding scientists and/or clinicians for their research and service contributions. Dr. Brien A Holden received a Special Recognition Award for his work on research in contact lenses and public service outreach to those with unmet visual needs.

The contact lens section was relatively small in number this year but certainly not in quality and spirit, presenting advances on basic and clinical science in contact lens research. Silicone hydrogel lenses generated much interest in the Contact Lens section, with nearly one third of the total presentations on the topic.

Silicone hydrogels provide adequate wettability, mechanical property and oxygen permeability, which has facilitated the rebirth of continuous wear. The degree of overnight corneal swelling with high Dk silicone hydrogel lenses was significantly lower and the time course of deswelling following overnight wear was shorter than with conventional low Dk lens as presented by Bullimore and co-authors. Hypoxia has been the cause of an increase in myopia during extended wear. McNally and colleagues examined the factors associated with change in refractive error during a year of 6 and 30 night extended wear. Results indicated that fewer subjects had increased myopia and even a reduction of myopia in some cases while wearing high Dk silicone hydrogel lens was found.

Oxygen supply to the cornea in four soft lenses with PMMA combination systems was investigated by Florkey and colleagues from the Ohio State University, College of Optometry. The findings suggested that the components of the combination system affected oxygen uptake relative to air under both static (no blinking) and dynamic (blinking) conditions, regardless of the Dk/t value of the soft lenses. They concluded that increasing the thickness or permeability of the soft lens component did not provide for a reservoir of oxygen to the cornea during lens wear.

Hypoxia and its deleterious side-effects on the ocular surface have been largely overcome. However, one of the key challenges remaining is to reduce adverse events and enjoy truly safe extended wear. Studies presented in the section comprised the incidence rate, underline mechanisms, and clinical factors relating to the adverse events with silicone hydrogel extended wear.

Sweeney and the team at CRCERT reported the inflammatory adverse event rates over 3 years with silicone hydrogel lenses as seen in the following Table.

Further, an investigation of the factors associated with unusual cases of Acute Infiltrative Keratitis (ACIK) in Silicone Hydrogel extended wear (EW) was conducted by Carnt, Sweeney and the group at CRCERT. They speculated that higher bulbar redness and signs of blepharitis at baseline and during EW and greater corneal staining during EW may be factors associated with the development of ACIK.

Cavanagh and co-workers from UT Southwestern Medical Center conducted a one year clinical trial to investigate the effects on bacterial binding to corneal epithelium cells using daily (DW) and extended wear (EW) of high Dk silicone hydrogels and conventional hydrogel lens. They found significantly less Pseudomonas aeruginosa (PA) binding to exfoliated corneal surface cells with the wear of high Dk materials compared to the conventional lens. Although all EW showed stagnation of the ocular surface such as increased surface cell size and decreased desquamation rate as well as epithelial thickness, it was significantly less with the wear of high Dk material. They therefore concluded that the use of the high Dk materials in DW and EW should decrease the incidence of, and prospective risks of, contact lens associated infectious keratitis.

Tomlinson and colleagues examined the effects of the surface treatment procedures which were used to overcome the hydrophobic nature of the silicone hydrogel materials. They found that the procedures of surface treatment did not have a significant effect on Acanthamoebal attachment to the lens.

The efficacy and safety of an organo-selenium coating on silicone hydrogel contact lens were investigated by Mathews and co-authors. The findings indicated that the organo-selenium coating successfully blocked the formation of a bacterial biofilm on a silicone hydrogel material in vitro. The coated lenses had no deleterious effects on the cornea of rabbit based models.

Dryness is a major complaint of soft contact lens wearers. Chalmers et al presented data to show that symptoms of dryness were less frequent among wearers of high Dk silicone hydrogel lenses and less likely to report dryness as the reason for discontinuing lens wear or for unscheduled lens removals, when compared to the wearers of conventional extended wear lenses.

To determine whether lens care regimen had impact on the in vitro wettability of conventional and silicone hydrogel lens materials, Jones and the group at University of Waterloo studied the dynamic surface tension as well as contact angle of lens care regimens, and the control fluid on different hydrogel lens materials. They found a relationship between lens material and care regimen for in vitro wettability. The influence of lens care regimen and materials on lysozyme deposition and activity was determined by Senchyna and co-workers at CCLR. They demonstrated that lysozyme deposition (quantity and conformation) was significantly influenced by both lens material and care regimen.

Du Toit and the group at CRCERT compared the subjective responses and ocular surface physiology between younger (<40 years) and older (>40 years) continuous wearers of silicone hydrogel lenses. They suggested that older lens wearers may be more successful candidates of silicone hydrogel extended wear.

Conclusion

The amount of research on silicone hydrogels has increased substantially over the past year using ARVO as an index. Hopefully this trend will continue.