Silicone hydrogels - the future looks bright

Serina Stretton, BSc, PhD Serina is a science writer for the Vision CRC and the Institute for Eye Research in Sydney, Australia and has written and contributed to a broad range of research papers in the fields of optometry, clinical science and public health.

This year silicone hydrogel lenses have made even further progress towards a lens of first choice for most patients and have shown that the positive attributes of these lenses are not only those associated with the elimination of hypoxia. Five silicone hydrogel lens types are now available (Table 1) and a new silicone hydrogel lens material, comfilcon A (Biofinity™; CooperVision), was very recently launched at the American Academy of Optometry (AAO) annual meeting in December. Moreover the large increase in the number of silicone hydrogel daily wearers over the year is confirmation that the majority of patients can be refitted from conventional hydrogel lens wear to silicone hydrogel daily wear with excellent results.

The considerable benefits of high levels of oxygen are now available to a broader range of lens wearers; there has been an increase in the range of lens powers for each silicone hydrogel lens type, two silicone hydrogel toric lenses are now available; and two silicone hydrogels are approved for therapeutic use. The toric silicone hydrogels currently available provide good visual acuity and comfort and induce far less corneal swelling compared with hydrogel toric lenses. Several case-studies presented over the year indicate silicone hydrogel therapeutic lenses are an excellent choice for recurrent corneal erosions, irregular corneas, keratoconus, and as bandage lenses, particularly when routinely applied after refractive laser surgery.

The first reports on population and hospital-based epidemiolgic studies of microbial keratitis and silicone hydrogel lens wear were published this year. These reports indicate that silicone hydrogel extended wear poses no greater risk of microbial keratitis compared to conventional hydrogel extended wear. Moreover the risk factors associated with silicone hydrogel extended wear and infection are very similar to all lens wear. For practitioners these reports tell us that we should constantly remind patients to comply with lens care and cleaning regimens, particularly when traveling and must stipulate that patients remove their lenses and contact a practitioner as soon as they are aware of red to painful eyes.

One of the key issues that has arisen this year has been what level of oxygen is sufficient for maintaining corneal health?  To answer this question, practitioners need to better understand the lens and material differences between each lens type and how calculated oxygen transmissibility varies across lenses of different powers and thicknesses. When choosing a lens that best suits their patients, practitioners must consider fitting characteristics, comfort, lens modulus and wettability in the highest Dk material available to give all patients the greatest benefit of high levels of oxygen. You can view a summary of the lens and material properties of the 5 currently available silicone hydrogels in this month’s poster by Ross et al, from Aston University, Birmingham in the UK.

The silicone hydrogel website team warmly thank you for your support and we look forward bringing you the latest in silicone hydrogel developments in 2006.