2003 AAO Annual Meeting, Dallas, Texas

Alisa Sivak, MA, DipEd

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

A lunch time seminar consisting of a panel discussion moderated by Rex Ghormley, past AAO president, provided an overview of the latest clinical research findings and practical information relating to silicone hydrogels.

Dallas, Texas, USA

Brien Holden, from Vision CRC, discussed the incidence of microbial keratitis (MK) with silicone hydrogels. Ongoing surveillance performed by the CCLRU has tracked 57 cases of MK in over 1 million wearers of high Dk contact lenses worldwide, and 17 cases in 83,000 wearers in Australia. Risk factors for MK include swimming without goggles, non-compliance with wear schedule, storing lenses in tap water or saline and reinserting lenses without disinfection. H. Dwight Cavanagh, from the University of Texas Southwestern Medical Center, presented the results of a study indicating that oxygen transmissibility, and not wearing schedule, regulates Pseudomonas (PA) corneal surface binding, a finding confirming an additional benefit linked to high Dk silicone hydrogels. Loretta Szczotka Flynn, from Case Western Reserve University and Cleveland University Hospitals, discussed the clinical uses of silicone hydrogels in practice, including continuous and daily wear as well as bandage and therapeutic uses. She also provided an overview of observations and complications associated with silicone hydrogel wear, including mucin balls, a transient microscyst rebound response and inflammatory complications, including CLPU.

Symptoms of Dryness and Discomfort

Kathy Dumbleton and Lyndon Jones, from the Centre for Contact Lens Research at the University of Waterloo, included silicone hydrogels in their continuing education lecture on successful contact lens wear for previously unsuccessful patients. The lecture examined common reasons for discontinuation, including (i) discomfort and redness - which can be less of a problem with the superior oxygen transmissibility of silicone hydrogels, and (ii) inconvenience associated with daily lens handling and care - which can be addressed through the continuous wear modality with these lenses.

Jeffery Schafer and colleagues from The Ohio State University displayed the results of a study aimed at characterising the dryness symptoms of 318 patients trying silicone hydrogel contact lenses for the first time. The study found that dryness symptoms decreased after six months of wear. Results also indicated that patients with less frequent and severe symptoms of dryness were more satisfied with their contact lenses, reported higher levels of comfort, and were more likely to achieve a longer continuous wearing time.

A poster presented by Carole Maldonado-Codina and Clare O'Donnell, from the University of Manchester Institute of Science and Technology reported on a case study involving a keratoconic patient with unacceptable visual acuity with spectacles and soft lenses and a history of intolerance to rigid lenses. Low Dk soft contact lenses provided good vision but comfort could not be sustained over the long wearing scheduled required by the patient. A piggy back system using a high Dk silicone hydrogel lens and a hyper Dk rigid lens provided significant improvement in visual acuity, comfort and lens wear time, with a marked reduction in corneal vascularisation and ocular hyperemia.

Ocular Health and Physiology

Philip Morgan and colleagues from Eurolens Research presented the results of a study comparing the clinical performance of a silicone hydrogel lens with that of an RGP lens when worn for up to 30 days of continuous wear for 12 months, with each lens type being worn by 50 subjects throughout the study period. Although the majority of subjects successfully completed the study without any adverse events, results revealed 16 events with silicone hydrogels compared to 6 with the RGP lenses, with no difference between experienced wearers and neophytes.

Low Dk lenses have been associated with a number of biomicroscopy signs and patient reported symptoms, particularly when worn on an extended wear basis. The results of a study examining biomicroscopy signs and symptoms in patients switching from low Dk daily wear and extended wear lenses to high Dk silicone hydrogel lenses were displayed by Sally Dillehay (CIBA Vision) and collaborators. Subjects demonstrated rapid improvement in corneal health when they began wearing high Dk silicone hydrogel lenses. These improvements, including biomicroscopy signs and patient reported symptoms, continued throughout the first year of wear.

The ability of silicone hydrogel lenses to mask astigmatism was the subject of a poster presented by Linda Edmondson and colleagues from Northeastern State University. The silicone component of silicone hydrogel lenses makes them stiffer than conventional hydrogel lenses, which means that the lenses do not drape over the cornea as readily as traditional lenses. This study, which compared a silicone hydrogel lens with a hydrogel lens, was aimed at investigating whether this lens "vaulting" can mask corneal astigmatism. The results however showed no difference in the level of astigmatism masked by silicone hydrogels compared with conventional lens materials.

Mohinder Merchea and colleagues from The Ohio State University presented the results of a study investigating the mechanisms contributing to changes in refractive error when low Dk extended (7-day) wear patients are refitted with continuous wear (up to 30 days) silicone hydrogel lenses. The study, which included fifteen patients, found a mean hyperopic shift or rebound of + 0.40 diopters, with statistically significant flattening of the anterior corneal curvature in the central and midperipheral regions.

Michael DePaolis provided an overview of the use of silicone hydrogel lenses as bandage lenses in his continuing education lecture on the contemporary uses of bandage contact lenses in primary optometric practice. The high oxygen transmissibility, deposit resistance and on eye mobility of silicone hydrogels offer many advantages for both acute and chronic applications in patients requiring bandage contact lenses.

Patient Compliance, Preferences, and Subjective Response

Lyndon Jones, from the Centre for Contact Lens Research at the University of Waterloo, provided an overview of patient and practitioner perceptions towards silicone hydrogels and refractive surgery. LASIK offers permanent vision correction, though the idea of surgery and the technique's irreversibility may deter some patients. Both convenient and reversible, silicone hydrogels offer superior oxygen transmissibility and clear, comfortable vision 24 hours a day, though consumers may worry about sleeping with lenses in their eyes, and cleaning guidelines and replacement schedules must be followed. According to Dr Jones, it is important that clinicians present their patients with all the available options, and silicone hydrogel contact lenses are a safe, reliable alternative to LASIK that many patients may find appealing.

The results of a 19-site study investigating patient experience with and management of high Dk silicone hydrogel contact lenses were displayed by Sally Dillehay (CIBA Vision) and collaborators. Results indicated that patients were very satisfied with the lenses, including lens handling for insertion and removal, comfort and vision. Few base curve and power changes were necessary in the first year of wear, and patients generally followed practitioner recommendations in terms of wearing schedule. The study also found a low incidence of complications throughout the first year of wear.

Elizabeth Hill and colleagues from Eurolens Research displayed the results of a study aimed at assessing changes in attitude to continuous wear and laser refractive surgery during twelve months of continuous wear of hyper transmissible soft and rigid contact lenses. 100 subjects wearing either silicone hydrogel or RGP lenses had an increasingly positive attitude towards continuous wear, with similar mean scores for both types of lenses. Mildly negative to mildly positive opinions of laser refractive surgery, found at the start of the study, changed very little.

Jennifer Choo and colleagues from Pacific University presented the results of a study indicating that, if worn while swimming, hydrophilic contact lens materials can accumulate microbial organisms present in the water. The study found no difference between results with silicone hydrogel and conventional soft lenses.

Also from Pacific University, Mark Fast and colleagues displayed the results of a study aimed at evaluating subjective response and overall patient preferences for either 30-day continuous wear of silicone hydrogel contact lenses or overnight corneal reshaping. In this crossover study in which each modality was worn for 60 days, 15 out of 16 subjects preferred either 30-day continuous wear or corneal refractive therapy over their current vision correction modality (soft contact lenses, RGPs, or spectacles).