Academy 2006 was held in Denver, Colorado. Silicone hydrogel lenses generated much interest in the meeting, with 23 posters and 8 paper presentations.

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Silicone hydrogel fitting trends

Samantha Hornberger (Indiana University) and co-workers reported on the silicone hydrogel fitting trends in the Indiana University School of Optometry (IUS0) clinic system. They showed a clear increase in the prescribing of silicone hydrogel materials in the IUSO clinics. The authors also concluded that this growth is probably attributable to both the release of new lens designs and to an overall increased awareness of the benefits of silicone hydrogel lenses.

Deborah Jones (University of Waterloo) and co-workers evaluated the contact lens fitting preferences of Canadian optometrists over the period of 2000 – 2006. The authors reported that soft contact lenses were fitted to 91.3% of the patients, of which a large proportion were silicone hydrogels The percentage of silicone hydrogel lenses fitted increased from 5.4% in 2000 to 42.9% in 2006. New products have been embraced by the profession and a significant market share increase has been demonstrated over the seven years of the survey.

Contact lens materials

Lyndon Jones and Kathryn Dumbleton (Centre for Contact Lens Research) conducted a course that described the development and usage of silicone hydrogel contact lens materials for a variety of “specialist” applications including keratoconus, grafts, piggybacking and therapeutic purposes. It also included information about novel future applications of custom, “made-to-order” silicone hydrogel lenses that could be used in aphakia, toric designs, multifocals, advanced post surgical designs etc.

Gary G. Gunderson (Illinois College of Optometry) and co-workers evaluated 30 eyes with corneal astigmatism between 0.62 D and 2.50 D. Five different silicone hydrogels (at -3.00D) with different lens modulus measures were evaluated for each of the 30 eyes. A negative correlation was found between the modulus of each lens and both the shape factor and corneal irregularity measurement. The authors showed a correlation between higher lens modulus (stiffer material) and a change in asphericity causing a decrease in irregularity on the front surface of the contact lens while being worn by patients.

Oxygen permeability and epithelial barrier function

Philip B Morgan, (Eurolens Research, The University of Manchester), measured the oxygen permeability (Dk) of currently-available silicone hydrogel contact lens materials. The values obtained were broadly similar to manufacturer-claimed values except for lotrafilcon B and balafilcon A lenses. The authors concluded that these differences may be caused because of the different measurement technique used or edge and/or boundary effects of the lens.

Klaus Ehrmann, (Vision Co-operative Research Centre, Sydney) generated the oxygen transmissibility (Dk/t) profile maps across various contact lenses in different powers. Lens thickness measurement, Dk/t measurement and calculation of material-specific Dk were performed on five silicone hydrogel lenses. The authors reported that the contact lenses made from the same material in different shapes supply different amounts of oxygen to the cornea. Dk/t based on centre thickness of a -3.00D lens is unrepresentative of physiological performance. A more relevant measure is to calculate the area-weighted mean transmissibility.

Percy Lazon de la Jara (Vision Co-operative Research Centre, Sydney) and co-workers determined the corneal oxygen consumption with different silicone hydrogel lenses under open and closed eye conditions. The results from this study showed that the human eye models relating equivalent oxygen percentage to lens lens oxygen transmissibility (Dk/t) showed higher concentrations of oxygen underneath the lenses with higher lens Dk/t for both open and closed eye conditions. The authors concluded that oxygen flux does not provide a useful way to assess and discriminate corneal oxygenation with different contact lenses on the eye.

Meng C. Lin (Clinical Research Center, UC Berkeley School of Optometry) compared the effects of 30-day continuous wear (CW) of gas-permeable (GP) and silicone hydrogel lenses on epithelial barrier function. The results from this study showed that there was a substantial decrease in epithelial barrier function during 30-day CW with silicone hydrogel lenses, but not with GP lenses.

Bandage lenses

A comparison between two silicone hydrogel lenses used in continuous-wear post LASEK was made by Raquel Gil-Cazorla, (Escuela Universitaria de Optica (UCM)) and colleagues. Patients were randomly fitted with balafilcon A in one eye and galyfilcon A in the other. The authors found that both balafilcon A and galyfilcon A can be used as bandage lenses on a continuous wear basis. There was no difference in epithelium integrity amongst lenses although patients report better comfort with Acuvue Advance.

Clinical trials

Anne N Brobst, (CIBA Vision Corporation) conducted a multi centre study that compared the clinical performance of lotrafilcon B toric to galyfilcon A toric lenses. After 2 weeks, lotrafilcon B toric lenses displayed better centration, axis orientation and lens wetting, while galyfilcon A toric lenses displayed less edge lift. After four weeks of lens wear, lotrafilcon B toric lenses also showed less front surface deposits, less conjunctival staining, overall lens preference and handling.

Priya Janakiraman (CIBA Vision Corporation) and co-workers compared the clinical performance of lotrafilcon B with galyfilcon A lenses during a 2 week period of daily wear use. Lotrafilcon B lenses were superior in performance compared to galyfilcon A lenses in terms of comfort, dryness, subjective redness, deposit resistance, corneal and conjunctival staining over two weeks of daily wear. There were no differences in objective redness measurements between the two lenses.

Noel A. Brennan (Brennan Consultants) evaluated the performance of Biofinity lenses during 12 months of continuous wear compared to other silicone-hydrogel lenses. Biofinity lenses were found to offer performance advantages over first generation silicone-hydrogel materials for continuous wear. On preference scales, the Biofinity lens was superior to both control lenses (lotrafilcon A and balafilcon A lenses) for comfort.

Priya Janakiraman (CIBA Vision Corporation) and co-workers evaluated the clinical performance of lotrafilcon B toric lenses on adapted ocufilcon D and alphafilcon A toric lens wearers. Each trial lasted 4 weeks and included 2-week and 4-week follow-up visits. The authors showed that lotrafilcon B toric lenses provided better visual acuity and showed better physiological response (showed significantly less limbal, palpebral and bulbar redness) when compared to the habitual, low Dk lenses. Subjects also reported better comfort and handling with lotrafilcon B toric lenses.