Alisa Sivak, MA, DipEd

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

Adverse events

Michael Wyss and Michael Baertschi (ODs) used grading scales to confirm the clinical presentation of follicular-like conjunctivitis associated with silicone hydrogels (FoCoSi), a subtype of papillary conjunctivitis.  Results showed an incidence of 3.8%.  Continuous wear of lotrafilcon A and senofilcon A lenses had the highest affinity for developing this condition, which has both an active and a dormant form.  Symptoms were closely correlated with flurorescein staining.  The development of FoCoSi appears to be associated with protein and lipid deposition and air pollution, rather than mechanical irritation.

Jerome Ozkan and colleagues (Brien Holden Vision Institute, Australia) reported the results of a study in which 100 subjects wore silicone hydrogel lenses on a continuous wear schedule, but replaced lenses daily, either before sleep or after waking.  Saline drops were instilled prior to insertion of the new lenses.  Results showed that compared to monthly replacement of lenses, daily replacement of lenses in the morning coupled with instillation of a drop during continuous wear leads to a reduction in mechanical events (mainly corneal erosion) but does not lead to a reduction in the rate of corneal infiltrative events. 

Although silicone hydrogel contact lenses provide the corneal surface with exceptional oxygen levels, problems with corneal inflammation and infection still arise. Michelle Flint and William Miller (University of Houston, USA) used in vivo fluorophotometry to determine tear exchange rate for 15 patients wearing 7 different silicone hydrogel contact lens materials, to see if these complications may be due to insufficient tear exchange and subsequent tear stagnation.  Lotfrafilcon A had the slowest decay rate, followed by lotrafilcon B, etafilcon A, galyfilcon A, senofilcon A, comfilcon A, balafilcon A, and enfilcon A. Lotrafilcon had the largest vertical movement, and senofilcon A had the smallest vertical movement.

In a study in which 205 subjects wore lotrafilcon A lenses for continuous wear over one year, Loretta Szczotka-Flynn (Case Western Reserve University Dept. of Ophthalmology, USA) reported that contact lens bioburden significantly increases the risk for symptomatic or significant corneal inflammatory events, but not less severe events.

Reviewing the clinical charts of 1,276 soft lens-wearing patients, Robin Chalmers (Indiana University, USA) and colleagues confirmed that the risk factors for inflammatory and infectious events in contact lens wearers associated with clinical practice is similar to those reported previously in prospective, controlled clinical trials.  Risk factors for all types of events included prescription over 5.0D, whereas a reduced risk was associated with male gender and hydrogel lens use. Risk factors for inflammatory events included age under 25 years and silicone hydrogel lens wear. Risk factors for infectious events included age less than 25 years. Daily disposable lenses were not associated with inflammatory or infectious events.

Staining

Jennie Diec and colleagues (Brien Holden Vision Institute, Australia) reported that a peroxide-based lens care solution had a statistically lower likelihood of being associated with first event solution-induced corneal staining with silicone hydrogel lenses, compared to polyquad- and PHMB-based multipurpose solutions.  Study subjects wore galyfilcon A, senofilan A, lotrafilcon A, lotrafilcon B, balafilcon A or comfilcon A lenses on a daily wear basis over three months, with overnight disinfection.

Daniel Tilia and colleagues (Brien Holden Vision Institute, Australia) confirmed that symptoms of discomfort may not be present with solution induced corneal staining, which they found during the course of a short-term study with silicone hydrogel lenses, worn contra-laterally and disinfected overnight in a polyquad-based lens care solution.  Subjective comfort ratings indicated that there was no significant difference between eyes with and without solution-induced corneal staining.  Over the course of the study, a total of 13% of eyes (n=20) developed solution-induced corneal staining, 85% wearing balafilcon A and 15% wearing galyfilcon A.

Bridgette Yeoh and colleagues (I & Vision Research Centre Pte. Ltd., Singapore) confirmed that silicone hydrogel lenses disinfected with a hydrogen peroxide system showed a significantly lower incidence of corneal staining.  When staining was present, its percentage area was significantly less.  Thirty subjects were randomly assigned to wear senofilcon A, lotrafilcon A, or balafilcon A lenses for 30 minutes, using a polyquad-, PHMB-, or peroxide-based lens care solution. The combination of balafilcon A lenses and polyquad-based solution produced the highest average area of staining. The combination of senofilcon A lenses with PHMB-based solution produced the highest average incidence of staining.

Daniel Krall (Southern California College of Optometry, USA) and colleagues confirmed that greater fluorescein dye diffusion is associated with higher levels of corneal staining.  Balafilcon A lenses were soaked in polyquad, PHMB or saline, and were worn by subjects for two hours, after which epithelial barrier function was determined, corneas were stained and graded, anterior chamber fluorescence was measured.

Clinical trials

Adam Coffee, Graeme Young and colleagues (Visioncare Research, Ltd., UK) fit 206 subjects with senofilcon A multifocal lenses.  If they were unsuccessful after one week, they were refit into another multifocal lens.  The senofilcon A lenses had a success rate of 74% after two visits, while the other multifocal lenses had a success rate of 68%.

Langis Michaud and colleagues (Université de Montréal L'École d'optométrie, Canada) compared the clinical performance of senofilcon A lenses to that of omafilcon A lenses with 30 patients who had contact lens-related dry eye. Senofilcon A induced less limbal hyperemia but did not differ from omafilcon A with respect to conjunctival hyperemia and corneal staining. Both materials provided more end-of-day comfort than subjects’ habitual lenses.  Two thirds of the patients preferred senofilcon A lenses, citing longer continuous hours of comfort and reduced ocular dryness at the end of the day.

Joseph Rappon (CIBA VISION Corporation) and Michael Rothschild (OD) compared two centre-near silicone hydrogel contact lenses in a multi-centre study with a total of 48 subjects.  While visual acuity and biomicroscopy findings were similar for both lenses, vision (e.g. distance/near vision, night vision, eye strain) and comfort ratings were superior with lotrafilcon B multifocal lenses than with balafilcon A multifocals. 

Innovative uses of silicone hydrogels

Susan Kovacich and colleagues (Indiana University, USA) reported three cases in which patients successfully piggybacked silicone hydrogel lenses on silicone hydrogel lenses.  In addition to allowing some patients to wear a GP lens more comfortably, combining two silicone hydrogel lenses makes it possible to calculate the final power of a high power lens, which the patient can wear until the correct prescription lenses can be ordered and dispensed.

Anne Brobst and colleagues (CIBA VISION Corporation) surveyed consumers and practitioners in three European regions about their experience with sifilcon A (custom) contact lenses. The majority of patients were satisfied with the comfort, vision and handling of these lenses, preferring them over their habitual contact lenses.

UV protection

Investigating the effects of irradiation with UV lamps on the eyes of rabbits, Li Lin and colleagues (Oakland University, USA) reported that a senofilcon A is highly protective of the lens and cornea against UVB-induced damage in vivo, including lens opacification, whereas a non-UV-absorbing lens did not protect the eye at all.