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Abstract
Ocular inflammation secondary to bacterial contamination of contact lenses during wear remains a problem. Rare but sight-threatening contact lens related corneal infection can also occur. Previous studies have shown that overnight lens wear in the same lens results in increased risk of corneal infection and contamination of the lens surface by bacteria has been associated with adverse responses. Increased bacterial load on lenses is a risk factor for development of corneal infection. The objective of this thesis was to investigate the effect on adverse event incidence when a range of lens maintenance interventions were adopted, during extended wear, including daily lens replacement, daily lens cleaning or daily antibiotic drop instillation. The hypothesis tested was that a new or cleaned lens or one exposed to an antibiotic, during extended wear, would result in less bacterially-driven adverse events.
A prospective extended wear clinical study (with no intervention) was conducted to determine the risks related to extended wear and adverse event incidence. This study determined the incidence rate of infiltrative and mechanical events and also showed that lens contamination increased the risk of developing inflammatory adverse events
This was followed by a series of extended wear studies, each investigating the effect of different lens maintenance interventions on adverse event incidence at the same study site. Nightly lens replacement during extended wear had the least reduction in adverse events. Handling lenses prior to overnight lens wear appeared to overwhelm the benefit offered by a new lens surface. Morning lens replacement during extended wear resulted in reduced incidence of mechanical (1.2% vs 5.2%, p = 0.02) and total adverse events (4.0% vs 8.9%, p = 0.04). The interventions of morning lens replacement, daily lens cleaning and daily antibiotic drop instillation, during extended wear, did not significantly reduce infiltrative adverse events. However, overall there was a consistent trend toward reduced adverse events with these interventions compared to the control groups suggesting that reduced exposure to potentially contaminated lenses might reduce complications which has implications for development of contact lenses with an antimicrobial surface.