Contact lens compliance and reducing the risk of keratitis

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Previously, there was a particular requirement to carefully scrutinise the ocular surface for signs of hypoxic changes, such as epithelial microcysts and vessel dilation. With the virtual elimination of corneal hypoxia due to the increased oxygen performance of SH materials, such changes have become much less significant. For example, limbal redness has been reported as being less marked with SHs than with conventional hydrogels for both extended wear2,3 and daily wear.4

The reduced prevalence of hypoxic changes and the increase in the use of extended wear lenses has led to a greater interest in the infiltrative response of the eye during contact lens wear. In the context of a contact lens wearer, the terms 'infiltrative response', 'infiltrative event' and 'keratitis' are essentially synonymous and describe the inflammatory response of the cornea, which is characterised by the ingress of leukocytes from the local vasculature to the site of inflammation. This is seen clinically as accumulations of small white areas in the cornea which can be readily viewed with a biomicroscope (Figure 1). A wide- ranging review of contact lens keratitis has recently been presented by Efron and Morgan.5