No relationship was found between Dk/t and comfort.1 It has already been shown that Dk/t is not a relevant measure when differentiating between silicone hydrogel lenses in terms of oxygen performance. This research now indicates that Dk/t does not influence comfort either. In fact Noel Brennan concludes that a silicone hydrogel lens should be selected on criteria other than Dk/t.1
A relationship was found between modulus and comfort.1 This is shown in the graph. The lower the modulus, the better the comfort. This tells us that, in general, recommending lenses with a lower modulus should be more comfortable for the wearer.
The strongest correlation was between surface lubricity (coefficient of friction) and comfort.1 A lens with a smoother surface resulted in greater comfort. Professor Brennan concludes his belief is that the defining feature for lens comfort is the surface finish.1
While there are many theories on the causes of discomfort, this finding helps in understanding the potential cause better. It is felt that the relationship between the conjunctival palpebral surface and the contact lens surface leads to discomfort.1 The pathology associated with this is lid wiper epithelopathy and a strong association between staining of this area and comfort has been found.2
References
1. Sulley, A. The best CL for my patient. Optician, March 2011; 30-34
2. Korb, D et al. Lid-Wiper Epitheliopathy and Dry-Eye Symptoms in Contact Lens Wearers. CLAO. October 2002; 28:4 211-216
