Contact lens part 3: the ocular surface in contact lens wear: course code C-13462
Optometry Today, March 26, 2010 by Christine Purslow
Solving symptomatic problems of a contact lens wearer often forms the primary focus of patient aftercare and management. However observing the mechanical and physiological impact of contact lenses on the ocular surface also forms a fundamental part of the management of our contact lens patients Not only is it important to observe the cornea, but also the conjunctiva and eyelids. This article reviews the current understanding of some of the most frequently seen responses of the ocular surface to contact lens wear and the recommended methods for their examination and observation.
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Grading the appearance of the ocular surface
Slit-lamp biomicroscope examination of the anterior eye and adnexa is integral in contact lens practice for eye care practitioners, and an important part of such examination is to assess the ocular surface for signs of mechanical or physiological irritation, such as staining, redness and swelling. Grading our observations with accuracy and repeatability is particularly important for ongoing patient management and to establish evidence of improvement or deterioration. Most UK practitioners will be familiar with clinical grading scales. These are generally photographic eg the Cornea and Contact Lens Research Unit (CCLRU) scale, (1) or pictorial eg the Efron scale (2) (Figure 1). Today’s eye care practitioners should certainly be using a suitable grading scale in practice as it has been shown to be superior to traditional verbal descriptors in terms of reliability and repeatability. (3) This is particularly important in a practice where several practitioners work together and may see each other’s patients; having a grading scale readily available within each consulting room is vital, but it must be the same scale since cross-comparisons cannot otherwise be made. (4)
What is perhaps less well-known is the importance of interpolation of grading scores between the discrete integer intervals that are provided on the scale. The CCLRU and Efron scales are based on a zero to four scale, where ’4′ represents the most severe anchor. By grading to decimal places that are representative of points in between two successive integer points on the scale, e.g. 1.3, 2.4, 3.5 etc., the scale is expanded and the sensitivity (ability of the scale to discriminate a difference) is thereby increased. (5) However, there is a limit to such interpolation; 0.1 increments are generally considered optimal as any finer intervals would promote poor concordance between observers. (4,5)
The variability of grading scores between practitioners can be wide and they generally tend to form clusters around whole numbers. (6) However, evidence suggests that this tends to improve with training or practice
contact lens review