Contact Lens Spectrum Supplements

Special Edition 2017

Contact Lens Spectrum

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52 C O N T A C T L E N S S P E C T R U M S P E C I A L E D I T I O N 2 0 1 7 c l s p e c t r u m . c o m SOFT LENSES W orking with stu- dents is always inter- esting for a variety of reasons. Certainly, when it comes to teaching them soft contact lens fitting, they often seem to ask the right questions. The protocol at many teaching institutions around the world is to take the central keratometry (K) values and "add something" to make the lens curvature a cer- tain amount flatter. That should be the ideal, or at least the first, trial lens to use. That sounds good for a start, but when students look for that lens, they often become disappointed to find that an "8.15-mm" base curve lens is not available in the material they had in mind. In fact, most disposable lenses have two base curves at most and usually only one diameter. In addition, we now know that an 8.6-mm base curve from company A is not the same as an 8.6-mm base curve from company B. 1 So, what then? CREDIBILITY We typically tell our students to look for the closest lens they can find — in this example, an 8.3-mm base curve maybe — somewhat undermining their belief in the strategy we presented to them. We teach them what to look for (centration and movement) when the lens is on the eye, and if the lens doesn't comply with our terms and regulations — and we test them on this — they must search for an alternative. If a lens appears to be too loose on the eye, we may not have an alternative, perhaps because only a flatter de- sign is available or no other lens parameter is available within that brand at all. At this point, our fitting method does not have much value. Worse yet, our credibility as educators begins to deteriorate. If the students wanted to choose a lens diameter based on the corneal diameter, the same problem exists. Basically, it doesn't make sense to them. Well, they have a point. It doesn't. THE BEST LENSES EVER We now have better lens materials than we've ever had and more frequent replacement of lenses than we ever could have dreamed. Replacing contact lenses once a day (daily disposables) is most likely the ultimate fre- quency. A recent study looked at replacing lenses more than once a day but found no benefits of doing that. 2 Despite having the best materials ever available and the option for daily replacement of lenses, the contact lens industry faces a large proportion of dropouts. Most of these patients state that they stopped wearing their lenses primarily because of suboptimal comfort. In the western world, for every new contact lens wearer, an- other one stops wearing contact lenses. Hence, in terms of number of wearers, the contact lens market has been relatively stable for the last several years in many parts of the world, excluding some new, up-and-coming markets. RETENTION RATE A recent study looked at factors related to the suc- cess of new contact lens wearers in the United King- dom and came to a few stunning conclusions. 3 Twelve months from the lens fitting, the retention rate (people still wearing lenses) was 74%. Of the dropouts, 25% dis- continued lens wear during the first month and 47% within 60 days. More stunningly, no alternative lens or management strategy had been attempted for 71% of dropouts. There was a wide variation in retention rates among sites, between 40% and 100%. In other words, in some practices the dropout rate was enormous (60%), while in others, it was almost zero. A n i n c o n v e n i e n t tr u t h a bo u t s o f t l e n s e d u c a t i o n THE SCIENCE AND SKILL OF FITTING A SOFT LENS E E F VA N D E R WO R P, B O P TO M , P H D

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