Article Date: 3/1/2014

Why Dropout Rates Spike Around Middle Age

Why Dropout Rates Spike Around Middle Age

In the presbyopic population, comfort may not be the primary reason why patients abandon their contact lenses.

Dr. Jedlicka: Those of us who fit contact lenses understand all too well the challenges associated with prescribing for patients with presbyopia. Surveys have shown that contact lens use drops off in the presbyopic population,1 even though the need for vision correction increases.

Traditionally, we have believed comfort — or more accurately, lack of comfort — is the primary reason people stop wearing their contact lenses; however, the dropout rate has not changed in 15 years, despite advances in lens materials and designs.2 In your experience, what other factors come into play when established lens wearers begin to exhibit signs of presbyopia?

Dr. Anderson: Even patients who have worn contact lenses successfully for a number of years often choose to drop out of contact lenses when their near vision begins to fade. They lose the incentive to wear contact lenses when they have to wear reading glasses over contact lenses. Rather than dealing with that inconvenience, they revert to wearing eyeglasses all day.

Dr. Russell: Vision quality becomes an issue, too. With some multifocal contact lenses, patients have to give up some distance or near acuity. They may be excited about seeing with contact lenses, but when they realize they’re not seeing as well as they thought they would, they become dissatisfied and, ultimately, drop out.

Dr. Robinson: The tear film may be a factor in vision quality as well. If a lens isn’t comfortable, especially when due to dryness, patients blink to alleviate the discomfort. Then the tears start flowing, further affecting their vision.

Dr. Geffen: When patients reach an age when the compromises outweigh the benefits of wearing contact lenses, they often decide the hassle isn’t worth it.

Dr. Vogt: Addressing these challenges, as well as the fitting challenges that practitioners face, was fundamental in the design of the PureVision®2 Multi-Focal Contact Lenses For Presbyopia.

Dr. Russell: The optics of this new design have significantly decreased the compromise in vision quality. I’m certainly impressed that patients have noted improved performance, as well. The advancements in this technology have taken a giant leap forward. I think it’s going to keep presbyopes in their lenses for a much longer time.

Dr. Jedlicka: Let’s discuss some of the previously unmet needs of this patient population and how PureVision2 For Presbyopia addresses them. ●

Unmet Needs in Presbyopia

Patients’ increasing visual demands create challenges for eyecare professionals.

Patients’ visual demands at near and intermediate distances continue to increase along with the growing number of personal electronic devices they use. Many spend more than 10 hours a day on computers.3 What’s more, 88% of American adults own a cell phone, 58% have a desktop computer, 61% have a laptop computer, 18% own an e-reader and 18% have an electronic tablet.4

In a recent survey, 80% of eyecare professionals agreed that correcting near or intermediate vision is their greatest challenge when providing vision correction for patients with presbyopia.5 They also noted it takes an average of 2.6 attempts before a presbyopic patient is successfully fit with contact lenses, and approximately 3 in 10 patients are never successfully fit.5

Dr. Jedlicka: When you see patients who are exhibiting early signs of presbyopia, how do you educate them about the condition, and how do you determine their visual needs?

Dr. Russell: I think most people are aware that they’ll lose near focus around age 40. For me, the more important part of the conversation is uncovering what limitations they’re noticing because of their presbyopia. I need a good understanding of what they can’t do, so I can help them.

Dr. Robinson: In the early stages of presbyopia, when patients can still focus at near, I think they’re more likely experiencing symptoms of eye fatigue. I demonstrate this by holding +1.00 trial lenses over their current contact lenses or eyeglasses, so they can feel how hard their eyes are working to stay focused when I take the trial lenses away. Then I explain that I can incorporate that same correction into their contact lenses.

Dr. Geffen: That’s an important point. Often, patients in the early stage don’t realize what they’re missing. Just popping a +1.00D or + 0.75D over their existing prescription can be revealing. These patients stare at their iPads, smartphones and computers all day long, and they’re simply not blinking enough.

Dr. Anderson: I think more people are concerned about their near vision than their distance vision. Frequently, when I fit patients with contact lenses, they immediately take out their cell phones to see if they can read their e-mails and text messages.

Dr. Jedlicka: Intermediate and near vision is vital to people’s lives today. Is there an aspect of the PureVision®2 For Presbyopia lens that addresses this crucial visual realm?

Dr. Vogt: Our goal in designing PureVision2 For Presbyopia was to achieve improved near and intermediate vision, because that’s where we’re all working frequently. We’re using our phones and computers all of the time.

Dr. Jedlicka: With the options we previously had in the soft multifocal category, did you sometimes have to compromise distance vision to achieve acceptable near and intermediate vision?

Dr. Geffen: In general, yes. I have a huge multifocal practice, and I use many different designs, but I’ve had to compromise quite a bit with previous multifocal lens designs.

Dr. Jedlicka: A study shows that more than 50% of patients who require good intermediate and near vision for their work aren’t getting it from their current mode of correction,5 and most practitioners agree that correcting intermediate and near vision is their greatest challenge when working with patients who are presbyopic. Do you agree?

Dr. Anderson: Absolutely. When I can’t correct everything 100%, I may have to adjust the prescription to accommodate the patient’s needs.

Dr. Robinson: I’m always concerned about chair time, which, of course, translates to profitability. I also have to consider the time a patient has to take away from his job and his life to come to the office and have his lenses checked again. It’s embarrassing when I don’t get it right the first time. So it’s a profitability issue and an image issue. A succinct process using a lens that can be fitted efficiently is a tremendous benefit.

Dr. Russell: If patients are disappointed early in the process, they’re more likely to think failure is just around the corner. I have a high level of confidence in the PureVision2 For Presbyopia lens, and that bolsters the patient’s confidence, as well.

Dr. Jedlicka: With current multifocal soft lenses, have you ever had any surprises with the lens powers? For example, were you prescribing lens powers that you didn’t anticipate based upon your initial fit or refraction, because the powers weren’t providing the vision that you expected?

Dr. Russell: There’s no doubt that was happening with previous multifocal lenses, and it was costing me an enormous amount of chair time. It was frustrating to my patients AND me, and that’s not a good combination.

Dr. Jedlicka: Did you feel the need to explain to patients that the fitting process would take a few visits and a few different lens trials? If so, how did patients react to that introduction to the process?

Dr. Geffen: That’s the way many practitioners used to talk to patients. We were preparing ourselves for failure and suggesting to patients that the lenses probably wouldn’t work. I don’t do that anymore. PureVision2 For Presbyopia lenses work the same way when patients return for their follow-up visits as they did on the day I dispensed them. Not only am I saving chair time, but now I can confidently tell patients that I can give them the vision they want. I’m creating a mindset of success up front.

Dr. Robinson: One of my frustrations when fitting multifocal lenses in the past, especially the high adds, was that I believed I was choosing the correct prescription based on the spectacle Rx and the add requirement. I’d tell patients their vision might be a bit blurry initially, but I encouraged them to go home and get used to the lenses. When they returned for follow-up and I did an over-refraction, I never knew what I’d get. If I had to give this person more plus, I wouldn’t know why. Or I’d wonder if I’d have to add more minus to get better distance vision. It didn’t seem to make any sense. With the PureVision2 For Presbyopia lens, my experience is that what you see is what you get, and that makes me more confident.

Dr. Jedlicka: Dr. Russell, you said your patients have become frustrated with the process if they don’t reach an endpoint within the first couple of visits. What’s the impact of that scenario on your practice?

Dr. Russell: Eyecare practitioners want to embrace technologies and processes that are successful. If my success rate has been only 30% on the last 10 patients I’ve fit with a lens, I’m not going to be inclined to keep trying that lens.

Dr. Jedlicka: In the past, were you concerned that you’d lose patients because they lost confidence in your ability to properly correct their vision?

Dr. Russell: Yes. As Dr. Robinson suggested, maybe I didn’t have the correct powers on the patient’s eyes in the beginning. If I can’t trust what I’m fitting, how can I predictably solve a problem?

Dr. Jedlicka: The inconsistencies in multifocal powers that we noted in clinical practice were verified through research at Bausch + Lomb. The PureVision2 For Presbyopia lens was designed to minimize inconsistencies and provide a more predictable fitting experience.6 ●

Understanding Multifocal Lens Designs

Inconsistencies across powers of previous multifocal contact lenses may produce variable visual outcomes from patient to patient and lens to lens.

Understanding the power profile of a contact lens is critical to successful outcomes. Until recently, however, scientists didn’t have instrumentation that could measure power changes from the center of a contact lens to its periphery. For this reason, the distance powers of multifocal contact lenses could be labeled inaccurately. In addition, current multifocal contact lenses have variable levels of add power; this variability is compounded by the distance power variability and may result in poorer near and intermediate vision than expected.7

Power distribution variability could be a cause of inconsistent fitting experiences or an inability to predict how a lens will perform from one power to the next. Patient to patient, current multifocal contact lenses perform differently, depending on distance powers and targeted add power. This lack of consistency may result in more frequent trial lens changes and follow-up visits, and frustration for patients and eyecare professionals.

Dr. Jedlicka: Dr. Vogt, you were involved in some of the research leading to the development of the PureVision®2 For Presbyopia lens. Please share what you learned during that process.

Dr. Vogt: Bausch + Lomb partnered with a small optics company in Germany, Optocraft, to develop a novel, innovative way to measure contact lens powers. Using a high-resolution Hartmann-Shack wavefront analyzer, we developed a technique to measure more than 6,000 points across the central 6 mm of a contact lens to understand precisely how power changes from the center of a lens to its periphery.

As I began measuring existing multifocal lenses, I found an immense amount of variability across the entire power range, even within one specific design. The discrepancies were astounding, which helps explain why practitioners were unable to predict how a lens would perform. By no means were manufacturers trying to make your job more challenging. We simply didn’t have the technology to measure contact lenses accurately when these previous multifocal lenses were designed.

Dr. Jedlicka: What are some of the challenges manufacturers face?

Dr. Vogt: In the optics world, using a single material to design something that has a front surface and a back surface is relatively easy. However, when that product is a contact lens that changes shape when placed on the eye, all of a sudden, it becomes a complex optical element. As contact lens designs advanced, the measurement methods to understand how they were being manufactured didn’t exist. Only after we developed our high-resolution Hartmann-Shack wavefront sensor were we finally able to understand precisely how the power changes from the center of a lens into the periphery. We now can translate that into meaningful results to use in the manufacture of a multifocal contact lens.

Dr. Jedlicka: Were you surprised by the variability in lens power profiles between prescription and design and labeled versus actualized powers?

Dr. Vogt: Surprised would be an understatement. I first measured a competitor’s lens that had just come onto the market. I measured –3.00D lenses with high and medium Adds. At first, I thought I must have done something wrong, but it turned out that both clinically and statistically, no difference existed between the medium and the high add. This happened repeatedly over many more measurements. After I expanded the study and measured lenses from different manufacturers, I understood that the metrology techniques had not previously existed to measure the lenses. All of the manufacturers were making designs that they thought were working a certain way, but, in fact, a great deal of variability existed. These findings were a great motivation for us to design a new multifocal lens to address all of the challenges we observed.7

Dr. Jedlicka: We’ve all seen the data from Dr. Vogt’s work, showing inconsistencies in actualized powers versus labeled powers, as well as differences from one power to the next. As a clinician, what is your response to seeing those data?

Dr. Robinson: I had an “a-ha” moment.

Dr. Geffen: Yes, it explains a lot. It’s no wonder fitting multifocal lenses has been an art versus a science.

Dr. Anderson: We’re listening to our patients and trying to address their visual needs. With our current products, however, we solve one problem but create new problems. As we correct near vision, for example, we start to lose some distance vision. As we try to improve the distance vision, we lose some near vision, and we end up compromising somewhere in the middle.

Dr. Russell: How can we reliably serve our patients’ needs when our tools aren’t necessarily what they’re advertised to be? It’s a multifactorial problem.

Dr. Jedlicka: When we fit multifocal contact lenses, we start with the distance spectacle prescription. How important is it for the distance prescription of the contact lens to be accurate, especially as it relates to near vision?

Dr. Anderson: Any change you make for distance vision will change the reading vision. The quality of vision at near may drop as you try to improve the distance vision.

Dr. Robinson: This is especially important if your patient is emmetropic or close to it. For emmetropes, distance is absolutely critical, because they’ve always had good distance vision. You can’t take that away. Now that we have the PureVision®2 For Presbyopia lens that provides good distance vision, it opens up a whole new group of patients for us that we’ve not been confident fitting before, because we didn’t have a contact lens that worked for them.

Dr. Jedlicka: We all have diagnostic sets in our offices. What is more important to you as a clinician: Having more accurately labeled lenses or having more lenses or more Adds in your diagnostic set?

Dr. Geffen: What’s the use of having a multitude of lenses or Adds if they’re not what they’re labeled? It’s much more important for me to have an accurately labeled lens that is reproducible time and time again. The beauty of the PureVision2 For Presbyopia lens is that we can depend on what the labeled power says for distance and we can count on a consistent Add power.

Dr. Russell: Now that I know what I’m dealing with, I can much more reliably differentiate a distance problem from a near problem and know what to fix.

Dr. Jedlicka: When a patient progresses to needing more near correction, how important is it to be able to reliably transition him to a higher add power and know that it’s going to be effective? Does PureVision2 For Presbyopia make it easier to fit these patients?

Dr. Russell: Absolutely, because I know that I can count on the intended Add power to be there, unlike previous multifocals where there was no significant difference in High or Medium Adds. I arrive at my end point a lot faster, and that allows everyone to be more efficient with their time.

Dr. Jedlicka: That comes back to the accuracy of the power profiles, lens-to-lens, power-to-power, add-to-add. If you look at the power profiles of other lenses, you see a labeled distance prescription and a labeled add power, but you don’t see a true intermediate zone. In our computer- and cell phone-focused world, how important is having a solid intermediate zone?

Dr. Robinson: Those of us who are presbyopic and wear progressive lenses in our eyeglasses know that when we switch from a traditional progressive to a computer lens, that opens up a much wider “sweet spot,” which is much more comfortable. I like to refer to the PureVision2 For Presbyopia design as opening up the sweet spot. ●

A Multifocal Designed to Optimize Success

The PureVision®2 Multi-Focal Contact Lenses For Presbyopia employ a next-generation 3-Zone Progressive Design for a more natural visual experience at all distances.

Researchers at Bausch + Lomb used extensive computer modeling to generate the PureVision2 For Presbyopia design. They obtained biometric data and information on higher-order aberrations, residual accommodation and pupil size from individuals with presbyopia, and they built individual computer eye models to predict visual acuity. They found a high degree of correlation between what computer modeling predicted and what patients saw in a clinical setting.

The PureVision®2 For Presbyopia lens incorporates a 3-Zone Progressive Design. The central zone is designed to have more add power for near vision. For intermediate vision, the lens has a wider zone, where add power gradually transitions to an accurate distance power. Distance vision is optimized for a more natural visual experience.

Dr. Jedlicka: Compared with other multifocal contact lenses, the PureVision2 For Presbyopia lens appears to have more consistency in the near and distance zones, and a distinct intermediate zone. Is that why vision is so clear and the lens performs so well?

Dr. Vogt: That’s exactly right. In addition to studying many current designs to understand their power profiles, we measured hundreds of individual eyes. Our goal was to design a multifocal with a strong near component, a large intermediate zone and a reliable, distinct distance zone that provides accurate power at every power.

Dr. Jedlicka: Dr. Geffen, what has been your experience refitting patients from other multifocal lenses into PureVision2 For Presbyopia lenses? Are you using their previous contact lens prescriptions as the basis for the refitting, or are you starting with their spectacle prescriptions?

Dr. Geffen: With what we now know about the power profiles of other multifocal lenses — that they’re not necessarily accurately labeled — how can we even think of starting with a previous lens prescription? I think it’s vital to start with a fresh refraction.

Dr. Jedlicka: Can practitioners feel confident that transitioning from another multifocal lens won’t entail a long, drawn-out refitting process?

Dr. Geffen: I haven’t had to refit anywhere near the number of patients I used to refit with other multifocal lens designs I used in the past. It’s been a much quicker process, with much less chair time and happier patients, particularly when following the fitting guide.

Dr. Jedlicka: Dr. Russell, how do you gauge a patient’s satisfaction with a new multifocal lens? What has been your experience fitting PureVision2 For Presbyopia lenses?

Figure 1. The new PureVision®2 for Presbyopia lens was created with a next-generation 3-Zone Progressive Design.

Dr. Russell: I usually ask patients to rate their satisfaction with their current lenses on a scale from 1 to 10. Almost without exception, patients whom I’ve refit with the PureVision®2 For Presbyopia lens increase their ratings substantially. Patients are much happier when we can provide products that exceed their expectations.

In a clinical study,8 39 eyecare professionals from 10 countries refitted 422 established wearers of soft multifocal contact lenses into PureVision2 For Presbyopia lenses. After 1 to 2 weeks of lens wear, researchers found the following:

    • 89% of patients agreed the PureVision2 For Presbyopia lenses provided clear vision while they used a mobile phone or worked on a computer

    • 95% of eyecare professionals agreed that PureVision2 For Presbyopia lenses helped maintain clear near, intermediate and distance vision in real-world conditions

    • 90% of eyecare professionals agreed that PureVision2 For Presbyopia lenses were easier to fit than other multifocal contact lenses.


See Fitting Recommendatios on page 14

Dr. Jedlicka: The PureVision2 For Presbyopia lens is thinner than the previous PureVision generation, and the edge profile has been refined to enhance the wearing experience. In your experience, how does the PureVision2 For Presbyopia perform?

Dr. Robinson: I have refit patients wearing every kind of lens, and without exception, their first comment is, “Wow, I can see!”

Dr. Russell: I can’t tell you how much my expectations were exceeded by PureVision2 For Presbyopia. I agree with Dr. Robinson. The optics and performance got my attention. Many of my patients who were wearing their lenses only 3, 4 or 6 hours a day are wearing this lens successfully for 10 to 12 hours.

Dr. Anderson: I’ve switched a number of patients who were wearing PureVision Multi-Focal into PureVision2 For Presbyopia, and they have noticed a significant improvement in vision. In fact, it’s been a pleasure for me to switch patients to this lens.

Dr. Russell: When you can provide something that exceeds patients’ expectations, they are fans for life. ●

Fitting Recommendations

Thanks to scientifically and clinically validated power profiles, fitting PureVision®2 For Presbyopia is fast and efficient.

Fitting guide recommendations for the PureVision2 For Presbyopia are based on the power profiles and optical modeling used to design this lens. What’s more, the fitting guidelines were validated in a study with 39 eyecare professionals who refitted 422 established soft multifocal lens wearers into PureVision2 For Presbyopia lenses.9 Eyecare professionals who followed the fitting recommendations in the guide reported their patients were successful with a variety of tasks at all visual distances.

Dr. Jedlicka: According to practitioners who tested the PureVision2 For Presbyopia lens, following the fitting guide produced better outcomes for their patients. After using the fitting guide yourselves, what is your opinion?

Dr. Robinson: The fitting guide was a big surprise for me. I’ve been fitting multifocal lenses for years and feel like I’m an expert in this arena. I didn’t think I needed to follow a fitting guide, but following the guide made these lenses easy to fit. I found when I start with a good refraction, I can follow the guide and not have to reinvent the wheel. Our time is extraordinarily valuable. Having an accurate and easy fitting guide significantly reduces chair time, which increases our profitability. Making patients happy is our number one goal and to have someone on day one walk out with confidence and feel good about his vision is everything.

Dr. Anderson: My practice is extremely busy, and we keep a very tight schedule. In the past, if a patient expressed interest in a multifocal contact lens, I almost cringed because I knew I’d soon be running behind schedule. I’m happy to report the PureVision2 For Presbyopia fits as described when you follow the fitting guide. It’s turned fitting multifocals into more of a pleasure for me.

Dr. Jedlicka: You are contact lens experts with years of experience fitting many designs. Do you have to resist the urge to tinker with the prescription of this lens because it’s more accurate?

Dr. Russell: I was inclined to want to change something, but I’m not hearing about problems, so there’s nothing for me to change.

Dr. Geffen: I’ve been following the fitting guide, and my results have been great. It’s a much more straightforward fit, and for that reason, practitioners will really appreciate the time it saves them overall.

Dr. Jedlicka: When we’re checking patients’ distance, intermediate and near vision, we often want to use our acuity charts, but obviously, our patients don’t have these charts at home. What other methods do you use to check vision?

Dr. Anderson: I try to use real-life situations. Typically, patients wear the lenses in the office for a while, and then I ask them to step outside and look across the street to check their distance vision. When a patient returns for follow-up, I ask how he’s seeing in the distance, particularly driving at night. I ask if he can see his computer clearly and if he can read his cell phone. Those are the main areas that people notice and those activities cover the gamut of distance, intermediate and near vision.

Dr. Robinson: Outside my examination room, there’s a hallway that leads to the front of the office and a window that looks out on a bank sign across the street. That’s my distance chart. I have patients step into the hallway, look toward the window and read the bank sign. That’s the real world in real lighting in real life. If patients can read the sign clearly, I feel confident they have great distance vision. If they can text and read their e-mails, as well, then I know I have a winner.

Dr. Jedlicka: Adapting to any new optical system takes days of wear. Is the PureVision®2 For Presbyopia lens so predictable that you can let a patient leave your office with the first pair without needing to refine the fit at the initial visit?

Dr. Anderson: I’ve found the initial pair of lenses performs as well at the follow-up visit as when I dispensed them.

Dr. Russell: In the past, I’ve told patients, “Try these lenses for a week. When you come back, let me know what’s not working and I’ll try to fix it.” Patients are coming back to the office, saying, “There’s nothing to fix.”

Dr. Jedlicka: We’re saving chair time at the initial fitting and at follow-up visits.

Accuracy, efficiency, profitability

Dr. Jedlicka: How would you sum up your experiences thus far with the PureVision2 For Presbyopia lens, particularly when compared to competitive, soft multifocal lenses?

Dr. Anderson: The PureVision2 For Presbyopia lens is extremely easy to fit. My chair time has decreased, and my success rate has increased. It is now my go-to lens.

Dr. Russell: It’s easy to fit. It’s predictable.

Dr. Robinson: Agreed. Patients have good vision. It’s a slam-dunk.

Dr. Jedlicka: What is the impact of PureVision2 For Presbyopia on your practice? Do you see this lens changing the way you practice?

Dr. Anderson: I expect to be fitting more multifocals, using less chair time and having more satisfied patients.

Dr. Geffen: This lens is making my patients much happier, and happy patients are great referral sources. In addition, I’ve eliminated 5% to 10% of my office visits because success is achieved more readily. Thus, I can add another 2 or 3 examinations a week, which increases profitability.

Dr. Robinson: I won’t hesitate to suggest contact lenses, even to patients whom I may have considered difficult to fit in the past. I can’t say enough about the value of contact lens patients to the practice. The more patients I have in contact lenses, the better.

Dr. Russell: I’m a patient myself. This lens allows me to more predictably work and see what I’m doing than eyeglasses or other contact lenses I’ve tried. I’m living the difference.

Dr. Anderson: All contact lenses achieve a certain level of success, but I found the new PureVision2 For Presbyopia has a much higher level of success than any other lens I’ve worked with. Patients are seeing well and doing well.

Dr. Jedlicka: This lens should allow all of us to offer soft multifocal lens correction to more patients with a simple trial and a quicker endpoint. ●

References

1. Multi-sponsor Surveys’ 2010 WW Consumer Contact Lens Market Study Interviews conducted in Western Europe, Sweden, Russia, China, India, Hong Kong, Taiwan, Singapore, South Korea, Thailand, Malaysia, Australia and the U.S.

2. Dumbleton K, Woods CA, Jones LW, Fonn D. The impact of contemporary contact lenses on contact lens discontinuation. Eye Contact Lens. 2013;39:93-99.

3. Ipsos OTX and Ipsos Gobal @dvisor. Socialogue: If You’re Awake, Chances Are You Are Well-Connected. Data from U.S. respondents. http://www.ipsos-na.com/news-polls/pressrelease.aspx?id=5725.

4. A Closer Look at Gadget Ownership. Vision Monday. August 13, 2012.

5. Vogt AKS, Raj S, Donnelly C. Eye Care Professional and Consumer Experiences with Presbyopia. Poster presented at the European Academy of Optometry and Optics Annual Conference. Malaga, Spain. April 18-21, 2013.

6. Vogt AKS, Hovinga K. Consistency of Multifocal Contact Lens Designs. Poster presented at the American Academy of Optometry Annual Meeting. October 23-26, 2013.

7. Vogt AKS, et al. Using power profiles to evaluate aspheric lenses. CL Spectrum, 2011 (January).

8. Orsborn G, Zhang L, Merchea M, Donnelly C. A multifocal contact lens fitting guide’s impact on patient satisfaction with vision. Poster presented at the American Academy of Optometry Annual Meeting. . October 23-26, 2013.



Contact Lens Spectrum, Volume: 29 , Issue: March 2014, page(s): 7-15