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Introduction to Bifocal Projects

While the NIDRR funded BIFOCAL PROJECT (grant #H133G050340) is the crown jewel of the R2D2 Centerís research on the subject of bifocal eyeglasses, it is far from the only project. Preceding the BIFOCAL PROJECT were two theses that were vital to obtaining the NIDRR Grant. The first thesis was completed by Abby Brayton, under the supervision of Dr. Roger O. Smith. This pilot study examined the functional vision of middle-aged participants while wearing bifocal glasses. The second thesis, conducted by Traceey Joerger, under the supervision of Dr. Roger O. Smith, compared the gait of novice young bifocal wearers to that of novice young users of walkers.

The BIFOCAL PROJECT grant produced three theses. The first was completed by Carleen Paprocki, under the supervision of Dr. Roger O. Smith. This project used a search and choice paradigm to examine the difference in bifocal wearersí performance in finding a target amongst an array. The second, completed by Kristi Vandenbush under the supervision of Dr. Roger O. Smith, examined the process of creating and testing a large screen display 3-D image paradigm for testing the depth perception of individuals wearing bifocal glasses. The third thesis, completed by Katie Stalberger, under the supervision of Dr. Roger O. Smith and Kathy Rust, examined the gait of new bifocal glasses wearers over six months.

Research in this field continued after the completion of the BIFOCAL PROJECT. Four projects were conducted, three funded by the UWM Office of Undergraduate Research (OUR), and one funded by the College of Health Sciences (CHS) Research and Graduate Committee SEED grant. Importantly, at this time, the projects were grouped under the heading of multifocal lens eyeglasses or MfLs for short, to account for the different types of multiple lens glasses. These include the traditional lined bifocals, but also include trifocals and unlined progressive eyeglasses. This reflects the trend of more people preferring the unlined progressive-type lenses. As we have begun to discover, while all MfLs have a lower, or add, region that magnifies for near distance viewing, the type of MfL may have a profound and different effect on a personís gait and the probability of falling in different circumstances.

A thesis completed by Autumn Milanowski, under the supervision of Drs. Roger O. Smith and Kurt Beschorner and Dennis Tomashek, examined the gait of novice bifocal wearers. What made the project unique was the introduction of motion capture to objectively measure changes in gait when wearing the bifocal glasses. The CHS SEED funded project, conducted by Dennis Tomashek and Drs. Kurt Beschorner and Kevin Keenan, also employed motion capture to measure the amount of foot displacement while stepping to a target caused by different strength MfLs. Most recently two Student Undergraduate Research Fellowship grants (SURFS) were conducted. The first, conducted by Traci Dolski under the supervision of Dennis Tomashek, pilot tested the addition of visual tasks to an established gait assessment in order to create a vision-specific gait assessment tool. The second SURF, conducted by Lauren Below under the supervision of Dennis Tomashek, pilot tested a search and choice paradigm to measure a personís distant edge contrast sensitivity using a large screen display.

Bifocal Project Summaries

Testing the effects of multifocal lenses on contrast sensitivity using a visual choice paradigm Below, L. & Tomashek, D. (2011-2012)

The objective of this research is to create a reliable and valid measure of distant edge contrast sensitivity which can discriminate between participants wearing single and multifocal lens glasses. This study used a within-subjects repeated measures design, to examine the mean differences between lens conditions. Participants were asked to make judgments about four figures projected onto a screen as they stood with their head in a stable position. Different lens conditions were used to determine the effect of no glasses and clear, bifocal, and progressive lens glasses. Each figure had one of 4 differently oriented contrast edges. One figure within each set had a different line of orientation which denoted the correct response. Reaction time was also measured to determine how quickly the participants were able to locate each response. Data analysis looked at both error rates and response times. The analysis revealed a hierarchy of performance. When wearing clear lens glasses, participants performed the same as wearing no glasses. When wearing progressive lenses, participants were significantly.

This study was funded through a grant from the UWM Office of Undergraduate Research (OUR) Student Undergraduate Research Fellows (SURF).

Comparing gait parameters while walking and performing visual tasks with and without the use of multifocal lens glasses, Dolski, T. & Tomashek, D. (2011-2012)

This exploratory pilot study explores whether modified tasks of the Dynamic Gait Index (DGI) assessment identified functional gait problems during walking and visual tasks caused by wearing multifocal lens glasses (MfLs). The DGI is intended to assess individual's ability to modify balance while walking in the presence of external demands. In this study the scoring scale and tasks have been modified from the Dynamic Gait Index (DGI) to be more sensitive for individuals who wear MfLs. Subjects completed the same set of visual and walking tasks while wearing MfLs and with single lenses. The tasks were designed to cause the participants to vary focal lengths by using near, middle or distant visual tasks while walking over or around obstacles. Emerging data reveals that functional gait is negatively affected while multitasking walking and visual tasks. There were significant differences in negative gait performance while wearing MFLs versus single lenses. There was also significantly decreased self-reported comfort while wearing MFLs versus single lenses. Further exploration is needed to continue to determine which combination of visual and walking tasks are most sensitive to MfL use while walking.

This study was funded through a grant from the UWM Office of Undergraduate Research (OUR) Student Undergraduate Research Fellows (SURF).

Influence of Corrective Lenses on Foot Displacement during Gait, Tomashek, D., Keenan, K., Beschorner, K., Moore, C., & Dolski, T. (2010-2012)

The purpose of the study is to test the research protocol for measuring foot displacement caused by various strength add lenses through the use of force plate and motion capture technology. Each participant completed 96 trials of a walking task will involve the participant stepping down from a 6" raised platform, which will abut a force plate. Three possible target locations will be projected in a vertical row on the force plate. Two test conditions will be performed. The first will have the participant stand at the edge of the platform. They will be instructed to step down onto the projected target. In the second condition, participants will begin walking at the prescribed pace toward the end of the platform. The participant will then proceed to step down onto the force plate, attempting to step on the projected target without stopping, and precede two more steps. Three add strengths (+1.75 [low strength], +2.50 [medium strength], and +3.50 [high strength]), and a no add region glasses condition will be randomly distributed over the 80 trials. The glasses will be clear, non-prescription on the top, and the add region will be in the lower portion. The glasses will be provided by the researchers to ensure uniformity. The main measures to evaluate the hypotheses will be center of pressure of the foot while stepping to the target, toe clearance of the foot stepping down from the platform, maximum ankle dorsiflexion during step down, and the time to step to the target.

This research was funded by a UWM College of Health Sciences (CHS) Research and Graduate Program Committee (RGPC) Stimulus for Extramural Enhancement & Development (SEED) grant.

Role of Multifocal Lens Glasses on Walking Balance, Milanowski, M., Beschorner, K., & Tomashek, D. (2010-2011)

Background: It is estimated that over 85% of adults over the age of 45 develop a condition called presbyopia (Holden et al., 2008). Multifocal lenses (MfLs) are used to functionally adapt to this condition to allow for convenient near and distance vision. However, this causes vision distortion in the lower part of the visual field at ground level while walking. Since safe ambulation relies on the lower visual field to detect obstacles (Marigold et al., 2008), and vision acts as a moderating factor for increased fall rates as individuals age (Heasley et al., 2005), there is a need to investigate the connection between MfLs, falls, and age. Objective: This study hypothesized that when wearing MfLs, both young and middle-aged individuals would experience a significant decrease in functional gait performance when compared to wearing single lenses. In addition, non-experienced MfLs wearers would both show similar within group gait performance decrement. Methods: Sixteen 18-35 year olds and seven 45-60 year old novice MfL wearers with no history of balance or gait impairments participated. A within-between subjects repeated measures ANOVA and t-tests evaluated the effects of MfLs and age on toe clearance, step force, and functional gait (the Dynamic Gait Index-Modified). Results: A statistically significant difference in toe clearance and DGI-m scores were found for young and middle-aged individuals between lens conditions. Young group: increase in toe clearance (t=4.801, p=.000) and decrease in DGI-m scores (t=-3.9, p=.001); Middle-aged group: increase in toe clearance (t=3.230, p=.018) and decrease in DGI-m (t=3.092, p=.021). No significant difference between groups was found (DGI-m F=.020, p=.836, toe clearance F=.015, p=.905, and maximum force F=.463, p=.505). Due to the multiple t- tests performed, an adjustment of a .0125 alpha was used for a significance threshold. Conclusion: MfLs appear to not only degrade visual performance, but also degrades key components of gait performance. The results of this study provided evidence that contributes to the validation of MfLs as a possible fall risk.

This study was partially funded through a grant from the UWM Office of Undergraduate Research (OUR) Student Undergraduate Research Fellows (SURF).

Immediate and Longitudinal Effects of the Adaptation to Multifocal Lenses by Middle-aged Adults, Stalberger, K., Smith, R., Rust, K., Tomashek, D. (2007-2009)

This study measures the effect of newly acquired multifocal lens eyeglasses on functional vision and gait performances, as well as falls rate over a six month period. The design of this study is a longitudinal, within-subjects repeated measures MANOVA. 28 middle aged adults who were transitioning to multifocal lens eyeglasses participated in this study which was conducted in a large hospital. Depth perception measured with the Howard-Dohlman apparatus; distant edge contrast sensitivity measured with an enlarged Melbourne Edge Test; functional gait measured with a modified Dynamic Gait Index; and number of falls. Results of this study showed significant reductions in both vision and gait performance were evident. Some performance improved slightly over 6 months, but did not return to pre-multifocal lens glasses levels. Falls did not increase. This study concludes that as a person ages, the risk for falls increases due to physiological decreases in such factors as strength, balance, and vision. Multifocal lens eyeglasses are commonly prescribed for people in the 40-60 age range to correct both near and far vision. The outcomes of this study found that for middle aged new multifocal lens wearers, profound decreases in depth perception, distant edge contrast sensitivity (both aspects of vision important for safe walking), and functional gait were immediately evident. These decrements were evident 6 months later, well past the currently ascribed 6-12 week period for adaptation, thus putting many aging adults at increased risk for falling. Clinicians and therapists need to take the use of multifocal lens eyeglasses into account and advise clients of all ages on the potential future perils of multifocal lens glasses when walking.

This study was funded through a U.S. Department of Education and Rehabilitative Services (OSERS) National Institute on Disability and Rehabilitation Research (NIDRR) grant (#H133G050340).

Falls and gait discomfort induced by multifocal lens eyeglasses: A longitudinal study of middle-aged new wearers, Tomashek, D., Smith,R., & Rust, K. (2007-2009)

This manuscript describes a study which compares self-reports of discomfort while performing walking tasks to gait performance using a modified version of the Dynamic Gait Index (DGI-m) when adapting to multifocal lens glasses (MfLs). The design of this study is a longitudinal within-subjects repeated measures that took place in a therapy room of a large Midwestern hospital. There were 28 (21 females, 7 males) participants, mean age = 48.4 (SD=5.19) who were first time MfLs users at the beginning of the study. A self-report questionnaire was used to measure discomfort levels while performing walking tasks, and ratings on the gait tasks of the DGI-m by a trained observer. This study found that participants reported significant increases in the level of discomfort when first wearing MfLs. For most participants, the levels of discomfort decreased over the 6 months. However, for a significant minority (9), discomfort levels remained high. Correlations between self-reported discomfort levels and performance ratings were non-significant, although trended negatively, as hypothesized. As expected, all participants reported immediate increases in self-reported discomfort levels and decreases in gait performance when wearing MfLs for the first time. Most participants returned to near pre-MfL levels in self-reports and gait performance. However, a significant portion of participants maintained high levels of discomfort and lower gait performance. These results have significant implications for clinicians and therapists. As 80% of all adults over 65 need multifocal glasses, the findings from this study indicate that for many, MfLs are not a viable option, and may lead to increases in falls and reduction in quality of life. Thus, there is a pressing need for screening and alternative interventions for this population.

This study was funded through a U.S. Department of Education and Rehabilitative Services (OSERS) National Institute on Disability and Rehabilitation Research (NIDRR) grant (#H133G050340).

The Effects of Multifocal Lenses on Visual Attention and its Interaction on Motor Performance, Vanderbush, K. & Smith, R. (2008-2009)

This study investigated the effect of multifocal lens use by recording response times through the development of a multifocal eyeglasses assessment of perceptual motor performance (MEA). Visual response conditions varied as the paradigm was developed with data collection runs focusing on luminance and depth. The study addressed three specific hypotheses: 1) A subject responding to a target in the lower visual field will perform faster when wearing single lenses than when wearing multifocal lenses. 2) The inclusion of a visual distracter will slow down response times when wearing single lenses. 3) A subject wearing single lenses will perform faster when presented with a target and a distracter in the lower visual field than when wearing multifocal lenses, as the distracter will have less of an effect in the lower field.

Hypothesis one, revealed that subjects 2, 4 and 5 showed a significant effect both visually and statistically. When wearing the multifocal lenses, these subjects performed more slowly in a visual-motor-perceptual task with targets in the lower visual field. For hypothesis two, subjects 1, 2, 3 and 6 were tested for the distracter effect. Single lens and multifocal lens response times were compared when targets were presented in the upper visual field with and without a distracter present. Subject Six demonstrated a distracter influence through visual analysis. Hypothesis three tested the relationship of multifocal and single lens use on visual attention. Subject Two showed a significant difference with inferential analyses, but this was not evident visually. To better understand the overall effects, the 14 complete data sets of the six subjects, were analyzed by running a two way ANOVA by each single subject. Nine data runs demonstrated a significant performance differences between single and multifocal lenses across all conditions.

The results of this study are consistent with the few previous studies that have compared the effects of wearing multifocal eyeglasses to single lens distance eyeglasses. Hypothesis one demonstrated a large lens effect between the upper and lower visual fields with subjects 2, 4, and 5. The ramifications of how this lens difference impacts mobility and function needs to be further examined. Exploring a distracter influence will lead researchers to understanding how visual attention is impacted by lens use and how stimuli in an environment may be misconstrued. Theoretical and clinical implications regarding the impact of lenses on visual motor performance will continue to evolve through comprehensive research using the MEA.

This study was funded through a U.S. Department of Education and Rehabilitative Services (OSERS) National Institute on Disability and Rehabilitation Research (NIDRR) grant (#H133G050340).

The effects of multifocal eyeglass use on visual-motor response times during a singleton visual attentional capture task, Paprocki, C. & Smith, R. (2008)

This study investigated the impact of multifocal lenses on visual motor response times using the additional singleton paradigm. Two hypotheses were formulated that addressed the difference between upper and lower lenses and between multifocal and single lens conditions. Using a paired samples design and a singleton visual attentional capture task, participants' visual-motor response times were recorded and analyzed. Participants completed an additional singleton paradigm that compared responses to upper and lower visual field stimuli wearing multifocal lenses and while wearing single lenses (n=20). Also, participants completed an eyeglass history questionnaire and a visual field assessment that was used to measure the visual field encompassed by the add region of their multifocal lens. Multifocal lens wearers demonstrated no significant difference in response times to a target singleton presented in the upper visual field, t(19)=1.013, p=.162 (1-tailed). Single lens wearers responded significantly faster than multifocal lens wearers to a target singleton presented in the upper visual field when a distracter was presented in the lower visual field, t(11)= 14.806, p=.000 (2-tailed). Three theories are posited to explain the results: 1) Multifocal lens wearers have a decreased attentional window, but a distracter singleton presented outside the attentional window captured attention and caused longer response times. 2) Multifocal lenses cause decreased contrast sensitivity and visual acuity, which make it more difficult to screen out and manage distracter singletons. 3) Multifocal lens wearers have a broad and diffuse attentional window with an increased attentional load due to the blur. Multifocal wearers took longer to filter out irrelevant stimuli than single lens wearers. The results suggest the possibility of substantial implications on recommended eyeglass use related to the health and safety of wearers.

This study was funded through a U.S. Department of Education and Rehabilitative Services (OSERS) National Institute on Disability and Rehabilitation Research (NIDRR) grant (#H133G050340).

Assistive Technology and the Risk of Falling, Joerger, T. & Smith, R. (2003)

The objective of the study was to examine if the use of assistive technology devices contributes to the risk of falling by impairing gait quality and speed. An experimental within-subjects design to examine two groups of 60 participants was completed. The participants used walkers or lined bifocal eyeglasses on the Get-Up-and-Go Test and the Timed-Get-Up-and-Go test under conditions using and not using assistive technology devices. Statistically significant t-test values at p<.000 resulted for three of four comparisons. Comparisons of Get-Up-and-Go Test and Timed-Get-Up-and-Go test scores with and without the use of a walker and comparison of the Get-Up-and-Go Test scores with and without the use of bifocals resulted in p< .000. Results strongly suggest that use of assistive technology devices impair gait speed and quality. Assistive technology device use needs to be further studied to better understand the contribution of assistive technology devices on falls and risk of falling.

 

Development of a test paradigm to measure the effects of bifocal lens eyeglass use as a risk factor for falls: A pilot study, Brayton, A. & Smith, R. (2005-2006)

This pilot study was designed to investigate the link between bifocal eyeglasses with an increased risk of falling with a young population by testing functional vision and gait to better understand the mechanisms of falling caused by bifocals, as found by Lord et al. (2002) in an older population. Components of the Lord et al. study were replicated with middle-aged participants, with the addition of a slightly modified version of the Dynamic Gait Index. Significant differences were found in depth perception between bifocal and single lens eyeglass wearers. Differences were not found in contrast sensitivity, functional gait, or falls (Χ2=.901). However, analyses found differences in vision within bifocal wearers upper and lower lens regions. Researchers theorize that bifocal wearers learn to ignore the distorted visual information in the lower region, leading to increased fall risk. Younger adults may be able to compensate for this via other body systems.