2005 Brayton Thesis Annotation
This thesis by Brayton work was funded in part by the ATOMS Project, highlighted some potentially negative consequences of AT, and was a pilot that helped to lay the ground-work for the BIFOCAL Project.
Brayton (2005) investigated the role of bifocal glasses as a contributing factor to the risk of falling. It was hypothesized that the use of bifocals will increase the user's risk for falling in adults aged 40-59. Specifically, hypotheses stated that viewing the environment through the lower lens of eyeglasses would have a more negative impact on the depth perception and distant edge contrast sensitivity in bifocal users than non-bifocal users. Additionally, bifocal users were hypothesized to have lower functional mobility scores and have experienced a greater number of falls or near falls in the month prior to testing.
The research design included comparisons of two groups, bifocal users and non-bifocal glasses users, on measures of depth perception, distant edge contrast sensitivity, functional mobility, and number of falls or near falls in the previous month. The study used the Howard-Dohlman depth perception apparatus to test depth perception; an enlarged version of the Melbourne Edge Test (MET) to test distant edge contrast sensitivity; a modified version of the Dynamic Gait Index (DGI) to test functional mobility; and a subjective questionnaire to assess number of falls or near falls in the previous month. The research design included two viewing conditions for both the depth perception and the contrast sensitivity test: upper and lower lens.
Forty-four individuals participated in the study, 32 in the bifocal group and 12 in the single lens distance corrected group. Participants were recruited through local ophthalmologists', optometrists', and opticians' offices, as well as from the campus community. All participants ranged between the ages of 40 and 59. Data analysis included the independent Mann-Whitney U tests as well as independent samples t-tests.
The results of the analysis did not statistically support the apriori hypotheses. However, a post-hoc analysis revealed statistically significant differences between the upper and lower viewing conditions in bifocal eyeglass users on the tests of depth perception (z = -2.362, p = .009) and distant edge contrast sensitivity (z = -2.707, p = .007). Overall, the results remain consistent with the theory that bifocals contribute to falls in the elderly with potentially major findings: (a) younger populations show differences in behavioral performance between upper and lower lenses; (b) the risk of falling injuries wearing bifocal eyeglasses may be distinguishable even in a younger population; and (c) more sensitive instruments to measure key variables related to bifocal use need to be created for a middle aged population. Future research is warranted on the use of bifocals as a contributing factor to risk of falling.
Brayton, A. (December 2005). The relationship between bifocal eyeglass use and risk factors for falling. Unpublished master's thesis, University of Wisconsin-Milwaukee, Milwaukee, WI.
