low vision is defined as vision or visual field disorders that cause trouble in carrying 
 out usual daily life , even after proper treatment or correction has been made for refractive 
 errors . the world health organization ( who ) defines good eye vision as a state having 6/18 
 vision and a visual field angle of less than 20 degrees1 , 2 . vision plays an important 
 role in maintaining a stable body balance by continuously providing information about 
 environment , body movement , and body position to the nervous system3 . low vision patients experience 
 difficulties in carrying out reading , leisure activities , and daily life due to eyesight 
 damage5,6,7 . in addition , low vision 
 leads to reduction in the proprioception and vestibular inputs that are required for balance 
 maintenance8 . among the various causes 
 of balance maintenance problems , viewing angle impairment , which commonly occurs in elderly 
 people , is the biggest cause9 . low vision 
 patients are exposed to the risk of falls by losing their postural balance10 . several studies have reported that viewing angle impairment is related to the causes of 
 falls by the elderly population11,12,13 . other studies have reported that vision and balance ability are the most decisive factors in 
 falls14 . in addition , harry and rhonda 
 ( 2003 ) reported that balance ability declined with the degree of vision loss . in humans , balance ability is an essential element for successful performance of daily life and body 
 movement , and it is balance ability that maintains body balance by using the principal 
 elements15 , 16 . langley and mackintosh emphasized balance ability an important 
 element that affects the ability to carry out daily life17 . in addition , postural imbalance causes falls , and the fear of 
 falling lowers independence or mobility limiting daily life18 . previous studies have suggested that falls are caused by impaired 
 balance ability , which is one of the causes the low levels of daily living activities of 
 low - vision patients26 . we have to help 
 low vision patients to put priority on their safety and to preserve their independence and 
 quality of life through reducing their risk of falls by improving their balance ability . the 
 evaluation of elements that affect the performance of activities of daily living ( adl ) of 
 low - vision patients play an important role in the rehabilitation of patients with low 
 vision . although many previous studies have been performed by focusing on the relationship 
 between low vision and the performance of adl or on the clinical analysis of low vision , no 
 study has been performed on the relationship of low vision with balance ability , which is 
 considered a major factor influencing the performance of daily living activities . the purpose of the present study was to evaluate the relationship of balance ability of low 
 vision patients with their performance of daily living activities to provide basic data for 
 a professional rehabilitation program for low vision patients . the subjects of the present study were 30 patients who visited the ophthalmology department 
 of a university hospital located in daejeon , korea who had an eye condition of less than 
 6/18 of vision in one or both of their eyes . data was collected performed during a 3-week 
 period from july 5 to july 23 , 2012 . all the test subjects understood the purpose of the 
 study , and consented to participation in the study . we 
 trained raters for 2 weeks in the use of the assessment tools to increase the assessment 
 reliability . the evaluation tool that 
 was used in the present study was the national eye institute 25-item visual function 
 questionnaire ( nei - veq-25 ) that was developed by mangione et al . at the national eye 
 institute ( nei ) . the nei - vfq-25 questionnaire is composed 12 sub - domains which contain a 
 total of 26 questions . all questions are in objective form , and 56 sample answers are 
 presented for each question . since the 6th of the sample answers indicates that the stoppage 
 of the activity is due to causes that are not related to vision , its scoring was excluded . for the balance ability test , we used the tetrax the biofeedback training system ( tetrax 
 portable multiple system , tetrax ltd . , ranmat gan , israel ) that was developed by sunlight 
 company of israel was used . the equipment is a device which is used to measure the risk of 
 falls and body balance state . it measures the postural sway on 4 forceplates located under 
 the left and right forefeet and heels . it not only calculates the stability index , an index 
 which can be measured on other balance measuring devices , but also various factors of 
 posture such as diagonal postural sway and weight displacement pattern . examinations were 
 performed with the subjects adopting the following 8 examination postures : looking straight 
 ahead with the eyes open ( no ) , and looking straight ahead with the eyes closed ( nc ) ; to 
 limit somatosensory input , looking straight ahead with the eyes open and an elastic pillow 
 ( 312  cm ) under the feet ( po ) , and looking straight ahead with the eyes closed and an 
 elastic pillow under the feet ( pc ) ; looking to the right with the eyes closed ( hr ) ; and 
 looking to the left side with the eyes closed ( hl ) ; and with the head tilted back looking at 
 the ceiling ( hb ) , and head tilted downward with the eyes closed ( hf ) . for the safety of the 
 test subjects , when they stood on the elastic pillow with their eyes closed , an examiner 
 stood at their side . in the present study , to assess the balance ability of patients with 
 low vision , the no posture incorporates visual , somatosensory and vestibular organ 
 information for the maintenance of balance was compared with the stability index measured in 
 the nc posture , which excludes visual information . the reliability of nei - vfq-25 is 0.85 , 
 and its validity is 0.90 . in order to be assessed by the nei - vfq-25 , patients need to be 
 able to communicate with the raters . for cognitive examination tool , the korean edition of 
 the mini - mental state examination ( mmse - k ) , that was developed by kwon & park for the 
 korean elderly , was used . it is a modified version of the mini - mental state examination 
 ( mmse ) that was developed by folstein , folstein , & mchugh . the reliability of this 
 examination tool was found to be 0.90 with a validity of 0.93 . for the statistical analysis of the data , the win spss 18.0 program was used . to analyze 
 the correlation of each variable finally , 
 to confirm the causality of the balance ability of the low vision patients in their 
 performance of daily living activities , regression analyses were performed using independent 
 variables . * p<0.05 , * * p<0.01 , * * * p<0.001 among the 30 test subjects , 17 test subjects were male ( 56.67% ) and 13 test subjects were 
 female ( 43.33% ) . the test subjects had a mean age of 64.37  years old with minimum age of 
 43  years and maximum age of 89  years . eight test subjects were found to have low vision in 
 both eyes ( 26.7% ) and 22 test subjects had a low vision in one eye ( 73.33% ) . the no posture 
 found a positively correlated not only with the nc posture ( p<0.01 ) , but also with age 
 ( p<0.05 ) . in addition , the no posture was found to have a negative correlation with the 
 nei - vfq-25 score ( p<0.05 ) . both binocular and monocular recognition showed a positive 
 relationship with the nei - vfq-25 score ( p<0.01 ) ( table 1 ) . to confirm the variables that affect ability to perform daily living activities , linear 
 regression analyses were performed using the tetrax stability indexes of the no and nc 
 postures , type of vision impairment(monocular , binocular ) , cognitive capacity , gender , and 
 age variables . when these variables were analyzed as a single model , the order of 
 statistical significance showed the type of vision impairment had the highest b value of 
 23.86 , and females showed higher values than males in both monocular and binocular vision 
 impairment . also , a higher balance ability in the no posture was associated with higher 
 levels of daily living activities . the model fit was statistically significant with an f 
 value of 6.77 ( table 2 ) . the present study investigated the effect of the balance ability of low - vision patients on 
 their ability to perform adl , to provide a basic data for a professional rehabilitation 
 program for use with low - vision patients . although other clinical evaluation tools that 
 measure balance ability are useful , there is a high possibility that they are subjectively 
 influenced by examiners or test subjects , and the evaluation of changes in balance ability 
 is difficult19 . in addition , a study of 
 27 healthy elderly people with approximate age of 60  years showed that both their berg 
 balance scale and tug ( timed up and go ) test times were normal and not significantly 
 different from young adults suggesting the presence of a problem in the precise evaluation 
 of balance abnormalities in the elderly20 . therefore , the present study used the highly sensitive tetrax that 
 is not affected by physical indexes such as body weight or height . daily living activities are the most basic and important activities of human life21 . for those people having impaired vision , many vision - dependent activities and daily tasks are difficult or impossible to perform , 
 reducing their ability to perform adl and independence , which has a negative impact on their 
 quality of life22 . with the progression 
 of vision loss , walking speed slows and the frequency of collision with obstacles increases , 
 and daily living activities such as walking become impossible23 . therefore , rehabilitation specialists emphasize the necessity of 
 providing rehabilitative education , such as the magnifier or recorder methods , to compensate 
 for lowered vision and to raise the level of daily living activities of low - vision patients , 
 along with the reorganization of their environments . in the causality analysis results of the present study , the type of vision impairment 
 ( monocular , binocular ) showed the most significant effect on daily life . monocular patients 
 were found to maintain significantly higher levels of daily living activities than the 
 binocular patients . patient interviews revealed that patients with monocular impairment had 
 normal vision in the other eye , or the correction of refractive errors made it possible to 
 perform general daily living activities . even when they reported failure to hold an object 
 at once because of problems of depth perception in one eye , they did not experience any 
 major difficulties in their daily living activities . therefore , we consider it most 
 important for patients with monocular low vision to have not only ophthalmological 
 treatments and regular periodic examinations , but also to make efforts to prevent the 
 development of binocular eye impairment through therapeutic health interventions redesigning 
 and checking their living patterns , delivering health promotion programs and appropriate 
 education , preventing complications , and improving their living environments . also , 
 rehabilitation for visual perception ( such as depth perception ) is necessary24 . gender also had a large on the 
 performance level of daily living activities , with the females showing higher levels than 
 the males . since the nei - vfq-25 includes activities that are considered gender specific such 
 as needlework , cooking , clothing , shopping and meetings , the results are expected to be 
 higher for women . since frequently conducted activities can be performed by training of 
 other sensory organs without dependence on vision , the daily living activity levels of the 
 female would tend to be higher . the mmse - k score was also confirmed to have an important 
 effect on the daily living activities of low vision patients . it indicates that better 
 cognitive ability of low - vision patients is suggestive of a higher level of daily living 
 activities . studies of the elderly population have shown that the relationship between daily 
 living activities and cognitive capacity has a positive correlation ( p<0.001)25 , 26 , similar to the result of the present study . according to result of 
 the present study , maintaining and improving the cognitive capacity of low vision patients 
 would have important positive consequences for daily living activities . among the test 
 subjects , due to their advanced age , they were 
 highly susceptible to dementia , which indicates the incorrectness of their nei - vfq-25 
 evaluations . a previous study compared the balance ability of an elderly population having 
 vision loss and an elderly population without vision loss9 , and reported that the elderly population with vision loss showed 
 lower balance ability ( p<0.001 ) . based on that , we considered the balance ability of 
 low - vision patients is impaired , and investigated its effect on daily life . most of the 
 low - vision patients had balance scores below of the mean of healthy subjects , and the 
 stability index of no posture , but not that of the nc posture , was significant in the 
 causality analysis ( p<0.05 ) . we consider that the no posture is affected by both visual 
 inputs and the inputs from the somatosensory and vestibular organs , but the nc posture only 
 is affected by inputs from the somatosensory and vestibular organs . this indicates that the 
 balance is affected by visual input , and the inputs , which has an important influence on the 
 performance of daily living activities , and low - vision patients maintain their balance and 
 carry out their daily living activities dependent on their remaining vision , and inputs from 
 the somatosensory , and vestibular organs . since the balance ability of low - vision patients 
 is lower than normal , raising their risk of falls and negatively affecting their daily life , 
 rehabilitation specialist should remind them of this when proving treatment . problems with 
 spacial cognition and object perception occur due to low vision , reducing balance ability 
 and raising the risk of falls17 . accordingly , it will be necessary for rehabilitation specialists to reorganize the living 
 and working spaces of low - vision patients , and efforts should be made to develop 
 interventions and supplementary tools to improve the balance ability of low - vision patients , 
 along with efforts to enhance their performance of daily living activity .
[ purpose ] this research investigated the relationship between balance measured by a 
 tetrax and activities of daily living ( adl ) assessed by nei - vfq 25 . 
 the results should 
 provide basic data for rehabilitation therapy for low - vision patients . 
 [ methods ] we used 
 the nei - vfq-25 vision - related activities of daily living evaluation , mmse - k , and tetrax to 
 evaluate 30 low - vision outpatients at k hospital in daejeon , south korea from july 5 to 
 july 23 , 2012 . 
 we performed linear regression analysis using a statistical significance 
 level of 0.05 . 
 [ results ] balance in the normal eyes open ( no ) posture correlated with the 
 normal eyes closed posture and age , but showed no correlation with nei - vfq 25 . the adl 
 level correlated with monocular vision , female gender , cognition , and no posture . 
 these 
 variables explained 54.4% of the aspects of their adl . 
 [ conclusion ] this research proves 
 that low vision adversely affects balance ability , and is influenced by type of vision , 
 gender , and cognitive assessment .