1. Introduction
alance is one of the most important and inseparable components of daily activities and exercises [1]. Effective balance is closely related to the ability to perceive the environment through the relevant sensory systems [1]. Sensory systems are proprioceptive, vestibular and visual systems [5]. These systems play an important role in controlling movement in humans [6]. Deficiency of any of this information can affect the balance of systems and lead to problems in balance, posture and coordination [2]. Sensory impairment is one of the most common causes of functional disability that affects mobility and daily living activities and may be associated with primary and secondary complications [8]. A number of studies have shown that balance is impaired when the ability to receive visual and auditory stimuli is reduced due to visual and auditory impairment or lack of visual and vestibular feedback [13].
Despite the high prevalence of people with sensory impairment in Iran, there is still no accurate information about the postural balance status of this group and the relationship between hearing and vision impairment with the postural balance in visually and hearing impaired people, and few studies have examined the postural balance of these groups of people in a single study. Therefore, it is necessary to conduct more studies on the functional balance of visually and hearing impaired people, which affects their daily living activities and performance. Since the functional balance test makes it possible to assess the actual movements of individuals, this study examined the functional balance of individuals with visual impairment and hearing loss.

This is a descriptive-analytical study. Study population consists of all boys aged 6-14 years with visual impairment and hearing loss. Samples were 30 visually-impaired, 30 hearing-impaired and 30 normal boys (Mean±SD age= 11.76±2.89 years, Mean±SD weight 52±29.47 kg, Mean±SD height= 135.15±13.13 cm) who were non-randomly selected using purposive sampling method. To evaluate the functional balance of subjects, the timed up and go test (r=0.93) was used. In this test, the subject rises from a chair without handle, walks and goes to a chair with handle, sittings on it and then turns around and walks back to the first chair and sits down again. The time of performing this test is considered as the subject’s score [15].
Descriptive statistics were used to describe the variables and inferential statistics were used to analyze them. In inferential statistics, after examining the normality of the data distribution by Shapiro-Wilk test, one-way ANOVA and Scheffe’s post hoc test were used to compare the three groups at the significance level of P<0.05. in SPSS v. 20 software.

As shown in Table 1, the results of ANOVA indicated significant difference in the mean functional balance of three study groups (P=0.001).



Scheffe’s post hoc test (Table 2) showed that there was a significant difference in functional balance between visually-impaired and hearing-impaired subjects, and between visually-impaired and healthy subjects, but no significant difference was reported between hearing-impaired and healthy subjects.


 

The purpose of this study was to evaluate the functional balance of children with visual impairment and hearing loss. The results of this study showed a significant difference in functional balance of two impaired groups compared to controls. This difference was significant between visually-impaired and hearing-impaired children, and between visually-impaired and hearing-impaired children, but no significant difference was observed between hearing-impaired and healthy children. In other words, visually-impaired children had poorer functional balance than healthy and hearing-impaired counterparts which is in line with the results of Farahani et al. and Valizadeh. The results of this study and previous studies in people with visual impairment show that sensory impairment affects the process of functional balance in individuals, such that visual information is more important for postural control than auditory and somatosensorial information. 
Therefore, it can be said that visual information is the richest information in maintaining balance [17]. Investigating the severity of balance disorders that occur in deaf children depends on the flow of information from other systems. This result is consistent with the results of Malekabazdizadeh et al. and Melo et al. It should be noted that in everyday life, vestibular system impairment does not necessarily cause a significant balance disorder due to the overlap of vestibular, visual and somatosensorial inputs and the effect of neural plasticity and the occurrence of central compensation [23]. The results of the present study also show that with the decrease in information receiving from vestibular and visual systems, the balance is impaired, and the person has to use other methods to compensate for this impairment.

All subjects voluntarily participated in the present studyafter signing a consent form.

This research did not receive any specific grant fromfunding agencies in the public, commercial, or not-profit sectors.

Conceptualization, methodology, supervision: All authors; Preparing the manuscript, resources: Chiman َAlyarnezhad; Review-editing: Hassan daneshmandi.

The authors declared no conflict of interest.

The authors would like to thank the Exceptional Education Organization of Gilan Province, school principals and students who participated in the study for their cooperation
 

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