Validation of the Functional Vision Evaluation for Children (FVEC) Battery

Background we validated the recently developed Functional Vision Evaluation for Children (FVEC) Battery, which quantitatively measures major eye and visual function for rehabilitation. Methods The protocol for this test comprises 12 items involving unique abilities of the functional vision evaluated for 3 subsequent periods. Validation procedure includes analysis of di�culty of the examiner performance, the reliability and symmetry evaluation of the battery items and the prediction of the children in low vision category on a 0-100 ranking scale of visual behaviors. Factor analysis evaluates the contribution of the items to functions of Ventral and Dorsal visual streams.


Background
Vision is a sophisticated sense and provides information from the external environment related to the size, position, distance, color and shapes of the environment around (Gagliardo, HGRG, 2003;Kandel, ER, 1997).In addition, the visual system plays an important role in the early months of a child's life in the development of communication, self-orientation, movement control, and many other behaviors (Gagliardo, 2003;Lindstedt, E, 2000;Kara-José, N., 2004).
The interest of researchers easily observed the importance of vision to be dedicated to the study of visual functions (Costa et al., 2017, Salomão & Ventura, 1995;Mayer et al., 1995).However, vision-guided functional demands in patients with developmental disorders have few descriptions (Barca et al., 2010).
When the visual affections occur early in life, they might affect overall development, compromising their cognitive and social development (Gieser, 2004).Assessing the child's visual behavior can favor the early detection of visual impairments (Gagliardo and Nobre, 2001), and con gure a forward measure against later detection and intervention, leading to a negative impact on neurodevelopment (Perez Ramos & Perez Ramos, 1992; Guralnick, 1993).
The signi cant discovery for professionals who are dedicated to visual rehabilitation -early visual stimulation -was to identify the visual skills affected when there is a situation that disturbs the normal course of visual development.In this sense, there are some assessments of functional vision for children, but most of those instruments have no support from psychophysical and psychophysiological studies.
Based on this concern, we developed a battery of visual tests to assess functional performance of infants and children (Lopes et al., 2020).Thus, in this study, we aimed to validate the FVEC battery and we evaluate if functions dominated by the major ventral and dorsal visual streams could be assessed considering the possibility of evaluating the visual function of patients considering these two visual pathways independently.The possibility of obtaining information about these visual pathways will be an important and innovative improvement for the visual assessment of children.The evaluators were composed of physiotherapists and occupational therapists, 2 professionals with great experience in the area and knowledge of the FEVC instrument test application, and 2 professionals with less experience in visual impairment and without previous experience with the FEVC instrument.Those nine professionals underwent an observational familiarization and pre-application training.They performed all applications on the same day, with an interval of approximately 1 hour.

Equipment
The instruments used in this research come from the FEVC battery for the assessment of functional vision for children (Lopes et al. 2020) (Fig. 1).The instruments were: checkered racket, face racket, checkered cube and striped band.

Procedure
We performed the evaluation at the Early Visual Stimulation Clinic of the Low Vision and Visual Rehabilitation Sector of the Department of Ophthalmology, Federal University of São Paulo-São Paulo, Brazil.In an environment free from clusters and visual distractions, with white walls and an interval of approximately 30 seconds between each successive presentation, at a distance of 20cm from the stimulus, the child's face, in midline, from the child's face, these being positioned according to chronological age, corrected, in relation to neurodevelopment, therefore, from 0 to 6 months of age were tested in semi-seated, while from 6 to 24 months in seated, while the position of the evaluator varied, but always remaining outside the functional visual eld of child.
The protocol for this test comprises 12 items involving different abilities in the functional vision.Table 1 shows those skills that are assessed in the battery of 3 presentations of this test and they should observe which answers should be noted.The detailing of the application procedure comprises three items: 1. instrument, which de nes which of the battery materials will be used for the respective testing; 2. activity, which describes how the evaluator must present the stimulus and the dynamics involved in this presentation; and 3. the expected response, for response score, presenting the expected behavior for the respective stimulation and dynamics of presentation of the activity.

Visual xation
Visual xation is the ability to maintain the eyes aligned, focused, and attended with the stimulus of interest.This maintenance of the ocular position causes the image of objects placed on the fovea, a region of the retina, with the possibility of better visual acuity.
1.2.Activity: the racket should be presented in midline and time taken from xation maintenance; there will be 3 presentations of 30 seconds each.The measure consists of the sum of the total xation time of the 3 presentations. 1.
3. Expected answer: xation on the chess racket for 2/3 of the time.

Eye contact with face
The face, the human face, is an extremely important visual stimulus for social interaction and environmental reading, especially for babies.The preference for complex patterns is innate, as is the preference for face.
2.2.Activity: presentation of the face racket must be done in midline and the time of xation maintenance must be measured; there will be 3 presentations of 30 seconds each.The measure comprises the sum of the total xation time of the 3 presentations.

2.
3. Expected answer: xation of the gaze on the face racket for 2/3 of the time.

Optokinetic Nystagmus
This is an involuntary and complex eye movement for moving stimuli, comprising three phases: xation, tracking, and corrective saccade.This movement is more easily elicited by periodic stimuli.When the stimulus is xed, a follow-up movement to the edge of the visual eld is started.Reaching this limit, the eyes perform a saccadic movement in the opposite direction, seeking another xation point.
3.2.Activity: present the moving range from right to left, crossing the midline, and vice versa; 2 presentations were made for each direction at a speed of approximately 0.5m/s.

3.3.
Expected response: presence of nystagmus with slow follow-up and rapid return to both sides and symmetrically.

Saccadic movements
They are ballistic movements, with great amplitude and high speed, aiming to direct the eyes to a point in the visual eld.There are two types of saccadic movements, in relation to their generation: voluntary, when the eyes are directed to some object in a motivated or intentional way; and involuntary, when some stimulus abruptly enters the visual eld, captures our attention and elicits a saccadic movement in its direction.
4.1.Instrument for this test: chess racket and face racket.

Vestibulo-ocular re ex
It is an important eye movement that is related to maintaining eye xation on stimulus of interest, regardless of head or body movement.Vestibular stimuli reach the nervous centers of eye movements, correcting their position in relation to head and neck movement or displacement of the body in space.
5.1.Instrument for this test: no instrument required.
5.2.Activity: with the child suspended and supported at a 45° backward inclination, drawing visual attention to the experimenter's face, move the child's head to the right and then to the left, starting from the midline.

5.
3. Expected answer: observing the triggering of eye movements at the same speed and in the opposite direction as head movements.

Vergence
It is the eye movement aimed at maintaining image xation in the foveal region when the stimulus moves in the proximal or distal direction of the eyes.
6.2.Activity: make the presentation of the chess cube in a midline, followed by approaching, slowly (1cm/s), the midpoint of the base of the nose, between the eyes.
6.3.Expected response: presence of eye convergence because of the midline stimulus approximation and convergence break at a distance of less than 10cm.

Horizontal Visual Tracking
Also called by some authors as slow pursuit movement, this eye movement has the function of keeping the fovea xed on the object of interest, while it moves horizontally in space.

Vertical Visual Tracking
Also called by some authors as slow pursuit movement, this eye movement has the function of keeping the fovea xed on the object of interest, while it moves vertically into space.
8.2.Activity: make the presentation of the chess racket in midline, and after visual xation and support to avoid head movement, move the racket slowly, to the up and down position at a speed of 1° of visual angle per second.
8.3.Expected response: visually follow the stimulus with eye or head movement along the entire trajectory, without losses during the course, or with the appearance of eye deviations.

Smile in response to eye contact
This is a social interaction and imitation response, based on real visual stimuli.Most babies, from four months of age onwards, have a smile as a social contact.9.1.Instrument: face racket.9.2.Activity: Make the midline face racket presentation.9.
3. Expected answer: x the racket on the face and smile spontaneously.We expect this response for babies between four and ve months old.

Increased global movement when viewing an object
This ability starts around two / three months of age and is related to greater neurological maturation, with increased intentional movement and decreased re exes.
10.2.Activity: make the presentation of the chess cube in the middle line of the tested child. 10.
3. Expected answer: observe variation in the child's motor behavior, such as body extension, agitation of upper limbs and/or lower limbs, global movement, while maintaining visual attention.We expect this response for babies from two / three months.

Attempting to reach the visualized object
This skill starts around two / three months of age and consolidates at four months.At this stage, babies ex and extend their upper limbs to the object of interest viewed in the midline, to apprehend it.
11. 2. Activity: make the presentation of the chess cube in the middle line.

11.
3. Expected answer: observe the intention or movement of at least one of the upper limbs towards the chess cube while maintaining visual attention.We expect this response for babies between two-three and four months.

Functional visual eld of confrontation
Our eld of vision comprises the full extent to which visual stimuli are perceived and elicit saccadic behavior towards them, in the perception of this stimulus in my space / visible eld.
12.2.Activity: make a presentation of one of the chess cubes in a midline, being necessary to maintain its xation.Then start approaching the other cube from the right, left, top and bottom towards the midline, at a speed of 1° of visual angle per second.
12.3.Expected response: observe the awakening of attention to the tested side, indicating vision in that perimetric visual quadrant.

Statistical Analysis
The Cochran Q test was used to evaluate whether the detection of presence or absence of the variables differ signi cantly among themselves.In our study, a signi cant Q test shows the items are of different di culty, since the participants answered different items correctly.McNemar's Chi-square test for signi cant changes in proportions of dependent variables was used.The reliability of the battery was accessed using Cronbach's alpha, and the attenuated split-half correlations were used to verify the reliability symmetry between items related to local aspects of vision and items related to global aspects of vision.Pearson Correlation was used to evaluating the time xating the grating and the Fantz's face stimuli.Classi cation trees were used to predict membership of patients in the classes of a categorical dependent variable from their measurements on predictor variables.Predictor importance was used to calculate the importance ranking on a 0-100 scale for each predictor variable in the analysis for the more complex behaviors evaluated, smile in facial contact, and manual reaching movement.A Factor Analysis considering varimax rotation extracting factor was used to detect the structure in the relationships between variables to classify variables in local visual stream and global visual stream.
Results 100 children were evaluated and consistent results were obtained from all children aging from 03 to 99 months (Mean = 24.3,SD = 17.3 mos; Median = 22.5 mos; 47 males).We show demographic data of the children in Table 2. Eye malformation 5

Retinopathy of prematurity 10
Peters syndrome 6

Diagnostics under investigation 10
We rst evaluate the item di culty using the Cochran Q test, considering the overall data and for each examiner.For the overall measurement, we obtained a signi cant difference (Q = 435,16; p < 0.001) showing that Saccadic movement to the right side, Saccadic movement to the left side, vestibule-ocular re ex, manual reaching movements had a higher di cult level of execution when compared with all other scale items.
The consistency between examiners was measured, and we found no statistical differences, showing a good consistency of evaluation suggesting robustness of our protocol.These results are presenting in Table 3.
The battery reliability using Cronbach's alpha showed high internal consistency in judgments for examiner 1 (α = 0.86), examiner 2 (α = 0.85) and examiner 3 (α = 0.87).It was also important to evaluate the consistency between stimuli with clear local aspects as xation to grating and face, OKN, convergence movement and smile to face contact, and stimuli with global aspects of vision as saccadic movements, VOR, smooth pursuit movement and manual reach attempting.Split-half correlations were also highly signi cant for examiner 1 (r a = 0.81), examiner 2 (r a = 0.83), and examiner 3 (r a = 0.82), with a high reliability level, respectively, r sb = 0.76, r sb = 0.75, and r sb = 0.75.
We consider the smile to facial contact and the manual reaching movements the more signi cant functional responses to complex visual stimuli and interactive behavior with the environment.We ranked the predictive evaluations regarding the visual functions in importance (Fig. 3).For the smile for facial contact, the more predictive visual functions were face perception, saccadic movements and opto-kinetic nystagmus, visual functions related to maintain and control xation behaviors improving detailed and stable perceptions.For the manual reaching movement, the predictors were vestibule-ocular re ex, smooth pursuit movement, and convergence movement present, which are important to spatial organization, localization, and motor planning.
A Factor Analysis con rms that we could arrange our data in two major factors after the two-factors rotating solutions.Factor 1 shows the highest loadings for the items pertaining to local visual processing stream.Factor 2 shows the highest loadings for the global visual processing stream related items.
Table 4-Factor analysis of two factor after varimax rotation.
As we can see in Table 4, saccadic movements, vestibule-ocular re ex, convergence vertical, smooth pursuit are strongly related to global visual processing stream, whereas the looking to grating, face, OKN and the horizontal smooth pursuit and the increase of body movements are related to local visual processing.

Discussion
The Functional Vision Evaluation for Children (FVEC) Battery presented robust results of internal validity and reliability considering 4 different examiners for the functional evaluation of vision in children with varied diagnoses of ophthalmological diseases and that have low vision as a functional result.Statistical analyzes show that our evaluation battery allows access to visual functions related to the ventral and dorsal visual pathways, responsible for processing local and global aspects of vision, respectively.This is an innovative feature of our assessment and, so far, we have not identi ed other evaluation that present these functional characteristics of relating the visual performances measured with the visual processing of the large visual cortical pathways.In this way, our work is innovative and has great potential to move forward the systematic planning of visual rehabilitation actions in children.
The multiplicity of visual changes to be tested often hinder the systematic organization of the ndings and hinder the development of a therapeutic plan seeking a more global development and often remain in stimulations of isolated visual functions, leaving a more integrative approach to the main axes functional.Studies as those of Anderson & Rizzo, (1995) and Dundon, Bertini, Ladavas, Sabel & Gall (2015) have represented this great concern in visual rehabilitation, pointing to the need to evaluate themselves in an appropriate and integrative way, seeking elements that allow clarity for the therapeutic decision of restorative or compensatory treatment.Our evaluation battery, allowing the identi cation of local and global losses, presents itself as a robust alternative to support this decision of fundamental therapeutic importance.
Assessment methods for children with low vision, especially with cortical visual impairment, are aimed at improving the quality of measures of basic visual functions such as grating acuity using electrophysiological methods (Birch & Bane, 1991; W.V. Good, 2001), Vernier's acuity (Skoczenski & Good, 2004), spatial luminance contrast sensitivity (W.V. Good, Hou, & Norcia, 2012), and even attention (Atkinson & Braddick, 2012) and behavioral measures that can help understand the functional use of vision (Riazi, 2018).Assessment methods for children with low vision, especially with cortical visual impairment, aiming to improving the quality of measures of basic visual functions such as visual acuity, and even behavioral measures that can help understand the functional use of vision.We know that part of the di culty in relating the measurements of visual functions to visual behaviors in children with low vision is the difference in the methods used to evaluate these functions, while electrophysiological methods present an estimate of the function generated in V1, behavioral measures re ect not only the sensory-perceptual aspects but also the integrative processing with cognitive areas such as language and motor structures (Dobson & Teller, 1978).This is especially true in children with severe cortical vision impairment.Zeki, 2001).As evidenced by factor analysis, our battery of visual assessment allows grouping the various tasks and stimuli used so that their contribution is more relevant to one or the other of these pathways.Certainly, this level of information has not been reported in the literature and, therefore, we consider being contributing importantly to the area of visual rehabilitation.
The attention to ease of application is relevant, since we had applicators with less experience in the area.
However, it is important to emphasize that there is a need for familiarization with the instruments and training with quali ed professionals to provide the correct instructions for this application to be successful.

Conclusion
We validated the Functional Vision Evaluation for Children (FVEC) battery, showing high reliability and internal consistency of the items evaluated.Di cult analysis showed that our battery is moderately easy to apply, but it could require some training for some examiners.We base the major contribution of our FVEC battery on the possibility of separate local from global visual functions, which improves the information regarding these two main visual streams.

Declarations
This study followed the principles of the Declaration of Helsinki, and was approved by the Research Ethics Committee of the Federal University of São Paulo.The informed assents were obtained from all the participant parents.
One hundred children with visual impairment, with a mean age of 24.57months (SD = 17.37-51 females) took part in the present study.All children were evaluated, and are being monitored, at the Early Visual Stimulation Clinic of the Low Vision and Visual Rehabilitation Sector of the Department of Ophthalmology and Visual Sciences, at the Federal University of São Paulo / Hospital São Paulo, Brazil.

4. 2 .
Activity: present the front to the children, in midline, after achieving the central xation for the checkered racket, perform the sequential presentation of the racket facing the 30° visual angle to the right, and immediately after, present it at the 30° angle visual on the left, of the checkered racket.4.3.Expected response: presence of xation on the central racket and change of gaze because of abrupt eye movement (presence of saccade movement) to the racket that appears in the sequence laterally, to the left and right.

7. 1 .
Instrument for this test: chess racket.7.2.Activity: make the presentation of the chess racket in midline, and after visual xation and support to avoid head movement, move the racket slowly, to the right and left sides at a speed of 1° of visual angle per second.7.3.Expected response: visually follow the stimulus with eye or head movement along the entire trajectory, without losses during the course, or with the appearance of eye deviations.

Figures Figure 1
Figures

Figure 2 High
Figure 2

Figure 3 The
Figure 3

Table 1 systematic
description of the test battery of the 12 skills for the assessment of functional vision for children.

Table 2 -
demographic description of the diseases present in this study.
(Pilling, Outhwaite, & Bruce, 2016)assessment battery used in children with low vision and severe neurological impairments is the Bradford visual function box(Pilling, Outhwaite, & Bruce, 2016).It was conceptually developed to answer basic information, comprising the tasks of light perception using bright light in dark room, blink re ex to windmill, the look and following a real face, if the child return to a silent smile, xation to a forced-choice cards and the duration that they hold xation.Also, visual attention is assessed by recording the time and duration of xation on toys of different sizes in different distances.In comparison with Bradford's battery, our FCVE battery has many functional advantages considering we evaluate not only the detection of stimulus but also the status of the voluntary and involuntary eyes movements, and allows for a more systematic diagnosis with standard visual stimuli, since we use 1°a ngle of visual stimuli as a criterion for all stimuli, as well as the measurements made allow us to separate compromise of local and global visual functions.
processing.The processing of local visual information is important for the discrimination of gures and objects, face perception and other functions that are used for categorization, classi cation, naming and other cognitive functions related to language.Stimuli processed globally are of great importance for functions such as visual attention, location and spatial orientation, perception of texture and distance, and for planning and other executive functions(Angelucci etal., 2002; Han et al., 2002; Solomon, Chen, Morley, & Solomon, 2015; Yoshida, Yoshino, Takahashi, & Nomura, 2007;