Development of a clinical measurement tool for measuring voluntary eye movements in typical infants six months of age

Abstract

Occupational therapy is an essential service in early childhood intervention but does not yet fully understand the impact of the child’s neuro-visual plasticity on function. Voluntary eye movements are part of visual functioning, which affects all performance areas. The visual brain is highly neuro-plastic during early infancy. The maturation of visual functions depends on the typical goal-directed visual experiences in a critical period of development. Development of visual function processes at different rates during the post-natal period including visual acuity, contrast sensitivity and visual fields. The primary visual cortex receives visual information from the eyes and is then further processed onto the primary visual cortex for contrast, colour, disparity, direction, speed and orientation for perception. Vision related activities that represent functional vision are not only refined by the retinogeniculate projections but also the extrastriate cortex that encompasses multiple functional areas. The post-natal development of the visual cortex, therefore, requires visual experiences during goal-directed participation. Vision for perception and vision for action provide a useful framework for understanding the functional organization of the human visual system. Perception and action depend on clear, stable, single vision and adequate control of voluntary eye movements, to convey the signals for processing. It was thus recommended to develop a clinical measurement tool for assessing voluntary eye movements in infants 6-to-7-months of age, as the maturation of visual processing depends on eye movements and visual experience in this age period. The researcher developed the voluntary eye movement measurement tool in infants 6-to-7-months of age to measure functional vision for participation. Voluntary eye movements are the foundation to process visual information efficiently for recognition, memory, organized purposeful actions, and attention on an ever-changing environment in all cultures to promote communication, social interaction, near task work, mobility and orientation. Each item of the voluntary eye movement measurement tool is developed and designed for related activity performances. The 4 domains are functional vision for participation, gaze holding, gaze shifting and attention. The aim of the study was to develop a clinical measurement tool for measuring voluntary eye movements in typical 6-to-7-months-old infants.

A systematic eight-step process was followed to develop the voluntary eye movement measurement tool. The aim of the study was achieved by four objectives. Quantitative and qualitative research approaches were followed. Construct analysis and theoretical validation were used to identify and select material to operationalize the construct. Processes of inductive and deductive reasoning contributed to the generation of the domains, sub-domains and measurable items. Theory on scale construction informed the final construction of the tool. Content validity index was determined where relevant. A pilot study confirmed that the voluntary eye movement measurement tool reflected a typical developed 6-to-7-months-old infant’s capability for using voluntary eye movements in a naturalistic interaction with persons, objects or the environment. Objective one was to identify, define and analyse the construct of voluntary eye movements in 6-to-7-months-old infants by means of a theoretical exploration of literature, reviewing existing voluntary eye movements instruments/tools in children, personal communication with authors/publisher consultation with experts and the researcher’s clinical experience. In objective two the voluntary eye movement measurement tool was constructed by observing voluntary eye movements performed during social interactions, near-tasks, mobility and orientation activities with attention as identified and defined in objective one, followed by scaling the steps for each item that reflected the quality of performance that was graded on a 3-point rating scale. Furthermore, the administrative user manual, administration procedures, outcomes, scoring criteria and scoring sheet were developed and designed.

The validity of the voluntary eye movement measurement tool was evaluated in objective three by using the content validity index quantified into a validity coefficient index. The study sample for this objective was obtained from experts in the paediatric neurology field of ophthalmology, optometry and occupational therapy. The expert panellist rated the voluntary eye movement measurement tool by using the content validity index to scale the: relevance of items for 6-to-7-months-old infants, the developed rating scale, user’s manual, administration and the scoring sheet. The content validity was determined to be extremely high. The fourth objective was to pilot the voluntary eye movement measurement tool. The defined 4 domains, 5 sub-domains and 26 items generated for the voluntary eye movement measurement tool reflected the 6-to-7-months-old infant’s capability for using voluntary eye movements in a naturalistic interaction with persons, objects or environment.

The voluntary eye movement measurement tool provides an opportunity for occupational therapists to measure voluntary eye movements that relate to visual performances for development of perception and action. This tool will allow occupational therapists practicing in early intervention, to identify, adapt and control the visual inputs that the infant constantly receives from the environment to enhance participation and performance for development in all aspects of life. This will also provide the opportunity for multidisciplinary, holistic management strategies.