THE EFFECT OF CONTRAST POLARITY ON AMPLITUDE OF ACCOMMODATION AND VISUAL COMFORT

ABSTRACT

The capacity of the human visual system, referred to as accommodation, to focus on things at different distances is essential to daily functioning. Contrast polarity is one of the many elements that have been investigated in order to have a better understanding of the components that influence accommodation. An important component of visual perception, the amplitude of accommodation, is examined in this study in relation to contrast polarity. The aim of this study was to access the effect of contrast polarity on amplitude of accommodation and visual comfort. A total of 33 healthy participants were used in this study, ages 18 to 25years, who are either emmetropes or corrected ammetropes. The push up technique was used to quantify the amplitude of accommodation while a likert questionnaire scale was used to evaluate the visual symptoms. Positive and negative contrast were the two contrast polarity circumstances under which these measurements will be made. Result showed amplitude of accommodation and visual comfort was significantly affected by positive polarity (86%) and negative polarity (82%) after 30mins of reading task (p= 0.000). Although comparing the two contrast polarity, there was no significant difference between them (p>0.05). Furthermore, visual symptoms level increased also after the reading regardless of the polarity. Intense blur (51.5%), intense level of tiredness and headache (45.5%), mild pain (42.4%) were experienced with positive polarity. Majority experienced moderate and intense level of tiredness (36.4%). It was therefore concluded that contrast polarity profoundly affect not only the ability of the eyes to adjust focus but also the comfort and efficiency of visual tasks.