Eyelids do a whole lot more than hold up our eyelashes and keep the sun out, Scott Read, a Queensland University of Technology PhD optometry researcher, has found. He stated that the biggest changes were amongst people who maintained a downward gaze for a long time while reading or doing close work. "The first study found that there were highly significant changes to the contours of the cornea throughout the day when we tested at 9am, 1pm and 5pm over three days of the week," Read said. "The study found horizontal bands of distortion appeared on the cornea where the eyelid would have been sitting and that this increased during the day but went back to normal by the next morning.”
"As these changes appear to be related to forces from the eyelids themselves and were more marked in people who spent a lot of time reading in downward gaze it is certainly one reason why people's vision may be slightly worse at the end of the day or after doing a lot of close work,” he stated. “It suggests that people should take a short break from reading or close work at least every hour."
In a second study on 100 normal-sighted young subjects, Read described the shape of the eyelid opening at different angles of gaze and compared this with the contours of the cornea to find out how eyelid characteristics and corneal shape affected each other. He found significant associations between the angle, shape and size of the eyelids and the shape of the cornea. "It appears eyelids do play a part in determining the shape of the cornea. One explanation is that pressure from the eyelids is involved in the cause of corneal astigmatism.
His findings would provide the groundwork for new understanding about astigmatism in children and in older age. "Children are born with a high degree of astigmatism and the cornea changes shape rapidly in the first four years of life, so the study's findings could shed light on how some people go on to develop astigmatism," he said.
MEDICA.de; Source: Queensland University of Technology