Effert R, Barry J C, Dahm M, Kaupp A
Augenklinik d. RWTH Aachen.
Klin Monbl Augenheilkd. 1991 Apr;198(4):284-9. doi: 10.1055/s-2008-1045966.
A new photographic method for measuring squint angles in children and infants is presented. A photographic picture is taken from the subject, using a camera with the three flashes bulle. One flashbulle is placed vertically over the lens, two other flashbulles are placed symmetrically in an angle of 10 degrees beside the middle flash. Six reflections can be seen on the photographic picture in each pupil. (1. and 4. Purkinje Sanson Images of each light source.) The horizontal distance of two reflections is determined by the distance of the flashguns. If the reflection lines in both eyes are symmetrical, there is no squint. If there is a shift, it can be measured on the slide and by using a simple formula the squint angle can be calculated. The accuracy of the method is between 2 and 3 degrees.