BACKGROUND Dyslexia is defined as a reading and/or writing disability persisting after exclusion of organic causes. Studies show that ocular disorders, especially small refraction errors, hypoaccommodation and symptomatic heterophoria, are often not detected or treated in cases of reading and/or writing problems which were otherwise diagnosed as dyslexia. METHODS We evaluated the data of pati...

The authors provide a consideration of the vergence system and suggest an extension of the original model proposed by H. Heuer, M. Drawer, T. Romer, H. Kroger, and H. Knapp (1991) to explain why preferred vertical gaze angle is downward when fixating proximal targets. The practical implication of the revised model is that heterophoria (open-loop vergence bias) provides an indication of potentia...