RT Book, Section A1 Motley, W. Walker A1 Asbury, Taylor A2 Riordan-Eva, Paul A2 Cunningham, Emmett T. SR Print(0) ID 55783287 T1 Chapter 12. Strabismus T2 Vaughan & Asbury's General Ophthalmology, 18e YR 2011 FD 2011 PB The McGraw-Hill Companies PP New York, NY SN 978-0-07-163420-5 LK accessmedicine.mhmedical.com/content.aspx?aid=55783287 RD 2024/10/14 AB Under normal binocular viewing conditions, the image of the object of regard falls simultaneously on the fovea of each eye (bifoveal fixation) and the vertical retinal meridians are both upright. Any ocular misalignment, such that only one eye views the object of regard with the correct vertical orientation, is called “strabismus.” The misalignment may be in any direction—inward, outward, up, down, or torsional. The amount of deviation is the angle by which the deviating eye is misaligned. Strabismus present under binocular viewing conditions is manifest strabismus, heterotropia, or tropia (see Box 12.1 for definitions). A deviation present only after binocular vision has been interrupted (eg, by occlusion of one eye) is called latent strabismus, heterophoria, or phoria.