Double vision, or diplopia, usually results from an acquired misalignment of the visual axes that causes an image to fall simultaneously on the fovea of one eye and on a nonfoveal point in the other eye. As stated earlier, the object that falls on these disparate retinal points must be outside Panum’s area to appear double. The same object is perceived as having 2 locations in subjective space, and the foveal image is always clearer than the nonfoveal image of the nonfixating eye. The perception of diplopia depends on the age at onset, its duration, and the patient’s subjective awareness of it. The younger the child, the greater the ability to suppress, or inhibit, the nonfoveal image. Adults with acquired strabismus commonly present to the ophthalmologist because of diplopia.
Figure 5-4 Rivalry pattern. A, Pattern seen by the left eye. B, Pattern seen by the right eye. C, Pattern seen with binocular vision.
(Reproduced with permission from von Noorden GK, Campos EC. Binocular Vision and Ocular Motility: Theory and Management of Strabismus. 6th ed. St Louis: Mosby; 2002:12.)
The loss of normal binocular fusion in an individual unable to suppress disparate retinal images results in intractable diplopia, referred to as central fusion disruption (horror fusionis). This condition is typically seen in adults or visually mature children and can occur in a number of clinical settings, including prolonged visual deprivation due to monocular occlusion or a mature cataract, traumatic brain injury, or long-standing strabismus. Management is challenging.
El-Sahn MF, Granet DB, Marvasti A, Roa A, Kinori M. Strabismus in adults older than 60 years. J Pediatr Ophthalmol Strabismus. 2016;53(6):365–368.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.