Editing Diplopia (section)

=== Binocular ===

Binocular diplopia is the other one in which the blurring of vision occurs only when the patient looks through both eyes simultaneously. It is common and occurs in approximately 10.0% to 40.0% of zygomatic complex injuries. Furthermore, diplopia may be transient or persistent. Inadequate diagnosis and treatment at improper times and tethering or fibrosis of muscles may lead to persistent diplopia.<ref>Shabbir, M., Shah, R., Ahmad, M., Issrani, R., Khan, Z., Salah, N. A. Qayyum, Z. (2023). Frequency of diplopia in zygomatic complex Fractures—A cross-sectional descriptive study. ''International Journal of Dentistry''. https://doi.org/10.1155/2023/7631634</ref>

Binocular diplopia is double vision arising as a result of [[strabismus]]<ref>{{cite journal | vauthors = Peragallo JH, Pineles SL, Demer JL | title = Recent advances clarifying the etiologies of strabismus | journal = Journal of Neuro-Ophthalmology | volume = 35 | issue = 2 | pages = 185–193 | date = June 2015 | pmid = 25724009 | pmc = 4437883 | doi = 10.1097/WNO.0000000000000228 }}</ref> (in layman's terms "cross-eyed"), the misalignment of the two eyes relative to each other, either [[esotropia]] (inward) or [[exotropia]] (outward). In such a case while the [[Fovea centralis|fovea]] of one eye is directed at the object of regard, the fovea of the other is directed elsewhere, and the image of the object of regard falls on an extrafoveal area of the [[retina]]. Acute diplopia is a diagnostic challenge. The most common cause of acute diplopia are ocular motor nerve palsies (OMP).<ref>{{cite journal | vauthors = Kremmyda O, Frenzel C, Hüfner K, Goldschagg N, Brem C, Linn J, Strupp M | title = Acute binocular diplopia: peripheral or central? | journal = Journal of Neurology | volume = 267 | issue = Suppl 1 | pages = 136–142 | date = December 2020 | pmid = 32797299 | pmc = 7718182 | doi = 10.1007/s00415-020-10088-y }}</ref>

The brain calculates the visual direction of an object based upon the position of its image relative to the fovea. Images falling on the fovea are seen as being directly ahead, while those falling on retina outside the fovea may be seen as above, below, right, or left of straight ahead depending upon the area of retina stimulated. Thus, when the eyes are misaligned, the brain perceives two images of one target object, as the target object simultaneously stimulates different, noncorresponding, retinal areas in either eye, thus producing double vision.<ref>{{cite journal | vauthors = Jain S | title = Diplopia: Diagnosis and management | journal = Clinical Medicine | volume = 22 | issue = 2 | pages = 104–106 | date = March 2022 | pmid = 35304368 | doi = 10.7861/clinmed.2022-0045 | pmc = 8966821 }}</ref>

This correlation of particular areas of the retina in one eye with the same areas in the other is known as [[retinal correspondence]]. This relationship also gives rise to an associated phenomenon of binocular diplopia, although one that is rarely noted by those experiencing diplopia. Because the fovea of one eye corresponds to the fovea of the other, images falling on the two foveae are projected to the same point in space. Thus, when the eyes are misaligned, two different objects will be perceived as superimposed in the same space. This phenomenon is known as 'visual confusion'.<ref>{{cite book | vauthors = Buffenn AN | chapter = Diplopia and Strabismus |date=2020  | title = Albert and Jakobiec's Principles and Practice of Ophthalmology |pages=1–20 | veditors = Albert D, Miller J, Azar D, Young LH |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-319-90495-5_291-1 |isbn=978-3-319-90495-5  | s2cid = 236868860 }}</ref>

The brain naturally guards against double vision. In an attempt to avoid double vision, the brain can sometimes ignore the image from one eye, a process known as [[Suppression (eye)|suppression]]. The ability to suppress is to be found particularly in childhood when the brain is still developing. Thus, those with childhood strabismus almost never complain of diplopia, while adults who develop strabismus almost always do.  This ability to suppress might seem an entirely positive adaptation to strabismus, but in the developing child it can prevent the proper development of vision in the affected eye, resulting in [[amblyopia]]. Some adults are also able to suppress their diplopia, but their suppression is rarely as deep or as effective and takes much longer to establish; thus, they are not at risk of permanently compromising their vision. In some cases, diplopia disappears without medical intervention, but in other cases, the cause of the double vision may still be present.

Certain people with diplopia who cannot achieve fusion and yet do not suppress may display a certain type of [[spasm]]-like irregular movement of the eyes in the vicinity of the fixation point (see: [[Horror fusionis]]).