Cyclotropia is a form of strabismus in which, compared to the correct positioning of the eyes, there is a torsion of one eye (or both) about the eye's visual axis. Consequently, the visual fields of the two eyes appear tilted relative to each other. The corresponding latent condition – a condition in which torsion occurs only in the absence of appropriate visual stimuli – is called cyclophoria.
In some cases, subjective and objective cyclodeviation may result from surgery for oblique muscle disorders; if the visual system cannot compensate for it, cyclotropia and rotational double vision (cyclodiplopia) may result. The role of cyclotropia in vision disorders is not always correctly identified. In several cases of double vision, once the underlying cyclotropia was identified, the condition was solved by surgical cyclotropia correction.
Conversely, artificially causing cyclotropia in cats leads to reduced vision acuity, resulting in a defect similar to strabismic amblyopia.
Cyclotropia can be detected using subjective tests such as the Maddox rod test, the Bagolini striated lens test, the phase difference haploscope of Aulhorn, or the Lancaster red-green test (LRGT). Among these, the LRGT is the most complete. Cyclotropia can also be diagnosed using a combination of subjective and objective tests. Before surgery, both subjective and objective torsion should be assessed.
If only small amounts of torsion are present, cyclotropia may be without symptoms entirely and may not need correction, as the visual system can compensate small degrees of torsion and still achieve binocular vision (see also: cyclodisparity, cyclovergence). The compensation can be a motor response (visually evoked cyclovergence) or can take place during signal processing in the brain. In patients with cyclotropia of vascular origin, the condition often improves spontaneously.
Cyclotropia cannot be corrected with prism spectacles in the way other eye position disorders are corrected. (Nonetheless two Dove prisms can be employed to rotate the visual field in experimental settings.)
For cyclodeviations above 5 degrees, surgery has normally been recommended. Depending on the symptoms, the surgical correction of cyclotropia may involve a correction of an associated vertical deviation (hyper- or hypotropia), or a Harada–Ito procedure or another procedure to rotate the eye inwards, or yet another procedure to rotate it outwards. A cyclodeviation may thus be corrected at the same time with a correction of a vertical deviation (hyper- or hypotropia); cyclodeviations without any vertical deviation can be difficult to manage surgically, as the correction of the cyclodeviation may introduce a vertical deviation.
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- See section "Discussion" in: Pradeep Sharma; S. Thanikachalam; Sachin Kedar; Rahul Bhola (January–February 2008). "Evaluation of subjective and objective cyclodeviation following oblique muscle weakening procedures". Indian Journal of Ophthalmology. 56 (1). pp. 39–43. doi:10.4103/0301-4738.37594. PMC 2636065. PMC 2636065.
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- G.K. von Noorden (July–August 1984). "Clinical and theoretical aspects of cyclotropia". J Pediatr Ophthalmol Strabismus. 21 (4). pp. 126–132. PMID 6470908.
- S.-J. Woo; J.-M. Seo; J.-M. Hwang (2005). "Clinical". Eye (19). pp. 873–878. doi:10.1038/sj.eye.6701675.
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- M. Ruttum; G. K. Von Noorden (August 1984). "The Bagolini striated lens test for cyclotropia". Documenta Ophthalmologica. 58 (1). pp. 131–139. doi:10.1007/bf00140911.
- Phyllis E. Weingarten and David L. Guyton, Volume=6, Chapter 97: Surgery to Correct Cyclotropia Archived 2015-02-10 at the Wayback Machine
- Joost Felius; Kirsten G. Locke; Mohamed A. Hussein; David R. Stager Jr; David R. Stager Sr (December 2009). "Photographic assessment of changes in torsional strabismus". Journal of American Association for Pediatric Ophthalmology and Strabismus. 13 (6). pp. 593–595. doi:10.1016/j.jaapos.2009.09.008.
- G.K. von Noorden (July–August 1984). "Clinical and theoretical aspects of cyclotropia". J Pediatr Ophthalmol Strabismus. 21 (4). pp. 126–132. PMID 6470908. As cited by: S.-J. Woo; J.-M. Seo; J.-M. Hwang (2005). "Clinical". Eye (19). pp. 873–878. doi:10.1038/sj.eye.6701675.
- "The patient fixates a vertical line target, and the dove prism is rotated in the direction to increase the action of the insufficient muscle while fusion is maintained." Quoted from: Mitchell Scheiman; Bruce Wick (2008). Clinical Management of Binocular Vision: Heterophoric, Accommodative, and Eye Movement Disorders. Lippincott Williams & Wilkins. p. 432. ISBN 978-0-7817-7784-1. Retrieved 22 July 2013.
- Ka Hee Park; Jin Hee Shin; So Young Kim (April 2012). "Surgical Results of Modified Harada-Ito Operation for Excyclotorsion". Journal of the Korean Ophthalmological Society. 53 (4).
- Genjiro Ohmi; Takashi Fujikado; Masahito Ohji; Yoshihiro Saito; Yasuo Tano (January 1997). "Horizontal transposition of vertical rectus muscles for treatment of excyclotropia". Graefe's Archive for Clinical and Experimental Ophthalmology. 235 (1). pp. 1–4. doi:10.1007/bf01007829.
- 2.22 Cyclotropia: Treatment, ORBIS Telemedicine (downloaded 19 July 2013)