Cyclotropia

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.

For the similar condition but where the eyes deviate inward, see esotropia. For the similar condition but where the eyes deviate outward, see exotropia.
Cyclotropia
SpecialtyOphthalmology 

Cyclotropia is often associated with other disorders of strabism, can result in double vision, and can cause other symptoms, in particular head tilt.[1]

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.[2][3] 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.[4]

Conversely, artificially causing cyclotropia in cats leads to reduced vision acuity, resulting in a defect similar to strabismic amblyopia.[5]

Diagnosis

Cyclotropia can be detected using subjective tests such as the Maddox rod test, the Bagolini striated lens test,[6] the phase difference haploscope of Aulhorn,[6] or the Lancaster red-green test (LRGT). Among these, the LRGT is the most complete.[7] Cyclotropia can also be diagnosed using a combination of subjective and objective tests.[8][9] Before surgery, both subjective and objective torsion should be assessed.[10]

Experiments have also been made on whether cyclic deviations can be assessed by purely photographic means.[11]

Treatment

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).[7][10] 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.[7]

Cyclotropia cannot be corrected with prism spectacles in the way other eye position disorders are corrected.[12] (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.[13] 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[14] or another procedure[15] to rotate the eye inwards, or yet another procedure to rotate it outwards.[16] 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.[13]

References
  1. Michael C. Brodsky (1 January 2010). Pediatric Neuro-Ophthalmology. Springer. p. 445. ISBN 978-0-387-69069-8. Retrieved 10 July 2013.
  2. 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.
  3. H. D. Schworm; S. Eithoff; M. Schaumberger; K. P. Boergen (February 1997). "Investigations on subjective and objective cyclorotatory changes after inferior oblique muscle recession". Investigative Ophthalmology & Visual Science. 38 (2). pp. 405–412.
  4. Burton J. Kushner (1992). "Unexpected Cyclotropia Simulating Disruption of Fusion". Archives of Ophthalmology. 110 (10). pp. 1415–1418. doi:10.1001/archopht.1992.01080220077025.
  5. Brian Timney; Carol K. Peck (November 1981). "Visual acuity in cats following surgically induced cyclotropia". Behavioural Brain Research. 3 (3). pp. 289–302. doi:10.1016/0166-4328(81)90001-2.
  6. G.K. von Noorden (July–August 1984). "Clinical and theoretical aspects of cyclotropia". J Pediatr Ophthalmol Strabismus. 21 (4). pp. 126–132. PMID 6470908.
  7. S.-J. Woo; J.-M. Seo; J.-M. Hwang (2005). "Clinical". Eye (19). pp. 873–878. doi:10.1038/sj.eye.6701675.
  8. Zia Chaudhuri; Murugesan Vanathi, M.D. (2012). Postgraduate Ophthalmology. JP Medical Ltd. pp. 1965 ff. ISBN 978-93-5025-270-3. Retrieved 19 July 2013.
  9. 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.
  10. Phyllis E. Weingarten and David L. Guyton, Volume=6, Chapter 97: Surgery to Correct Cyclotropia Archived 2015-02-10 at the Wayback Machine
  11. 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.
  12. 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.
  13. "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.
  14. 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).
  15. 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.
  16. 2.22 Cyclotropia: Treatment, ORBIS Telemedicine (downloaded 19 July 2013)

Further reading
  • Lemos, João; Eggenberger, Eric: Clinical utility and assessment of cyclodeviation, Current Opinion in Ophthalmology, November 2013, Volume 24, Issue 6, pp. 558–565 doi:10.1097/ICU.0000000000000003
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