Cyclotropia is a form of

strabismus Strabismus is a vision disorder in which the eyes do not properly align with each other when looking at an object. The eye that is focused on an object can alternate. The condition may be present occasionally or constantly. If present during a ...

in which, compared to the correct positioning of the eyes, there is a

torsion Torsion may refer to: Science * Torsion (mechanics), the twisting of an object due to an applied torque * Torsion of spacetime, the field used in Einstein–Cartan theory and ** Alternatives to general relativity * Torsion angle, in chemistry Bi ...

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. Cyclotropia is often associated with other disorders of strabism, can result in

double vision Diplopia is the simultaneous perception of two images of a single object that may be displaced horizontally or vertically in relation to each other. Also called double vision, it is a loss of visual focus under regular conditions, and is often v ...

, and can cause other symptoms, in particular

head tilt Torticollis, also known as wry neck, is a dystonic condition defined by an abnormal, asymmetrical head or neck position, which may be due to a variety of causes. The term ''torticollis'' is derived from the Latin words ''tortus, meaning "twisted ...

. 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.

Diagnosis

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 In the fields of optometry and ophthalmology, the Lancaster red-green test is a binocular, dissociative, subjective cover test that measures strabismus in the nine diagnostic positions of gaze. The test is named after Walter Brackett Lancaster, w ...

(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.Phyllis E. Weingarten and David L. Guyton
Volume=6, Chapter 97: Surgery to Correct Cyclotropia
Experiments have also been made on whether cyclic deviations can be assessed by purely photographic means.

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 Cyclodisparity refers to the difference in the rotation angle of an object or scene viewed by the left and right eyes. Cyclodisparity can result from the eyes' torsional rotation (''cyclorotation'') or can be created artificially by presenting to t ...

cyclovergence Cyclovergence is the simultaneous occurring cyclorotation (torsional movement) of both eyes which is performed in opposite directions to obtain or maintain single binocular vision. Normal cyclovergence and cycloversion Conjugate cyclorotations ...

). The compensation can be a motor response (visually evoked

) 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 prism A Dove prism is a type of reflective prism which is used to invert an image. Dove prisms are shaped from a truncated right-angle prism. The Dove prism is named for its inventor, Heinrich Wilhelm Dove. Although the shape of this prism is similar ...

s can be employed to rotate the visual field in experimental settings.) For cyclodeviations above 5 degrees, surgery has normally been recommended."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: 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 The Harada–Ito procedure is an eye muscle operation designed to improve the excyclotorsion experienced by some patients with cranial nerve IV palsy. In this procedure, the superior oblique tendon is split, and the anterior fibers ...

or another procedure to rotate the eye inwards, or yet another procedure to rotate it outwards.2.22 Cyclotropia: Treatment
ORBIS Telemedicine (downloaded 19 July 2013) 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.

References

External links

{{Eye pathology Disorders of ocular muscles, binocular movement, accommodation and refraction

Diagnosis

Treatment

References

Further reading

External links