Ocular Torsion According to Trochlear Nerve Absence in Unilateral Superior Oblique Palsy

Abstract

Citation: Lee JE, Yang HK, Kim JH, Hwang J-M. Ocular torsion according to trochlear nerve absence in unilateral superior oblique palsy. Invest Ophthalmol Vis Sci. 2017;58:5526-5531. DOI:10.1167/iovs.17-22452 PURPOSE. To investigate the relationship between objective ocular torsion and the presence or absence of the trochlear nerve in subjects with unilateral superior oblique palsy (SOP). METHODS.A total of 159 subjects with congenital and acquired unilateral SOP were reviewed. Eighty-four subjects who had a normal trochlear nerve (present group) and 75 subjects without a trochlear nerve (absent group) were included. Cyclovertical motility parameters and objective ocular torsion were compared between groups, and factors related to ocular torsion were evaluated. RESULTS.The degree of ''net'' excyclotorsion in the paretic eye was larger in the absent group compared to the present group (P ¼ 0.002). The proportion of net excyclotorsion in the paretic eye was greater in the absent group (11% vs. 37%), while net incyclotorsion was greater in the present group (41% vs. 23%) (P < 0.001). Net excyclotorsion of the paretic eye was associated with absence of the trochlear nerve (P < 0.001) and smaller size of the paretic SO (P < 0.001). Net incyclotorsion of the paretic eye was related with a normal trochlear nerve (P ¼ 0.005), larger size of the paretic SO (P ¼ 0.002), and greater hypertropia during ipsilateral gaze (P ¼ 0.024).CONCLUSIONS. The status of the trochlear nerve, paretic SO size, and hypertropia during ipsilateral gaze which reflects the tensile strength of the ipsilateral superior rectus, significantly contribute to ocular torsion in unilateral SOP.Keywords: superior oblique palsy, trochlear nerve, ocular torsion R ecent investigations based on advanced imaging modalities and functional anatomy have offered novel approaches to understand the etiology and pathophysiology of superior oblique palsy (SOP).1-11 Absence of the trochlear nerve has been well recognized as one of the major pathologic etiologies of SOP. 5,6,10 In our earlier study of congenital SOP, 73% showed ipsilateral trochlear nerve absence and a variable extent of SO hypoplasia, whereas the remainder had a normal-appearing SO and trochlear nerve on both sides. 10The relevance of ocular torsion in the diagnosis of SOP is well recognized.12,13 Identification of bilateral excyclotorsion provides essential information in diagnosing bilateral SOP, 14 and incyclotorsion of the hypertropic eye suggests skew deviation. 15 However, torsional patterns in unilateral SOP have shown inconsistent results, and little is known about the torsional changes in SOP according to its pathogenic etiology. To date, there are only few studies 10,11,16 investigating subjective and objective torsion in SOP according to its major etiologies. In our previous report, 10 objective ocular torsion using fundus photographs with an internal fixator did not show any differences according to the presence of the trochlear nerve; however, the investigation was conducted only in con...

Effect of inferior oblique myectomy on ocular torsion according to the absence of the trochlear nerve in unilateral congenital superior oblique palsy

“…It should be noted that the excyclotorsion of the non-paretic eye was larger in the present group than in the absent group. Lee et al previously observed that the “net” incyclotorsion in the paretic eye was more frequent in the absent group than in the present group, suggesting that excyclotorsion in the non-paretic eye was more pronounced in the present group [ 7 ]. In this study, we also found a larger excyclotorsion of the non-paretic eye in the present group.…”

“…Accordingly, the absence of the trochlear nerve and superior oblique muscle (SO) hypoplasia, which can be classified as a congenital cranial dysinnervation disorder, has been accepted as one of the pathophysiologies of unilateral congenital superior oblique palsy (UCSOP) [2][3][4]. Several studies have reported clinical characteristics according to the absence of the trochlear nerve, and Lee et al revealed that the absence of trochlear nerve can contribute to the amount of ocular torsion in unilateral SOP [5][6][7].…”

Ocular Torsion in Children with Horizontal Strabismus or Orthophoria

“…This phenomenon is the result of a monocular sensorial adaptation to the cyclodeviation by means of a reordering of the spatial response of retinal elements along new horizontal and vertical meridians [ 20 ]. There is inconsistency and paradoxical measurement when the non-paretic eye or both eyes are measured for extorsion, and sometimes no extorsion is measured despite superior oblique palsy [ 21 ].…”

“…In contrast, in adults, acquired strabismus causing diplopia is the presenting symptom of new paralytic strabismus. For example, superior oblique palsy with a torsional effect that causes diplopia is commonly reported or diagnosed due to signs such as head tilt [ 21 ]. The visual cortex must calibrate the torsion to enable stable vertical orientation under conditions of alternating monocular fixation.…”