|Year : 1985 | Volume
| Issue : 4 | Page : 209-211
Proprioceptive reflexes in exodeviations
Prem Prakash, Rajiv Garg, Vimala Menon
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, A.I.I.M.S. New Delhi, India
Professor of Ophthalmology, Dr. Rajendra Prasad Centre for Ophthalmic Sciences, New Delhi-110029
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Prakash P, Garg R, Menon V. Proprioceptive reflexes in exodeviations. Indian J Ophthalmol 1985;33:209-11
The importance of non-optical ocular reflexes is being realised increasingly. The existence of the proprioceptive afferents from the extra ocular muscles is known for a long time but their contribution to the control of eye movements is not clear yet.
Ishikawa (1978) demonstrated the reverse phase reflex movement of the eye. The magician's forceps phenomenon was demonstrated in exodeviations. In the present study, these two proprioceptive reflexes were studied in exodeviations.
| Material and methods|| |
Forty three cases of exodeviation were studied for the reverse phase reflex and the magician's forceps phenomenon. The magician's forceps phenomenon was performed by the following method : surface anaesthesia was given, using 4% xylocaine drops. A fixation forceps was used to hold the eyeball at the nasal limbus and a slight adductive force was applied to the eye. The position of the othor eye was noted. A positive Magician's forceps phenomenon consisted of disappearance of the exodeviation. Return of the exodeviation occurred on leaving the adductive force on the dominant eye. [Figure - 1]A-C
The phenomenon was provoked by a quick horizontal motion of dominant eye by about 40° to 60° at the rate of 2-3 sec. in case it was negative in the first attempt. This phenomenon was tested for in both eyes of patients with alternating strabismus. In the latter, it was important to distinguish the positive phenomenon from a simple alternation of fixation. In alternation of fixation or a pseudo-positive magician's forceps phenomenon, the non-dominant eye did not return to its exodeviated state as soon as the adductive force was discontinued (Fir. ID-F.) It took up fixation, so that the dominant eye deviated.
The reverse phase reflex was elicited by forced movements of the dominant eye in abduction, adduction. supraduction and infraduction and observing the effect of these movements on the fellow eye. In positive reverse phase reflex [Figure - 2]A-E the nondominant eye moved in the direction opposite to that of the forced duction of the dominant eye.
The total number of cases in which the magician's forceps phenomenon, was tried was 43, out of which 15 showed a positive phenomenon, a positivity rate of 35%
The reverse phase reflex was also tried in 43 cases but it was found to be positive in only one case. Both these reflexes were elicited only from the dominant eye.
| Discussion|| |
The rate of positivity of the magician's forceps phenomenon was 35% in this study. This is in contrast to the positivity rate of 65% in the 40 cases studied by Mitsui et al. This difference may be that they did repeated examinations at different times whereas in the present study only one examination was done. Mitsui et al have postulated that as far as the cases of exotropia with positive Magician's forceps phenomenon are concerned, the physiological rest position of exodeviations is orthophoria. Orthophoria, exophoria and exotropia are reversible conditions depending on the balance of fusion and abnormal proprioceptive impulses from the dominant eye, one of which may suppress the other. This implies that the above postulation does not cover all exotropias and there may be other etiological factors responsible for those cases in which the magician's forceps phenomenon is absent.
In all, we had 7 out of 12 cases of unilateral exotropia, 6 out of 13 cases of alternating exotropia and 2 out of 18 cases of intermittent exotropia which showed a positive magician's forceps phenomenon. This suggests that the phenomenon is more commonly elicited in the unilateral and alternating exotropia as compared to the intermittent exotropia. The intermittent exotropia formed the major proportion (18 out of 43) of cases in our study. This may explain the overall lower occurrence rate of the Magician's forceps phenomenon as compared to the series reported by Mitsui et al.
In this study the reverse phase reflex was elicited only in one case which was a patient of a unilateral exotropia with a primary optic atrophy associated with a high degree of visual disturbance. No case with good vision in both eyes demonstrated this reflex. This observation is in contrast to 47% positivity of the reflex in Mitsui et al series. Moreover they had 80% positivity in cases with unilateral high loss of vision. This observation could not be compared because of an isolated case meeting their criterion in the present series.
The reflex movement of the non-dominant eye was obtained in the opposite direction to the forced movement of the dominant eye in both horizontal and vertical direction. This observation supports the findings of Mitsui et al. Reverse phase reflex and the Magician's forceps phenomenon are two distinct, though closely related phenomena. The present study supports this view though based on a single case exhibiting the revers phase reflex.
It is difficult to differentiate between the two phenomena when they occur simultaneously in the same individual. The main difference being that in the Magician's forceps phenomenon there is an "all or none" effect i.e. the non-dominant eye does not adduct farther even if more adduction is applied to the dominant eye. The reverse phase reflex, however, shows a dose response, with the non-dominant eye moving farther along with increasing forced movement of dominant eye. Moreover, the reverse phase reflex is elicitable in all directions of movement compared to horizontal adduction movements of the Magician's forceps phenomenon. Thus, the reverse phase reflex occurs when a new reflex is excited, whereas the Magician's forceps phenomenon occurs when a standing impulse is cancelled, leading to the disappearance of the exodeviation.
Thus, these two phenomena may co-exist in a given patient. Mitsui et al have also described the reverse phase reflex and the Magician's forceps phenomenon as being intermittent, being elicted in some of the cases at certain times. We had no opportunity to observe these temporal inconsistencies. The postulation that exodeviations are caused by a proprioceptive reflex from the dominant eye, is worth giving more thoughts. It is likely that this mechanism is operative in cases with a positive Magician's. forceps phenomenon.
| References|| |
Ishikawa. S. 1978. Acta. Soc. Ophthalmol. Japan 82: 233.
Mitsui. Y., Hirai, K., Akazawa, K., and Masuda, K. : 1979, Jap, J. Ophthalmol : 23:227
[Figure - 1], [Figure - 2]
[Table - 1]