|Year : 1988 | Volume
| Issue : 4 | Page : 168-170
Proprioceptive reflexes in exodeviations
Rajiv Garg, Vimala Menon, Prem Prakash
Dr. Rajendra Prasad Centre For Ophthalmic Sciences A.I.I.M.S., New Delhi - 110 029, India
Dr. Rajendra Prasad Centre For Ophthalmic Sciences A.I.I.M.S., New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
The importance of non-optical ocular reflexes is being increasingly realised. The existence of proprioceptive afferents from the extra ocular muscles has been known for a long time but their contribution towards the control of eye movement is not yet clear.
Ishikawa (1978) demonstrated the reverse phase reflex; movement of the eye'. The Magician's forceps phenomenon was demonstrated by Mitsui et. al (1979) in exodeviation sub . In the present study these two proprioceptive reflexes were studied in exodeviations.
|How to cite this article:|
Garg R, Menon V, Prakash P. Proprioceptive reflexes in exodeviations. Indian J Ophthalmol 1988;36:168-70
| Material and Methods|| |
Forty three cases of exodeviation (12 cases of unilateral, 13 cases of alternating and 18 cases of intermittent variety) were studied for the reverse phase reflex and the Magician's forceps phenomenon. The Magician's forceps phenomenon was performed by the following methods: 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 other eye was noted. A positive Magician's forceps phenomenon consisted of disappearance of the exodeviation. Return of the exodeviation occured on leaving the adductive force on the dominant eye [Figure - 1].
The phenomenon was provoked by a quick horizontal motion of the dominant eye by about 40° to 60osub 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 [Figure - 2] but 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 - 3] the non-dominant eye moved in the direction opposite to that of the forced duction of the dominant eye.
| Results|| |
The results of the study are shown in the following table:
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 (1979) .
One of the reasons for this difference may be that in their series, Mitsui et. al (1979) used repeated examinations at different times whereas in the present study only one examination could be done. Mitsui et. al (1979) have postulated that as far as the cases of exotropia with positive Magicians 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 propricceptive 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 unilateral and alternating exotropia as compared to intermittent exotropia. 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 published by Mitsui et. al (1979).
In this study, the reverse phase reflex was elicited only in one case, a patient with 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 the 47% positivity of the reflex in Mitsui et al's series (1979) . Moreover they had 80% positivity in cases with unilateral high loss of vision. This observation could not be compared with the present series because of an isolated case meeting their criterion.
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 directions. This observation supports the findings of Mitsui et. al (1979). 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 reverse phase reflex.
It is difficult to differentiate between the two phenomena when they occur simultaneously in the same individual. The main difference is 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 alongwith increasing forced movement of the dominant eye.
Moreover the reverse phase reflex is elicited in all directions of movement compared to the horizontal adduction movement of the Magician's forceps phenomenon. Thus, the reverse phase reflex occurs when a new reflex is initiated, 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 (1979) have also described the reverse phase reflex and the Magician's forceps phenomenon as being intermittent, being elicited in some of the cases at certain times . We had no opportunity to observe these temporal inconstancies.
It is worth giving more thought to the postulation that exodeviations are caused by a proprioceptive reflex from the dominant eye. It is likely that this mechanism is operative in cases with a positive Magician's forceps phenomenon.
| References|| |
Ishikawa, S Proprioception of the extraocular muscle: A review & recent findings: Acta Society Ophthalmology, Japan: 82 (4) : 233-249,1978.
Mitsui, Y., Hirai, K., Akazawa, K., and Masuda, K., Sensorimotor reflex and strabismus: Japanese J. of Ophthal - 23 (3) : 227-256, 1979.
[Figure - 1], [Figure - 2], [Figure - 3]