|Year : 1984 | Volume
| Issue : 6 | Page : 467-475
Dominant eye surgery in exodeviation
Prem Parkash, Rajiv Garg, Vimala Menon
Dr Rajendra Prasad Centre for Ophthalmic Sciences, A.I.I.M.S. New Delhi, India
R. P. Centre for Ophthalmic Sciences, A.I.I.M..S., New Delhi-29
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Parkash P, Garg R, Menon V. Dominant eye surgery in exodeviation. Indian J Ophthalmol 1984;32:467-75
Surgery on the dominant eye in exodeviations has been advocated. ,,. This study was undertaken to compare the results of surgery on the dominant eye versus non-dominant eye in terms of alignment of the eye, improvement in visual acuity, convergence; binocular functions and the visual evoked response (V.E.R).
| Material and methods|| |
A total of 43 patients with exodeviations irrespective of the type were included in this study. They were assigned alternately into two groups, Dominant eye surgery (22 cases.) Non-dominant, eye surgery (21 cases)
A detailed history, ocular and orthoptic examination followed by cycloplegic refraction was done. The deviation, the near point of convergence the range of fusion, and the stereopsis was recorded. The dominant eye was determined by the cover test and sensory test for binocularity. The magician's forceps phenomenon was tested for by using an adductive force with a fixation forceps holding the eye at the limbus and noting the position of the exodeviated eye. A positive response consisted of disappearance of the exodeviation [Figure - 1] The V.E R. was recorded using pattern reversal stimulation on the Nicolet CA-1000 clinical signal averaging computer. Recession of the lateral rectus and resection of the medial rectus was done. No strict rule of millimeters to prism diopters could be followed. However, taking into account all the variable factors, the decision of amount of surgery was made as per experience. Post operatively the patients were assessed for the same parameters.
| Observations|| |
The difference in results of surgery performed in either dominant or non dominant eye in intermittent, unilateral or alternating [Table - 1] exodeviation in not significant statistically.
The results of the surgery was also classified according to the initial amount of deviation. There was no statistically significant difference [Table - 2].
On analysing the mean correction achieved in the different groups based on the pre-operative amount of deviation it was found that there was no significant difference in the dominant and non dominant eye surgery [Table - 3]
There was a pre-operative visual acuity difference of more than one line between the two eyes in 7 cases. There was an improvement by one line in 6 cases out of 7 (85%) in the dominant eye surgery group and 1 case out of 6 (16 % in the non-dominant eye surgery group. This difference is statistically significant (9=05).
Twelve cases in the dominant eye surgery group and 9 cases in the non dominant eye surgery group had no binocular functions elicitable under the various methods of examination employed. The post-operative status was as shown in [Table - 4] The maximum range of fusion achieved was statistically insignificant in different groups as shown in [Table - 5]. The post operative development of convergence and near point of convergence achieved are shown in [Table - 6][Table - 7]. They were found to be statistically insignificant.
The post-operative development of stereopsis and stereoacuity as shown in [Table - 8][Table - 9] are statistically insignificant.
Post operative changes in the (V.E.R.) were seen in the form of an improvement in the waveform [Figure 2][Figure 3]. There was a general improvement in the amplitude of V.E.R. of the non-dominant eye after surgery [Table - 10][Table - 11], No differences were noted in terms of dominant or non-dominant eye surgery, and it occurred irrespective of concurrent betterment of visual acuity of the non dominant eye.
A difference of more than 5 milliseconds between the implicit time of two eyes was considered as significant in the study. The implicit time of N2 wave of the two eyes was equalized after surgery in all the cases which had a significant difference whether the dominant or non-dominant eye was operated upon [Table - 12][Table - 13]. There was no correlation between abnormality of the implicit time and the preoperative presence of binocular single vision as there were many cases which did not have binocular single vision but had an implicit time, within the normal range of difference between the two eyes and many who bad binocularity but the implicit time of the two eyes had a significant difference.
| Discussion|| |
The surgery on the dominant eye in exodeviation is a concept which has not been given much thought ,,.
The effect of unilateral recession-resection on the deviation revealed that the ortho range was achieved in 16 cut of 22 cases (71.7%) in the dominant eye surgery group and 14 cut of 21 cases (66.6%) in the non dominant eye surgery group. It can be therefore, said that the ocular alignment is not significantly different after surgery on dominant or non dominant eyes.
When the effect of surgery is analysed on the basis of the initial amount of deviation, there was no significant difference between the two groups. Similar results were found in the subgroups of dominant and non dominant eye surgery groups.
On analysing the mean correction in the different groups bases on the preoperative amount of deviation it was found that there was no significant difference in the dominant and non dominant eye surgery as against other authors views. 
In the series published by Mitsui et al , adjustable sutures have been employed so that the eye position attained is not due to the dominant eye surgery per se. They have reported straight eye position in 73.4% cases after the adjustable surgery. The present study show ortho range in 72.7% in the dominant eye surgery group and 66.6% in the non dominant eye surgery group and these figures compare favourably well with the results of Mitsui et a1 .
As far as the improvement in the visual acuity is concerned, there is a statistically significant difference between the two groups (P=05) though the improvement in vision is small. The improvement in the visual acuity was always limited to one line only in our series. whereas in the series reported by Mitsui et a14.65% of total cases of amblyopia improved to an acuity of 6/6 or better from a preoperative acuity of 6/6-P (7 cases) 6/9P (2 cases), 6/12 (4 cases). Their postulation is that the proprioceptive impulse from the dominant eye suppresses the visual perception of the contralateral eye at a cortical level and this suppression is released after operating on the dominant eye. In the present study only 3 out of the 6 cases which showed visual improvement in the dominant eye surgery group also had a positive magician's forceps phenomenon. Thus it appears the forceps phenomenon may not be indicative of visual prognosis after dominant eye surgery. A probable factor for minimal visual acuity improvement may be the short period of occlusion entailed after the surgery on the dominant eye. The binocular functions like fusion and stereopsis achieved after surgery were not significantly different in two groups. It therefore implies that binocular vision may not be dependent on the release from suppression from the dominant eye as postulated by Mitsui et al , The recovery of convergence also did not significantly differ in the two groups, which therefore implies that the effect on convergence may just be an outcome of a favourable post-surgical alignment of the eyes alongwith development of binocularity.
The improvement in the V.E.R. amplitudes occurred irrespective of whether the dominant or the non-dominant eye was operated upon. Similarly, the equalisation of the implicit ti re occurred irrespective of the eye operated upon. Thus it appears that the better performance of the eye in terms of vision, fusion range, convergence, stereopsis and favourable changes in V.E.R. are dependent upon the favourable ocular alignment postoperatively which somehow reduces the interocular rivalry irrespective of the eye operated upon.
| References|| |
Lebensohn, J.E. 1959 Amer. J. Ophthalmol., 40 : 844
Knapp, P. 1968 : Surg. Orthoptics : International Strabismus Symposium Giessen, p. 302: 1966 (Karger-1968).
Mitsui, Y., Hirai, K., Akaziwa, K. and Misuda, K., 1979 Jap. J. Ophthalmol 23 : 227,
Mitsui, Y., Hirai, K., Akazawu, K., and , Massada, K., 198OJap.J.Ophthalmol 24:221
[Figure - 1]
[Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5], [Table - 6], [Table - 7], [Table - 8], [Table - 9], [Table - 10], [Table - 11], [Table - 12], [Table - 13]