|Year : 1995 | Volume
| Issue : 1 | Page : 9-11
Effect of monocular vertical displacement of horizontal recti in A V phenomena
Pradeep Sharma1, Manoj Halder1, Prem Prakash2
1 From Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi 110 029, India
2 From Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi 110 029vvvvvv, India
From Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi 110 029
Source of Support: None, Conflict of Interest: None
Twenty-one cases of A V phenomena were subjected to monocular recession-resection procedure with vertical displacement of 8 mm in 11 cases and 5 mm in 10 cases. Both 8 mm and 5 mm shifts were found to be equally effective even in cases with mild or moderate cyclovertical muscle imbalance. However, in cases with oblique muscle dysfunction, residual vertical incomitance was observed in all such 13 cases and should therefore be avoided. Eight cases showed horizontal incomitance in extreme gazes and this was more with 8 mm shift compared to 5 mm shift.
Keywords: Squint surgery - A V phenomena - Vertical displacement - Monocular surgery - Shifting - Transposition - Horizontal recti.
|How to cite this article:|
Sharma P, Halder M, Prakash P. Effect of monocular vertical displacement of horizontal recti in A V phenomena. Indian J Ophthalmol 1995;43:9-11
The surgical management of A and V phenomena is complex because of its varied clinical picture and presentation. Surgical procedures on different extraocular muscles and their transposition have been practised for many years and many ophthalmologists agree that in cases with no obvious oblique muscle dysfunction, symmetrical vertical displacement of horizontal recti muscle should be performed.This may be done as a symmetrical surgery on either lateral rectus or medial rectus; or when the surgeon prefers to confine the surgery to one eye, it may be performed with monocular recession-resection procedure. Goldstein performed monocular vertical displacement of horizontal recti, comparing 5 mm and 8 mm shifting and concluded that though both the procedures were effective for reducing the vertical incomitance, an 8-mm shift appeared to be more effective. Metz and Almeida performed only 5 mm shift, and claimed that the procedure was effective in reducing A and V phenomena.
In our study, we compared the effectiveness of surgery in both 8 mm and 5 mm shift groups and evaluated the horizontal and vertical effects of this procedure. As an uniform procedure, we chose the recession-resection model of squint surgery as the base to study the effect on the operated as well as unoperated fellow eye.
| Materials and methods|| |
Twenty-one cases of A V phenomena were selected from the squint clinic of Dr. Rajendra Prasad Centre for Ophthalmic Sciences for a prospective study to evaluate the effect of different amounts of vertical shifting in A V phenomena. A complete orthoptic evaluation with due refractive correction was done, whereby deviations were measured in primary position, 25° upward gaze and 25° downward gaze by tilting the head and measuring the head tilt on the cephalodeviometer. A difference of 15 prism dioptres or more in V phenomena and 10 prism dioptres or more in A phenomena in measurements (25° upward and downward gaze) were taken as criteria for designating these patterns. Measurements in all 9 positions of gaze were done using synoptohore, and the tests for binocularity were done with Bagolini glasses and Worth 4 dot test. The overaction of the obliques was graded as mild, moderate, or severe based on the degree of elevation or depression of the adducted eye in the lateral version of the fixing eye. (Mild = upto 15 prism dioptres; Moderate = 16 to 30 prism dioptres; Severe = more than 30 prism dioptres of hyper or hypotropia of the adducted eye).
The appropriate recession-resection procedures were done for the deviation in the primary position, in addition to vertical displacement of horizontal recti. For V pattern the medial rectus was depressed and lateral rectus was elevated and the reverse was done for A pattern. The surgical technique used was the same for all cases except for the amount of shift, i.e., 5 or 8 mm. This was randomised by drawing chits.
We divided the cases into two groups, one with no significant overaction of obliques and the other with mild to moderate overaction of obliques. An 8-mm shifting was done in 11 cases and a 5-mm shift was done in 10 cases, in both groups randomly. Patients were assessed on the first postoperative day and thereafter at one week, one month and three months.
| Results|| |
[Table:1] shows distribution of cases and the mean preoperative deviation observed in the 8 mm and 5 mm shift groups of A or V patterns. [Table:2] shows the postoperative correction achieved. In the A pattern, in the 8 mm shift group the mean correction achieved was 23.54 ± 4.9 prism dioptres and in the 5 mm shift group, it was 22.5 ± 3.6 prism dioptres. This was, however, not found to be statistically different (p = 0.74).
In the V pattern, in the 8 mm shift group the mean correction achieved was 20.28 ± 4.64 prism dioptres and in the 5 mm shift group, it was 17.95 ± 4.03 prism dioptres. The difference was not statistically significant (p = 0.35).
We observed changes in vertical deviation of more than 6 prism dioptres in primary position in 13 cases, compared from the preoperative deviation [Table:3]. Ten patients had oblique overaction and three had underaction. There was no correlation between amount of recession, resection or vertical incomitance. But none of the. cases that had no cyclovertical muscle imbalance preoperatively, showed vertical incomitance. [Table:4] shows the mean of the vertical incomitance in the two groups showing no difference between the 5 mm and 8 mm groups (p = 0.82).
Of the 21 cases, 8 cases showed horizontal incomitance of 8 prism dioptres or more [Table:5]. Maximum incomitance was found in the 8 mm shift group and the mean incomitance between levo and dextro version was 12 prism dioptres. In the 5 mm shift group, the mean incomitance between levo and dextro version was 8.6 prism dioptres. This difference was not significant but indicates more limitation of horizontal gaze after an 8-mm shift.
| Discussion|| |
Monocular vertical displacement of horizontal recti was successful in decreasing the AV phenomena. Since the amount of displacement is related to the amount of correction, we decided to study the effectiveness in both 5 mm and 8 mm shifts. Almeida reported supraplacement or infraplacement of horizontal recti in the same eye with average correction in A and V patterns of 25 prism dioptres. In 85% of his study, the vertical incomitance was reduced to 5 prism dioptres and in more than 20% of cases vertical incomitance was reduced to 10 prism dioptres or less. However, he performed only 4 to 5 mm shift. Metz also reported 15 prism dioptre correction with 5 mm shift. Our study confirmed the findings of Almeida and Metz that 5 mm shift was effective in correcting AV phenomena. Since we could not detect any statistical difference of correction between 5 mm and 8 mm shifts, our finding contradicted with Goldstein's observation that 8 mm shift was more effective than 5 mm shift.
The effectivity of vertical displacement was seen even in cases with mild to moderate oblique overaction but we observed vertical incomitance of more than 6 prism dioptres in primary position in all such 13 patients. Goldstein in his study observed vertical incomitance in 6 patients from a total of 18 cases. Burian et al have cautioned not to perform monocular vertical displacement of horizontal recti in the presence of oblique overaction especially in cases where hyper or hypotropia was present prior to surgery. This vertical element in horizontal strabismus could not be explained solely on the basis of mechanical limitation to ocular rotation following muscle shift. Had it been so, the vertical component would have been present in our cases without oblique malfunction. We also observed that following surgery the oblique overaction was decreased in all cases and eliminated in 2 cases, each of A and V phenomena.
In our study, eight of the 21 cases showed horizontal incomitance. Goldstein also observed horizontal incomitance of over 15 prism dioptres in 5 cases. Costenbader reported 50% incomitance after monocular surgery. The lesser incomitance in our study could be due to better dissection of the fascial attachments. It also appears that underaction of both operated recti in extreme gazes results due to loss of mechanical advantage in extreme gazes after muscle transposition.
To conclude, a 5-mm shift is as effective as an 8-mm shift, done along with a monocular recession-resection procedure to correct the A or V phenomenon. The vertical incomitance induced was equal in the two groups and related to preexistent cyclovertical muscle imbalance. While the overactions of obliques decrease after the transposition surgery, the prospect of vertical incomitance does not allow recommendation in presence of cyclovertical muscle imbalance. The horizontal incomitances or underactions in extreme gazes appear to be more with the 8 mm shift group and is apparently due to loss of mechanical advantage. It is therefore recommended that a 5-mm shift may be done in cases with no associated cyclovertical muscle imbalance.
| References|| |
Burian HM, Cooper EL, Costenbader FD. The A-V pattern in strabismus. Trans Am Acad Ophthalmol 68:375, 1964.
Noorden GK von, Olson CL. Diagnosis and surgical management of vertically incomitant horizontal strabismus. Am J Ophthalmol 60:433-442, 1965.
Prakash P, Menon V, Nath J. Surgical management of A and V patterns. Indian J ophthalmol 31:463, 1983.
Goldstein GH. Monocular vertical displacement of horizontal rectus muscle in A and V patterns. Am J Ophthalmol 64:265, 1967.
Metz HS. The treatment of A and V patterns by monocular surgery. Arch Ophthalmol 95:251, 1978.
Almeida HC. Correction of A and V syndrome acting upon only one eye. Proceedings of the International Strabismological Association, France, 1974, pp. 134-137.
Prakash P, Khadka KB, Menon V. Cephalo-deviometer: A new instrument for diagnosis of A V patterns. Proceedings of the Fifth meeting of the International Strabismologist Association, Rome 1986, pp. 251-254.
Costenbader FD, Bair DR. Strabismus surgery: monocular or binocular ? Arch ophthalmol 52:655, 1954.
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