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Sir,

Recently, Foster1 has described an augmented transposition operation for use in horizontal muscle deviation caused by VI nerve palsy and type 1 Duane syndrome. We have reported the dramatic benefit that can be produced by the procedure.2 While the possibility of using a similar approach for large vertical deviations has been mentioned,3 no case reports or series have been published.

We report our experience in using the Foster modification of transposition surgery in a patient with acquired superior rectus palsy.

Case report

An 8-year-old boy was referred to the strabismus service because of a vertical squint. The family reported that recently his right eye tended to drop downwards especially on right gaze, that he adopted a markedly abnormal head posture of chin elevation, and tended to close one eye when reading. There was no past ocular history and his general health prior to presentation had been good. He was not taking medication and there was no relevant family history of ocular problems.

On initial examination, visual acuities were right 6/5 and left 6/4. There was a right hypotropia measuring 20Δ at 1/3 m and 12Δ at 6 m with a 4Δ esotropia. He also had right upper lid retraction and limitation of right eye dextroelevation (Figure 1a). While he attempted to maintain alignment with a head posture, there was evidence of right eye suppression as tested by Bagolini glasses. The remainder of the eye and neurological examination was unremarkable.

Figure 1
figure 1

HESS charts: (a) Preoperatively, there is an isolated limitation of superior rectus muscle function. (b) Postoperatively, there is limitation of downgaze in the operated eye. Consequently, there is diplopia in marked downgaze.

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MRI, liver function tests, thyroid function tests, full blood count, and plasma viscosity were normal. A diagnosis of isolated superior rectus palsy was made.

He was reviewed at monthly intervals. After 6 months, his deviation had increased to 30Δ right hypotropia at near and distance. Following discussion with the family, surgery was performed despite the changing size of the deviation in the hope of preserving binocular function.

Forced duction test at surgery revealed no restriction. Adjustable 6 mm right inferior rectus recession and 5 mm superior rectus resection were performed. A 2 mm adjustment of the inferior rectus (ie a final recession of 4 mm) was utilised to achieve orthophoria for near and distance.

At 10 days postoperatively, he had developed an 11Δ right hypotropia. At 2 months following surgery, his deviation had returned to the preoperative state of 35Δ right hypotropia.

After 6 months, a stable situation had been reached and a cosmetic procedure was requested. A full muscle transposition of the medial and lateral recti was combined with posterior fixation sutures to the horizontal recti 7 mm posterior to the insertion of the superior rectus muscle.

Postoperatively, a 5Δ right hypotropia was present that drifted to orthophoria over 2 weeks. Stereopsis of 60″ was now present. An initial 4 mm ptosis gradually resolved over the next 3 weeks. Ocular motility has remained unaltered 5 months following surgery. However, there is limitation of right downgaze (Figures 1b and 2).

Figure 2
figure 2

Postoperative alignment in nine positions of gaze.

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Comment

Large incomitant vertical deviations present a challenge to the strabismus surgeon, particularly if an attempt is made to preserve binocularity.

The results of conventional transposition surgery are often disappointing.1,6 The value of a Foster procedure has been clearly demonstrated before in the management of horizontal palsies,1,2 but there is little information regarding use of the technique for vertical strabismus.

In our case, augmented vertical transposition was used following a return of the deviation after initial standard resection/recession, which may explain the presence of limitation in downgaze postoperatively. It is also possible that the posterior fixation suture may also contribute to the limitation in downgaze postoperatively, although we would need to perform forced duction testing to elucidate this further. In retrospect, use of an augmented transposition procedure at the initial surgery may have been the optimal initial management.

It is possible that this patient may require further surgery for the depression deficit, although children can be remarkably tolerant of such difficulties and currently, he is managing extremely well. Late overcorrection and the risk of anterior segment ischaemia caused by multiple operations on extraocular muscles are two other important considerations.

The HESS chart confirms the clinical finding of isolated superior rectus underaction rather than double elevator palsy (Figure 1a). There is paucity of information on the management of idiopathic superior rectus palsy in the literature.4,5 Despite this, it is a condition that is encountered occasionally in specialist strabismus practice and, if marked, may be an indication for augmented transposition. However, the technique is still in its infancy and only time and experience will delineate its optimal use.