Macular translocation surgery

The transposition creates: 1. Incyclotropia

2. Exotropia

3. Hypotropia

Fovea

45˚

Papilla

Figure 2. Upward rotation of the right macula, schematically.

Figure 3. Gaze straight ahead after macular translocation of the right eye. Above: Left eye fixates, below: right eye fixates, see text.

A simple diagram shows the postoperative situation on the fundus of an operated right eye. The fovea is rotated upward 45°. When a primarily orthotropic patient fixates with his left eye the fixated object projects on the right rotated retina below and temporally in relation to the fovea. When the fixation switches to the right eye both eyes move upwards and to the left. In orthoptic terms there is a right hypoand exotropia additionally to the incyclotropia.

Figure 3 shows a patient after macular translocation of the right eye. In the upper photo she looks straight ahead with her left non-operated eye. The corneal reflexes are in normal position. On the lower photograph she fixates with her right eye. The right corneal reflex is displaced downward and somewhat temporally. The reflex on the left cornea demonstrates the exoand hypertropia of the left eye. After Freedman there is no clear relationship between incyclotorsion and hypotropia (Freedman, Holgado et al. 2003).

The cyclotropia leads to a severe disturbance in the peripheral visual orientation under binocular conditions of seeing, even when the partner eye has a large central scotoma, and the patient has therefore no double image in the visual field centre.

Under monocular conditions an adaptation of the subjective absolute localization to the objective contour orientation develops in a few days when the patient is in a normal environment with known outlines (Seaber and Machemer 1997; Tschermak 1931). But the subjective horizontal in the dark shows again a tilt corresponding to the objective rotation of the retina.

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Table 1. Dosis-effect relationship of different procedures for counterrotation.

Despite this monocular adaptation most patients tilt their head to the side of the operated eye when the macula was rotated upwards as in most cases. The head tilt takes place unconsciously and the patient is not aware of it. Obviously, there exist subcortical connections between the subjective contour orientation and the vestibular apparatus, which try to diminish a retinal tilt.

This observation corresponds to the findings of an experiment in normal observers. In this experiment a large visual stimulus with vertical stripes was tilted and the stimulated eye reacted with a partial compensating static torsional movement (Heßel and Herzau 1984).

A further aspect of a possible sensorial problem after macular translocation arises from the fact that the rotation involves the retina only and not the optic nerve. The line of photoreceptors, which provides the perception of horizontal, is thus not shifted in a straight but in a curved line. The amount of torsion increases therefore from the blind spot in the temporal periphery to the center of the visual field; and straight contours should be perceived not only tilted but also curved. The patients do not report corresponding complaints, but the different torsional angle depending on eccentricity is certainly a further obstacle for binocular fusion.

3TREATMENT FOR BINOCULAR PROBLEMS AFTER MACULAR TRANSLOCATION SURGERY

The major complaint from all these disturbances of binocular vision after macular translocation is the image tilt. It requires a counterrotation of the globe by muscle surgery either in the same session when the retinal rotation is done (Eckardt, Eckardt et al. 1999; Fujikado, Shimojyo et al. 2002) or at a later stage. In most cases counterrotation is carried out together with the silicon oil removal 3 to 6 month later. The stepwise procedure has the advantage that a subjective measurement of the induced cyclotropia is possible and that the amount of dosage can be adjusted. Furthermore, it can be judged if a counterrotation is actually necessary in the individual patient.

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Figure 4. Schematic drawing of inferior oblique advancement with secured superior oblique tenotomy (center), and rectus externus supraposition (right picture), see text.

The assessment of the cyclodeviation is mostly done with the double Maddox-rod technique for measurement of the subjective horizontal and the cyclotropia. We use in Germany preferably the Harms tangent screen for both.

A literature survey of the different procedures for counterrotation and the respective rotational effect is given in table 1. Our observations in Tübingen are included. Only excyclorotational operations are taken into account.

In almost all cases a combined surgery of the oblique muscles of the involved eye was done with large recession or tenotomy of the superior oblique and maximum advancement of the inferior oblique. But the rotational effect of 16 degrees is not sufficient in almost all cases. Further muscle displacements are therefore added. This includes the vertical transposition of one or both horizontal rectus muscles, or a partial transposition of all four rectus muscles. In the latter method only stripes of the rectus muscles were transposed by crossing the stripes under the not sectioned part of the muscle in a clockwise direction in the right eye and in a counterclockwise direction in the left eye. The stripes are then fixated at the insertion of the adjoining rectus muscle. It is obvious that a re-operation after this procedure will be difficult.

The described cyclorotational effect of these 3 to 6 muscle operations is quite different in the literature. There is a range between 20 and 38 degrees, which can be possibly explained by a different manoeuvre on the oblique muscles.

Our standard procedure up to now was a three or four muscle surgery as depicted in figure 4. The left picture shows a right eye from the temporal side preoperatively with the insertions of both oblique muscles. In the center the inferior oblique muscle is advanced to the superior oblique insertion, and a superior oblique tenotomy has been done, secured by a loose suture. This rotates the globe about 17 degrees outwards. The rotation is then augmented by a vertical transposition of the lateral rectus muscle or of both horizontal recti.

Because the macular translocation produces incyclotropias of mostly 30 to 50° many patients are not freed from their image tilting after the first operation. Further surgery on the other eye is then necessary. At the second muscle operation additional deviations, such as an exotropia can be taken into account.

An other option, which induces a stronger excyclorotational effect, is the transposition of the superior oblique tendon from the upper temporal to the lower nasal quadrant at the nasal inferior rectus insertion by crossing the tendon under the medial rectus muscle. In combination with inferior oblique advancement and vertical transposition of two horizontal recti effects up to 45° are published.

The described muscle surgery with very large dosage for a comitant deviation induces necessarily unwanted incomitances, as the photographs in different gaze positions demonstrate (fig. 5). The operation on the oblique muscles for incyclotropia produces a depression deficit with a V-phenomenon similar to a long-standing superior oblique palsy. It reduces the hypotropia in primary position, but in down gaze an esoand hypertropia with diplopia can occur. A vertical transposition of the horizontal recti may partly diminish the V-effect.

In the primary position the cyclotropia and the hypotropia of the left eye are almost repaired in this patient, but the corneal reflex of the left fixating eye is still displaced downward. We explain

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Figure 5. First postoperative day after an excyclorotational procedure of the left eye as in figure 4.

Figure 6. Residual incyclotropia after macular translocation and muscular counterrotation, see text.

this finding by the different centres of rotation: The retinal surgery rotates around the optic nerve head, the muscular counterrotation around the posterior pole of the globe.

Figure 5 shows the central fundus of a right eye after macular translocation and after muscular counterrotation, which has reduced the incyclotropia from 35 to 10 degrees. The chorioidal scar marks the posterior pole of the globe around which the counterrotation has taken place. By this, the muscle surgery rotates the optic nerve head upwards and shifts the fovea only a small amount temporally. To fixate with the fovea the patient has therefore to rotate the eye upwards, which moves the corneal light reflex downwards.

The indication for the correction of a residual horizontal or vertical strabismus should be made dependent on the degree of problems with diplopia. Many of the patients do not suffer so much from double vision once the cyclotropia has been successfully treated. Obviously, when the double image is not tilted it can be suppressed much easier.

Scotomata in the visual field centre of the non-fixating eye hinder additionally the perception of a double image. In cases with disturbing vertical or horizontal diplopia often a prismatic correction is sufficient to provide a diplopia free field around the primary position, otherwise conventional eye muscle surgery is necessary, taking into account the blood supply of the anterior segment. In general, the better the visual outcome from the macular transposition the more binocular problems arise.

ACKNOWLEDGEMENT

This study has been supported by the Tistou and Charlotte Kerstan Stiftung

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Session 1 2: Amblyopia