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Histological examination of the pigment epithelium-Bruch membrane-choriocapillaris complex after macular translocation
  1. A BERECZKI,
  2. J TOTH,
  3. I SUVEGES
  1. 1st Department of Ophthalmology, Tomo u25–29, H-1083 Budapest, Hungary
  1. Dr Bereczki

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Editor,—Macular degeneration is the leading cause of blindness in the older population, and it is becoming more and more prevalent.1 At present there is no treatment for the dry type of macular degeneration; for treatment of the wet form, several medical and surgical therapies have been tried, with varying results.2-6

Photodynamic therapy with verteporfin had a significant treatment benefit in predominantly classic choroidal neovascularisation (CNV) lesions.7

Surgical removal of the subretinal membrane is a promising method, but in many cases the visual acuity does not improve. A new technique has been proposed by Machemer and Steinhorst, where after surgical removal of the subretinal membrane the fovea is translocated to an area with healthier pigment epithelium, Bruch's membrane, and choroid.8 9

Variants have been described where only the temporal part of the retina was detached, or the retinal detachment was created in the temporal side through the sclera, without retinotomy. Here the scleral resection will ultimately shift the relation of the pigment epithelium to the fovea.

CASE REPORT

In this case we performed a macular translocation using the Machemer and Steinhorst technique, with some modifications from Eckardt (personal communication, 24 October 1997), and from our experience. After surgery usually we see a retinal fold starting from the optic disc and extending to the periphery, but this fold usually disappears after 5–7 days.

Our patient died (from intracranial haemorrhage) on the fifth day after the operation, and it was possible to examine the operated eye pathologically.

At gross examination we found that rotation had been achieved through an angle of 25–30 degrees. The next step was to perform sections of the translocated macula and in the region of the former subretinal membrane, and our findings are discussed below.

COMMENT

As we expected we found a thickened Bruch's membrane, few points of calcification, some remnants from the surgically removed subretinal membrane underneath and above the pigment epithelium (Fig1),10 and choriocapillaris atrophy. The outer retina seems not to be affected at the time of surgery.

Figure 1

The choroidal neovascular membrane breaks through the Bruch's membrane and retinal pigment epithelium in the macular area. Haematoxylin and eosin, original magnification ×6.3.

From our point of view it was of interest to examine the attachment of the pigment epithelium to the retina or Bruch's membrane along the temporary postoperative retinal fold. We found that the pigment epithelium was attached mainly to the retina (Fig 2) and not to the Bruch's membrane; we were able to follow this from the optic disc through the macular region, up to the temporal periphery. Even at the site of one of our retinotomies, which happened to be on the line of the retinal fold, we found basically the same picture.

Figure 2

Cross section in the translocated macular area, showing massive fibroblastic pigment epithelium (arrows) attachment to the neuroretina which shows stunted photoreceptors (arrowhead). Haematoxylin and eosin, original magnification ×16.

This can be caused by the presence of subretinal proliferation before surgery, or more probably occurred during surgery; this is supported by the wide extent of this finding.

We know that in some cases after surgery there is no improvement in visual acuity, and we hypothesise that this is because a significant part of the pigment epithelium has been translocated along with the retina.

From our histological sections, we see that some part of membrane remains in place even after surgical “removal” and from the membrane remaining we were able to see that this is a mixed membrane with extension underneath and above the pigment epithelium.

We tentatively believe that this may be connected with the fact that the pigment epithelium remained attached to the retina in such a drastic manipulation; in a type 1 subretinal membrane situated only above the pigment epithelium this will not occur. We think that more research is needed to discover if there is any connection between the type of membrane, related to the condition of the pigment epithelium, and the apparent stronger adhesion between the pigment epithelium and retina (or relatively weaker adhesion to the Bruch's membrane).

References

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