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Macular Translocation: A Surgical Approach to
Central Vision Recently
Damaged Moderately by Subfoveal Neovascularizations
by Philip Filner, Ph.D. The Problem The fovea is a very small zone at the center of the
macula, in which the color-sensing cones of the retina are concentrated. Because of this concentration, the fovea plays a much larger role in seeing color and detail than its size
relative to the rest of the macula or retina would suggest. When central vision is damaged as a result of subfoveal choroidal neovascularizations, i.e. leaky new blood vessels forming
in the choroid tissue behind the fovea, laser photocoagulation is not an appropriate treatment because the overlying foveal tissue is destroyed by the energetic laser used in
photocoagulation. That destruction harms central vision to an extent which outweighs the potential benefit from temporarily slowing or stopping leakage by laser photocoagulation.
The Proposed Surgical Solution
For a number of years, some ophthalmic surgeons have been experimenting with a surgical approach to alleviating the damage done to central vision by subfoveal neovascularizations. The
surgical approach is called macular translocation. The idea behind it is that if intervention is early enough, the light-sensing cones and rods in the fovea might still be functional,
i.e. able to transmit electrical signals to the brain in response to light, at a time when the cells of the retinal pigment epithelium (RPE), which function in recycling components of
the cones and rods which are spent in the light-sensing reactions, are non-functional immediately behind the fovea. The retina can be detached from the underlying RPE, moved, and
fixed in the new position relative to the RPE without destroying the neuronal connections between the cones and rods, and the optic nerve. The surgeon's objective is to move
(translocate) the fovea relative to the RPE, so that the presumptively functional cones and rods of the fovea are repositioned in front of presumptively functional RPE just outside
the original fovea position. If translocation achieves what the surgeon hopes it will achieve, recycling of the byproducts of light-sensing in the fovea will be restored by the new
patch of RPE behind the translocated fovea. Translocation is actually rotation The retina cannot be completely detached. The
part of the retina at the optic nerve remains attached, probably because of the neuronal connections. However the rest of the retina can be fully detached, by a combination of
injecting fluid behind the retina, and cutting places at the outer edge of the retina where it remains attached. The retina can then be rotated about the optic nerve. A rotation of
the retina, e.g. through 45o - 50o , will reposition the fovea over healthy RPE. However, the rotation has the undesirable effect of giving vision with that eye
a tilted horizon. While most of the ophthalmic surgeons have been trying rotation of the retina alone, Eckhardt et al (1999) in Germany have been experimenting with rotational
movement of the retina, combined with counter-rotation of the eyeball via surgery on eye muscles, to minimize the disorienting effect of the rotation. De Juan (1998, 1999) has been
experimenting with a more limited movement of the retina, which does not require full detachment in order to achieve useful macular translocation. Results So Far The procedure has not yet been standardized, and results seem to vary substantially between surgeons. Lewis et al. (1999) reported that the
procedure had unpredictable results. When macular translocation was performed, there was at least as great a chance of worsening visual acuity as improving it. However, Eckhardt et al
(1999) reported 60% of patients' visual acuity improved sufficiently to read normal newsprint. Ohji et al. (1998), using two surgical techniques in Japan, found that 40% of patients
had improved visual acuity, and 20% of patients had visual acuity improved sufficiently for reading. A review of the surgical procedures being tried to achieve macular
translocation can be found in Toth & Machemer 1999). Conclusions Macular translocation can sometimes improve the visual acuity
of people with ARMD who recently experienced a decline of central vision because of subfoveal neovascularizations. However, the procedure, and selection of patients, need to be
standardized, so that more consistent results can be obtained by different surgeons, and so that the success rate can be consistently high. References De Juan E, Lowenstein A, Bressler N M, Alexander J.
Translocation of the retina for management of subfoveal choroidal neovascularization II. A preliminary report in humans. Am J Ophthaomol (1998. 1999) 125:635 - 646.
Eckardt C, Eckardt U, Conrad HG Macular rotation with and without counter-rotation of the globe in patients with age-related macular degeneration. Graefes Arch Clin Exp Ophthalmol
(1999) 237:313-325 Lewis H, Kaiser PK, Lewis S, Estafanous M Macular translocation for subfoveal choroidal neovascularization in age-related macular degeneration: a prospective
study. Am J Ophthalmol (1999) 128:135-146 Ohji M, Fujikado T, Saito Y, Hosohata J, Hayashi A, Tano Y Foveal translocation: a comparison of two techniques. Semin Ophthalmol
(1998) 13:52-62 Toth C A, Machemer R Macular Translocation, in Age-Related Macular Degeneration, J W Berger, S L Fine, M G Maguire, eds., Mosby, St. Louis, pub, 1999, pp 353-
362. October 29, 1999 |
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