MACULAR TRANSLOCATION SURGERY
MANISH
NAGPAL, SHASHANK BANAIT
Retina Foundation, Near Shahibag
Underbridge, Shahibag, Ahmedabad - 4, Gujarat.
Macular translocation involves moving
the neurosensory retina in an eye with recent onset subfoveal location to a
new location with presumable healthier RPE and choriocapillaries. This review
article outlines the current indication, techniques and outcome of this procedure.
Age related macular degeneration is a leading
cause of severe, irreversible central visual loss among adults aged 65 years
and above causing nearly 60% blindness in this population. In about 75% of cases
the decrease in vision is associated with choroidal neovascularisation (CNV).
The pathology is usually limited to the central macular area. The inner aspect
of Bruchs membrane is diffusely thickened, impeding adequate passage of nutrients
from choroid to the pigment epithelium and metabolic products from pigment epithelium
to choroid. Macular photocoagulation study had observed that the natural course
of the sub foveal CNV was always poor because of the damage that can be caused
to the fovea because of treatment or lack of it. In MPS,[1]
very few patients with subfoveal membrane and AMD whether lasered or not retained
visual acuity 20/100 and most of the patients had vision less than 10/160 after
four years. Other treatment modalities such as photodynamic therapy or transpupillary
thermotherapy have shown to stabilize the vision in about 65 to 70% patients.[2]
In patients having minimally classic or poorly defined membranes the treatment
modality still remains elusive although recent VIP trial has shown some promise.[3]
One limitation in all these treatments is the inability to correct for the absence
of RPE-Bruchs membrane -Choriocapillaries support of the photo receptors that
occurs with macular degeneration.
HISTORY OF MACULAR TRANSLOCATION SURGERY
Lindsey and associates in 1983 achieved
successful shifting of retina in rabbits and primates and determined that foveal
photoreceptors are not totally dependant on foveal RPE and choroid.[7]
Tiedeman and associates in 1985 reported successful 45 degrees rotation of macula
in rabbits by creating RD of the area to be rotated and performing relaxing
retinotomy, as fluid exchange, retinal tacking and silicon oil tamponade.[8]
Machemer and Steinhorst in 1993 developed an animal model in rabbits in which
RD was created by infusing fluid into subretinal space, 360 degrees peripheral
retinotomy done, retina was rotated by 60 degrees around optic nerve axis and
reattached. These authors also reported similar procedure performed in 3 patients
after 5 months of follow up one patient improved to 20/80, remaining two developed
PVR.[9]
Kazuyuki I et al in 1988 reported limited translocation of central retina in
15 rabbit eyes.[10]
Eugene De Juan Jr et al in 1998 reported limited macular rotation in 3 patients.
This technique according to them was less extensive than performing 360 degrees
retinotomy.[11]
Eckardt in 1999 reported a 60% success in the series of 30 eyes in which he
performed a modified 360 degree translocation procedure.
Rationale for macular translocation
The mechanisms responsible for visual loss in eyes with disorders may be
either reversible or irreversible. In early stages of neovascular AMD, the visual
deterioration may be secondary to such factors as subretinal fluid or haemorrhage
in the foveal region. In later stages the irreversible stages of the disease
fibrovascular proliferation causes permanent damage of the photoreceptors. Therefore
by moving the neurosensory retina in an eye with recent onset subfoveal lesion
to a new location with presumably healthier RPE and choriocapillaries away from
lesion, the fovea may be able to recover or maintain its visual function.[5]
In addition by moving fovea away from such foveal lesions as CNVs may permit
the removal of the CNVs or its destruction by laser photocoagulation.
Indications of macular translocation
The commonest indication of the surgery
currently is CNV related to AMD, ocular histoplasmosis syndrome, pathologic
myopia. Other potential indications for macular translocation include RPE defects
created after removal of type I subfoveal CNV and also cases having central
geographic atrophy.
Definition and terminology used in macular translocation[4]
In order to avoid confusion between the usage of multiple terms related to the
procedures of macular translocation a multicentric group decided upon a fixed
terminology to describe the various aspects of procedure.
Macular translocation has been defined as any surgery that has a primary
goal of relocating the central neurosensory retina or fovea intra operatively
or postoperatively specifically for the management of macular disease.
Effective macular translocation : It is defined as successful intraoperative
or postoperative relocation of the fovea overlying subfoveal lesion to an area
outside the border of the lesion, that is a previously subfoveal lesion becomes
either Juxtafoveal (1-199 microns from the foveal centre) or Extrafoveal (200
or more microns from the foveal centre) after the surgery.
Minimum desired translocation : The distance between the foveal centre and
a point either on the inferior or superior border of the lesion depending upon
whether the translocation is inferior or superior all of these points being
equidistant from the temporal edge of the optic disc. For nasal translocation
it is the distance between the foveal centre and nasal border of the lesion.
Classification of macular translocation (MT) surgery[6]
MT with large curvilinear incisions of the retina
- MT with 360 degrees retinotomy
MT with punctate or no retinotomy
1. With chorioscleral shortening
Chorioscleral infolding (imbrication or inpouching)
Chorioscleral outfolding (outpouching)
2. Without chorioscleral shortening
General surgery principles
The patients potential for vision has to be determined before surgery. Only
those patients who do not have atrophic retina, having a site with healthy RPE,
Bruchs membrane and choriocapillaries will have some improvement following surgery.
As a general principle vitrectomy is followed by the creation of retinal detachment
by infusion of fluid under the retina either through sclera or from inside through
the retina.
1. One can detach the retina completely, cut it free with a 360 degrees peripheral
retinotomy at the ora serrata, rotate it around the optic nerve head to a desired
degree and reattach the retina.[9,12]
This procedure was advocated by Machemer et al in which total RD was performed
through trans-scleral route, 360 peripheral retinotomy was done, retina was
reattached in new position and silicone oil tamponade was given. The extent
of translocation was determined by the extent of the pathology noted. Total
translocation causes around 4500 microns of macular translocation.[9]
Toth and Machemer, Eckardt and Conrad each have applied modification to original
Machemer technique. These include transretinal infusion to create detachment,
using wide field chandelier illumination or illuminated cannula, wide field
viewing systems[14] or performing oblique or rectus muscle
transposition.[15]
2. Only the temporal part of the retina may be detached and cut free in the
periphery with a 180 degree retinotomy. The macula can be moved upward, downward
resulting in radial fold that extends from the disc to the inferior or the superior
edge of the retinotomy, respectively. A radial retinotomy may be added which
will allow reattachment without a fold.[13]
Ninomiya and Tano described detachment of temporal retina only and created 180
degree peripheral retinotomy with a superior or inferior radial incision to
move the fovea inferiorly or superiorly.[13] This procedure
had a higher risk of PVR because of the posterior extent of the retinotomy and
the additional retinopexy around it.
3. A retinal detachment may be created on the temporal side without a retinotomy.
Thereafter the sclera is shortened in the area of detachment by a scleral resection
resulting in shift of the sclera and choroid in relation to the fovea. The retina
is reattached with a redundant small fold.[10,11]
De Juan has described this method called limited macular translocation in which
only temporal retina is detached and limbal parallel arcuate shortening of choroid
and sclera is done and later on the CNV was photocoagulated. With scleral resection
about 1500 microns translocation is possible.[11]
In modification of this procedure absorbable sutures were used for temporary
scleral infolding and the advantage cited of this modification was that the
distance of the translocation did not regress whereas the corneal astigmatism
induced by the scleral infolding resolves over a period of time.[16]
The size and the location of the pathology
also determines the type of surgery that is required.
Outcome of translocation surgery
The early history showed that some patients retained good central vision after
translocation but since the total number of surgeries done world wide is limited
and also since no long term follow up is available it is difficult to predict
long term results.
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.
Machemer et al reported macular rotation surgery with 360 degrees retinotomy
performed in 3 patients; after 5 months of follow up one patient improved to
20/80, remaining two developed PVR.[9]
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.
In earlier report by De Juan et al all 3 patients who underwent limited macular
translocation with partial thickness scleral resection for subfoveal CNV, had
postoperative visual improvement upto 6 months of follow up.[11]
Eckhardt et al (1999) reported 60% of patients’ visual acuity improved sufficiently
to read normal newsprint.[15]
With modified macular translocation surgery with 360 degrees peripheral retinectomy,
(MTS 360) central vision has been salvaged for almost one year of follow-up
in patients presenting with vision loss from subfoveal CNV and ARMD. The average
post operative visual acuity of the patients undergoing modified MTS 360 was
better than in patients undergoing conventional macular translocation.[14]
Foveal translocation was reported to be effective in myopic neovascular maculopathy.
The patients post operatively developed diplopia and anseikonia but these complaints
resolved as suppression developed.[17]
The results of the limited macular translocation surgery were better in patients
having subfoveal CNV due to AMD. The improvement of 2 lines or more was seen
in 67% eyes in myopia as against 30% in AMD.[18]
The macular translocation surgery is also effective in other causes of subfoveal
CNVs. The vision improved by 2 Snellen lines in 47.82% and within 1 line in
30.43% patients following translocation in patients of subfoveal CNV due to
various causes as myopia, ocular histoplasmosis syndrome, angioid streaks, idiopathic
neovascularization, and multifocal choroiditis.[19]
Our Experience
We have done 11 cases of MTS with 360 rotation and 1 case of MTS with no retinotomy
with scleral infolding technique. Of the 11 cases which underwent 360 degree
rotation anatomical successful rotation was achieved in 8 eyes. Five eyes have
improved the central visual acuity by 1 or more lines and have reduced scotoma
while reading. Two eyes have remained stable at the same acuity and 1 eye worsened
by 2 lines. Of the remaining 3 eyes 2 developed retinal detachments with eventual
proliferative vitreoretinopathy changes and underwent multiple surgeries for
the same. One case developed a massive choroidal haemorrhage and eventually
developed optic atrophy and lost perception of light. The single case of limited
macular rotation improved by 3 lines of visual acuity.
COMPLICATIONS
The most serious complication was retinal detachment and PVR. In the earlier
series by Machemer the incidence of retinal detachment was 66% (2/3 patients
developed PVR).[9] The rate of retinal detachment in modified
MTS 360 is 0% (no RD in 10 consecutive patients) as against 5/16 reported by
same author in the earlier group. The decrease in the rate of post operative
retinal detachment has been attributed to refinements in the surgical techniques,
use of perfluorocarbon liquids, wide angle viewing system, wide field illumination
and technique of inducing retinal detachment using fine guage needles for fluid
injection.[14]
Other complications which can occur are cataract, neovascularization of iris,
corneal decompensation, recurrence of the membrane, CME, diplopia.
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