Juniper Publishers-Journal of Ophthalmology
Introduction
The High intra ocular pressure (IOP) is the only risk
factor that we can control in glaucoma treatment, and it has been shown
that reducing this pressure will stop or reduce glaucoma progression.
Usually, when the patients diagnosed, wesill start treatment with drops
that reduce aqueous humor production or increase its out flow in the
trabecular mesh work in order to reduce the pressure inside the eye. But
sometimes, this reduction is not enough and we can´t reach to our
planified Target Intraocular pressure and it´s necessary to plan a
surgical procedure that could reduce this pressure even more too finally
achieve our intended IOP.
Glaucoma surgery has multiple variations but the gold
standard procedure is still the trabeculectomy, creating a pathway from
the anterior chamber, to the subconjunctival space by a scleral ostium
and and peripheraliridotomy. This surgical technique is usually not very
difficult to perform, but the chances of having surgery or post
operation complications are very high, specially, those related to
ocular hypotension due to unexaggerated and not controlled out flow.
Another usual problem is when we try to control or reduce the out flow,
and we perform really small ostiums or very tight sutures in the scleral
flap and we get a poor result in the reduction of the intraocular
pressure.
So there are many options to develop a surgery that
can provide good intraocular pressure reduction with fewer complications
than the penetrating procedures like trabeculectomy or valve implants.
The development of Non penetrating Deep Sclerectomy became one of the
most promising of this new surgical techniques. It is described as a
good option for open angle glaucoma, especially if the target IOP, is
not very low, or when the risk of hypotonic is high (phakic,
nanoftalmos, Hypermetropia). This technique consist carving a first
superficial scleral flap of about 4 or 5 mm wide and 1/3 of scleral
thickness, then its carved a second Deep scleral flap is about 3 to 4 mm
and almost 2/3 of scleral thickness arriving just choroid darkness.
This Deep flap goes forward until we see the change of the scleral
fibers when the scleral spur is located, then we find the external Wall
of Schlemm's canal, Schwalbe´s line and continue forward at least one or
two millimeters into clear corneal stroma. At this moment an anterior
chamber paracentesis can be done to avoid prolapse of schlemm´s cannel
tissue or the perforation of this very thin tissue that remains between
anterior chamber and the outside, that we call trabeculo-Descemet
membrane. These cond deepest flap is cutted and then next step is to
remove that schlemm´s cannel outer Wall and at that moment we will see a
continue controlled filtration or aqueous humor, without collapsing or
abrupt compression of the anterior chamber.
This technique has shown good results in intraocular
pressure reduction, compared to trabeculectomy, with an important
difference in the incidence of complications related with hypotonic
(atalamy, cataracts, endothelial damage, hypotonic aculophaty, retinal
detachment, choroidal effusion or detachment) or to the communication of
the outside environment with the inside of the eye (Endophthalmitis).
This is a safe, effective technique but with a very
high learning curve, especially at the moment of the second Deep flap
carving when the trabeculo-descemetic membrane is created, the
perforation of this very thin tissue is a common complication and
usually learning specialists try to avoid it by not going very Deep,
over the choroidal plane and that is a reason, why the surgeons can´t
get the correct plane, that will guarantee and adequate aqueous
filtration trough the trabeculode scemtic membrane into the scleral lake
as a decompression chamber, sub conjunctival space. The use of laser
goniopunctures were needed to get the IOP lowering effects pected.
This was our main problem when we tried to learn and
teach this technique in Bolivia, we had to convertion to trabeculectomy
due to perforation or not enough IOP lowering effect.
The solution was to perform the surgery with the same
steps as the original but when we found the remaining tissue was too
thick to achieve a good filtering function, the risk of perforation
trying to go deeper, we used a 30 gauge needle to perform about 5-10
micro perforations in the trabeculode scemetic like membrane we created,
turning this membrane into a net like tissue that kept the resistance
of the aqueous out flow, avoiding fast decompression problems. And
hypotony problems in the post operation period without requering an
extra procedure like yag laser goniopunctures or surgery revision.
Results
66 cases have been conducted from which (9.09%)
should have been turned into trabeculectomy by perforation of the
trabecular descemetic membrane. On a 3-year average follow-up, a 17+-3
IOP was obtained during the first year in 54 patients (81,8%) in 50
(75,7%) after 2 years, and in 48 patients (72,7%) after 3 years of
control, and them education had to be restarted in the rest. Out of the
operated patients, only 7required a new surgical procedure (Ahmed valve
implant) on the 3rd year of the follow-up. No cases of hypothonia, at
halamia, choroid detachment or end ophthalmitis were reported 3 years
after the control.
Discussion
On our first years of experience with the non
penetrating Deep sclerectomy, we found our selves continuosly with the
situation of membrane perforation, or a thickker, non functioning
membrane created. We need to turn many surgeries into big
trabeculectomies, that increased the incidence of hypontony related
complications in the post operatory time or if we were conservative,
filtering surgeries that worked bad or didn´t work at all, needing new
medications, new surgeries, oryag laser retreatment.
Turning Non Penetrating Deep sclerectomy surgeries
into Micro Perforation Deep Sclerectomy give us a safe, effective
option, that we used a lot in the beginning, with practice and gaining
experience. We need to use less over time, once having dominated the
surgery planes we needed to reach, when the learning curve was passed.
Its is a good option for learning residents or
experienced surgeons who want to start with the Non penetrating
surgeries to reduce the chances of complications and increse
effectiveness of the filtering technique, until they achieve the needed
practice to perform a perfect flaps carving and reaching a
trabeculo-decement level needed to really reduce IOP.
Learning non penetrating surgeries, allows Glaucoma
surgeons to identify and reach schlemm´s channel, and that opens options
for other Glaucoma surgeries, like visco canalostomy, canaloplasty,
ortrabeculotomy.
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