Transcript Ab-interno rescue of an externally migrated glaucoma tube

Makati Medical Center
Philippines
David H. Gosiengfiao
Jeffrey N. Racoma
Mikhail Pador
Santiago A. Sibayan
* None of the authors have any financial interest to disclose
Introduction
External migration of tube shunts is of
particular concern in growing eyes.
Management includes repositioning,
adding a tube extender, replacement of the
drainage device or additional glaucoma
surgery. These frequently involve
conjunctival surgery and consequent risks.
We present a novel approach to the rescue of
an intra-stromally migrated Ahmed tube.
The case
An externally migrated Ahmed valve was found in
a 7 year old who had previously undergone
successful implantation.
Examination revealed an uncontrolled IOP of 60
mmHg recalcitrant to medical management with
the tip of the tube located intra-stromally,
occluded by the posterior corneal lip.
We used radiofrequency energy delivered through
a sclerothalamotomy tip† (Oertli, Switzerland) to
ablate the posterior lip, ensure the patency of
the tract and re-establish flow.
†
not US-FDA approved
1,2
Sclerothalamotomy

Uses RF energy to
create thalami in TM
to lower IOP
 Tip dimensions
○ 300 um wide x 600
um high x by 1000
um long
 RF energy
○ 500 kHz
○ 7W
1.
2.
B.Pajic, G.Pallas, G.Heinrich, M.Boenke. A novel technique of ab interno
glaucoma surgery: follow up after 24 months. Graefe’s Arch Clin Exp
Ophthal 2006 Jan;244(1):22-7
Operating Instructions CataRhex VC820100S. Oertli Instruments AG,
Switzerland
Methodology
The tube is externally migrated and no
longer visible on gonioscopy
The anterior chamber was entered using a
1.6 mm keratome and filled with a cohesive
viscoelastic
The internal lip was ablated using RF delivered
via STT probe
A spatula was used to ensure the patency
of the tract
The Ahmed valve was re-primed resulting
in a good bleb
Outcome
The post-operative course was uneventful.
1 day after surgery, the eye was quiet
with IOP at 12 mmHg. A mature bleb
was observed around the body of the
Ahmed valve. The IOP remained
controlled at 16 mmHg at last follow up
1 year after surgery.
Discussion
While outright replacement of the glaucoma drainage
device or additional glaucoma surgery are possible,
the advent of commercially available tube
extenders has made them less desirable
alternatives.
Restoration of flow using tube extenders often leads to
rapid IOP control to pre-migration levels because of
the presence of an already mature pseudocyst or
bleb around the plate.3
Tube extension however, entails conjunctival
dissection and may cause unwanted inflammation
in close proximity to the bleb.
Ab interno ablation using RF re-establishes flow while
avoiding conjunctival dissection.
3. S.Sarkisian
and P.Netland. Tube extender for Revision of Glaucoma Drainage
Implants. J Glaucoma 2007;16:637-639
Ab-interno RF rescue of externally
migrated shunt
Pro’s



No conjunctival
dissection
No conjunctival
inflammation
Short procedure
Con’s



Violates the anterior
chamber
May release inflammatory
cytokines from ablated
tissue
Introduces energy
Conclusion
An ab-interno approach to the rescue of an
externally migrated glaucoma tube shunt
may be a good alternative to
conjunctival surgery
Further studies should be conducted to
assess long term success and lentoiridocorneal effects.