Deep sclerectomy (DS) is a little understood anti-glaucoma surgery by most ophthalmologists.
It is a non-penetrating filtering surgery for both primary and secondary open angle glaucoma.
In this surgery, the aim is to surgically excise the inner wall of the Schlemm’s canal and juxta-canalicular trabecular meshwork where aqueous encounters maximum resistance during its outflow.
I will describe the surgical technique comparing it with the trabeculectomy which still remains the gold standard anti-glaucoma filtering surgery.
Conjunctiva and Tenon’s are dissected in the same fashion as in trabeculectomy.
Antimetabolites can be applied in the same way and washed.
A limbus based 5 X 5 mm of one-third scleral thickness is fashioned.
It is extended into the cornea at least 1.5 mm.
So far it has been nearly same as in trabeculectomy.
Now a second scleral flap is dissected such that the scleral bed that remains below it would be just 50 to 100 microns thick.
This flap is smaller measuring 4 X 4 mm.
A step is left so that it will allow for the suturing back of the superficial flap.
While fashioning this deep scleral flap, as one progresses towards the clear cornea, the Schlemm’s canal gets deroofed.
This deep scleral block is eventually excised.
Both the Schlemm’s canal and juxtacanalicular trabecular meshwork gets deroofed.
Overlying it is the trabeculo-Descemet’s membrane (TDM) which is what prevents this surgery from becoming a full-thickness filtering surgery.
The superficial flap is then sutured back with 10-0 nylon as in trabeculectomy.
As you can see, the filtration in DS will obviously be more, at least initially before scarring occurs, than in trabeculectomy.
And having a base of TDM ensures it from being a full-thickness thus securing it the safety of all partial thickness filtering surgeries.
