Aniridia and Anterior Segment Dysgenesis

Syndromes

In aniridia and anterior segment dysgenesis syndromes the angle structures are abnormal and may not suit Ex-PRESSª implantation. In these cases, MPGS should be avoided unless all other operations have failed and the surgeon is conÞdent of having found a site where the Ex-PRESSª can be safely positioned. Obviously, the Ex-PRESSª should be implanted only by an experienced surgeon who has already performed many implantations in less complicated cases.

Narrow-Angle Glaucoma

The Ex-PRESSª should not be used in narrow-angle glaucoma (NAG) unless the lens is extracted at the same time. At present, many glaucomatologists suggest that cataract/lens extraction should be considered as an important step in the treatment of NAG. Laser iridotomy or surgical iridectomy provide a temporary measure only, whereas removal of the crystalline lens, irrespective of its transparency, deepens the anterior chamber and widens its angle. When NAG has persisted for some time, the TM may not recover its function even when the lens has been extracted. In that case, Þltration surgery may be needed in combination with lens extraction.

Posttrauma Angle-Recession Glaucoma

In angle-recession glaucoma, the TM has been damaged and its Þltering function may not recover. MPGS with the Ex-PRESSª implant is feasible because of its minimal tissue manipulation. The outcomes might be less rewarding than in OAG because of the scarring and the reactivity of the ocular tissues following the trauma.

or in proliferative diabetic retinopathy (PDR). Until the present, Þltering surgery for NVG has been difÞcult because of the high risk of intraoperative bleeding and the intense postoperative inßammatory response. The high risk of postoperative hyphema in MPGS is a serious drawback because the Ex-PRESSª implant oriÞces can be totally occluded by the blood clot. Furthermore, the intense postoperative inßammatory response might cause severe adhesions of the scleral ßap, impairing adequate Þltration.

8.2.1.3Absolute Contraindications for MPGS with the Ex-PRESS™ Mini-Shunt Under a Scleral Flap

Narrow-Angle Glaucoma in a Young Patient

Because the Ex-PRESSª requires a deep A/C and an open angle its application in NAG without lens extraction is absolutely contraindicated. The Ex-PRESSª implant may be too close to the iris and cornea in a crowded A/C. Consequently, it may cause damage to these tissues.

Pseudophakic Glaucoma with an A/C IOL

The presence of an A/C IOL in cases of pseudophakic glaucoma complicates the outcome of any Þltration operation. The immediate postoperative risk of hypotony and A/C loss endangers further the corneal endothelium that is often already compromised. Removal of an A/C IOL can be complicated and traumatic; therefore, such a procedure is best left for the experienced anterior segment surgeon. The potential corneal endothelial damage occurring in the case of immediate postoperative A/C loss cannot be ignored in pseudophakic eyes with A/C IOLs.

Neovascular Glaucoma

Neovascular glaucoma (NVG) is a unique form of glaucoma that results from ocular or extraocular disease that produces ischemia of the eye. It is characterized by intractable ocular hypertension caused by neovascularization of the iris and the anterior chamber angle. NVG can occur after central retinal vein occlusion (CRVO)

8.2.1.4 Preoperative Considerations

Candidates for MPGS with the Ex-PRESSª are often under maximal topical antiglaucoma treatment. Some of these medications might have adverse effects on the conjunctiva. When feasible, topical medication should be reduced to a minimum with the temporary help of oral acetazolamide. This will reduce the postoperative inßammatory response and favor efÞcient Þltration.