A long
glaucoma valve implant attached to an external scleral explant was used during
filtration surgery in 72 eyes: 39 eyes with
neovascular glaucoma and 33 eyes with other types of secondary
glaucomas or with primary
glaucoma in which prior
filtration surgery had failed. The implant consisted of an open
Silastic tube (outside diameter, 0.64 mm), which was placed into the anterior chamber. The external end of the tube contained a pressure-sensitive (opening pressure, 11 mmHg) and unidirectional slit-valve, and was sutured within the groove of a #220
Silastic explant. The 180 degree explant was placed beneath three rectus muscles and then sutured so that the grooved side was against the sclera, with the anterior edge 8 to 12 mm posterior to the limbus. The long
glaucoma valve implant resulted in a large, posterior
bleb extending over the area of the
Silastic explant. The mean preoperative intraocular pressure (IOP) of 43.9 mmHg in the eyes with
neovascular glaucoma was reduced to 17.4 mmHg after a mean follow-up of 20.2 months. The mean preoperative IOP of 38.1 mmHg in the eyes after failure of previous
filtration surgery was reduced to 17.6 mmHg at a mean follow-up of 21.0 months. Postoperative IOP was less than 21 mmHg in 77% of eyes with
neovascular glaucoma (47% required additional medication) and in 82% of eyes with previous failure of
filtration surgery (56% required additional medication).