10
Complications were encountered in 30 eyes (30/60 50%) and are presented in Table 2.
The most common was hypotony, defined as an IOP < 5mmHg or shallowing of the anterior
chamber without evidence of aqueous misdirection (14/60 eyes, 23%). This usually occurred
early in the postoperative course (average 1.6 ± 1.3 months post surgery) and resolved within
a maximum of 2 months. Five patients required anterior chamber reformation. In two
patients, hypotony had a devastating visual outcome: one patient had a choroidal effusion
which left a foveal fold after resolution, and in another patient, chronic hypotony due to self
inflicted injury resulted in phthisis.
Tube exposure occured in 8 eyes (8/60, 13%), 4 of which had uveitic glaucoma (50%
of the 8 eyes of uveitic patients). Two additional patients, with aphakic glaucoma, had
episodes of uveitis prior to tube exposure. Thus, 75% (6/8) of the eyes with tube exposure
had uveitis prior to exposure (Fisher's Exact Test P=0.006). Exposure always appeared
within the first postoperative year (average 8.0 ± 3.5 months). The earliest exposure occurred
1 month postoperatively. The site of exposure was always adjacent to the limbus, in
proximity to the entry site of the tube into the eye. In one patient with uveitic glaucoma, tube
exposure was accompanied by plate erosion through the sclera into the supra-choroidal space.
The tube exposure site was re-covered with donor sclera and the plate was stable and
functioning during a 12 month follow-up with no choroidal effusion or retinal detachment.
Tenon cyst formation occurred in 4 eyes (4/60, 7%) of 4 patients and resolved in all
but one patient after needling or partial cyst excision. One patient required tube removal and
insertion of a new Ahmed drainage implant.
Endophthalmitis occurred in three eyes (3/60, 5%). All cases were treated with
implant removal, vitrectomy and intravitreal antibiotics. In one case, tube exposure was
documented 2 days earlier, 6 months following valve implantation. The second child, with
bilateral implants, presented with bilateral Hemophilus influensa conjunctivitis that was
