15
children, treated with Ahmed implant, without any case of exposure.
29
They used human
pericardium as opposed to donor sclera to cover the tube entry site. They also treated the
patients postoperatively with oral prednisone 1mg/kg for the first month regardless of the
activity of the uveitis. Donor sclera is commonly used for tube coverage, however, dura
mater,
30
fascia lata,
31
pericardium,
32
and autologous sclera
33
have been proposed. It may be,
that for uveitic patients, materials other than donor sclera should indeed be considered for
tube coverage.
Only two of our patients (3%) developed strabismus. Our results support the low
incidence found by Coleman and coworkers report 5% of 60 adult patients developing post-
operative diplopia.
34
Similarly, in a group of pediatric patients, the incidence of strabismus
was only 4% of 21 eyes with the Ahmed valve.
11
Strabismus with the Baerveldt implant
(BGI, Pharmacia and Upjohn, Kalamazoo, MI), with its larger plate size, has been reported to
be as high as 77%.
35
Postoperative strabismus has also been reported to occur with the
Krupin valve (2-100%),
36,37
and anecdotally with the Molteno implant.
38
The Ahmed and
Molteno implants seem to produce a lower incidence of post-operative ocular motility
disturbance. It is likely that this reflects implanting the implant between rather than partially
under the rectus muscles with minimal manipulation of the muscles.
Our results with the Ahmed implant has led us to implant earlier, as the first surgical
treatment for most diagnostic categories except primary congenital/infantile glaucoma where
it is now our first procedure after failed attempts at angle surgery. We no longer consider
pediatric drainage implant surgery to be a "last resort". However, for patients with uveitic
glaucoma, although pressure control was usually adequate, the relatively large proportion of
tube exposure still poses a problem.
As evident from a Medline search, our study describes the largest published series of
pediatric eyes with Ahmed valve implantation, with the longest follow-up period. We feel
