8
Results
The study group included 44 consecutive patients who underwent Ahmed implant
insertion in 60 eyes. In four eyes, a second Ahmed valve was implanted following failure of
the first device bringing the total number of implanted valves to 64. However, to avoid
confusion, these four valves were not included in the statistical analysis, and the eyes were
counted as failures. Table 1 summarizes the demographics of our study population. In 46 eyes
of 32 patients (46/60 77% and 32/44 73% respectively) one or more glaucoma surgery
procedures were done before Ahmed implantation (average 2.42 ± 1.42 procedures per
patient). Most patients (31/32 97%) had at least one angle surgery, usually goniotomy (28/46,
61%). Only 4 eyes (4/46 9%) had cycloablation prior to valve implant. No patient had prior
drainage implantation. Most of the patients who had previous surgery (14/32, 44%) had
congenital/infantile glaucoma. The Ahmed valve was implanted as the first line of surgical
treatment in 12 patients (14 eyes). The diagnoses for these patients were aphakic glaucoma (3
patients, 3 eyes), Sturge-Weber syndrome (3 patients, 3 eyes), uveitic glaucoma (3 patients, 3
eyes), juvenile glaucoma (1 patient, 2 eyes), congenital rubella (1 patient, 2 eyes) and anterior
segment dysgenesis (1 patient, 1 eye).
Follow up averaged 24.3 ± 16 months (range 3-60 months). Figure 1 represents the
entire cohort of patients divided by the various follow-up periods. At last follow up visit, IOP
was controlled with or with out medications in 46 (46/60, 77%) eyes. Of 64 tubes implanted
12 (12/64, 19%) were classified as unqualified success, 34 (53%) as qualified success and 18
(28%) as failure. Figure 2 presents the Kaplan-Mayer survival curve of operated eyes in the
entire patient population. Overall successful survival (total qualified plus unqualified) was
93% (Confidence Interval (CI 86-100%), 86% (CI77-96%), 71% (CI 59-87%), and 45% (CI
28-80%) at 12, 24, 36 and 48 months of follow-up. Evaluation of survival using only one eye
per patient (selecting only the right eye when both eyes were operated on) yielded similar
