9
results and is not shown. No statistically significant difference between survival curves of
patients with different diagnoses was found. This however may be due to the relatively small
number of patients in each diagnostic group (statistical power 0.29).
Prior to surgery, mean IOP in the entire group was 32.8 ± 6.2 mmHg (range 21-
50mmHg) with patients using an average of 4.45 ± 1.97 medications. On last follow up visit
of the entire cohort, IOP averaged 16.6 ± 8 mmHg (range 2-57 mmHg) with a mean of 2 ± 2
medications (paired student-t test, p<0.0001 for both parameters). However, after a follow up
period of more than 3 years, the reduction in medication number was not statistically
significant (P=0.3-0.94). The mean number of anti-glaucoma medications used throughout
the follow-up period is presented in Figure 3. Mean percentage reduction in IOP was 47 ±
25%. Number of previous operations, length of follow-up, preoperative IOP, and number of
preoperative medications was similar for the success, qualified success and failure groups
(one way ANOVA with post test P = 0.42, 0.096, 0.93, 0.87 respectively). Proportional
hazard regression did not show any significant difference in qualified or unqualified success
rates between patients younger than or older than 18 months or patients who did or did not
have prior surgery. After 21 ± 14.3 months of follow-up, of the 14 eyes (10 patients) who had
the implant as a first line of surgical treatment, 13 eyes had IOP controlled with or without
medications (6 and 7 eyes respectively) representing a 93% success rate. The only tube
failure in this group was related to self-inflicted injury in a developmentally delayed patient
with congenital rubella syndrome.
Figure 4 presents IOP measurements during the entire follow up period. After a period
of relatively low IOP during the first 3-5 postoperative months, pressure values reached a
plateau of around 15-17mmHg, which was sustained during the first 42 months of follow-up.
Beyond that period, average IOP fluctuates, likely due to the relatively small number of
patients being followed.
