Date of Award

January 2012

Document Type


Degree Name

Medical Doctor (MD)



First Advisor

James C. Tsai

Second Advisor

Iqbal I. Ahmed

Subject Area(s)

Ophthalmology, Medicine, Surgery


Purpose: The Ahmed Versus Baerveldt Study is a prospective, international, multicenter, randomized clinical trial which compares the two most frequently used aqueous drainage devices for the treatment of refractory glaucoma.

Methods: Patients aged 18 or older with uncontrolled glaucoma refractory to medicinal, laser and traditional surgical therapy were randomized to undergo implantation of an Ahmed-FP7 valve implant (New World Medical, Inc., Rancho Cucamonga, CA) or a Baerveldt-350 implant (Abbott Medical Optics, Inc., Santa Ana, CA) to be followed for 5-years.

Outcome Measures: The primary outcome measure is failure, defined as intraocular pressure (IOP) out of target range (5-18 mmHg with >20% reduction from baseline) for two consecutive visits after 3 months, vision-threatening complications, additional glaucoma procedures, or loss of light perception. Secondary outcome measures include IOP, medication use, visual acuity, complications, and interventions.

Results: A total of 238 patients were enrolled in the study; 124 received the Ahmed-FP7 valve implant and 114 received the Baerveldt-350 implant. The two treatment groups did not differ in any baseline demographic or ocular characteristics with the exception of sex. The mean age of the study group was 66±16 years and 55% were women. The mean baseline IOP of the study group was 31.4±10.8 mmHg on a mean of 3.1±1.0 glaucoma medications. The median Snellen visual acuity was 20/100, mean number of previous laser therapies was 0.9±1.1, and mean number of previous surgeries was 1.7±1.2. Five (4%) patients in the Ahmed group and 4 (4%) patients in the Baerveldt group experienced significant intraoperative complications (p=1.0). The cumulative probability of failure at 3-years was 51% in the Ahmed group and 34% in the Baerveldt group (p=0.026). The mean IOP at 3-years was 15.7±4.8 mmHg in the Ahmed group (49% reduction from baseline, p<0.001) and 14.4±5.0 mmHg in the Baerveldt group (55% reduction from baseline, p<0.001; comparison between groups: p=0.08). The mean number of glaucoma medications required was 1.8±1.4 in the Ahmed group (42% reduction from baseline, p<0.001) and 1.1±1.3 in the Baerveldt group (65% reduction from baseline, p<0.001; comparison between groups: p=0.002). There was a moderate but similar decrease in visual acuity in both groups (p<0.001). The two groups had similar complication rates (52% Ahmed vs. 62% Baerveldt, p=0.12), however, the Baerveldt group had a higher rate of hypotony-related devastating complications (Ahmed 0%, Baerveldt 7%, p=0.002). Also, the Baerveldt group required a greater number of interventions (73 Ahmed vs. 103 Baerveldt, p=0.006; 38% Ahmed vs. 50% Baerveldt, p=0.07). Overall, most complications were transient and most interventions were minor slit-lamp procedures.

Conclusions: Both devices were effective in reducing IOP and glaucoma medications. The Baerveldt group had a lower failure rate and required fewer medications than the Ahmed group after 3-years of follow-up, but suffered from a higher rate of hypotony-related devastating complications and required more interventions.


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