Abstract
Purpose:
The Low Pressure Glaucoma Treatment Study (LoGTS) is the only study to demonstrate a potential neuroprotective effect with brimonidine (BR). Assuming that the results of LoGTS could be observed over longer time horizon, we modeled the potential impact of BR on clinical, economic, falls (FL) and driving loss (DL) outcomes in a population of normal tension glaucoma (NTG) patients in the U.S.
Methods:
A population model was constructed to simulate the long-term outcomes of 3 treatment strategies for NTG: BR, timolol (TM), and no treatment (NT). Data on visual field progression (mean deviation (MD) change per year) from LoGTS (for BR and TM) and the Collaborative Normal Tension Glaucoma Study (CNTGS) (for NT) was used to project changes in MD over a patient’s lifetime. Cases of NTG and outcomes including bilateral vision impairment (BVI) (MD ≤ -16 dB), bilateral blindness (BB) (MD ≤ -22 dB), DL, FL and cost of blindness were linked to MD scores based on published literature. For each outcome, the number of cases and the time to outcome, with 95% simulation intervals (95% SI) were estimated. Scenario analyses were performed to assess uncertainty around modeling visual field progression.
Results:
Among approximately 1.44 million persons with NTG, NT was estimated to result in 310,493 cases of BVI (95% SI: 146,405 - 572,638) and 127,810 cases of BB (95% SI: 45,100 - 256,496). BR treatment was estimated to reduce the number of cases of BVI by 211,520 (95% SI: 73,641 - 419,478) and BB by 107,785 (95% SI: 29,024 - 232,744). Compared to NT, the model predicted that BR may prolong the time until BVI by 2.0 years (95% SI: 0.7 - 4.2 years) per person and until BB by 0.9 years (95% SI: 0.2 - 2.0 years) per person. Small differences between BR vs. NT were estimated for the time until driving loss (~0.5 year) or a fall (~1 year). No substantial differences in any of the outcomes (for both number of cases and time until outcome) were estimated between TM and NT. Fewer cases of BB associated with BR treatment may produce savings in direct medical costs (vs. NT: $2.5 billion, 95% SI: $0.5-$5.6 billion; vs. TM: $2.4 billion, 95% SI: $0.4 - $5.5 billion.
Conclusions:
In a U.S. population of NTG patients, BR has the potential to result in improved vision-related outcomes and cost savings while TM may result in similar outcomes and costs as NT.