advertisement
Editors Selection IGR 7-3
Lifetime outcome in glaucoma
Comment by Gisela Kobelt on:
13212 Clinical outcomes of glaucoma treatments over a patient lifetime: a Markov model, Nordmann JP; Lafuma A; Deschaseaux C et al., Journal of Glaucoma, 2005; 14: 463-469
The goal of treatment in glaucoma is to prevent vision loss. In prevention, treatment occurs today while the health benefit will occur much later. Thus, the final outcome can rarely be observed but must be simulated. Such models require large amounts of information on the natural progression of a disease and the long term effect of different treatment options. Unfortunately, such data are scarce in the field of glaucoma - but this should not preclude modeling entirely, in view of the need to assess the cost-effectiveness of treatments.
The attempt to predict the lifetime outcome in glaucoma by Nordmann et al. (1011) has to be seen in this context. The advanced statistical and modeling techniques used cannot hide the fact that the data underlying the estimates are limited. The estimates on the frequency of switches between topical treatments and the incidence of surgery and laser interventions are well supported in the medium term with data from 337 patients,1 but it may be less obvious whether and how they apply to a life-time scenario. The use of visual field defects (VFDs) as 'steps' in progression is an interesting approach, but the steps are neither clearly defined nor supported by adequate data. In fact, the variable is based on 12 patients over a mean of 2.4 years from a pilot study,2 and it is not clear how six VFD events lead to blindness. The same small sample was used to estimate the association of VFD and visual acuity (VA), which is stated to be limited, and calculate utility. Utility score for different levels of VA in turn came from samples of patients with ophthalmic diseases that included almost no glaucoma patients.3,4
Nevertheless, the model is an interesting approach to building a tool to estimate long term outcome in glaucoma. The limitations in the underlying data mean, however, that the detailed output should be considered as an indication only of how different variables may affect the results rather than actual results. An example of this is the study conclusion that using more effective treatments in first line would contribute more to preserving vision than using them in second line. While intuitively acceptable, it is difficult to see how this conclusion is supported with data - but the model provides an indication that it is well worth exploring this question further.
Comments
The comment section on the IGR website is restricted to WGA#One members only. Please log-in through your WGA#One account to continue.Log-in through WGA#One
