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Editors Selection IGR 24-3
Therapeutic outcomes: Visual Field Improvement
Comment by Kouros Nouri-Mahdavi on:
57034 Visual field improvement in the collaborative initial glaucoma treatment study, Musch DC; Gillespie BW; Palmberg PF et al., American Journal of Ophthalmology, 2014; 158: 96-104.e2
Visual field improvement as an (or the) outcome measure for treatment of glaucoma was originally suggested by Dr. George Spaeth and although some of us are firm believers, solid proof has been scant. Musch and colleagues tested the hypothesis that clinically significant visual field improvement happens after significant reduction of the intraocular pressure (IOP) in glaucoma patients in the CIGTS database. A minimum improvement in MD of three dB was required before a given eye was considered improving. Similar criteria were used to detect visual field deterioration (i.e., a loss of ≥ three DB). A similar proportion of eyes demonstrated improvement or progression through five years of follow-up, after which worsening of the visual field was slightly more common. The investigators went to great length to rule out potential confounding issues such as a regression to the mean effect. Interestingly, visual field improvement was associated with IOP measures demonstrating better control during follow-up such as lower mean or minimum IOP. The latter is a very interesting finding as previously, worsening of glaucoma has been linked to higher peak IOP in some studies.
There was also a dose-response relationship between better IOP control and likelihood of VF improvement
There was also a dose-response relationship between better IOP control and likelihood of VF improvement. This begs the question whether achieving IOPs lower than estimated target pressures could actually lead to better outcomes barring hypotony and potential side effects of such treatment.
One caveat is that although worsening cataract was predictive of visual field deterioration, it is not clear how much of the persistent VF improvement could have been due to cataract extraction. The authors do mention that a visit prior to CE was predictive of worsening VFs. By nature, the stringent guidelines of the study protocol with regard to enrollment and baseline VF measurements reduce the risks that improvements seen were purely caused by noise or learning effect. Based on changes in the VFs between the two baseline fields, the investigators determined that about 4% of repeat tests would demonstrate a gain or loss that met their criteria for change. An interesting finding was the more remarkable improvement in eyes with more advanced glaucoma (average of -10 dB) that underwent surgery compared to eyes treated medically.
Overall, the results present solid evidence for and confirm our collective experience that visual field improvement after IOP reduction is a real phenomenon in glaucoma. As yet unpublished results from our research team have shown improvement in regional rates of change consistent with the results of this study. It may be finally time to think out of the box and expect more than disease stability in our glaucoma patients.
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