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Editors Selection IGR 21-3
Quality of Life: Real-life impact of visual field loss
Comment by David Crabb on:
54660 The Relationship between Better-Eye and Integrated Visual Field Mean Deviation and Visual Disability, Arora KS; Boland MV; Friedman DS et al., Ophthalmology, 2013; 120: 2476-2484
Binocular visual field (VF) tests are rarely performed, except when assessing socio-legal criteria for vision, like examining fitness to drive. Quantifying VF damage at a 'person level' is however important and can be simply done by considering the patient's 'bettereye' given a fellow eye compensates for loss of visual function in one eye. An alternative is to calculate the integrated visual field (IVF) by 'overlapping' monocular VF points and taking the best sensitivity at each corresponding point from the two eyes. Arora and colleagues report data from retrospective analysis of population- and clinic-based samples of adults and conclude that IVF mean deviation (MD) rarely differs from better-eye (BE) MD. The likelihood of IVF MD being better than BE MD increases as VF defects in both eyes worsen. The authors did not highlight this point in their main conclusions even though they found a difference of more than 2 dB in more than one third of patients when the MD was worse than -15 dB in both eyes. Nevertheless, authors did show that associations between VF loss and selfreported quality of life measures were similar using either MD, suggesting the IVF proffers no extra benefit. This was certainly true in their data but few of the patients had advanced glaucoma. It would be helpful to repeat this study in a cohort that has more patients with advanced VF loss.
BE MD was higher than IVF MD in many people in the study because perhaps of the summation method used. To me this seems illogical - How can someone perform functionally better with one eye than two? Authors also conclude IVF MD inconveniently requires 'extra software/calculation'. This is true, but also a tad nihilistic. Shouldn't we be demanding that perimetry manufacturers provide better information on VF charts? After all, in some patients with advanced asymmetric loss (between eyes) the IVF will provide supplementary information.
Arora and colleagues should be encouraged to extend their useful research because we need more evidence about the impact of precise patterns of VF loss on a person. After all, successful clinical management of glaucoma should equate to correct decisions about intensifying treatment when patients are at risk of developing 'visual disability' rather than imperceptible changes on a clinical chart.
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