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Editors Selection IGR 13-3
Perimetry: Seasonal visual field fluctuations
Comment by Chris Johnson on:
53113 Seasonal changes in visual field sensitivity and intraocular pressure in the ocular hypertension treatment study, Gardiner SK; Demirel S; Gordon MO et al., Ophthalmology, 2013; 120: 724-730
The authors of this paper evaluated visual fields from 33, 873 visits of 1,636 patients who were enrolled in the Ocular Hypertension Treatment Study (OHTS) and were tested every six months for an average of approximately 20 visual fields obtained over a mean of slightly more than ten years. The results of participants were divided into six geographic zones within the USA to evaluate whether there were seasonal variations in visual field sensitivity for participants living in these regions. To minimize the influence of visual field damage confounding this analysis, the authors evaluated the change in Mean Deviation (ΔMD) for different months. Both Full Threshold and SITA strategies were used for testing at various times during this investigation. The authors found that there was a statistically significant seasonal variation in ΔMD for five of the six geographic regions, with the southeast exhibiting a nonsignificant trend. The peak visual field sensitivity occurred between January and April. However, the magnitude of these changes for these populations was quite small, amounting to 0.03 to 0.21 dB shifts for the geographic groups. This is an order of magnitude smaller than the test retest variability for visual fields obtained in an individual participant. The authors are to be congratulated for evaluating this question by using a large visual field dataset that is probably the most carefully and rigorously collected longitudinal visual field dataset that has been obtained to date. These findings may be useful for assessment of underlying pathophysiologic mechanisms that are produced by glaucoma and their response to environmental influences. However, it is not clear whether adjusting for seasonal variations that are quite small in the aggregate that are different for certain geographic regions will be beneficial for future clinical trials, particularly when other factors may also be important and can possible be confounding variables (e.g., the time of day that testing was performed, the participants attentional state and medical health, the activity level of the eye clinic, the participant's experience with visual field testing, instructions that are given, and the attentiveness of the perimetric examiner).
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