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Editors Selection IGR 16-4
Anatomical Structures: Choroidal thickness and provocative tests
Comment by Remo Susanna Jr on:
54700 Assessment of Choroidal Thickness and Volume during the Water Drinking Test by Swept-Source Optical Coherence Tomography, Mansouri K; Medeiros FA; Marchase N et al., Ophthalmology, 2013; 120: 2508-2516
This is an interesting and clinically relevant study evaluating the effect of the water-drinking test (WDT) on choroidal thickness and volume. It attempts to understand the mechanism for the rise of intraocular pressure (IOP) during the WDT, a test that has been recently used to compare the effect of hypotensive drugs on glaucoma treatment and to detect IOP peaks not detected during office hours.
The strength of the present study is twofold. It is a prospective study in which the participants were not under the use of ocular hypotensive drugs, which could interfere with the results. In addition, the study has used swept-source OCT with automated segmentation for measurement of the choroid. This method can obtain operator-independent and objective measurements of thickness and volume OCT.
Fifty-six eyes of 28 healthy volunteers were studied. The authors found that the IOP increased from 14.9 ± 2.7 mmHg at baseline to a peak of 16.8 ± 3.0 mmHg 15 minutes after the WDT. After the WDT, peripapillary and macular choroidal thickness increased by a maximum of 5.7% and 4.3%, respectively.
The reason why the WDT increases IOP remains enigmatic
Choroidal volumes increased by 6.4% and 3.9%, respectively. There was no association between change in IOP and peripapillary or macular choroidal thickness.
The authors concluded that there is a significant increase in choroidal thickness and volume observed after the WDT in healthy subjects. However, this phenomenon was of a small magnitude and it is unlikely to explain the WDT-related increase in IOP. The reason why the WDT increases IOP remains enigmatic. One hypothesis that remains to be confirmed is that the IOP elevation during the test may be caused by an increase in episcleral venous pressure.
In summary, the authors should be congratulated for this welldesigned study that helps clarify the mechanism of IOP rise after water ingestion.
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