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Katrin Lorenz, Rene Goedkoop, Marcel Keilani, Nele Berssenbruegge, Christina Korb, Joanna Wasielica-Poslednik, Norbert Pfeiffer; Intraocular pressure measured by tonometry and a contact lens sensor in patients with open angle glaucoma. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5641. doi: https://doi.org/.
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To investigate the relationship between 24-hour intraocular pressure (IOP) fluctuation pattern as measured by repeated, specific-point-in-time tonometry (TM) and continuous recording with a contact lens sensor (CLS) in patients with primary open angle glaucoma (POAG).
A single center, prospective, randomized, controlled, open, crossover observational study was designed to investigate the relationship between the nycthemeral IOP pattern as measured by conventional TM every 2 hours and the CLS (Triggerfish®, Sensimed, Lausanne, Switzerland). For IOP measurement the Goldmann applanation tonometry (GAT) was used for erect and the Perkins for supine measurements. Following baseline examination, patients with POAG were hospitalized for 48 hours. Eyes were randomized to TM and CLS for the first session (S1) and the reverse for S2 on the subsequent day. Relationships between TM and CLS were computed within each patient separately and summarized over all patients.
Eleven eligible patients were analyzed. Mean age was 70.3±7.8 years, 33.3% were female. Mean baseline GAT IOP was symmetric for both eyes for both sessions (S1: 14.9±3.4 and 14.5±2.4 mmHg; S2: 15.6±3.1 13.8±2.4). In S1 the correlation between TM and the CLS was 0.40±0.22 (Spearman, p=0.0011) and in S2 -0.20±0.29 (ns). GAT-CLS correlations differed between S1 and S2 (p<0.001). In S1 the correlation was positive for all patients, 45% low (<0.4) and 55% moderate to high correlation (≥0.4). Mean 24-hour IOP in S2 was 12.9±1.4 mmHg, similar to that of S1 (14.3±2.6 mmHg, ns), whereas the mean 24-hour CLS output was significantly lower in S2 (17.0±159.5 arbitrary units (AU)) as compared to in S1 (93.4±193.6 AU; (p<0.0001, Wilcoxon Signed-rank test). The correlation for TM between eyes and sessions was 0.18 (p=0.28) and for CLS 0.42 (p=0.002). Between sessions the TM correlation between eyes was negative, low and moderate to high in 40%, 10% and 50% of patients, respectively. Similarly the CLS correlation was 0%, 30% and 70%.
The 24-hour IOP as measured by repeated TM and continuous CLS in the contralateral eye correlate inconsistently. At the moment we do not know whether this is due to a small correlation between GAT and CLS or due to fluctuation of IOP between days. The 24-hour IOP measurement between eyes and sessions appears to be less reliable when using repeat TM as compared to the use of the CLS.
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