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Erica A Borges, Nassim S Calixto, Sebastiao Cronemberger, Bruno P Figueiredo, Eveline A Melo, Alberto Diniz-Filho; Comparison of Daily Curve of Intraocular Pressure Using Measurements at 6 am and at 8 am in Glaucoma. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):105.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the relationship between measurements of intraocular pressure (IOP) performed at 6 am and at 8 am as part of daily curve of intraocular pressure (DCPo) in glaucoma patients and suspects.
The IOP measurements in DCPo were obtained in the sitting position at 9 am, 11 am, 6 pm, and 10 pm using a Goldmann tonometer. The measurements in the morning were performed using a Perkins tonometer in the supine position at 6 am upon awaking (before getting out of the bed), and repeated at 8 am after remaining 60 minutes in the same position, both in a dark room. The IOP measurements at 6 am and at 8 am during the DCPo were compared using a paired t-test. Correlations between these measurements were obtained by Pearson correlation coefficient (r) and linear regression.
The present study included 113 eyes of 113 patients. The mean IOP at 6 am was 20.9 ± 5.9 mmHg and the mean IOP at 8 am was 19.2 ± 5.1 mmHg (P < 0.001). There was a strong correlation between the IOP measurements at 6 am and at 8 am (r = 0.808; P < 0.001). The correlation remained strong (r = 0.700; P < 0.001) when only subjects with an IOP ≥ 21 mmHg at 6 am were evaluated. The equation obtained using a linear regression model would be written as: "Estimated IOP at 6 am = 3.00 + 0.93 × IOP at 8 am".
The IOP measurements performed at 8 am in the supine position were strongly correlated with the IOP readings at 6 am (as the first measure of the DCPo). They demonstrated statistically significant differences, although these differences were not clinically significant. Therefore, the IOP measurement obtained at 8 am is an option for identifying IOP peaks hidden in the usual office hours and could be useful in daily practice since it spares the need for hospitalization. However, better results are obtained with IOP measurement taken at 6 am in supine position upon awaking in a dark room.
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