1. IOP = intraocular pressure; SD = standard deviation.
105-B0113
Comparison of Daily Intraocular Pressure Using Measurements at 6 AM and at 8 AM in Glaucoma
Érica A. Borges1,2, Nassim Calixto1,2, Sebastião Cronemberger1,2, Bruno P. Figueiredo1,2, Eveline A. Melo1,2, and Alberto Diniz-Filho1,2
1 Department of Ophthalmology and Otorhinolaryngology, Federal University of Minas Gerais, Belo Horizonte, Brazil; 2 Hospital São Geraldo, Federal University of Minas Gerais, Belo Horizonte, Brazil
INTRODUCTION
Glaucoma is a progressive optic neuropathy characterized by degeneration of retinal ganglion cells resulting in a characteristic appearance of the optic disc and visual loss.1
The IOP is still considered the most important risk factor for the development and progression of glaucoma and also remains the only known modifiable risk factor.2-6
Nevertheless, little is known about some IOP characteristics such as circadian rhythm (short-term fluctuation) or postural variation, and what effects they may cause.3-5,7
The difficulties of the 24-hour IOP monitoring in daily practice are the most challenging barrier to the study of these IOP characteristics.
DISCUSSION
Diurnal IOP fluctuation is an important prognostic factor for glaucoma progression.4,8
Previous studies shown that IOP peaks are usually in the late dark period.2-5
Sampaolesi et al2 presented the first DCPo results using 7 measurements and showed that the highest IOP measurement occurs at 6 AM in supine position.
Liu et al5 performing IOP measurements taken every 2 hours during a 24-hour period observed that nocturnal supine IOP was higher than diurnal sitting IOP.
Rodrigues et al9 found that the diurnal curve did not detect 60.4% of the peaks in glaucomatous eyes and 88.2% of the peaks in eyes suspected of glaucoma.
Borrone10 proposed a practical alternative method for the estimation of the 6 AM IOP by recording the 8 AM IOP after 30-minute supine position under pre-established conditions with no need for hospitalization and found a Pearson correlation coefficient of 0.97 (P < 0.05) between the two IOP measurements.
Undetected IOP peaks can be responsible for a substantial amount of unidentified diagnosis of glaucoma.6,9
There are several factors that may influence IOP curve, as central corneal thickness, disease severity, medications, hemodynamic and neurohormonal conditions. Despite these limitations, the present study assessed measurements of IOP under the same conditions: supine position, upon awaking, before getting out of the bed. It is necessary to correlate the IOP measurements when the patient arrives at the office and after one hour in the supine position.
TABLE 1. Measurements of daily curve of intraocular pressure in glaucoma patients and suspects.
IOP
Mean SD
Median (Range)
6 AM
20.9
5.9
21 (4 – 40)
8 AM
19.2
5.1
19 (6 – 38)
9 AM
14.2
3.2
14 (5 – 23)
11 AM
14.1
3.4
14 (3 – 22)
6 PM
13.9
3.3
14 (5 – 26)
10 PM
13.6
14 (4 – 24)
IOP = intraocular pressure; SD = standard deviation.
PURPOSE
To investigate the relationship between measurements of IOP performed at 6 AM and at 8 AM as part of daily curve of intraocular pressure (DCPo) in glaucoma patients and suspects.
TABLE 2. Agreement between the intraocular pressure peaks at 6 AM and at 8 AM.
Peak at 8 AM
Peak at 6 AM + -
Total
38 (33.6%)
21 (18.6%)
59 (52.2%)
6 (5.3%)
48 (42.5%)
54 (47.8%)
44 (38.9%)
69 (61.1%)
113 (100.0%)
METHODS
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.
CONCLUSIONS
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).
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.
Efforts must be concentrated in order to determine a reliable and practical way to predict IOP peaks.
RESULTS
The present study included 113 eyes of 113 patients.
Mean age of the patients was ± 14.2 years and 64 (56.6%) were female.
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) (Table 1).
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 agreement between the peaks (IOP ≥ 21 mmHg) at 6 AM and at 8 AM is shown in Table 2.
The equation obtained using a linear regression model would be written as: "Estimated IOP at 6 AM = × IOP at 8 AM” (Figure 1).
REFERENCES
1. Weinreb RN, Aung T, Medeiros FA. The pathophysiology and treatment of glaucoma: a review. JAMA. 2014;311(18):
2. Sampaolesi R, Calixto N, Carvalho CA, Reca R. Diurnal variation of intraocular pressure in healthy, suspected and glaucomatous eyes. Bibl Ophthalmol. 1968;74:1-23.
3. Sultan MB, Mansberger SL, Lee PP. Understanding the importance of IOP variables in glaucoma: a systematic review. Surv Ophthalmol. 2009;54(6):
4. Leidl MC, Choi CJ, Syed ZA, Melki SA. Intraocular pressure fluctuation and glaucoma progression: what do we know? Br J Ophthalmol. 2014;98(10):
5. Liu JHK, Zhang X, Kripke DF, et al. Twenty-four-hour intraocular pressure pattern associated with early glaucomatous changes. Invest Ophthalmol Vis Sci. 2003;44(4):
6. Cronemberger S, Silva ACL, Calixto N. Importance of intraocular pressure measurement at 6:00 a.m. in bed and in darkness in suspected and glaucomatous patients. Arq Bras Oftalmol. 2010;73(4):346-9
7. Mansouri K, Weinreb RN, Liu JHK. Effects of aging on 24-hour intraocular pressure measurements in sitting and supine body positions. Invest Ophthalmol Vis Sci. 2012;53(1):112-6
8. The Advanced Glaucoma Intervention Study (AGIS): 7. The relationship between control of intraocular pressure and visual field deterioration. The AGIS Investigators. Am J Opthalmol. 2000;130(4):
9. Rodrigues LD, Silva MRBM, Schellini AS, et al. Intraocular pressure peaks: comparison between the circadian curve, diurnal curve and the 6 a.m. measurement. Arq Bras Oftalmol. 2004;67:
10. Borrone R. A new strategy for diurnal intraocular pressure curve. Eur J Ophthalmol. 2012;22(6):
Commercial Relationships: Érica A. Borges, None; Bruno P. Figueiredo, None; Nassim Calixto, None; Sebastião Cronemberger, None; Eveline A. Melo, None; Alberto Diniz-Filho, None • Support: None
FIGURE 1. Scatterplot of 6 AM and 8 AM intraocular pressure (IOP) measurements.