Correlation between Intraocular Pressure and Bottle Heights during Vitrectomy

Sang Uk Park; Sang Beom Han; Moo Sang Kim; Seung Jun Lee

doi:10.7469/JKOS.2015.56.05.727

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Park, Han, Kim, and Lee: Correlation between Intraocular Pressure and Bottle Heights during Vitrectomy

Original Article

J Korean Ophthalmol Soc 2015;56(5):727-731.

Published online: 7 September 2015

DOI: https://doi.org/10.7469/JKOS.2015.56.05.727

Correlation between Intraocular Pressure and Bottle Heights during Vitrectomy

Sang Uk Park, MD, Sang Beom Han, MD, Moo Sang Kim, MD, Seung Jun Lee, MD

Department of Ophthalmology, Kangwon National University School of Medicine, Chuncheon, Korea

￭ Address reprint requests to Seung Jun Lee, MD Department of Ophthalmology, Kangwon National University Hospital, #156 Baengnyeong-ro, Chuncheon 200-722, Korea Tel: 82-33-258-2014, Fax: 82-33-258-9490 E-mail: opticus@kangwon.ac.kr

Received 12 September 201420 October 2014 Accepted 9 April 2015

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

초록

Purpose:

To determine the correlation between intraocular pressure (IOP) and the bottle heights during vitrectomy using TONO-PEN^Ⓡ XL applanation tonometer and Icare^Ⓡ PRO rebound tonometer.

Methods:

Twenty-four eyes of 24 patients who underwent 23-gauge sutureless vitrectomy were evaluated. After complete vitrectomy, the IOP was gradually increased by lifting the irrigation bottle height from the trocar insertion site by 40 cm, 45 cm, 50 cm, and 55 cm. The distance between the floor and patient's eye was consistent in all cases (105.5 cm). Before the removal of 23-gauge microcannulas, IOP was measured five times using each of the two methods, Tono-Pen^Ⓡ XL and Icare^Ⓡ PRO.

Results:

The mean IOPs were 8.25 ± 0.35 mm Hg for TONO-PEN^Ⓡ XL and 8.96 ± 0.32 mm Hg for Icare^Ⓡ PRO at 40 cm bottle height. As the bottle height increased, the differences in IOP was also increased, 10.71 ± 0.37 mm Hg at 45 cm, 14.18 ± 0.39 mm Hg at 50 cm and 17.93 ± 0.40 mm Hg at 55 cm for TONO-PEN^Ⓡ XL and 11.48 ± 0.31 mm Hg at 45 cm, 14.64 ± 0.31 mm Hg at 50 cm and 18.13 ± 0.38 mm Hg at 55 cm for Icare^Ⓡ PRO. In TONO-PEN^Ⓡ XL, the linear equation was Y = 0.65 X - 18.108 (R² = 0.794, p = 0.000) and the quadratic equation was Y = 0.013 X² - 0.569 X + 10.446 (R² = 0.801, p = 0.000). In Icare^Ⓡ PRO, the linear equation was Y = 0.614 X - 15.842 (R² = 0.820, p = 0.000) and the quadratic equation was Y = 0.010 X² - 0.306 X + 5.688 (R²= 0.825, p = 0.000). The results show correlation of the quadratic equation was stronger than the linear equation in both tonometers.

Conclusions:

The differences of IOP were positively correlated with bottle heights in the form of a curve during vitrectomy. Therefore, the patients who are susceptible to retina or optic nerve damage during vitrectomy should be closely monitored.

Keywords: Bottle height, Intraocular pressure, Pars plana vitrectomy

References

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Figure 1.

Scatter plots showing intraocular pressure measurements with TONO-PEN^Ⓡ XL (A) and Icare^Ⓡ PRO (B). In, nonlinear regression analysis, the correlation of quadratic equation is more stronger than that of the linear equation. In TONO-PEN^Ⓡ XL, the linear equation is Y = 0.65 X - 18.108 (R² = 0.794, p = 0.000) and the quadratic equation is Y = 0.013 X² - 0.569 X + 10.446 (R²= 0.801, p = 0.000). In Icare^Ⓡ PRO, the linear equation is Y = 0.614 X - 15.842 (R² = 0.820, p = 0.000) and the quadratic equation is Y = 0.010 X² - 0.306 X + 5.688 (R² = 0.825, p = 0.000). IOP = intraocular pressure.

Table 1.

Demographic characteristics of study subjects

	Participants (n = 24 eyes of 24 subjects)
Sex (M:F)	8:16
Age (years)	64.17 ± 8.42
Axial length (mm)	22.88 ± 0.79
Central corneal thickness (μ m)	560.73 ± 43.43
Spherical equivalent (diopter)	+0.14 ± 1.08
Vitreoretinal disease
Proliferative diabetic retinopathy	3
Diabetic macular edema	4
Vitreous hemorrhage	4
ERM	8
Vitreous opacity	5

Values are presented as mean ± SD unless otherwise indicated.

ERM = epiretinal membrane.

Table 2.

Summary of mean IOP measurements and differences between the 2 methods

Bottle height	IOP (mm Hg)		Difference of IOP (mm Hg)	95% CI of difference	p-value
Bottle height	TONO-PEN^Ⓡ XL	Icare^Ⓡ PRO	Difference of IOP (mm Hg)	95% CI of difference	p-value
40 cm	8.25 ± 0.35	8.96 ± 0.32	0.71 ± 0.47	1.66~+0.24	0.139
45 cm	10.71 ± 0.37	11.48 ± 0.31	0.77 ± 0.48	1.75~+0.20	0.118
50 cm	14.18 ± 0.39	14.64 ± 0.31	0.46 ± 0.50	1.47~+0.55	0.365
55 cm	17.93 ± 0.40	18.13 ± 0.38	0.21 ± 0.55	1.32~+0.91	0.771

Values are presented as mean ± SD.

IOP = intraocular pressure; CI = confidential interval.

Table 3.

Intraclass correlation coefficients of the 2 tonometers

Bottle height	Tonometers		p-value
Bottle height	TONO-PEN^Ⓡ XL	Icare^Ⓡ PRO	TONO-PEN^Ⓡ XL	Icare^Ⓡ PRO
40 cm	0.968	0.991	0.000	0.000
45 cm	0.973	0.980	0.000	0.000
50 cm	0.970	0.977	0.000	0.000
55 cm	0.966	0.980	0.000	0.000

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