Diagnostic Availability of Ocular Response Analyzer in Korean Patients with Normal Tension Glaucoma

Ah Ran Cho; Yun Jeong Choi; Jin Young Rhew; Kyu Ryong Choi

doi:10.3341/jkos.2015.56.1.86

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Cho, Choi, Rhew, and Choi: Diagnostic Availability of Ocular Response Analyzer in Korean Patients with Normal Tension Glaucoma

Original Article

J Korean Ophthalmol Soc 2015;56(1):86-92.

Published online: 6 September 2015

DOI: https://doi.org/10.3341/jkos.2015.56.1.86

Diagnostic Availability of Ocular Response Analyzer in Korean Patients with Normal Tension Glaucoma

Ah Ran Cho, MD¹, Yun Jeong Choi, MD², Jin Young Rhew, MD¹, Kyu Ryong Choi, MD, PhD^1,

¹Institute of Ophthalmology and Optometry, Department of Ophthalmology, Ewha Womans University Medical Center, Ewha Womans University School of Medicine, Seoul, Korea

²Department of Ophthalmology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea

Address reprint requests to Kyu Ryong Choi, MD, PhD, Department of Ophthalmology, Ewha Womans University Medical Center, #1071 Anyangcheon-ro, Yangcheon-gu, Seoul 158-710, Korea, Tel: 82-2-2650-5154, Fax: 82-2-2654-4334 E-mail: ckrey02@ewha.ac.kr

Received 28 March 201418 April 2014 Accepted 24 November 2014

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.

Abstract

Purpose

To compare the parameters measured with the ocular response analyzer (ORA; Reichert Inc., Depew, NY, USA) between normal control subjects and patients with normal tension glaucoma (NTG) and to investigate clinical usefulness of ORA.

Methods

Intraocular pressure (IOP) and central corneal thickness (CCT) were measured using the Goldmann applanation tonometer (GAT) in 100 eyes of 100 normal subjects and 100 eyes of 100 NTG patients. Four types of ORA parameters, corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated IOP (IOPg), and corneal-compensated IOP (IOPcc) were also measured.

Results

The mean CH values were 11.2 mm Hg and 10.3 mm Hg and the mean CRF values were 10.8 mm Hg and 9.9 mm Hg in the normal subjects group and the NTG group, respectively. Mean CH and CRF were significantly lower in NTG patients (p < 0.001) and the IOPcc were higher than normal subjects (p = 0.004). IOPg was in agreement with the GAT IOP (ICC = 0.811) and IOPcc was not correlated with CCT. The cutoff value of ‘IOPcc - IOPg’ as the diagnostic standard parameter was -0.05 mm Hg (sensitivity; 76%, specificity; 55%).

Conclusions

IOPg measurements were similar to GAT IOP, and other ORA parameters (CH, CRF, IOPcc) were significantly different between normal subjects and NTG patients. Consequently, the difference of IOPcc and IOPg could be a useful parameter in NTG diagnosis.

Keywords: Biomechanical properties, Intraocular pressure, Normal tension glaucoma, Ocular response analyzer

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Figure 1.

Bland-Altman plots of the agreement between the Goldmann applanation tonometer (GAT) intraocular pressure (IOP) and Goldmann-correlated IOP (IOPg) (A), the GAT IOP and the corneal-compensated IOP (IOPcc) (B). These plots are generated by plotting the difference between the measurements against the average of the measurements. The solid line represents the trend line and the dashed lines represent the mean bias and the 95% limits of agreement. SD = standard deviation.

Figure 2.

Receiver operating characteristics (ROC) curves of ocular response analyzer (ORA) parameters. IOPg = Goldmann-correlated intraocular pressure; IOPcc = corneal-compensated intraocular pressure factor; CRF = corneal resistance factor; CH = corneal hysteresis.

Table 1.

Clinical and ocular characteristics of the 200 eyes in the normal (N) and normal tension glaucoma (NTG) groups

	N (n = 100)	NTG (n = 100)	p-value
Age (years)	48.3 ± 14.0	49.9 ± 11.7	0.358^∗
Female (%)	59 (59.0)	47 (47.0)	0.089^†
GAT (mm Hg)	13.7 ± 2.4	13.8 ± 2.1	0.645
SE (diopter)	-1.0 ± 2.0	-1.7 ± 2.6	0.040^∗
Mean K (diopter)	44.0 ± 1.4	43.3 ± 1.5	0.005
CCT (μ m)	541.2 ± 24.3	544.7 ± 32.7	0.381^∗
CH (mm Hg)	11.2 ± 1.8	10.3 ± 1.2	<0.001^∗
CRF (mm Hg)	10.8 ± 1.9	9.9 ± 1.2	<0.001^∗
IOPg (mm Hg)	13.5 ± 3.0	14.1 ± 3.2	0.247^∗
IOPcc (mm Hg)	13.4 ± 3.4	14.9 ± 3.3	0.004^∗

Values are presented as mean ± SD unless otherwise indicated. GAT = Goldmann applanation tonometer; SE = spherical equivalent; K = keratometry; CCT = central corneal thickness; CH = corneal hysteresis; CRF = corneal resistance factor; IOPg = Goldmann-correlated intraocular pressure; IOPcc = corneal-compensated intraocular pressure factor.

^∗ Independent sample t-test

^† Chi-square test.

Table 2.

Statistical correlations between the CH, CRF, GAT IOP, IOPg, and IOPcc and various clinical/ocular characteristics

	CH	CRF	IOPg	IOPcc
GAT	0.082 (0.249)	0.363 (<0.001)	0.722 (<0.001)	-0.574 (<0.001)
SE	0.088 (0.217)	-0.066 (0.350)	-0.258 (<0.001)	-0.225 (0.001)
CCT	0.421 (<0.001)	0.448 (<0.001)	0.249 (<0.001)	0.003 (0.972)
CH	-	0.759 (<0.001)	-0.096 (0.176)	-0.472 (<0.001)
CRF	0.759 (<0.001)	-	0.338 (<0.001)	-0.066 (0.355)

Datas are presented as Pearson’s coefficient (p-value).

CH = corneal hysteresis; CRF = corneal resistance factor; IOPg = Goldmann-correlated intraocular pressure; IOPcc = corneal-compensated intraocular pressure; GAT = Goldmann applanation tonometer; IOP = intraocular pressure; SE = spherical equivalent; CCT = central corneal thickness.

Table 3.

Intraclass correlation coefficient (ICC) of IOPg and IOPcc using ocular response analyzer (ORA) comparing with GAT as standard

	ICC	95% CI
IOPg	0.811	0.751-0.857
IOPcc	0.692	0.593-0.767

CI = confidence interval; IOPg = Goldmann-correlated intraocular pressure; IOPcc = corneal-compensated intraocular pressure; GAT = Goldmann applanation tonometer.

Table 4.

Area under the receiver operating characteristic curves (AUCs), sensitivities, specificities of ocular response analyzer (ORA) parameters

	AUC	95% CI	Sensitivity (%)	Specificity (%)	Cut-off value^∗ (mm Hg)
CH	0.356	0.278-0.433	98	3	8.10
CRF	0.363	0.285-0.441	97	7	8.05
IOPg	0.559	0.479-0.639	44	72	14.75
IOPcc	0.622	0.544-0.699	45	80	15.65
IOPcc – IOPg	0.646	0.568-0.724	76	55	-0.50

CI = confidence interval; CH = corneal hysteresis; CRF = corneal resistance factor; IOPg = Goldmann-correlated intraocular pressure; IOPcc = corneal-compensated intraocular pressure.

^∗ Highest value of Youden’s index.

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