Evaluation of Ocular Risk Factors Related to Asymmetric Visual Field Defects in Normal Tension Glaucoma

Jin Ho Yim; Sung Chul Park; Chang Won Kee

doi:10.3341/jkos.2008.49.9.1507

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Yim, Park, and Kee: Evaluation of Ocular Risk Factors Related to Asymmetric Visual Field Defects in Normal Tension Glaucoma

Original Article

J Korean Ophthalmol Soc 2008;49(9):1507-1514.

Published online: 7 September 2008

DOI: https://doi.org/10.3341/jkos.2008.49.9.1507

Evaluation of Ocular Risk Factors Related to Asymmetric Visual Field Defects in Normal Tension Glaucoma

Jin Ho Yim, M.D.¹, Sung Chul Park, M.D.², Chang Won Kee, M.D.²

¹Department of Ophthalmology, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea

²Department of Ophthalmology, Samsung Medical Center, College of Medicine, Sungkyunkwan University, Seoul, Korea

Address reprint requests to Chang Won Kee, M.D. Department of Ophthalmology, Samsung Medical Center, School of Medicine, Sungkyunkwan University #50 Ilwon-dong, Gangnam-gu, Seoul 135-710, Korea Tel: 82-2-3410-3564, Fax: 82-2-3410-0074, E-mail: cwkee@smc.samsung.co.kr

Received 2 July 2008 Accepted 5 March 2008

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 evaluate ocular risk factors related to asymmetric visual field defects in normal tension glaucoma (NTG).

Methods

We retrospectively evaluated 92 NTG patients (184 eyes) with asymmetric visual field defects; these patients were classified as having more affected eye (ME) group or less affected eye (LE) group. The differences between ME and LE based on the intra-individual comparison were assessed with several ocular risk factors such as best corrected visual acuity, refractive error, intraocular pressure (IOP), the number of glaucoma medications, disc hemorrhage, central corneal thickness, zone β of peripapillary atrophy (PPA), and disc size. All subjects were divided into two groups according to the severity of bilateral mean deviation (MD, Δ6dB) and evaluated.

Results

The MD was -11.2±6.5 in the ME group, and -5.9±5.4 in the LE group ( p=0.00). The optic disc size was 2.62±0.8 in the ME group, 2.48±0.5 in the LE group ( p=0.00), and there were no statistically significant differences in the other factors. Regarding the difference in the MD, the optic disc size was statistically significant in the less different group, and the angle of PPA was statistically significant in the more different group ( p=0.00 and p=0.01, respectively).

Conclusions

The optic disc size is a risk factor related to visual field defects in the ME group and the less affected patients, and the PPA is a risk factor, thought to be associated with ischemia, related to visual field defects in the more affected patients with asymmetric normal tension glaucoma.

Keywords: Normal tension glaucoma, Optic disc, Peripapillary atrophy, Visual field

References

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Table 1.

Comparison of the more affected eye (ME) and the less affected eye (LE)

Parameter	ME	LE	P value
Mean deviation (range, dB)	-11.2±6.5 (-1.6∼-29.7)	-5.9±5.4 (1.4∼-23.8)	<0.01∗
Pattern standard deviation (range, dB)	13.1±4.6 (1.9∼19.9)	7.9±4.3 (1.6∼16.9)	<0.01∗
Best corrected visual acuity (LogMAR)	0.02±0.02	0.01±0.02	0.10^†
Spherical equivalent (range, diopters)	-2.6±2.3 (2.2∼-7.8)	-2.5±2.6 (2.1∼-7.8)	0.13∗
Intraocular pressure (range, mmHg)	15.3±2.7 (8∼21)	14.8±2.8 (8∼21)	0.35∗
Antiglaucoma medication (number)	1.3±0.4	1.2±0.6	0.48^†
Central corneal thickness (range, µm)	513.0±44.3 (432∼617)	513.5±44.5 (418∼617)	0.31∗
Disc hemorrhage	14 (15%)	7 (8%)	0.15^‡
Disc size (range, mm²)	2.62±0.8 (1.3∼5.0)	2.48±0.5 (1.2∼4.2)	<0.01∗
Zone β parameters
Prevalence	56(52%)	52 (48%)	0.50^‡
Area (range, mm²)	0.97±0.7 (0.1∼3.2)	0.94±0.7 (0.1∼2.7)	0.76∗
Angular extent (range, degree)	132.2±64.4 (62∼360)	108.6±75.2 (74∼360)	0.71∗
Radial extent (range, mm)	0.4±0.3 (0.2∼1.2)	0.5±0.2 (0.1∼1.0)	0.91∗

Values are described as mean±standard deviation;

^∗ Paired t test

^† Wilcoxon signed rank test

^‡ McNemar test.

Table 2.

Demographic characteristics between two groups according to the severity of bilateral mean deviation

Parameter	Group I	Group II	P value
Sex
Male	34	18	0.83∗
Female	25	15	0.83∗
Age
mean±SD	58.1±16.2	54.5±13.2	0.57^†
Range	20∼83	25∼78	0.57^†
Systemic disease (%)	17 (29)	12 (36)	0.95∗
diabetes mellitus	8	5
Hypertension	8	4
Migraine	1	3

Group I=MD<Δ6dB; Group II=MD≥Δ6dB;

^∗ Chi-square test

^† Independent samples test.

Table 3.

Comparison between the group I and group II according to the severity of bilateral mean deviation

	Group I (n=59)			Group II (n=33)
	ME	LE	P value	ME	LE	P value
Mean deviation (dB)	7.2±4.5	4.6±2.3	0.00∗	15.2±6.2	7.2±4.7	<0.01∗
Pattern standard deviation (dB)	8.9±5.2	6.2±3.7	0.00∗	17.3±8.1	9.6±6.3	<0.01∗
BCVA (LogMAR)	0.01±0.03	0.01±0.02	0.53^†	0.04±0.04	0.01±0.03	0.49^†
Spherical equivalent (diopters)	-2.3±2.8	-2.4±2.8	0.31∗	-2.7±2.9	-3.1±2.9	0.25∗
Central corneal thickness (µm)	508±43	511±42	0.14∗	518±48	516±50	0.5∗
Intraocular pressure (mmHg)	15.7±2.8	15.9±2.8	0.41∗	15.9±3.4	16.0±3.3	0.70∗
Antiglaucoma medication (number)	1.1±0.5	1.0±0.5	0.26^†	1.2±0.6	1.2±0.6	0.32^†
Disc hemorrhage	7 (12%)	5 (8%)	1.0^‡(less)	7 (21%)	2 (6%)	0.10^‡(more)
Disc size (mm²)	2.65±0.6	2.46±0.6	0.00∗	2.59±0.9	2.50±0.7	0.26∗
Zone β parameters
Prevalence	29	30	0.72^§	27	22	0.32^§
Area (mm²)	0.88±0.7	0.86±0.6	0.27∗	1.06±0.6	1.02±0.8	0.27∗
Angular extent (degree)	112±58	103±71	0.32∗	152±76	114±82	0.01∗
Radial extent (mm)	0.4±0.3	0.5±0.2	0.77∗	0.5±0.3	0.5±0.3	0.83∗

Values are described as mean±standard deviation. Group I=MD<Δ6dB; Group II=MD≥Δ6dB; LE=less affected eye; ME=more affected eye; BCVA=best corrected visual acuity

^∗ Paired t test

^† Wilcoxon signed rank test

^‡ Fisher's exact test

^§ McNemar test.

Table 4.

Correlation between IOP and peripapillary atrophy in two groups

Zone β parameters	Group I		Group II
Zone β parameters	ME	LE	ME	LE
Area	0.06	0.06	0.31	0.84
Angular extent	0.13	0.82	0.95	0.55
Radial extent	0.11	0.09	0.68	0.72

Pearson correlation analysis and Spearman correlation analysis were used; Group I=MD<Δ6dB; Group II=MD≥Δ6dB; IOP=intraocular pressure; ME=more affected eye; LE=less affected eye.

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