ORIGINAL STUDY

Test-Retest Variability of Retinal Nerve Fiber Layer Thickness and Macular Ganglion Cell-Inner Plexiform Layer Thickness Measurements Using Spectral-Domain Optical Coherence Tomography Meenakshi Wadhwani, MS,* Shveta J. Bali, MD,w Raji Satyapal, MD,* Dewang Angmo, MD,* Reetika Sharma, MD,* Veena Pandey, MA, MSc,* and Tanuj Dada, MD*

Purpose: To evaluate the test-retest variability of spectral-domain optical coherence tomography (OCT) in measurement of retinal nerve fiber layer (RNFL) thickness and macular ganglion cell-inner plexiform layer (GCIPL) thickness. Methods: A total of 65 eyes of healthy subjects were enrolled in this observational cross-sectional study. RNFL thickness and GCIPL thickness were measured using the repeat scan optic cube and macular cube protocol using Cirrus HD-OCT (software version 6.0). A single operator obtained 3 measurements during 1 session to determine test-retest variability. Intrasession repeatability was defined by intraclass correlation, limits of agreement, and coefficient of variation. Results: The mean age of patients was 37.89 ± 15.11 years (range, 10 to 70 y). The mean RNFL thickness readings as measured during 3 sessions were 93.89 ± 9.73, 93.63 ± 10.00, and 93.55 ± 9.64 mm and average GCIPL thickness measurements were 82.90 ± 4.61, 82.98 ± 4.24, and 83.06 ± 4.36 mm, respectively. Coefficient of variation was 1.2 for average RNFL thickness and 0.82 for average GCIPL thickness. The intraclass correlation coefficient showed a good correlation between repeat measurements for both average RNFL and GCC thicknesses (0.994 and 0.990, respectively). The limits of agreement (95% confidence interval) for the 3 sessions ranged from 3.61 to 4.13 mm for the average RNFL thickness and 2.55 to 2.40 mm for GCIPL thickness measurements. Conclusions: In healthy eyes, Cirrus HD-OCT shows excellent intrasession repeatability for RNFL and GCIPL thickness measurements. Key Words: ganglion cell layer, glaucoma, test-retest, repeatability, optical coherence tomography

(J Glaucoma 2015;24:e109–e115)

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maging has gained a key role in modern glaucoma management. Glaucoma is a progressive optic neuropathy characterized by loss of retinal ganglion cells and their

Received for publication February 6, 2014; accepted November 8, 2014. From the *Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India; and wIvey Eye Institute, Schulich School of Medicine and Dentistry, London, ON, Canada. Disclosure: The authors declare no conflict of interest. Reprints: Tanuj Dada, MD, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi 110029, India (e-mail: [email protected]). Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/IJG.0000000000000203

J Glaucoma



respective axons, which comprise the retinal nerve fiber layer (RNFL). These changes may precede the clinically detectable visual field defects by at least 5 years.1,2 Several diagnostic imaging techniques are available to quantitatively evaluate the optic nerve head and circumpapillary RNFL. These techniques allow preperimetric diagnosis of glaucoma and form an important role in identifying progression, nonprogression, and progression rate for these patients.3–5 Optical coherence tomography (OCT) uses low coherence interferometry to capture images by determining the echo time delay and magnitude of back-scattered light reflected off an object of interest.6 Since its introduction in 1991, this technology has rapidly evolved.7 Whereas the time-domain OCT was limited in scan speed (100 to 400 Ascans/s) and had an axial resolution of about 10 mm, the commercially available spectral-domain OCT instruments have a scan speed ranging from 26,000 to 57,000 A-scans per second and an axial resolution of approximately 5 mm.8 Optic disc and the RNFL can also be imaged using topologic optic nerve assessment using confocal scanning laser ophthalmoloscopy9 or scanning laser polarimetry measurements of RNFL retardance10; however, OCT has an added advantage of providing measurements of optic nerve head, RNFL, and macular ganglion cell complex for detection of glaucoma and its progression. Recent studies have evaluated ganglion cell thickness in glaucomatous eyes and evidence suggests that this may be of considerable value in diagnosing and detecting progression in early as well as advanced glaucomatous eyes.11–16 Ganglion cell complex comprises the ganglion cell layer, inner plexiform layer, and RNFL. Studies have shown that using the RTVue spectral-domain OCT, macular ganglion cell complex measurements could have the same sensitivity in detecting glaucomatous changes as the peripapillary RNFL.15,16 However, the inclusion of RNFL thickness in ganglion cell complex may impart a potential dimension of physiological and pathologic variation to the same. An ideal diagnostic instrument should be able to provide measurements that are free of patients’ subjective responses. Test-retest variability is an important quality measure of an instrument tool and is indispensable in determining the optimal frequency of performing a diagnostic test.17 This study was initiated to determine the test-retest variability of RNFL and ganglion cell-inner plexiform layer (GCIPL) thickness measurements measured with spectral-domain OCT (Cirrus HD-OCT; Carl Zeiss Meditec Inc., Dublin, CA) in healthy eyes.

Volume 24, Number 5, June/July 2015 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.

www.glaucomajournal.com |

e109

Wadhwani et al

J Glaucoma

METHODS Sixty-five eyes of healthy individuals were enrolled in this prospective observational study between January 2013 and December 2013. The study conformed to the ethical standards stated in the 1964 Declaration of Helsinki. An informed written consent was obtained from all the participants of the study. All subjects underwent a thorough ophthalmologic examination including detailed medical and family history, visual acuity testing with refraction, slitlamp biomicroscopy, gonioscopy, Goldmann applanation tonometry, and dilated stereoscopic fundus examination. Visual fields were evaluated using the Humphrey Field Analyzer (Humphrey-Zeiss Systems, Dublin, CA) 30-2 Swedish interactive threshold algorithm standard automated perimetry. The inclusion criteria for all participants were: bestcorrected visual acuity of 20/40 or better, a spherical refraction within ± 5.0 D and cylinder within ± 3 D, intraocular pressure of

Test-retest variability of retinal nerve fiber layer thickness and macular ganglion cell-inner plexiform layer thickness measurements using spectral-domain optical coherence tomography.

To evaluate the test-retest variability of spectral-domain optical coherence tomography (OCT) in measurement of retinal nerve fiber layer (RNFL) thick...
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