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Clinical and Experimental Ophthalmology 2014; 42: 711–712 doi: 10.1111/ceo.12427
Editorial Objective optic nerve head assessment using optical coherence tomography and Heidelberg retinal tomograph In this edition of Clinical and Experimental Ophthalmology, Kratz, Lim and Goldberg describe the differences and similarities in optic nerve head measurements between Heidelberg retinal tomograph (HRT) and optical coherence tomography (OCT – Cirrus) imaging.1 They also demonstrate their comparative discriminative ability to detect moderate glaucoma from normal glaucoma. This is a well-designed study with excellent and illustrative use of discriminative statistics. Kratz et al. found a proportional bias with HRT measures of neuroretinal rim area (RA) being somewhat larger than OCT measures and that measures of cup volume were somewhat lower than OCT measures.1 There was very strong measurement correlation between these two imaging techniques. These results are similar to a previously published work, but the authors added a novel twist to their study. They categorized the participants into normal (n = 88) and glaucoma (n = 85) subjects and examined the sensitivity and specificity of the measurements at varying thresholds to distinguish the disease. The result of the receiver operator characteristics (ROC) analysis, which is regarded as the most useful method for assessing diagnostic ability of clinical tests, demonstrated that the Cirrus and HRT are equivalent in discriminating between these two groups. Spectral domain optical coherence tomography (SD-OCT) generates an enormous amount of anatomical related data concerning the optic disc and peripapillary retina. The majority of work examining SD-OCT data involves optimizing the analysis of various anatomical measurements. Many authors have described similar ROC for RA, retinal nerve fibre layer (RNFL), Bruch’s membrane termination to minimum rim width (BMO-MRW) and macula ganglion cell/inner plexiform layer/nerve fibre layer complex (ganglion cell complex [GCC]).2 Recently, among various anatomical structure measurements, the comparative merits of certain indices have been
examined and have shown possible advantage of BMO-MRW over RNFL for example.3 It is important to note that the major utility of imaging devices is not so much for their diagnostic ability, but rather for detection of glaucoma progression because none is superior to a well-trained observer. The HRT has been the gold standard in objective measurement of glaucomatous optic nerve progression for more than 10 years. The HRT software applies a subtraction analysis with the production of maps indicating change in optic nerve tissue height along with the significance of this change.4 This was a revolutionary development in the evolution of optic nerve comparison techniques and has allowed clinicians and researchers to move away from subjective and time-consuming photographic comparison techniques. It also allowed a more-consistent, objective assessment of optic nerve progression in the clinics, in the same way that automated field analysis revolutionised visual field assessment, rendering it possible to perform greater numbers of visual field assessments without the need for experienced operators as in the days of Goldmann perimetry. Validation studies show that agreement between HRT and disc photograph determined progression was 81%, although lower (29%) when HRT was compared with visual field determined progression.5 The reason for this difference in agreement is likely to be partly related to variation in test performance at different stages of disease. There has been much recent work developing OCT methods to judge glaucoma progression. They tend to use cruder global indices such as the average RNFL thickness rather than multiple measurements, which could allow more subtle statistical analysis.2 There appears to be some advantages in the use of macula GCC measurements.2 Comparisons of the utility of global index detection for glaucoma progression using visual field progression as the gold standard show that HRT RA (20% agreement) still outperforms OCT RNFL (11% agreement).6
Competing/conflicts of interest: No stated conflict of interest. Funding sources: No stated funding sources. © 2014 Royal Australian and New Zealand College of Ophthalmologists
712
Editorial
The major drawback of HRT is that it is only useful for one task – optic nerve progression judgement. Thus, its use tends to be restricted to glaucoma subspecialty practices, whereas OCT technology has become almost ubiquitous. Kratz et al.1 and other authors demonstrated equivalence of certain optic nerve head measurements between HRT and OCT. There is much work being conducted in developing ways to compare OCT optic disc and nerve fibre layer parameters over time using clever and accessible statistical techniques like that used in the HRT. The work of Kratz et al. helps to add a brick in the wall of that construction. To date, OCT does not yet measure up to the progression detecting capacity of HRT, as proven in longitudinal clinical studies. However, the amount of data produced by frequency domain OCT measurement should theoretically allow the development of analogous subtraction techniques similar to or better than that developed for HRT use. Many of us eagerly await the arrival of such analytical software for OCT that will detect glaucoma progression with equivalent or better ability than HRT and be available on the ubiquity of OCT machines. William H Morgan PhD FRANZCO and Min-Hye Kang MBBS Lions Eye Institute, University of Western Australia, Nedlands, Western Australia, Australia
REFERENCES 1. Kratz A, Lim R, Goldberg I. Optic nerve head assessment: comparison of Cirrus optic coherence tomography and Heidelberg Retinal Tomograph 3. Clin Experiment Ophthalmol 2014; 118: 734–44. 2. Bussel II, Wollstein G, Schuman JS. OCT for glaucoma diagnosis, screening and detection of glaucoma progression. Br J Ophthalmol 2014; 98 (Suppl. 2): ii15–9. 3. Chauhan BC, O’Leary N, Almobarak FA et al. Enhanced detection of open-angle glaucoma with an anatomically accurate optical coherence tomography-derived neuroretinal rim parameter. Ophthalmology 2013; 120: 535–43. 4. Chauhan BC, Blanchard JW, Hamilton DC, LeBlanc RP. Technique for detecting serial topographic changes in the optic disc and peripapillary retina using scanning laser tomography. Invest Ophthalmol Vis Sci 2000; 41: 775– 82. 5. Chauhan BC, McCormick TA, Nicolela MT, LeBlanc RP. Optic disc and visual field changes in a prospective longitudinal study of patients with glaucoma: comparison of scanning laser tomography with conventional perimetry and optic disc photography. Arch Ophthalmol 2001; 119: 1492–9. 6. Leung CK, Liu S, Weinreb RN et al. Evaluation of retinal nerve fiber layer progression in glaucoma a prospective analysis with neuroretinal rim and visual field progression. Ophthalmology 2011; 118: 1551–7.
© 2014 Royal Australian and New Zealand College of Ophthalmologists
Copyright of Clinical & Experimental Ophthalmology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
Clinical and Experimental Ophthalmology 2014; 42: 711–712 doi: 10.1111/ceo.12427
Editorial Objective optic nerve head assessment using optical coherence tomography and Heidelberg retinal tomograph In this edition of Clinical and Experimental Ophthalmology, Kratz, Lim and Goldberg describe the differences and similarities in optic nerve head measurements between Heidelberg retinal tomograph (HRT) and optical coherence tomography (OCT – Cirrus) imaging.1 They also demonstrate their comparative discriminative ability to detect moderate glaucoma from normal glaucoma. This is a well-designed study with excellent and illustrative use of discriminative statistics. Kratz et al. found a proportional bias with HRT measures of neuroretinal rim area (RA) being somewhat larger than OCT measures and that measures of cup volume were somewhat lower than OCT measures.1 There was very strong measurement correlation between these two imaging techniques. These results are similar to a previously published work, but the authors added a novel twist to their study. They categorized the participants into normal (n = 88) and glaucoma (n = 85) subjects and examined the sensitivity and specificity of the measurements at varying thresholds to distinguish the disease. The result of the receiver operator characteristics (ROC) analysis, which is regarded as the most useful method for assessing diagnostic ability of clinical tests, demonstrated that the Cirrus and HRT are equivalent in discriminating between these two groups. Spectral domain optical coherence tomography (SD-OCT) generates an enormous amount of anatomical related data concerning the optic disc and peripapillary retina. The majority of work examining SD-OCT data involves optimizing the analysis of various anatomical measurements. Many authors have described similar ROC for RA, retinal nerve fibre layer (RNFL), Bruch’s membrane termination to minimum rim width (BMO-MRW) and macula ganglion cell/inner plexiform layer/nerve fibre layer complex (ganglion cell complex [GCC]).2 Recently, among various anatomical structure measurements, the comparative merits of certain indices have been
examined and have shown possible advantage of BMO-MRW over RNFL for example.3 It is important to note that the major utility of imaging devices is not so much for their diagnostic ability, but rather for detection of glaucoma progression because none is superior to a well-trained observer. The HRT has been the gold standard in objective measurement of glaucomatous optic nerve progression for more than 10 years. The HRT software applies a subtraction analysis with the production of maps indicating change in optic nerve tissue height along with the significance of this change.4 This was a revolutionary development in the evolution of optic nerve comparison techniques and has allowed clinicians and researchers to move away from subjective and time-consuming photographic comparison techniques. It also allowed a more-consistent, objective assessment of optic nerve progression in the clinics, in the same way that automated field analysis revolutionised visual field assessment, rendering it possible to perform greater numbers of visual field assessments without the need for experienced operators as in the days of Goldmann perimetry. Validation studies show that agreement between HRT and disc photograph determined progression was 81%, although lower (29%) when HRT was compared with visual field determined progression.5 The reason for this difference in agreement is likely to be partly related to variation in test performance at different stages of disease. There has been much recent work developing OCT methods to judge glaucoma progression. They tend to use cruder global indices such as the average RNFL thickness rather than multiple measurements, which could allow more subtle statistical analysis.2 There appears to be some advantages in the use of macula GCC measurements.2 Comparisons of the utility of global index detection for glaucoma progression using visual field progression as the gold standard show that HRT RA (20% agreement) still outperforms OCT RNFL (11% agreement).6
Competing/conflicts of interest: No stated conflict of interest. Funding sources: No stated funding sources. © 2014 Royal Australian and New Zealand College of Ophthalmologists
712
Editorial
The major drawback of HRT is that it is only useful for one task – optic nerve progression judgement. Thus, its use tends to be restricted to glaucoma subspecialty practices, whereas OCT technology has become almost ubiquitous. Kratz et al.1 and other authors demonstrated equivalence of certain optic nerve head measurements between HRT and OCT. There is much work being conducted in developing ways to compare OCT optic disc and nerve fibre layer parameters over time using clever and accessible statistical techniques like that used in the HRT. The work of Kratz et al. helps to add a brick in the wall of that construction. To date, OCT does not yet measure up to the progression detecting capacity of HRT, as proven in longitudinal clinical studies. However, the amount of data produced by frequency domain OCT measurement should theoretically allow the development of analogous subtraction techniques similar to or better than that developed for HRT use. Many of us eagerly await the arrival of such analytical software for OCT that will detect glaucoma progression with equivalent or better ability than HRT and be available on the ubiquity of OCT machines. William H Morgan PhD FRANZCO and Min-Hye Kang MBBS Lions Eye Institute, University of Western Australia, Nedlands, Western Australia, Australia
REFERENCES 1. Kratz A, Lim R, Goldberg I. Optic nerve head assessment: comparison of Cirrus optic coherence tomography and Heidelberg Retinal Tomograph 3. Clin Experiment Ophthalmol 2014; 118: 734–44. 2. Bussel II, Wollstein G, Schuman JS. OCT for glaucoma diagnosis, screening and detection of glaucoma progression. Br J Ophthalmol 2014; 98 (Suppl. 2): ii15–9. 3. Chauhan BC, O’Leary N, Almobarak FA et al. Enhanced detection of open-angle glaucoma with an anatomically accurate optical coherence tomography-derived neuroretinal rim parameter. Ophthalmology 2013; 120: 535–43. 4. Chauhan BC, Blanchard JW, Hamilton DC, LeBlanc RP. Technique for detecting serial topographic changes in the optic disc and peripapillary retina using scanning laser tomography. Invest Ophthalmol Vis Sci 2000; 41: 775– 82. 5. Chauhan BC, McCormick TA, Nicolela MT, LeBlanc RP. Optic disc and visual field changes in a prospective longitudinal study of patients with glaucoma: comparison of scanning laser tomography with conventional perimetry and optic disc photography. Arch Ophthalmol 2001; 119: 1492–9. 6. Leung CK, Liu S, Weinreb RN et al. Evaluation of retinal nerve fiber layer progression in glaucoma a prospective analysis with neuroretinal rim and visual field progression. Ophthalmology 2011; 118: 1551–7.
© 2014 Royal Australian and New Zealand College of Ophthalmologists
Copyright of Clinical & Experimental Ophthalmology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
