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Glaucoma Dialogue IGR 17-4
Comment
Comment by Chris Johnson on:
67306 Structural and Functional Progression in the Early Manifest Glaucoma Trial, Öhnell H; Heijl A; Brenner L et al., Ophthalmology, 2016; 123: 1173-1180
See also comment(s) by Tae-Woo Kim • Chris Leung • Hanna Maria Öhnell •The Early Manifest Glaucoma Trial is one of the prominent multicenter trials in glaucoma that has had an important, meaningful impact on how eye care specialists manage and treat patients with glaucoma. In this paper, the authors have evaluated approximately eight years of follow-up results to determine the ability of functional (perimetry) and structural (optic disc photos) test procedures to detect glaucomatous progression.
The results are somewhat surprising since it has been repeatedly found over the past 150 years that structural glaucomatous deficits tend to be detected earlier and more frequently than functional losses
The findings indicated that for eyes with normal visual fields at baseline, there was no difference between structural and functional indicators of glaucomatous progression, both indicating that it occurred 15-18% of the time over the eight year period of evaluation. However, in eyes with visual field abnormalities at baseline, visual field evaluations were able to determine progression about four times greater than structural indicators (52% versus 12%). These results are useful for practitioners who manage patients with glaucoma or are at risk of developing glaucoma. The results are somewhat surprising since it has been repeatedly found over the past 150 years that structural glaucomatous deficits tend to be detected earlier and more frequently than functional losses, in spite of dramatic variations in technology and diagnostic procedures.1 "The results are somewhat surprising since it has been repeatedly found over the past 150 years that structural glaucomatous deficits tend to be detected earlier and more frequently than functional losses,..."
There are several factors that should be kept in mind when assessing the conclusions from this study. The performance of a particular method of assessing progression depends on the decision rules that are used and the analysis method employed.2 Previous investigations have demonstrated that structural and functional glaucomatous changes are not necessarily detected clinically at the same time, either structure or function can be the initial indicator of change, and that both structure and function are important factors to be monitored for proper management of glaucoma patients and glaucoma suspects.3-6 Additionally, the recent advent of new technologies (optic disc and retinal nerve fiber layer imaging, continuous IOP monitoring and other issues) reminds us that the management of glaucoma is constantly changing and that prior evaluations of older technologies may not be relevant for more current procedures. Non-stereo optic disc photographs are but one method of evaluating structural damage, and glaucoma change probabilities is one of many approaches to the assessment of functional loss.
References
- Johnson CA, Cioffi GA, Liebmann JR, et al. The relationship between structural and functional alterations in glaucoma: A review. Seminars in Ophthalmology 2000;15:221-233.
- Vesti E, Johnson CA, Chauhan BC. Comparison of different methods for detecting glaucomatous visual field progression. Invest Ophthalmol Vis Sci 2003;44:3873-3879.
- Keltner JL, Johnson CA, Anderson DR, et al. and the Ocular Hypertension Treatment Study Group. The association between glaucomatous visual fields and optic nerve head features in the Ocular Hypertension Treatment Study (OHTS). Ophthalmology 2006;113:1603-1612.
- Medeiros FA, Alencar LM, Zangwill LM, et al. Prediction of functional loss in glaucoma from progressive optic disc damage. Arch Ophthalmol 2009;127:1250-1256.
- Medeiros FA, Zangwill LM, Bowd C, Mansouri K, Weinreb RN. The structure and function relationship in glaucoma: implications for detection of progression and measurement of rates of change. Invest Ophthalmol Vis Sci 2012;53:6939-6946.
- Abe RY, Diniz-Filho A, Zangwill LM, et al. The relative odds of progressing by structural and functional tests in glaucoma. Invest Ophthalmol Vis Sci 2016;57:421-428.
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