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Editors Selection IGR 21-4

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Comment by Tae-Woo Kim 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

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It is common that detectable progressive structural change does not coincide temporally with the functional progression in glaucoma eyes. Ohnell et al. investigated the temporal relationship between detection of glaucomatous optic disc progression by fundus photography and visual field progression using the patient cohort included in Early Manifest Glaucoma Trial (EMGT).

It is possible that the optic disc examination is not as sensitive to detect progressive change as RNFL based examination such as red-free photography or OCT RNFL thickness measurement

The optic disc progression was defined by the subjective assessment of three disc readers, who defined the progression mainly based on changes in the course of small vessels on the optic disc surface. The visual filed progression was defined using the EMGT criteria. They found that progression in the visual field was detected first more than four times as often as progression in the optic disc in eyes with manifest glaucoma. Among fellow eyes without visual field loss at baseline, progression was detected first as frequently in the optic disc as in the visual field.

It is possible that the optic disc examination is not as sensitive to detect progressive change as RNFL based examination such as red-free photography or OCT RNFL thickness measurement. It is possible that the optic disc examination is not as sensitive to detect progressive change as RNFL based examination such as red-free photography or OCT RNFL thickness measurement. This is because the axons are distributed in a widespread nature in the RNFL while they are densely packed in the optic disc. In this regard, the current finding should not be interpreted that the visual field testing detects the glaucoma progression earlier than the structural examination. In other words, it is possible that structural glaucoma progression might be detected earlier than in visual field testing using an RNFL based technique. Another factor to consider is that the ability of detecting glaucoma progression of structural and functional examination may be dependent on the stage of disease. It is generally considered that progressive structural changes are detected more commonly early in the disease, whereas functional progression is observed more commonly at later stages of the disease. These factors should be considered when interpreting the result of this study.

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