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Relationship between structure and function with regard to glaucoma
The study by Kanadani et al1 to elucidate the relationship between structure and function, especially with regard to glaucoma, is timely. Their paper is particularly interesting in that it provides information on not one but two measures of function: the visual field and the multifocal visual evoked potential technique. The investigators report that macular thicknesses (measured by optical computerized tomography) were in agreement with the 10-2 Humphrey visual field and multifocal visual evoked potential technique to the same degree as the two functional tests. Local agreement was present as well; inferior and superior sectors showed abnormal macular thickness in 78% and 65% of the points.
These results, obtained at the macula, give a message similar to that of other structural measures such as peripapillary nerve fibre layer thickness and morphometry of the optic nerve head. The message seems to be that though there is good overall agreement between structure and function, it is not sufficient to yield a test that provides an unequivocal measure of damage in a given patient. Gone are the days when we hoped that a unique quantitative objective measure would be found and would replace subjective tests prone to noise and artefacts and demanding expert interpretation.
Does this means that we should give up on our effort to perform quantitative and objective tests in glaucoma? I opine that the answer is “no”, but clearly we are forced to delve more deeply into the subject and accept the fact that valuable information will be gleaned …