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Editors Selection IGR 19-3
Clinical Forms of Glaucoma: Glaucoma diagnosis in high-myopia eyes
Comment by Andrew Tatham on:
53937 Macular Imaging in Highly Myopic Eyes With and Without Glaucoma, Nakano N; Hangai M; Noma H et al., American Journal of Ophthalmology, 2013; 156: 511-523
Glaucoma diagnosis can be challenging in high myopia, as myopic optic discs frequently have an anomalous appearance. Features such as myopic parapapillary atrophy may also reduce the diagnostic ability of optical coherence tomography (OCT) circumpapillary retinal nerve fiber layer (cpRNFL) measurements. Nakano et al. hypothesize that OCT macular parameters may be less affected by axial length and better able to detect glaucomatous change in high myopia.
The study found poor inter-observer agreement for diagnosing glaucoma from optic disc stereophotographs in high myopia. Agreement was better using visual inspection of macular OCT images, perhaps due to the observation that many non-glaucomatous myopic eyes had anomalous optic disc appearances, whereas macular structures were not distorted allowing glaucoma to be more easily detected. The effect of disease severity and axial length on diagnostic ability of cpRNFL and macular ganglion cell complex (mGCC) thicknesses was examined. cpRNFL and mGCC had similar ability to detect glaucoma in early disease, however, in more severe disease cpRNFL performed better than mGCC. Conversely, cpRNFL had lower diagnostic ability in eyes with longer axial length whereas mGCC had good performance even in high myopia.
The study findings support the hypothesis that macular OCT imaging may be particularly useful in eyes with high myopia but there are limitations
The study findings support the hypothesis that macular OCT imaging may be particularly useful in eyes with high myopia but there are limitations. Exclusion of eyes with pathological myopia may have led to selection bias due to omission of eyes with myopic macular abnormalities. This may have favored macular parameters, especially as eyes with anomalous optic discs were included. Also, the study did not include eyes with pre-perimetric glaucoma, in which cpRNFL parameters have recently been reported to have better diagnostic ability than mGCC. Despite these limitations the study adds to the growing body of evidence showing the importance of evaluating the macula in glaucoma and highlights that a different approach to diagnosis may be needed in high myopia.
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