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Editors Selection IGR 10-3

Optical Coherence Tomography: Recognizing glaucoma in high myopes

Comment by Tin Aung & Mani Baskaran on:

27757 Assessment of Glaucomatous Changes in Subjects with High Myopia Using Spectral Domain Optical Coherence Tomography, Shoji T; Sato H; Ishida M et al., Investigative Ophthalmology and Visual Science, 2011; 52: 1098-1102

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Ganglion cell complex (GCC) mapping is a novel method of glaucoma discrimination using Spectral Domain Optical Coherence Tomography. ¹ RT-vue-100 (Optovue) 4.0 SDOCT software utilizes GCC scan protocols to provide global loss volume (GLV) and focal loss volume (FLV). These have been utilized to differentiate glaucoma in high myopes in comparison to normal subjects.²

Shoji T et al. (185) used this technique to discriminate perimetric glaucoma (n = 51) in high myopes (-5 DS or more) in comparison to 'normal' high myopes (n = 31). They compared GCC parameters to optic nerve head (ONH) and retinal nerve fiber layer (RNFL) parameters, after excluding eyes with neuro-ophthalmological, retinal or choroidal diseases that can cause visual field loss. The largest areas under ROC were found for vertical cup-disc ratio (0.844), average RNFL thickness (0.826) and GLV (0.954) with the latter outperforming the others (p < 0.05). The authors suggested that GCC may be less influenced by myopic changes compared to ONH parameters and the average specificity of 0.968 at 80% sensitivity was encouraging.

Ganglion Cell Complex may be less influenced by myopic changes compared to optic nerve head parameters in high myopia

Manual adjustment of the contour line for disc margin/GCC to avoid the temporal crescent, limited normative database for GCC and low signal strength indicator values (8.9%) were limitations of the study. Besides, it is noted that with increasing sensitivity, the GCC parameters tend to have dramatic reductions in specificity, especially for FLV. This may affect overall diagnostic accuracy especially with increasing severity of glaucoma and abnormal disc configurations.⁴ The authors have to be commended for their novel work studying eyes with glaucoma and high myopia, which is a difficult group of patients to manage. This study gives insights into GCC loss in high myopia. Further research to establish a normative database for GCC parameters and its variation in myopia is useful to establish novel diagnostic and prognostic markers for glaucoma detection and progression in such patients.

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