Abstract
Purpose:
Spectral-domain optical coherence tomography (SD-OCT) instruments has their own normative database, and the significance map built from the normal range is helpful for the diagnosis of glaucoma. However, individuals with high myopia were usually excluded from the normative populations. The RS-3000 SD-OCT system (NIDEK, Aichi, Japan) had two types of normative databases, that is, for non-highly myopic eyes and for highly myopic eyes. The purpose of this study was to evaluate the clinical usefulness of the specific normative database for highly myopic eyes on early glaucoma diagnosis based on macular ganglion cell complex (mGCC) thickness measured in the SD-OCT images.
Methods:
Forty-seven eyes of 47 subjects with high myopia (axial length ≥26.0 mm) were enrolled, including 20 normal eyes and 27 eyes with early glaucoma. The SD-OCT examinations was underwent using RS-3000, and the mGCC thickness/significance maps within a 9-mm diameter circle were generated by a built-in software program. The sensitivity and specificity of the SD-OCT's significance maps when using the highly myopic normative database for distinguishing highly myopic early glaucoma from highly myopic normal eyes was compared to when using the non-highly myopic normative database in the same SD-OCT images. The mGCC scans were classified as abnormal if at least 1 sector of the significance map was <1%, i.e., red color coding.
Results:
Age, men to women ratio, and axial length were not statistically different between highly myopic normal and early glaucoma group. The mGCC thicknesses of the early glaucoma group (81.1±8.4 µm) were significantly thinner than that of the normal group (91.4±7.6 µm) (P <1×10-4). Sensitivity was 96.3% and specificity was 50.0% when using the non-highly myopic normative database. When highly myopic normative database was used, the sensitivity was 88.9% and the specificity was raised to 90.0%. The false positive rate was significantly lower when using the highly myopic normative database (P <0.05).
Conclusions:
The evaluations of glaucoma in eyes with high myopia using non-highly myopic normative database may lead to a frequent misdiagnosis in normal eyes, and a specific database for highly myopic eye is useful to rise the diagnostic accuracy.