Alterations in the Retinal Nerve Fiber Layer Thickness Color Map in Non-Glaucomatous Eyes with Myopia

Optic disc tilt and rotation effects on positions of superotemporal and inferotemporal retinal nerve fibre layer peaks in myopic Caucasians

CLINICAL RELEVANCE

In myopic eyes, the optic disc may become tilted and rotated, making glaucoma diagnosis more difficult.

BACKGROUND

To determine the presence of tilted optic disc, the degree of optic disc rotation, and their effects on the angular location of superotemporal and inferotemporal retinal nerve fibre layer (RNFL) peaks in healthy myopic Caucasians.

METHODS

Non-glaucomatous healthy myopic Caucasian eyes with an axial length > 24 mm were evaluated. ImageJ was used to quantify optic disc tilt and torsion on red-free fundus photography. The RNFL was scanned using spectral-domain optical coherence tomography. The angle of the superotemporal and inferotemporal peaks with the vertical-horizontal meridian was measured.

RESULTS

Fifty-four eyes of 54 individuals were evaluated. The axial length was correlated with the angular location for both the superotemporal (r = -0.549, p < 0.001) and inferotemporal (r = -0.415, p = 0.002) RNFL peaks; they were placed more temporally in eyes with higher axial lengths. For each 1 mm increase in axial length, the angle between the superotemporal peak and the temporal horizontal meridian decreased by 3.976°, and the angle between the inferotemporal apex and the temporal horizontal meridian decreased by 3.028°. The angle between the inferotemporal peak and the temporal horizontal meridian decreased by 0.231° for each 1° increase in optical disc torsion (R2 = 0.09 Regression coefficient = -0.231, p = 0.027).

CONCLUSIONS

The temporal shift of superior and inferior peaks, the thickening of temporal and nasal RNFL, the presence of tilted optic disc, and optic disc rotation may cause misinterpretation of the RNFL in myopic Caucasians. When evaluating peripapillary RNFL thickness in myopic individuals, it would be better to consider these to avoid misinterpretation.

A Myopic Normative Database for Retinal Nerve Fiber Layer Thickness using Optical Coherence Tomography

PRCIS

The purpose of this study was to determine changes in OCT color codes after applying a myopic normative database. The diagnostic performance of the retinal nerve fiber layer analysis improved with the use of this database.

PURPOSE

To evaluate the pRNFL color codes based on a newly generated myopic normative database in comparison to the built-in normative database.

METHODS

A total of 371 subjects were included in this validation study in an attempt to generate a myopic normative database. Eighty myopic glaucomatous and 80 myopic healthy eyes were evaluated to determine the diagnostic performance of this database. The distribution of the color codes was investigated among the groups with reference to the built-in and myopic normative databases, and the two databases were compared in terms of abnormal color code frequency. The diagnostic performance of the myopic database was presented with sensitivity, specificity and area under the receiver operating characteristics curve (AUROC) values.

RESULTS

The agreement between the databases decreased with increasing myopia degree. The distribution of the color codes of the built-in software significantly differed among the study groups in all sectors (P=0.009 for the temporal sector and P<0.001 for the remaining sectors). When the myopic database was used, there were no longer significant differences among the groups for the temporosuperior, temporoinferior, temporal and nasal sectors (P=0.561, 0.299, 0.201, and 0.089 respectively). After applying the myopic normative database, the specificity of the pRNFL color codes increased from 70.1% to 90.2%, and the AUROC value from 0.851 to 0.945.

CONCLUSIONS

The use of a myopic normative database for pRNFL using SD-OCT significantly decreased differences among myopia severity groups, and may help to more reliably assess glaucoma in myopic eyes.