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

Abstract

Objectives: To determine the normal values for retinal nerve fiber layer thickness (RNFLT) in myopic patients without glaucoma and analyze the changes in their color map. Materials and Methods: A total of 245 eyes without glaucoma were included in the study. According to the degree of myopia, the cases were divided into 4 groups: control group (+1.00/-1.00 D; n=70), Group 1 (-1.00/-3.00 D; n=50), Group 2 (-3.00/-6.00 D; n=75), and Group 3 (>-6.00 D; n=50). Intra-group comparisons were performed in terms of superotemporal, superonasal, nasal, inferonasal, inferotemporal, temporal, and global RNFLT (Heidelberg Spectralis, Optic Coherence Tomography, Germany) and the color coding of these quadrants (green: within normal limits, yellow: borderline, red: outside normal limits). Results: All groups were similar in age and gender (p>0.05). As the degree of myopia increased, RNFLT became thinner in the upper and lower temporal and upper and lower nasal quadrants (p<0.01). The rate of measurements considered borderline and outside normal limit in at least 1 quadrant was higher in groups with higher myopia for all quadrants (p<0.05). This rate was found to be 8/70 (11.4%) for the control group, 9/50 (18.0%) for Group 1, 21/75 (28.0%) for Group 2, and 33/50 (66.0%) for Group 3 (p<0.01). Conclusion: The high rate of RNFLT classified as borderline or outside normal limits in myopic patients is a finding to which clinicians should pay attention in order not to make a misdiagnosis, especially in cases of suspected glaucoma.

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

“…In the current study, temporal pRNFL thickness significantly increased with increasing myopia degree, and the number of eyes with abnormal color codes also increased. This can be explained by the temporalization of the TS and temporal-inferior pRNFL bundles and the larger standard deviations in myopic eyes, and it is in line with our previous findings 7. We applied all the pRNFL thickness data to the normative database created for each group, and as expected, the significance of the distribution difference disappeared for most sectors.…”

“…This can be explained by the temporalization of the TS and temporalinferior pRNFL bundles and the larger standard deviations in myopic eyes, and it is in line with our previous findings. 7 We applied all the pRNFL thickness data to the normative database created for each group, and as expected, the significance of the distribution difference disappeared for most sectors. Seol et al 10 measured the RNFL thickness using another commercially available OCT device (Cirrus SD-OCT, Carl Zeiss Meditech) and generated a myopic normative database, which produced similar results to our findings.…”

“…It is now well known that the color probability codes for the pRNFL thickness based on built-in normative databases of OCT devices are not reliable in myopic eyes. 7,8,17 There are several potential sources of error with the retinal nerve fiber layer (RNFL) measurement in myopic eyes, including temporal displacement of retinal ganglion cell axons and blood vessels, torsional changes in the RNFL topography, problems with the correct centering of the measurement circle on a myopic disc, various focusing errors caused by the tilting of the ONH, magnification issues related to myopic refraction, and segmentation errors. This does not mean that OCT is completely useless in the diagnosis of glaucoma in myopic eyes without a myopic normative database.…”

“…An accurate and reliable measurement of the pRNFL thickness is critical in the diagnosis and management of glaucoma 5,6. However, several studies have demonstrated that when compared with the normative database of the OCT software, myopia can alter the peaks of the pRNFL thickness, leading to misinterpretation of pRNFL data and color probability codes (green, within normal limits; yellow, borderline; and red, outside normal limits) 7–9…”

“…5,6 However, several studies have demonstrated that when compared with the normative database of the OCT software, myopia can alter the peaks of the pRNFL thickness, leading to misinterpretation of pRNFL data and color probability codes (green, within normal limits; yellow, borderline; and red, outside normal limits). [7][8][9] Previous studies have attempted to improve the diagnostic performance of OCT using a myopic normative database. [10][11][12] However, only a few studies are available on the use of the OCT color probability codes after applying a normative database, 10 and none has provided information on myopic changes in the pRNFL data collected using the Spectralis OCT-2 (Heidelberg Engineering, Heidelberg, Germany).…”