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Divya Singh, Mona Pathak, Tanuj Dada; Effect of Myopia on Retinal Nerve Fibre Layer Thickness Measurements by Cirrus HD Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2014;55(13):954.
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To evaluate the relationship between retinal nerve fibre layer (RNFL) thickness measured by Cirrus HD optical coherence tomography (OCT) and the axial length/refractive error of the eye.
A total of 100 eyes of 100 healthy subjects (age, 20-34 years with M/F ratio of 57/43), comprising 50 eyes with emmetropia , 25 eyes with moderate myopia (SE between -4D and -8D) and 25 eyes with high myopia (SE between -8D and -12D) were analyzed in this cross sectional study. Average and mean clock hour RNFL thicknesses were measured by Cirrus HD OCT and compared between the three groups. Associations between RNFL measurements and axial length and spherical equivalent were evaluated by linear regression analysis.
The average RNFL measurements were significantly lower in high myopia (78.68 +/- 5.67) and moderate myopia (83.76 +/- 3.44) group compared with emmetropia group (91.26 +/- 2.99), also in the superior and inferior mean clock hours. Significant correlations were evident between RNFL measurements and the spherical equivalent and axial length. The average RNFL thickness decreased with increasing axial length (r = - 0.8115, P <0.001) and negative refractive power (r = 0.8397, P<0.001). As the axial length increased and the spherical equivalent decreased, the thickness of the superior and inferior peripapillary RNFL decreased.
The axial length / refractive error of the eye affected the average RNFL thickness, and the RNFL thickness distribution. Analysis of RNFL thickness in the evaluation of glaucoma should always be interpreted with reference to the refractive status. When interpreting the RNFL thickness of highly myopic patients by OCT, careful attention must be given to the inherently thinner RNFL to avoid a false diagnosis of glaucoma.
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