Evaluation of Optic Nerve Head Parameters and Retinal Nerve Fiber Layer Thickness in Axial Myopia Using SD OCT

The purpose of this research was to study the effect of increased axial myopia, in non-glaucomatous eyes, and its correlation with ONH parameters, and RNFL thickness, using Cirrus HD 4000 SD-OCT.

The myopia group included 86 eyes of 86 patients, while the control group involved 92 eyes of 92 patients, attending the Ophthalmology Outpatient Clinic in Minia University Hospital, between November 2013 and March 2015. ONH parameters and peripapillary RNFL thickness measurement were evaluated by using SD-OCT, selecting the standard optic disc cube 200 × 200.

The mean age of the myopia group was (36.55 ± 9.44), the mean spherical equivalent was (-12.70 ± 3.87 D), and the mean axial length was (27.88 ± 1.92 mm). The control group had mean age of (34.82 ± 8.87), mean spherical equivalent of -0.65 ± 0.41 D, and mean AL of (22.16 ± 0.82). A significant difference was reported between the two groups, regarding disc area (p = 0.01), rim area (p = 0.001), vertical C/D (p = 0.01), average C/D ratio (p = 0.001), average and temporal RNFL thickness (p = 0.0001, p = 0.001, respectively).

A significant difference was found between highly myopic non-glaucomatous eyes and the control group, regarding ONH parameters and RNFL thickness as measured by SD-OCT. As OCT magnification adjusted ONH parameters were larger, global and the temporal RNEL were thicker in the myopia group, those magnification adjusted parameters helped in an accurate evaluation of ONH and RNFL in highly myopic eyes, in order to avoid misdiagnosis of glaucoma in such eyes.