Circumpapillary Course of Retinal Pigment Epithelium Can Be Fit to Sine Wave and Amplitude of Sine Wave Is Significantly Correlated with Ovality Ratio of Optic Disc

Abstract

The purpose of this study was to develop a method of quantifying the degree of optic disc tilt in normal eyes. This was a prospective, observational cross sectional study of 126 right eyes of 126 healthy volunteers. The optic disc tilt was determined from the circular peripapillary optical coherence tomographic (OCT) scan images. The course of the retinal pigment epithelium (RPE) layer in the peripapillary cross sectional scan images was fit to a sine wave curve, and the amplitude of the sine curve was used to reflect the degree of the optic disc tilt in the optical axis. The repeatability of the amplitude determinations was calculated. The correlation between the amplitude and the ovality ratio of the optic disc was determined. The correlation between the amplitude and the body height was also calculated. The mean amplitudewas 36.6 ± 17.5 pixels, which was significantly and inversely correlated with the ovality ratio of the optic disc (R = -0.59, P<0.001). The intra-rater and inter-rater correlation coefficients of the amplitude were significant high (P<0.001, both). The amplitude was significantly and inversely correlated with the body height (R = -0.38, P<0.001), but not with the axial length. In conclusion, a sine wave function can be used to describe the course of the RPE in the circumpapillary OCT images. The results indicate that the amplitude of the sine wave can be used to represent the degree of optic disc tilt. Thus, the sine wave analyses can be used as a quantifiable and repeatable method to determine the optic disc tilt.

Correlations between local peripapillary choroidal thickness and axial length, optic disc tilt, and papillo-macular position in young healthy eyes

“…All eyes had a standard ocular examination as reported elsewhere [27, 28] including; slit-lamp biomicroscopy of the anterior segment, ophthalmoscopy of the ocular fundus, pneumo-tonometric (CT-80, Topcon, Tokyo, Japan) measurements of the IOP, and AL-2000 ultrasonographic (TOMEY, Nagoya, Japan) measurements of the axial length. The refractive error (spherical equivalent) was measured with the Topcon KR8800 autorefractometer/keratometer.…”

“…Degree of optic disc tilt was determined by our method reported previously [27]. In brief, the course of the retinal pigment epithelium (RPE) was marked on the OCT B-scan images manually.…”

“…Then, the optic disc tilt examined was represented by the angle between the optic axis and the optic disc tilt. The amplitude of the sine wave, ‘a’, was considered to represent the degree of the optic disc tilt relative to the optical axis [27]. The eyes were stationary throughout the measurements, and the retinal plane of the macular area was vertical to the optical axis of the eye.…”

“…To accomplish this, we measured the axial length of the eye by ultrasonography, the optic disc tilt by a new method [26–27], and the PMP angle in the fundus photographs. We then determined the association of these factors with the ppCT of each sector of the optic disc.…”

Peripapillary Nerve Fiber Elevation in Young Healthy Eyes

“…25 Briefly, the optic disc tilt was quantified using a sine curve method of the Topcon 3D OCT-1000 Mark II RNFL 3.4-mm circle scan, B scan images. The course of the RPE was marked on the B-scan images manually.…”