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Teresa Tee, Lekha Gopal, Ian J Murray, Ivan Y-F Leung; Comparison of Parapapillary Autofluorescence and Retinal Nerve Fiber Thickness in Emmetropic and High Myopic Eyes. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1886.
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© ARVO (1962-2015); The Authors (2016-present)
We hypothesized that retinal nerve fibre layer (RNFL) thickness affects parapapillary autofluorescence (PAF). To test this idea, we compared the relationship between RNFL thickness and PAF in emmetropic and high myopic eyes.
Seventy-two healthy subjects (aged 29.5±12.0 years) were recruited. Thirty-two were emmetropes (≤±0.75D) and 40 were high myopes (≥-6.00D). Thirty-degree PAF images were captured using Spectralis HRA+OCT. PAF intensities were sampled around the optic disc. RNFL segment measurements were obtained from optic disc cube scans using Cirrus OCT (Carl Zeiss). Correlation coefficient was calculated between PAF intensity and RNFL thickness (Fig. 1). Statistical significance was set at P<0.05.
RNFL was thickest inferior-temporally and thinnest nasally (n=72). In myopic eyes, RNFL was thicker temporally and thinner superiorly and inferiorly compared to emmetropic eyes (P<0.04). PAF intensities were highest nasally and lowest inferior-temporally (n=72). PAF intensity was negatively correlated with RNFL thickness in 59.4% (n=19) of emmetropic and 55.0% (n=22) of myopic eyes (r=-0.914 to -0.588, P<0.05).The 13 emmetropic eyes that showed no PAF-RNFL correlation were older (36.3±12.6 vs 25.0±7.4 years, P=0.007) and had more negative refraction (-0.27±0.69D vs 0.23±0.45D, P=0.018) than those emmetropes with PAF-RNFL correlation. In the myopic eyes, there was no significant difference in age, refraction or axial length (AL) between those with or without correlation in PAF intensity and RNFL thickness.
PAF is negatively correlated with RNFL thickness in most young emmetropic eyes, showing that RNFL may attenuate PAF. Lack of PAF-RNFL correlation in older emmetropic eyes and longer eyes suggests changes in the parapapillary retinal pigment epithelium and/or RNFL. Age and AL are not major factors in PAF-RNFL correlation in high myopic eyes.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Figure 1. The infra-red image from disc OCT scan (left) was aligned with the PAF image of the optic disc (middle). PAF intensities were sampled from 5x5 pixel squares at the same location where RNFL thickness was measured. PAF intensities of 4 sampling squares were averaged at each of the 12 segments. The RNFL thickness of the 12 segments of the optic disc is shown at the right.
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