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Alexandre Plouznikoff, Paul Harasymowycz; Parapapillary Autofluorescence and its Correlation with Retinal Nerve Fiber Layer Anomalies in Normal Tension Glaucoma. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1026.
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© ARVO (1962-2015); The Authors (2016-present)
To study the size, the polar distribution and the intensity of parapapillary autofluorescence (AF), as well as its progression and its correlation with retinal nerve fiber layer (RNFL) thinning in normal tension glaucoma (NTG).
Patients with NTG were randomly selected. Those with a condition interfering with the measurement of AF (ex. cataract, keratopathy, hemorrhage, AMD, 4+-dioptre ametropia) were excluded, as were patients with non-glaucomatous optic neuropathies. AF images and parapapillary RNFL thickness were acquired using a confocal scanning laser ophthalmoscope. The RNFL polar coordinate system was used to locate the AF areas, after registering the two sets of images using vascular markers. AF areas were segmented using automatic region growing with a floating threshold and manually selected seed points.
27 fundi were divided into 3 groups (Jonas' classification). There were no statistically significant differences between the groups in regard to sex, age, ethnicity, maximum corrected intraocular pressure, pachymetry and best corrected visual acuity. The number of AF areas, as well as their size, both in mm2 and in degrees, were strongly correlated with the stage of glaucoma (Spearman, ρ=0.64, 0.70 and 0.69 respectively, p<0.001). Almost no AF zones were detected in the supero and inferonasal parapapillary areas in stage 1 (Χ2 goodness-of-fit test, p=0.02). The presence of AF was correlated with borderline RNFL thinning (p<0.05) (Spearman, ρ=0.49, p<0.001). However, 39.6% of the isolated AF areas weren't matched to RNFL anomalies; we suspect they could precede the detection of statistically significant RNFL thinning. Finally, no statistically significant differences were found in terms of AF intensities between the stages of glaucoma (Spearman, ρ=-0.10, p=0.23).
Since AF correlates with glaucoma progression and RNFL anomalies in NTG, we believe AF could be used to track NTG progression, in addition to repeat RNFL optical coherence tomographies and visual fields tests. A prospective study will determine if AF precedes detectable RNFL thinning; if so, AF could help us act before permanent RNFL damage occurs.
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