A method for quantifying sectoral optic disc pallor in fundus
  photographs and its association with peripapillary RNFL thickness
Samuel Gibbon Graciela Muniz-Terrera Fabian SL Yii Charlene Hamid Simon Cox Ian JC Maccormick Andrew J Tatham Craig Ritchie Emanuele Trucco Baljean Dhillon Thomas J MacGillivray
Purpose: To develop an automatic method of quantifying optic disc pallor in
fundus photographs and determine associations with peripapillary retinal nerve
fibre layer (pRNFL) thickness.
  Methods: We used deep learning to segment the optic disc, fovea, and vessels
in fundus photographs, and measured pallor. We assessed the relationship
between pallor and pRNFL thickness derived from optical coherence tomography
scans in 118 participants. Separately, we used images diagnosed by clinical
inspection as pale (N=45) and assessed how measurements compared to healthy
controls (N=46). We also developed automatic rejection thresholds, and tested
the software for robustness to camera type, image format, and resolution.
  Results: We developed software that automatically quantified disc pallor
across several zones in fundus photographs. Pallor was associated with pRNFL
thickness globally (\b{eta} = -9.81 (SE = 3.16), p < 0.05), in the temporal
inferior zone (\b{eta} = -29.78 (SE = 8.32), p < 0.01), with the nasal/temporal
ratio (\b{eta} = 0.88 (SE = 0.34), p < 0.05), and in the whole disc (\b{eta} =
-8.22 (SE = 2.92), p < 0.05). Furthermore, pallor was significantly higher in
the patient group. Lastly, we demonstrate the analysis to be robust to camera
type, image format, and resolution.
  Conclusions: We developed software that automatically locates and quantifies
disc pallor in fundus photographs and found associations between pallor
measurements and pRNFL thickness.
  Translational relevance: We think our method will be useful for the
identification, monitoring and progression of diseases characterized by disc
pallor/optic atrophy, including glaucoma, compression, and potentially in
neurodegenerative disorders.