Optic nerve head characteristics in eyes with papillomacular bundle defects in glaucoma

Abstract

To evaluate the pattern of retinal nerve fibre layer defects (RNFLD) with regard to involvement of papillomacular bundle (PMB) in glaucoma. This observational study included patients attending glaucoma imaging services at our centre from 2011 to 2012. All images were exported to Image J software for analysis and rescaled to a unified scale for measurement of degree of RNFLD defined by its angular width, pattern of involvement with regard to involvement or sparing of PMB in particular and horizontal and vertical distance of central vessel trunk (CVT) from the disc margin. Association of clinical data with pattern of defects with regard to PMB involvement was analysed. Sixty-two fundus photographs with discernible nerve fibre layer defects on red free images were selected, including 48 normal tension glaucoma, two primary angle closure glaucoma (PACG) and 12 primary open angle glaucoma (POAG) eyes. Discernible PMB involvement was seen in 35 eyes which included 31 defects in inferior quadrant while CVT exit was placed in the quadrant opposite to the quadrant of RNFLD in that eye. The mean vertical distance from the nearest disc margin was greater in eyes without PMB involvement, 0.4 ± 0.02 mm, than eyes with PMB defects, 0.3 ± 0.01 mm, p < 0.001. On multivariate logistic regression, PMB involvement was significantly associated with decreased linear horizontal of the CVT from the disc margin, p = 0.003. Selective involvement of superior and inferior PMB suggests different retinotopic representation within the optic disc. Exit of the CVT towards the disc margin may be a predisposing factor for RNFLD and involvement of the PMB.