The Importance Of Ocular Anatomical Variables On The Mapping Of Retinal Locations To The Retinal Nerve Fibre Layer And Optic Nerve Head

Abstract

Purpose: : Considering a patient’s individual structure-function profile may improve glaucoma diagnosis and management. It is the purpose of this study to evaluate whether variation of ocular parameters between individuals has an influence on the structure-function relationship.

Methods: : One hundred eyes from 100 healthy subjects and glaucoma suspects were assessed using blue filter retinal nerve fibre layer (RNFL) bundle photographs and superimposed 24-2 visual field grid patterns. RNFL bundles were manually traced using customized software. The angle at which each bundle entered the optic nerve head (ONH) was recorded. Ocular parameters (axial length, spherical equivalent, size, rotation, shape and tilt of the ONH) were assessed using partial coherence interferometry, spectral domain optical coherence tomography, and scanning laser ophthalmoscopy. The association of these parameters with the entry angle into the ONH was assessed using a linear model.

Results: : Refractive error (sphere, cylinder, and spherical equivalent) and shape of the ONH did not have a significant effect on the entry angle into the ONH. However, the size, rotation and tilt of the ONH as well as axial length were significant predictors (p<0.0001).

Conclusions: : The entry angle of RNFL bundles into the ONH and, therefore, the structure-function relationship, is highly influenced by ocular parameters including axial length, and the size, rotation, and tilt of the ONH. Myopic patients, who are at a higher risk of developing glaucoma, may particularly benefit from an individualized assessment of their structure-function relationship since it is significantly influenced by their axial length and disk tilt.

Keywords: nerve fiber layer • imaging/image analysis: clinical • optic disc