Case Series: Nerve Fiber Bundle Shift and Glaucoma Misdiagnosis Risk in African American Patients

Purpose: To show how various patients of African descent possess principal superior-temporal and inferior-temporal retinal nerve fiber layer (RNFL) bundle peaks that are anatomically shifted relative to the optical coherence tomography (OCT) normative database majority. This anatomical discrepancy may present as false-positive thinning on RNFL deviation maps thereby appearing like early glaucomatous damage. Observations: Three patients of African descent presented with cup-to-disc ratios of 0.6 or higher and were flagged with bilateral retinal nerve fiber layer thinning in superior-temporal and/or inferior-temporal RNFL sectors relative to the Cirrus OCT normative database population. Thinning on RNFL deviation maps in all three patients showed wedge-defects that traveled towards the superior-temporal and inferior-temporal vulnerability zones of the disc. However, all three patients demonstrated bilateral robust macular ganglion cell thicknesses and had automated visual fields inconsistent with glaucoma. Inspection of the RNFL in these patients showed their principal superior-temporal and inferior-temporal nerve bundle peaks were shifted more vertically and less temporally relative to the database population. Conclusion: As OCT becomes more common in early glaucoma detection, it may be important to recognize how the RNFL anatomy of some patients of African descent differs relative to the normative database majority. All three of the patients in our series had high-risk appearing superior-temporal and/or inferior-temporal RNFL ‘thinning’ attributable to anatomical shifting of these bundle peaks. This may result in improper flagging of sectors known to be vulnerable in early glaucoma thereby increasing the likelihood of misdiagnosis, particularly if ganglion cell thickness is not concurrently inspected.