African Descent and Glaucoma Evaluation Study (ADAGES): II. Ancestry differences in optic disc, retinal nerve fiber layer, and macular structure in healthy subjects

Abstract

Objective: To define differences in optic disc, retinal nerve fiber layer, and macular structure between healthy participants of African (AD) and European descent (ED) using quantitative imaging techniques in the African Descent and Glaucoma Evaluation Study (ADAGES).

Methods: Reliable images were obtained using stereoscopic photography, confocal scanning laser ophthalmoscopy (Heidelberg retina tomography [HRT]), and optical coherence tomography (OCT) for 648 healthy subjects in ADAGES. Findings were compared and adjusted for age, optic disc area, and reference plane height where appropriate.

Results: The AD participants had significantly greater optic disc area on HRT (2.06 mm(2); P < .001) and OCT (2.47 mm(2); P < .001) and a deeper HRT cup depth than the ED group (P < .001). Retinal nerve fiber layer thickness was greater in the AD group except within the temporal region, where it was significantly thinner. Central macular thickness and volume were less in the AD group.

Conclusions: Most of the variations in optic nerve morphologic characteristics between the AD and ED groups are due to differences in disc area. However, differences remain in HRT cup depth, OCT macular thickness and volume, and OCT retinal nerve fiber layer thickness independent of these variables. These differences should be considered in the determination of disease status.

Trial registration: ClinicalTrials.gov NCT00221923.

Figure 1

Global and regional mean ratio of the rim to disc area in African descent (AD) and European descent (ED) groups as measured on confocal scanning laser ophthalmoscopy (Heidelberg retinal tomography [HRT]). Bars indicate standard error. I indicates inferior; S, superior.

Figure 2

Regional differences in average optical coherence tomography retinal nerve fiber layer (RNFL) thickness between African descent (AD) and European descent (ED) groups. Bars indicate standard error.

Figure 3

Mean (SD) regional macular thickness measurement in African Descent and Glaucoma Evaluation Study participants of African descent (AD) (A) and European descent (ED) (B). All measurements are in micrometers; regions showing significant differences are shaded.