Abstract
Purpose:
Optical coherence tomography (OCT) has been used to image the optic nerve head and peripapillary retinal nerve fiber layer (RNFL) with a view to differentiating optic disc edema (ODE) from optic nerve head drusen (ONHD). In this study we have used OCT for the first time to compare the macular structure in patients with ODE and ONHD and also healthy participants.
Methods:
High-resolution spectral domain OCT (Copernicus, 3µm resolution, 7x7x2mm volumetric scans) was used to image the macula parameters in 36 ODE, 76 ONHD patients and 57 healthy participants. Average retinal and nerve fiber layer (RNFL) thickness were measured using a semi-automated method with manual correction of the internal limiting membrane, NFL and pigment epithelium layers to minimize inaccuracy. Retinal and RNFL thickness were measured in 3 circular zones (central - 1mm diameter, inner annulus - 3 mm and outer annulus - 6 mm) and the inner and outer annulus was separated into quadrants (superior, inferior, temporal and nasal) and analyzed in three groups. Groups were comparable in age and refractive error.
Results:
Retinal thickness in the inner annulus was larger in ONHD patients compared to ODE and normal groups. This difference was significant in temporal and superior segments (p=0.01 and p=0.04, respectively). In contrast, ODE patients had thicker retina in outer annulus with exception of outer temporal sector where retina was thicker in ONHD patients compared to ODE and healthy volunteers. Difference was significant in temporal and inferior segments (p=0.02 for both). The retinal nerve fibre layer (RNFL) was significantly thinner (p<0.05) in ONHD patients and thicker in ODE patients compared to healthy controls in all areas except inner temporal and outer nasal and superior segments where difference was not significant.
Conclusions:
This study shows for the first time macula involvement in patients with optic nerve pathology (ODE and ONHD). ODE was characterised by the thickening of the RNFL while ONHD patients showed thinning of RNFL in macula compared to healthy participants. These factors must be taken into consideration when pathology of optic nerve is suspected.
Keywords: 613 neuro-ophthalmology: optic nerve •
585 macula/fovea