Abstract
Purpose: :
Around or adjacent to some optic discs, most typically in myopic eyes, the retina and choroid are thin or absent, exposing underlying tissue layers. It is not certain to what degree such white peripapillary crescents may result from acquired atrophy or be congenitally abnormal anatomy. The goal of this study is to study the micro-anatomy of white peripapillary atrophy (PPA) in myopic eyes with spectral domain optical coherence tomography (SD-OCT).
Methods: :
Patients with myopia (greater than 4 diopters myopia and/or axial length greater than 24 mm) and white peripapillary crescents had their optic nerve heads (ONHs) photographed with a simultaneous stereo Nidek camera. SD-OCT images were obtained with prototypes of Cirrus HD-OCT (Carl Zeiss Meditec). The en face SD-OCT images were registered with the digital ONH photographs. Cross-sectional B-scan images across the areas of white PPA were then examined for the micro-anatomic features that correspond with white PPA.
Results: :
White PPA has two distinct anatomical variants which are described by the SD-OCT cross-sectional histology of the ONH. One variant of white PPA has some degree of mottled pigment. It lacks the photoreceptor and retinal pigmented epithelial (RPE) layer of the retina, but the sclera is covered with a choroidal layer. The other variant lacks choroid as well as the inner retina and RPE, and is starkly white on clinical examination or in color photographs. In both types, the regions of PPA appear bright in the en face SD-OCT image, and correspondingly the SD-OCT cross-sectional B-scans demonstrate high transmission through the regions of white PPA.
Keywords: optic nerve • imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)