Abstract
Purpose: :
Optic nerve crescent or peripapillary atrophy (PPA) is known to be associated with not only myopia but also glaucomatous optic neuropathy, especially normal-tension glaucoma. PPA has been classified into zone α and β. Zone β represents the central zone of atrophy adjacent to the optic disc characterized by complete loss of the retinal pigment epithelium (RPE) and choriocapillaries with visibility of large choroidal vessels and sclera, while zone α is the outer zone of PPA with RPE hypo or hyperpigmentation. Studies on the cross-sectional or three dimensional (3D) configurations of PPA are not available except histological investigations. This study aims to evaluate the 3D configurations of PPA in normal subjects using a newly developed spectral-domain optical coherence tomography (SD-OCT).
Methods: :
Subjects had complete ophthalmic examination including slit-lamp biomicroscopy, gonioscopy, intraocular pressure (IOP), funduscopy, standard automated perimetry (SAP), disc imaging with photography and SD-OCT (3D-OCT1000, Topcon Inc.). PPA-α and β were identified from disc color photographs. Cross-sectional B-mode images obtained with SD-OCT were analyzed in correspondence with the optic disc photographs.
Results: :
Ninety-eight eyes of 53 (27 males and 26 females) normal subjects were included. Age averaged 51.6±15.7 (mean ± SD) years, refractive error -0.7±1.8 diopters, and IOP 14.1±2.3 mmHg. Of 98 normal eyes, 98 (100%) had PPA-α and 58 (59.2%) had PPA-β. Based on SD-OCT images, the cross-sectional configurations of the scleral bed corresponding to the PPA were classified into four groups: ‘flat’, ‘slope’, ‘step’ and others. The frequency of ‘flat’, ‘slope’ and ‘step’ configurations were 66.3%, 81.6% and 5.1% respectively. There were 10 eyes with configurations classified in "others". The mean clock hours of the ‘flat’, ‘slope’ and ‘step’ configurations in eyes with these configurations were 2.9, 2.9 and 1.0 hours, respectively. The clock hours of ‘slope’ and ‘flat’ configurations were not significantly different (P=0.75, unpaired t-test).
Conclusions: :
Using SD-OCT we were able to describe and classify the cross-sectional configurations of PPA. Further studies with larger sample sizes should be performed to evaluate the associations of these PPA configurations with myopia and glaucoma.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical • optic disc