Optic disc margin anatomy in patients with glaucoma and normal controls with spectral domain optical coherence tomography.
OBJECTIVE
To characterize optic nerve head (ONH) anatomy related to the clinical optic disc margin with spectral domain-optical coherence tomography (SD-OCT).


METHODS
Cross-sectional study.


METHODS
Patients with open-angle glaucoma with focal, diffuse, and sclerotic optic disc damage, and age-matched normal controls.


METHODS
High-resolution radial SD-OCT B-scans centered on the ONH were analyzed at each clock hour. For each scan, the border tissue of Elschnig was classified for obliqueness (internally oblique, externally oblique, or nonoblique) and the presence of Bruch's membrane overhanging the border tissue. Optic disc stereophotographs were co-localized to SD-OCT data with customized software. The frequency with which the disc margin identified in stereophotographs coincided with (1) Bruch's membrane opening (BMO), defined as the innermost edge of Bruch's membrane; (2) Bruch's membrane/border tissue, defined as any aspect of either outside BMO or border tissue; or (3) border tissue, defined as any aspect of border tissue alone, in the B-scans was computed at each clock hour.


METHODS
The SD-OCT structures coinciding with the disc margin in stereophotographs.


RESULTS
There were 30 patients (10 with each type of disc damage) and 10 controls, with a median (range) age of 68.1 (42-86) years and 63.5 (42-77) years, respectively. Although 28 patients (93%) had 2 or more border tissue configurations, the most predominant one was internally oblique, primarily superiorly and nasally, frequently with Bruch's membrane overhang. Externally oblique border tissue was less frequent, observed mostly inferiorly and temporally. In controls, there was predominantly internally oblique configuration around the disc. Although the configurations were not statistically different between patients and controls, they were among the 3 glaucoma groups. At most locations, the SD-OCT structure most frequently identified as the disc margin was some aspect of Bruch's membrane and border tissue external to BMO. Bruch's membrane overhang was regionally present in the majority of patients with glaucoma and controls; however, in most cases it was not visible as the disc margin.


CONCLUSIONS
The clinically perceived disc margin is most likely not the innermost edge of Bruch's membrane detected by SD-OCT. These findings have important implications for the automated detection of the disc margin and estimates of the neuroretinal rim.
Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada.
Alexandre S C
AS
Reis
Glen P
GP
Sharpe
Hongli
H
Yang
Marcelo T
MT
Nicolela
Claude F
CF
Burgoyne
Balwantray C
BC
Chauhan
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016570:Bruch Membrane / Q000473:pathology; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology; D009898:Optic Disk / Q000033:anatomy & histology / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D011446:Prospective Studies; D041623:Tomography, Optical Coherence; D014786:Vision Disorders / Q000175:diagnosis; D014794:Visual Fields