Abstract
Purpose: :
Adaptive optics provides high resolution images of the living retina and optic nerve head. Our purpose was to assess the repeatability of imaging pores in the lamina cribrosa of normal living eyes using an adaptive optics scanning laser ophthalmoscope (AOSLO) prior to examining changes in these structures in diseased eyes.
Methods: :
Reflectance images of the anterior lamina cribrosa (840 nm) were obtained using an AOSLO in at least 2 different sessions (separated by ≥ 1 week) in 2 normal rhesus monkeys and 1 normal human subject. Monkeys were anesthetized and a contact lens was placed on the eye during high resolution imaging. AOSLO videos were analyzed off-line using MATLAB, ImageJ, and Adobe Photoshop to produce registered images and identify individual pores that were quantitatively compared across imaging sessions. Morphological parameters of laminar pores (e.g., pore area, length of major/minor axes of best-fitting ellipse, and pore centroid location) were calculated and measurement repeatability was assessed by their variance across imaging sessions.
Results: :
The same laminar pores were clearly observed in multiple imaging sessions. Pore areas ranged from 160 to 4629 µm2 in monkeys, and 377 to 4380 µm2 in the human. The variabilities in measuring pore area and lengths of major/minor axes (calculated as the standard deviation of measurements made for the same pores across imaging sessions) were 53 µm2 and 3.2 µm, respectively, in the monkeys, and 77 µm2 and 2.0 µm, respectively, in the human. The mean differences in centroid positions were 2.5 µm (range = 0.6 to 5.6 µm) in monkeys and 2.8 µm (range = 0.9 to 6.1 µm) in the human.
Conclusions: :
The anterior lamina cribrosa can be consistently imaged in vivo in normal monkey and human eyes. The small intersession variability in pore geometry (likely due to intensity differences in the reflectance images between sessions) suggests that AOSLO imaging can track changes in laminar pores in vivo during the progression of glaucoma.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • lamina cribrosa • imaging/image analysis: non-clinical