Purchase this article with an account.
Q. Wang, B. Cense, O. Kocaoglu, R. S. Jonnal, W. Gao, D. T. Miller; Imaging Retinal Capillaries Using Optical Coherence Tomography and Adaptive Optics. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4774.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Fluorescein angiography and entoptic viewing are the most common methods for viewing in vivo the complex network of small vessels and capillaries in the retina. Such detection is essential for early diagnosis and effective treatment of disease such as diabetic retinopathy, yet these methods remain limited in the vessels they can detect, and often have undesirable attributes such as being invasive or subjective. On the other hand, recently-developed imaging systems that combine optical coherence tomography (OCT) and adaptive optics (AO) do not share these attributes and furthermore provide the necessary 3D resolution and sensitivity to visualize the smallest capillaries in the retina. To ascertain whether this expectation is correct or not, we investigate the capability of AO OCT to image capillaries in the parafovea region and in particular the defining capillaries of the foveal avascular zone.
The ultrahigh resolution (UHR) AO OCT system used in the experiment consists of a Superlum BroadLighter (T-840-HP, center wavelength 840 nm, bandwidth 115 nm), a customized achromatizing lens for compensating the ocular chromatic aberrations across the BroadLighter spectrum, and a 2048 pixel linescan detector in a spectral-domain OCT configuration. The UHR-OCT acquired up to 30,000 A-scans/s. The AO consisted of a Shack-Hartmann wavefront sensor (20x20 lenslet array), and a 37-element AOptix deformable mirror and 144-element BMC deformable mirror in a woofer-tweeter configuration. Volume scans (3°x3°) centered on the fovea were acquired in four subjects during dynamic AO compensation. Focus was optimized for visualizing retinal capillaries. Image processing was used to extract the capillary layers and reduce speckle noise.
The woofer-tweeter AO provided near-diffraction-limited imaging based on the SH measurement; UHR-OCT provided an axial resolution of 3.3 µm based on the width of the foveal reflex. The foveal avascular zone was readily distinguishable in the volume images including the individual capillaries that define its perimetry. Depth variation of the capillaries was found to increase with distance from the fovea center.
UHR AO OCT permits non-invasive observation of individual capillaries in the parafoveal arcade, and in particular those that define the foveal avascular zone.
This PDF is available to Subscribers Only