Adaptive optics imaging of the retina

Abstract

Adaptive optics is a relatively new tool that is available to ophthalmologists for study of cellular level details. In addition to the axial resolution provided by the spectral-domain optical coherence tomography, adaptive optics provides an excellent lateral resolution, enabling visualization of the photoreceptors, blood vessels and details of the optic nerve head. We attempt a mini review of the current role of adaptive optics in retinal imaging. PubMed search was performed with key words Adaptive optics OR Retina OR Retinal imaging. Conference abstracts were searched from the Association for Research in Vision and Ophthalmology (ARVO) and American Academy of Ophthalmology (AAO) meetings. In total, 261 relevant publications and 389 conference abstracts were identified.

Figure 1

Schematic outline of adaptive optics imaging system. A beam of light enters the eye, and a small amount is reflected back out of the eye and into the optical system. Reflected light is altered by the deformable mirror for optical aberrations based on measurements made by the wave-front senor. Information about the aberrations of the wave front is processed by the control system that provides feedback to the deformable mirror

Figure 2

Raw image before analysis from the rtx 1 (from a normal subject). Note the multiple white dots corresponding to the cones

Figure 3

Cone packing density in a normal subject on the rtx 1. The encircled area shows the mean and Standard Deviation (SD) of cone density and cone spacing in the central 4° X 4°

Figure 4

Voronoi tessellation of photoreceptors (cones) in a normal subject on the rtx 1. The colour scale shows the packing density in the central 4° X 4°. The apparent low cone density depicted in the foveal centre is due to a lack of adequate resolution of the device in that region. In this patient, the mean cone count was 17428 ± 6743/mm²

Figure 5

Voronoi tessellation of cones in a 4° X 4° square of a normal subject. The color scale shows the Voronoi legend

Figure 6

Voronoi tessellation of photoreceptors (cones) in a patient with rod-cone dystrophy on the rtx 1. The colour scale shows the packing density in the superior 100 μ×100 μ (0.34° X 0.34°). In this patient, the mean cone count was 2683 ± 4006/mm²

Figure 7

High resolution image of the venule and arteriole. The black arrow points to the vessel wall (venule). Note the defocused retinal nerve fibre layer in the background