**1.2 AO scanning laser ophthalmoscopy**

AO scanning laser ophthalmoscope provides a higher contrast relative to AO flood illumination by recording scattered light from a focused beam across the

retinal surface through confocality. A pinhole conjugated to the focal retinal plane removes beams of light whose origin is outside the point spread function. By modifying the pinhole size, different transversal and axial resolutions of the system can be obtained, allowing imaging of the retinal structures (nerve fiber layers, photoreceptors, blood vessels). Its accuracy is increased by the AO constituent. In addition to this, continuous scanning allows the study of larger areas at a superior rate relative to conventional fundus imaging [22]. AOSLO is being used in highresolution imaging, eye-tracking, laser modulations setups, psychophysics and electrophysiology studies [23].

### **1.3 AO optical coherence tomography**

OCT started to be used as a retinal imaging tool in 1991, while the association of AO technology with the OCT was first introduced more than 10 years ago [24]. An advantage of the AOOCT its ability to adjust images in all three coordinates (both axial and lateral) and to offer great visualization of individual cells because of its outstanding axial resolution. Axial resolution increases with the bandwidth of the imaging coherent light source [23]. Time-domain OCT might reach an axial resolution of 2–3 μm, whereas spectral-domain OCT an axial resolution between 2.1 and 2.5 μm [25]. Nevertheless, individual cells cannot be visualized because of low acquisition speed and low lateral resolution (>15 μm). Swept source OCT has a higher acquisition speed, but with an axial resolution of 5.3 μm and a lateral one of 20 μm. Lateral resolution is influenced by the eye's aberrations effect on focal spot size. After coupling AO with OCT imaging, the lateral resolution of the system reached 2–3 μm [26], and 3D imaging of retinal structures (RPE, ganglion cells, lamina cribrosa, nerve fiber layer) was achieved [27].
