**2. Problem statement**

A variety of retinal diseases such as AMD, central serous chorio-retinopathy, macular hole, vitreo-macular interface syndrome and diabetic maculopathy have taken advantage from the introduction of OCT in the clinical practice. Among these, AMD is the ocular condition that benefited the most from the enormous advantages offered by OCT imaging techniques, in terms of diagnosis, response to treatment and monitoring. Future progress in OCT techni‐ ques has already brought and is expected to bring new insights in understanding the patho‐ physiology of this potentially blinding disease. With the aim of defining the role of OCT in the assessment and follow up of AMD, the theoretical principles at the foundation of this retinal imaging technique are outlined, making a clear distinction between TD-OCT and SD-OCT methods. The advantages of SD-OCT over TD-OCT methods are revealed. The role of OCT in AMD management is emphasized by the description of typical OCT aspects in vari‐ ous AMD lesions: macular edema, CNV membranes, occult and classic choroidal neovascu‐ larization, pigment epithelial detachments (PED), external retinal cysts, vitreo-macular adhesions. OCT has a crucial role in monitoring AMD and establishing the indication of treatment with anti-VEGF intravitreal injections in the wet form of the disease. The place of OCT in the evaluation of AMD patients is completed by its comparative presentation with retinal biomicroscopy, fluorescein and indocyanine green angiography. The impact of OCT in AMD diagnosis and monitoring is illustrated with examples of various aspects that AMD can display, both with a TD-OCT device (Stratus OCT) and a SD-OCT one (Cirrus OCT). Fu‐ ture directions in OCT techniques development close the current presentation.

(OCT and ultrasounds) are similar, but OCT uses light instead of sound. The primary differ‐ ence between ultrasonic and optical imaging derivates from the different speed of sound and light. The light propagates nearly a million of times faster than sound, which allows the obtaining of measurements resolutions in the range of 10 μm or less at the posterior pole of the eye. Also, the use of light makes the examination more comfortable for the patient, as

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The device operates as a fundus camera: a condensing lens of +78 dioptres is used so that the retina could be imaged in the same plane with the instrument. The magnification of the reti‐ nal image is determined by two factors: the refractive power of the condensing lens and the magnification of the ocular. At the lowest magnification, the typical field of view is 30º. If the visual acuity of the eye to be examined is very low and therefore the patient has fixation problems, a guiding light can be placed in front of the fellow eye, in order to stabilize the eyes during image acquisition. With the first generation OCT devices, pupil dilation was recommended with the aim of obtaining high quality images, but the latest generation OCT machines deliver good quality pictures with a 3-mm diameter pupil. The OCT technology can be limited by various conditions of the eye: lens or vitreal opacities, subretinal haemor‐

OCT is based on the interferometry that uses a low-coherence light in order to measure the difference between the reflected light waves from the examined tissue and that from a refer‐ ence path [9]. The light reflected from the retinal structures interferes with the light of the reference beam. The detection of echoes resulting from this interference is measuring the

*Axial resolution.* Axial resolution is given by the bandwdith of the light source and the level of coherence that depends upon the central wavelength [10]. The light from a superluminis‐ cent diode has long coherence that generates images with poor axial resolution. With shortcoherence light, interference is possible over short distances and therefore high axial

*Transverse resolution.* The transverse resolution is determined by the size of the light spot that can be focused on the retina. The best structural resolution is obtained when the light is focused on the tissue to be examined. The absorbtion of central light by the tissue of interest

TD-OCT produces two-dimensional images of the sample internal structure. An A-scan rep‐ resents a reflectivity profile in depth which is gradually built up over time by moving a mir‐

**3.5. Time Domain (TD-OCT) versus Spectral Domain (SD-OCT)**

OCT is applied by two main methods: TD-OCT and SD-OCT.

there is no need for physical contact with the examined eye [8].

**3.3. OCT Instrumentation for retinal imaging**

rhages, lack of foveal fixation, nystagmus [8].

**3.4. Principle of OCT**

light echoes versus depth [9,10].

resolution is possible [10].

must also be considered [10].
