Before year 1895, the doctors could only make a probable diagnosis based on what the patient could tell and it was hurt and there was no discernable change to the outside of the body. With X-ray, it was possible to see inside the patient without first cutting it, you can say that the X-ray was the starting point for diagnostic imaging.The further development of X-ray gave CT (Computed Tomography), where X-ray tubes and detectors rotate around the patient while the patient table moves. Besides CT also developed MRI (Magnetic Resonance Imaging), PET (Positron Emission Tomography) and Ultrasound. Common to these methods is that the produced 3D images.In 1990 a completely new approach for diagnostic imaging, OCT (optical coherence tomography), by measuring the phase shift and the intensity of reflected light, it provides real-time and non-destructive measurements (in vivo) a resolution of 1 to 15 microns, much higher than all other standard imaging techniques. You could say that OCT machine can be compared to ultrasound, which uses the reflection of sound waves to interpretation.The first OCT machines were of type TD (Time Domain), these had low resolution and low scanning speed. In 2005 came the SD-OCT, they had higher resolution and scanning speed, SD stands for spectral domain, SD-OCT is sometimes called FD-OCT as Fourier transformed signals and operating in the frequency domain.The development of OCT machines are only in their infancy, resolution, scanning speed and accuracy will increase all the time, this allows new uses and ways to diagnose developed. OCT can be used in such Oncology, MSD (Musculoskeletal disorders), cardiovascular medicine, teeth, nerves, but the largest field is the eye and then the back of the eye called the retina (retina).This thesis is limited to the eye, the purpose is to provide input to those who are likely to purchase an OCT-machine, but also show the measurement data OCT-machines are performing and how to use the OCT-machine more than to see age-related macular degeneration. Another aim is to increase understanding of the physics behind an OCT-machine for ease of understanding the output given.The manufacture/model that have selected for evaluation are Zeiss Cirrus 4000, Topcon 3D OCT-2000 and Heidelberg Spectralis, the reason is that there are only these three on the Swedish market and all are SD-OCT. The way to evaluate OCT-machines is to scan performance and what the various analysis programs can handle. Furthermore, each OCT-machine scans the macula and optic disk on a experimental person/ reference eye, in order to get the output of the precision, or if you want to call it repeatability, which is very important if one wants to follow a solitary disease course.The conclusion of this thesis is to OCT machines are quite similar. When it comes to ease of use when doing scans is the Cirrus is lightened by the use of the extra screen where you always look eye (iris camera), which makes it easy to adjust the sharpness and position of the mouse buttons. Topcon and Heidelberg is not difficult to use but requires more experience of the person making the OCT scans. Most measurement functions in the analysis program is Topcon and Heidelberg and best accuracy/repeatability is Heidelberg, both the macula and RFNL.OCT machine is a good tool to use on the anterior segment, but in the case the precision allows the precision used to monitor RNFL thickness changes in those with glaucoma. / <p>Validerat; 20131029 (global_studentproject_submitter)</p>