Aberdeen Biomedical Imaging Centre
Research Facility: Scanning Laser Opthalmoscope (SLO)
The ophthalmology imaging group is actively involved in two different areas.
- Development of novel optical instrumentation for clinical and biological applications.
- Image processing and quantitative image analysis.
Ophthalmic instrumentation
The group has developed novel optical instrumentation for imaging the eye. A scanning laser ophthalmoscope (SLO) was designed, constructed and used for imaging various pathological conditions. Examples of images are shown below.
Macular drusen: Drusen are waste products of metabolism accumulated under the retina. Drusen are associated with with age-related macular degeneration and they appear as yellow spots. If they are buried under a layer of tissue, then they are not easily detected. With SLO, it is possible to clearly see them in the indirect mode where a confocal aperture allows only scattered light.
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| Direct mode image of drusen | Indirect mode image of drusen |
Macular hole: It is a full-thickness defect which occurs in the visual centre of the retina. The retina is pulled away from the central part of the retina known as fovea causing loss of central vision. Fluid is usually filled around the hole. Sometimes, it is difficult to see the hole clearly with the fundus camera. The SLO with the use of an infrared laser can highlight the hole and the fluid around the hole.
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| Fundus camera image of macular hole | SLO infrared image of the same hole |
Colour Scanning Laser Ophthalmoscope: This is a patented technique of using three lasers, red, green and blue to capture a true colour image of the retina. The major advantages are reduced light intensity to image the retina and better contrast images due to single point scanning which reduces the effect of scattered light.
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| Fundus image of a patient with optic disc drusen | SLO image of the same patient |
Cell tracking using SLO angiography: Leukocytes play a central role in the pathogenesis of retinal and choroidal inflammatory disease. The infiltration of these cells into retinal and choroidal tissues may lead to tissue destruction and vision loss. Such infiltration requires the cells to pass from the intravascular space into extravascular space. However, until recently it was not possible to observe this movement of the leukocytes in-vivo.
The scanning laser ophthalmoscope (SLO) provides real-time images of the ocular fundus, which may be used to visualise leukocyte traffic in-vivo by labelling leukocytes with a fluorescent dye. The real-time nature of the method allows the velocity of the cells to be measured. Software was developed to automatically locate cells from their appearance on the interlaced image frames, measure the distance travelled and calculate the cell velocities in different parts of the retina.