Anna Brouwer

10 Chapter 1 Introduction Both anatomy, which describes the structure of organisms and their parts, and histology, which describes the structure of tissues, have helped scientists and doctors tremendously in their understanding of diseases. This understanding has led to new treatments and better prognoses for many patients. However, anatomy and histology do not always correspond with function. The development and improvement of imaging techniques such as X-rays, magnetic resonance imaging (MRI), and optical coherence tomography (OCT) have improved the diagnostic capacities of doctors even more, because they help to visualize structures in a non-invasive, and 3D manner. But, even though structures can tell us a lot about a tissue, function is often far more important for patients in their daily functioning. In ophthalmology, patients can surprise their physicians with a great visual function, despite a very abnormal scan. Unfortunately, the opposite may also be true. This thesis focusses on one aspect of function: the electrophysiological function of the retina in a disease called uveitis. Uveitis Anatomy and anatomical classification of uveitis When physiologists started to examine the eye, the ocular vascular bed appeared to them to have a some-what grape-like shape, after the sclera had been peeled off. They called it uvea: the Latin word for grape. The anatomical structure that we call the uvea nowadays, comprises the choroid, the ciliary body, the pars plana, and the iris. An inflammation of the uvea is called a uveitis. Interestingly, when ophthalmologists use the term uveitis, not only an inflammation of the uvea is implied; the adjacent structures, such as the retina, vitreous and anterior chamber may also show signs of inflammation. 1 When ophthalmologists describe and classify uveitis, they try to determine the predominant site of the inflammation. This may be localized in the front, the middle, or in the back of the eye. Based on this anatomical localization, uveitis is called an anterior, intermediate, or a posterior uveitis. Sometimes no predominant site of inflammation can be defined: the entire eye appears to be inflamed. In such cases ophthalmologists call it a panuveitis. 1 Figure 1 illustrates this anatomical classification of uveitis.