Muller and retinal pigment epithelium cells normally release immunosuppressive factors, but certain combinations of cytokines may stimulate retinal pigment epithelium cells to release factors encouraging inflammation.Generally, mild intraocular inflammation results in a small, discrete, evanescent lesions. Larger dots, having less discrete borders, are the result of high intensity intraocular inflammation. In essence, an immune response with the normal amount and appropriate cytokine release will result in small white dots and a misregulated response eventually will produce scarring of the retinal tissue. Treatment is required in the latter case to combat loss of vision. The white dots usually disappear naturally. Corticosteroids have been shown to speed up this process. The differences in the immune response of each patient may contribute to the differences seen between the white dot syndromes. Distinct diseases
Due to the number of common features among the multiple syndromes, many suggest that the white dot syndromes are not distinct and represent a spectrum of one disease. Gass described the AZOOR complex which consists of multiple evanescent white dot syndrome, nultifocal choroiditis, punctate inner choroiditis, acute idiopathic blind spot enlargement, acute macular neuroretinopathy, acute annular outer retinopathy, and acute zonal occult outer retinopathy. He suggested these diseases represent one disease due to common factors such as a high occurrence in females, unexplained visual field loss, and reduced electroretinographic amplitudes. Reddy et al. conducted a study on the blind spots in multifocal choroiditis, punctate inner choroiditis, multiple evanescent white dot syndrome, and diffuse subretinal fibrosis syndrome. Clinical and electroretinographic evidence suggested the diseases are distinct.
Punctate inner choroiditis is one of the so-called White dot syndromes which come under the heading posterior uveitis. The appearance of punctate (punched out) areas is at the level of the inner choroid. These lesions are typically located centrally at the back of the eye, or the posterior pole. Serpiginous choroiditis
Serpiginous choroiditis, also known as geographic or helicoid choroidopathy, is an uncommon chronic progressive inflammatory condition affecting adult men and women equally in the second to seventh decades of life. Nature of white dots
The white dots of the white dot syndromes are lesions that vary in their location in the fundus and in most cases tend to disappear. White dots appear early in the disease stages of punctate inner choroiditis and multiple evanescent white dot syndrome. In this case, the white dot is localized in the posterior pole, small (between 25 and 100 μm), and do not clump together. In contrast, white dots appear later in the disease stages of birdshot choroidopathy, serpiginous choroiditis, and acute posterior multifocal placoid pigment epitheliopathy. The white dots in these diseases may be present throughout the entire fundus, larger (50 to 500 μm), and tend to clump together. Among all these syndromes, there exists some retinal vessel inflammation. The differences in the dots are usually in the size, position, and depth of the lesion within the choroid.The way in which the dots form in some of the white dot syndromes has been reported. The dot appears as a small granuloma which is composed of lymphocytes and macrophages.