[Functional characteristics of macular telangiectasia type 2].

The first symptoms of macular telangiectasia type 2 usually occur between 50 and 70 years of age. Functional alterations topographically correspond to the morphological changes. Characteristic paracentral scotomata due to focal photoreceptor atrophy can be detected using microperimetry. The predominant paracentral functional loss may cause reading difficulties despite visual acuity in the range between 20/20 and 20/50. Visual acuity around 20/200 may occur once the paracentral photoreceptor atrophy extends centrally, or due to the development of a macular hole or a secondary neovascular membrane. Progression of functional loss can often only be detected by mapping scotoma size or occurrence using microperimetry, while visual acuity may remain unchanged.