Synopsis of different sensory examinations in early glaucoma diagnosis

Background: Of the three glaucoma-defining criteria intraocular pressure, o ptic-nerve damage, and visual field damage, the latter is a tate symptom. T herefore, in order to improve an early sensory diagnosis, new tests are nec essary, it is the aim of the present paper to test new sensory methods, to rank them in an order of sensitivity, and to base them on possible pathophy siological mechanisms. Patients and methods: The tests were carried out in subjects of the Erlange n Glaucoma registry: Normals, patients with ocular hypertension, and patien ts with open-angle glaucoma without or with field defects. The tests are de signed to preferentially probe the function of different groups of ganglion cells. Psychophysical methods: Temporal contrast sensitivity in a ganzfeld as "Ertangen flicker test" and spatio-temporal contrast sensitivity to tes t Magno-cell function. Electrophysiological methods: Pattern-reversal elect roretinogram with a luminance-contrast pattern to test Magno- cell function , color-contrast pattern electroretinogram for Parvo-cell function, and blu e-on-yellow visual evoked potential to test the "blue-sensitive" pathway. Results: The most sensitive test is the temp.CS, it is significantly reduce d in OHT (p<0.01). The spatio-temp.CS is reduced in perimetric stages (p<0. 01). The BY-VEP is altered in the preperimetric stage (p<0.01), the PR-ERG in perimetric stages (p<0.01). The CC-ERG is reduced in even later stages. These results are in agreement with the hypothesis that tests selective for non-redundant neurons are of early diagnostic value. Multivariate analyses increase the early diagnostic value when different functions are tested in combination. Conclusions: When a particular test is taylored to the the special needs of certain groups of ganglion cells sensory defects can be observed before th e occurrence of optic-nerve damage (OHT). The most sensitive psychophysical test is the "Erlangen flicker test" which is a screening test selective fo r M cells. The most sensitive electrophysiological test is the BY-VEP testi ng the blue-sensitive ganglion cells.