97th DOG Annual Meeting 1999
THE OPTIC NERVE HEAD COMPONENT IN MULTIFOCAL PATTERN-ERG IN NORMALS AND GLAUCOMA PATIENTS
M. Harrer, F. Horn, M. Wisse, M. Korth
Purpose: To study the optic nerve head component described by Bearse und Sutter (1,2) in the multifocal pattern-ERG of glaucoma patients.
Patients and Methods: We examined 17 eyes of 14 normals (10 right, 7 left, mean age 39,1±10,6, 25-59 years) and 9 eyes of 9 glaucoma patients (3 right, 6 left, mean age 52,3±9,12, 43-68 years) in advanced stage (MD > 5,5) with the multifocal ERG technique (RETIScan system, Roland Consult, Brandenburg, Germany) in mydriasis (tropicamide). We used a stimulus pattern of 37 hexagons, each consisting on 6 triangles (alternating black and white areas). The pattern changes in accordance to the structure of a corrected binary m-sequence (length 512, 10 cycles with 39 seconds each). For all recordings DTL-electrodes were used (reference electrode at the canthus, earlobe grounded). Screen distance was chosen to stimulate a visual field of about 60º. The signals were bandpass filtered (10-100 Hz). The recordings of areas of similar nerve fiber length with respect to the optic nerve head were averaged. An iterative algorithm has been implemented in MatLab (The Mathworks Inc., Natick, USA) to separate possible optic nerve head components from retinal components.
Results: The averaged recordings in normals showed an absolute maximum at a latency of about 31 ms and a following relative maximum (at about 39 ms in the first averaged ring close to the optic nerve head), whose latency increases by about 10 ms with increasing distance of stimulation from the optic nerve head. The iterative algorithm separated the potential wave forms in their retinal (at 31,45±1,8 ms) and optic nerve head contri-butions (from 39,5±2,7 ms close to the optic disc to 49,8±1,4 ms in the periphery). In 7 of the 9 examined glaucoma patients we found the optic nerve head components to be significantly reduced and/or delayed or to be absent. This was shown in the averaged recordings and also in the wave forms of retinal and optic nerve head components after separation processing.
Conclusions: In accordance with studies of Bearse und Sutter (1,2) we would interpret the second relative maximum as an optic nerve head component. As this component could be isolated in all normals and is changed in the glaucoma patients, it could be an indicator for functional optic nerve head damage in glaucoma diseases.
1. Bearse et al., Vision Science and Its Applications, 1997, Vol. 1, pp. 280-283
2. Sutter et al., Vision Research, 1999, 39, 419-436
Supported by Deutsche Forschungsgemeinschaft (SFB 539)
Department of Ophthalmology, Univ. Erlangen-Nürnberg, Schwabachanlage 6,