97th DOG Annual Meeting 1999
ELECTROPHYSIOLOGICAL INVESTIGATIONS ON INFLUENCES OF A SINGLE DOSE OF SILDENAFIL ON VISUAL FUNCTION
U. Kretschmann, R. Gockeln, M. Meschi, C. G. Stief, R. Winter
After administration of 100 mg Sildenafil (ViagraTM) disturbances of vision were reported in 11 % of volunteers. The purpose of this study is to test the electrophysiological correlates of this disturbances.
Patients and methods: The visual function was tested in 6 patients aged 29 - 60 with a diagnosis of erectile dysfunction before and 1 - 2 hours after a single dose of 100 mg Sildenafil. The tests included a basic ophthalmological examination, pattern reversal VEPs (check sizes of 15´, 30´, and 1°; 100%, 60%, 30% contrast; black-white and blue-yellow stimulation), fullfield ERG according to ISCEV standards, and multifocal ERG (Roland ConsultTM).
Results: In fullfield electroretinography the implicit times of the scotopic b-wave were in average 86.2 ms before and 100,9 ms after Sildenafil, the values of the dark-adapted maximal response were 43,7 ms and 53,1 ms respectively. We observed no pronounced effects on amplitudes of the scotopic b-wave, the maximal response was decreased from 463 mV to 386 mV. No effects on amplitudes and timing of oscillatory potentials and photopic responses could be observed. In the multifocal ERG the implicit times after Sildenafil were delayed in a minor degree throughout the tested field, the amplitudes were normal. The P100 implicit time of 1°check-VEP was 106,5 ms before Sildenafil and 110,33 ms after. No major changes in implicit times were observed with other check-sizes.
Conclusions: After intake of 100 mg Sildenafil the dark-adapted ERG responses were altered. The implicit time was delayed. The photopic ERG responses remained unaltered. Since Sildenafil is an inhibitor of cGMP phoshodiesterase the principle side of action within the eye seems to be the outer segments of rod photoreceptors. The changes to the therapeutic dose of 100 mg were moderate compared to the previously reported data on 200 mg doses.
Supported by DFG, Bonn (grant Sti 96/10-1)
Augenklinik und Urologische Klinik der Medizinische Hochschule Hannover, Carl-Neuberg-Str.1, D - 30625 Hannover