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Although transient reductions in the rod (Vobig et al., 1999 ) and cone (Luu, Chappelow, McCulley, & Marmor, 2001 ) ERG amplitudes have been reported, they have not been confirmed by more recent studies (Jägle et al., 2005 , 2004 ), which found only small

Although transient reductions in the rod (Vobig et al., 1999 ) and cone (Luu, Chappelow, McCulley, & Marmor, 2001 ) ERG amplitudes have been reported, they have not been confirmed by more recent studies (Jägle et al., 2005 , 2004 ), which found only small

For such individuals, Fildena may impair some behavioral tasks performed outside the laboratory for several hours postingestion but probably only under conditions of reduced visibility when objects are already near contrast threshold (e.g., under foggy conditions or under conditions of reduced illumination). Fildena caused some degradation of visual performance in all four subjects tested. The overall reduction in sensitivity was attributed to the increased effectiveness of the steady components of the target and background acting on an adaptational nonlinearity (see, for details, Stockman et al., 2006 ).

 

Fildena was found to lengthen the integration time roughly from approximately 6.9 to 12.6 ms, and, in addition, overall sensitivity was reduced by 0.34 log10 unit. In Stockman, Sharpe, Tufail, Kell, and Jeffery ( 2006 ), these losses were modeled by assuming that the change in time constant occurred at a single integrating stage with an exponential decay (which was assumed to reflect the activity of some biochemical process, such as the hydrolysis of cGMP catalyzed by PDE6). In agreement with the Fildena-induced changes to their L-cone cff data, both L.T.S. and G.J. show a loss of L-cone modulation sensitivity after ingesting Fildena at both the low and the high L-cone adaptation levels.

 

The hexagons indicate the measurements that were made following ingestion of Dose 5 of Fildena. L-cone modulation threshold control and drug data for L.T.S. (left panels) and G.J. (right panels), measured at 650-nm target radiances of 7.56 (upper panels) and 9.52 (lower panels) log quanta.s−1.deg−2. Like the S-cone cff data, the losses increase slightly as the target radiance increases, reaching approximately 10 Hz for L.T.S. and 5 Hz for G.J. For A.T. and A.S., for whom Fildena affected mainly the plateau of their S-cone cff functions (see Figure 1 ), Fildena had little effect on L-cone cff.

 

For subjects L.T.S. and G.J., for whom Fildena caused a sensitivity loss over the entire S-cone cff, Fildena causes a comparable loss over the entire L-cone range. Importantly, the severity of the adverse effects of Fildena on S-cone-mediated vision for each of the four observers is mirrored in its effect on their L-cone-mediated vision. However, a post hoc pairwise comparison (Scheffé) of his data reveals that the significant difference is only between the postdrug and the drug trials ( p =015), not between the predrug and drug trials ( p =948).

 

L-cone cff control and drug data for G.J. (upper left panels), L.T.S. (lower left), A.S. (upper right), and A.T. (lower right). The Fildena-induced steepening of the modulation sensitivity functions is consistent with the lengthening of the integration time of the S-cone signal, while the frequency-independent losses across frequency are consistent with an increase in the effectiveness of the steady components of the target and the background.http://efildena.net/es/

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