May 2006
Volume 47, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2006
Viagra® Can Slow the Visual Response to Flicker and Impair Visual Sensitivity
Author Affiliations & Notes
  • A. Stockman
    Institite of Ophthalmology, University College London, London, United Kingdom
  • L.T. Sharpe
    Institite of Ophthalmology, University College London, London, United Kingdom
  • A. Tufail
    Moorfields Eye Hospital, London, United Kingdom
  • P.D. Kell
    Archway Sexual Health Clinic, Whittington Hospital, London, United Kingdom
  • G. Jeffery
    Institite of Ophthalmology, University College London, London, United Kingdom
  • Footnotes
    Commercial Relationships  A. Stockman, None; L.T. Sharpe, None; A. Tufail, None; P.D. Kell, None; G. Jeffery, None.
  • Footnotes
    Support  Wellcome Trust
Investigative Ophthalmology & Visual Science May 2006, Vol.47, 5356. doi:
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      A. Stockman, L.T. Sharpe, A. Tufail, P.D. Kell, G. Jeffery; Viagra® Can Slow the Visual Response to Flicker and Impair Visual Sensitivity . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5356.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: : As an undesirable side effect, sildenafil citrate (Viagra®) partially inhibits the phosphodiesterase enzyme, PDE6, which plays an essential role in phototransduction. PDE6 not only activates the visual transduction cascade, but also controls the speed (or integration time) of the visual response. Reports of any detrimental effects on visual performance, however, have so far been largely inconclusive or anecdotal; but this may be due to the use of insensitive and/or ill–matched visual tests. Here, we adopt standard tests sensitive to the slowing of the visual response likely to result from the inhibition of PDE6 by Viagra.

Methods: : Four subjects orally ingested standard, therapeutic, 100 mg doses of Viagra. Their temporal vision was then measured using conventional psychophysical measures of sensitivity and resolution. The target and background conditions were chosen to isolate either the short–wavelength–sensitive (S–) or the long–wavelength–sensitive (L–) and/or middle–wavelength–sensitive (M–) cones.

Results: : We find that Viagra causes mild to moderate transient losses in human temporal sensitivity. All four subjects showed clear sensitivity losses when their vision was mediated by S–cones. Those subjects who showed large S–cone losses also showed comparable losses when their vision was mediated by the L– and/or M–cones. The frequency–dependent L–cone sensitivity losses caused by the inhibition of PDE6 by Viagra are consistent with an almost doubling of the time over which visual events are normally integrated (at the particular level tested, from c. 6.9 to 12.6 ms, assuming a single integration stage).

Conclusions: : Viagra caused some transient losses in visual sensitivity in all subjects. Though it may compromise vision in the more affected individuals under some conditions, Viagra also provides a unique tool for pharmacologically investigating the role of PDE6 in human light adaptation in vivo.

Keywords: temporal vision • photoreceptors: visual performance • drug toxicity/drug effects 
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