Sildenafil and the Retina: Cyanopsia and Beyond

Sildenafil and the retina are linked by a shared enzyme, because the drug also blocks a photoreceptor phosphodiesterase.

The result is a transient blue tinge to vision in some users.

Therefore, patients who report color changes after a dose usually have a benign, reversible effect.

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Why Sildenafil and the Retina Interact

Sildenafil inhibits PDE5 in the penile vasculature, and it also inhibits PDE6 in photoreceptors.

PDE6 breaks down cyclic GMP in the phototransduction cascade.

Also, sildenafil is only about ten times more selective for PDE5 than for PDE6, so retinal effects appear at higher plasma levels.

Laties and Zrenner reviewed the data and found changes in the electroretinogram that reverse within hours.

Visual Symptoms From Sildenafil and the Retina

• Cyanopsia, which is a blue tinge to vision
• Increased brightness and light sensitivity
• Blurred vision for a few hours

Marmor and Kessler found that the symptoms peak near one hour and resolve by the next day.

The effects are dose related, and they do not damage the retina.

Vascular Events and Sildenafil

Cases of nonarteritic anterior ischemic optic neuropathy have been reported after use (see NAION).

Fraunfelder and colleagues documented these reports, but the causal link is unproven.

Also, many men who take the drug share vascular risk factors with NAION.

Case reports also describe central serous chorioretinopathy and retinal vascular occlusion.

Counseling on Sildenafil and the Retina

Advise patients to stop the drug and seek care for sudden vision loss.

Use caution in patients with retinitis pigmentosa, since the disease involves PDE6 mutations in some families (see retinitis pigmentosa).

Tadalafil inhibits PDE6 far less, so color effects are rare with it.

Dose and Timing of Retinal Effects

Visual symptoms usually begin within one to two hours of the dose.

They occur more often with higher doses than with 25 to 50 mg.

Also, they resolve as the plasma level falls.

Therefore, patients who take the drug repeatedly can usually continue after counseling.

Safety Advice for Sildenafil and the Retina

Document the symptom, and record visual acuity, color vision, and the fundus if the complaint persists.

Advise that persistent or one-sided blurred vision needs examination.

Also tell patients that the drug is not known to damage the healthy retina.

Evidence for retinal vascular occlusion comes from case reports, so a firm link has not been shown.

Finally, review all PDE5 inhibitors in patients with prior ischemic optic neuropathy, and involve the prescriber in the decision.

Electroretinogram Changes With Sildenafil

Laties and Zrenner summarized studies in healthy volunteers.

At doses above the usual range, the b-wave amplitude fell, and the changes reversed within hours.

Therefore, the effect is functional, and it does not signal retinal damage.

Questions About Sildenafil and the Retina

Patients ask whether the drug can harm the eyes over years.

The available data show no clear long-term retinal damage in healthy users.

Azzouni and Abu Samra reviewed the vision-threatening events and found that a causal link has not been proven.

However, report any new event so that safety data keep growing.

Practical Points for the Clinician

Ask men with visual complaints about erectile dysfunction drugs, because they may not volunteer it.

Also record the dose and the timing of the last tablet.

Then examine the fundus, and obtain optical coherence tomography when vision is reduced.

Which Patients Need Extra Care

Patients with retinitis pigmentosa, a history of ischemic optic neuropathy, or a crowded optic disc deserve discussion.

Also review patients with severe vascular disease.

Because the data are limited, decisions should be individual, and the prescriber should be part of them.

Other Drugs With Visual Effects

Several other drugs change color vision or cause photopsia, including digoxin and some antiepileptics.

Therefore, take a full drug history in any patient with new visual symptoms.

Key Points for the Clinician

Blue-tinted vision after the drug is common at high doses and is reversible.

Also, serious events are rare and unproven as drug effects.

Because patients worry, explain the mechanism in simple terms.

Then advise prompt examination for any persistent change.

Finally, remember that the underlying vascular risk matters more than the tablet itself.

Documenting a Visual Event

Record the dose, the time of the symptom, and how long it lasted.

Also note whether one eye or both were affected.

Because the details separate benign effects from ischemic events, take them carefully.

Then arrange an examination for any symptom that does not settle within a day.

For the latest studies, see the PubMed results for sildenafil and the retina.

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References

1. Marmor MF, Kessler R. Sildenafil (Viagra) and ophthalmology. Surv Ophthalmol. 1999;44:153-162.
2. Laties A, Zrenner E. Viagra (sildenafil citrate) and ophthalmology. Prog Retin Eye Res. 2002;21:485-506.
3. Fraunfelder FW, Pomeranz HD, Egan RA. Nonarteritic anterior ischemic optic neuropathy and sildenafil. Arch Ophthalmol. 2006;124:733-734.
4. Azzouni F, Abu Samra K. Are phosphodiesterase type 5 inhibitors associated with vision-threatening adverse events? A critical analysis and review of the literature. J Sex Med. 2011;8:2894-2903.