Does sildenafil cause eye problems? Sildenafil, widely known as Viagra, is a phosphodiesterase type 5 (PDE5) inhibitor used to treat erectile dysfunction and pulmonary arterial hypertension. Whilst generally well-tolerated, sildenafil can affect vision in some individuals due to its mild inhibitory effect on PDE6 enzymes in the retina. Common visual side effects include blurred vision, light sensitivity, and temporary colour perception changes, particularly a blue-green tinge. These effects are typically mild, dose-related, and resolve within hours. Rare but serious ocular complications, such as sudden vision loss, require immediate medical attention. Understanding the risks and warning signs is essential for safe use.

Does Sildenafil Cause Eye Problems?

Sildenafil, commonly known by the brand name Viagra, is a phosphodiesterase type 5 (PDE5) inhibitor primarily prescribed for erectile dysfunction and pulmonary arterial hypertension. Whilst sildenafil is generally well-tolerated, it can affect vision in some individuals due to its mechanism of action. The drug works by inhibiting PDE5 enzymes, which increases blood flow to specific tissues. However, sildenafil also has a mild inhibitory effect on PDE6 enzymes found in the retina, which can lead to temporary visual disturbances.

The most commonly reported eye-related side effects are generally mild and transient. These include blurred vision, increased sensitivity to light (photophobia), and changes in colour perception—particularly a blue-green tinge to vision or difficulty distinguishing between blue and green colours. According to the Summary of Product Characteristics (SmPC), these visual effects are typically dose-related and transient, usually resolving within a few hours as the drug is metabolised.

Clinical studies indicate that visual side effects are common (affecting between 1 in 10 and 1 in 100 patients) at standard doses of sildenafil (25–100 mg). The incidence increases with higher doses. Most cases involve temporary colour vision changes or mild visual blurring that does not require medical intervention. However, whilst rare, more serious ocular complications have been documented in the medical literature, including non-arteritic anterior ischaemic optic neuropathy (NAION) and retinal vascular occlusion. It is important to note that establishing a definitive causal relationship between sildenafil and these serious conditions remains challenging, as many affected individuals have pre-existing cardiovascular risk factors that independently increase their risk of such events.

It is worth noting that sildenafil is contraindicated in patients taking nitrate medications due to the risk of severe hypotension.

Serious Eye Side Effects and Warning Signs

Whilst most visual disturbances associated with sildenafil are benign and self-limiting, there are rare but serious ocular complications that require immediate medical attention. Non-arteritic anterior ischaemic optic neuropathy (NAION) is the most concerning condition potentially linked to PDE5 inhibitor use. NAION occurs when blood flow to the optic nerve is suddenly reduced, resulting in painless vision loss that typically affects one eye. The condition presents as a sudden decrease in vision, often noticed upon waking, and may be accompanied by an alteration in the visual field.

Another serious concern is retinal vascular occlusion, which involves blockage of blood vessels supplying the retina. This can manifest as sudden, painless vision loss or the appearance of a dark curtain or shadow across the visual field. Central serous chorioretinopathy, characterised by fluid accumulation under the retina, has also been reported in rare cases following sildenafil use, leading to distorted or blurred central vision. However, a causal relationship between sildenafil and these rare conditions has not been definitively established.

Warning signs that require urgent medical assessment include:

• Sudden loss of vision in one or both eyes

• Persistent visual disturbances lasting beyond 24 hours

• Appearance of flashing lights or floaters

• A curtain-like shadow across the visual field

• Severe eye pain or redness

• Double vision that does not resolve

If you experience any of these symptoms whilst taking sildenafil, stop taking sildenafil immediately and seek urgent medical care. Contact NHS 111, attend an eye casualty department, or see an optometrist for same-day assessment. For sudden vision loss, go to your nearest Accident & Emergency department. Do not take further doses of sildenafil or any other PDE5 inhibitor until evaluated by a healthcare professional. Prompt treatment may help preserve vision.

Who Is at Higher Risk of Eye Problems with Sildenafil?

Certain patient populations face an elevated risk of developing ocular complications when using sildenafil. Understanding these risk factors is essential for safe prescribing and informed patient decision-making. Individuals with pre-existing cardiovascular disease are at increased risk, as conditions such as hypertension, diabetes mellitus, hyperlipidaemia, and coronary artery disease are independent risk factors for both erectile dysfunction and ischaemic optic neuropathy. The overlap of these conditions makes it challenging to determine whether sildenafil directly causes NAION or whether it occurs coincidentally in a high-risk population.

Patients with anatomical variations of the optic disc, particularly a "crowded" optic disc with a small cup-to-disc ratio, appear more susceptible to NAION. This structural characteristic reduces the space available for the optic nerve fibres and may compromise blood flow under certain conditions. Age is another significant factor, with men over 50 years being at higher risk of serious ocular events. Additionally, individuals with a history of NAION in one eye face a substantially increased risk of developing the condition in the fellow eye.

Other risk factors include:

• Smoking and tobacco use

• Obstructive sleep apnoea

• Previous episodes of temporary vision loss

• Concurrent use of medications that may affect blood pressure

• Renal or hepatic impairment (which affects drug metabolism)

Patients with retinitis pigmentosa should note that sildenafil is not recommended in this condition, as stated in the SmPC. This inherited retinal disorder involves retinal degeneration, and sildenafil's effect on retinal PDE6 enzymes may theoretically exacerbate visual symptoms.

It's important to note that sildenafil is absolutely contraindicated with nitrate medications due to the risk of severe hypotension, which is a general safety concern rather than specifically an ocular risk. The SmPC recommends that prescribers consider the cardiovascular status of patients before initiating sildenafil therapy, particularly in those with multiple risk factors.

When to Seek Medical Advice About Vision Changes

Knowing when to seek medical advice regarding vision changes whilst taking sildenafil is crucial for preventing potential complications and ensuring appropriate management. Immediate emergency care is warranted for sudden vision loss, whether partial or complete, in one or both eyes. This constitutes a medical emergency regardless of whether it occurs during or after sildenafil use. Similarly, the sudden onset of persistent visual field defects, such as a curtain or shadow obscuring part of your vision, requires urgent ophthalmological assessment.

The appearance of new flashes or floaters should prompt same-day urgent assessment by an optometrist or at an eye casualty department. These symptoms can indicate retinal problems that require prompt evaluation. Call NHS 111 if you're unsure where to go or if it's outside normal hours.

For less severe symptoms, the timeframe and persistence of visual disturbances should guide your decision to seek medical advice. Mild, transient colour vision changes or slight blurring that resolves within a few hours of taking sildenafil are generally expected side effects and do not typically require immediate medical attention. However, if these symptoms persist beyond 24 hours, worsen with subsequent doses, or cause significant functional impairment, you should contact your GP for review. Your doctor may need to adjust your dosage, switch to an alternative medication, or arrange specialist referral.

Contact your GP promptly if you experience:

• Visual disturbances that do not resolve after the drug has been metabolised

• Progressive worsening of vision with continued use

• Persistent headache accompanied by visual changes

• Concerns about the appropriateness of sildenafil given your medical history

Before your appointment, document the timing, duration, and nature of your visual symptoms, as well as the dose of sildenafil taken. A comprehensive ophthalmological examination may include visual acuity testing, visual field assessment, and fundoscopy to evaluate the optic disc and retina. Your healthcare provider will determine whether sildenafil remains appropriate for you or whether alternative treatments for erectile dysfunction should be considered.

If you experience concerning visual symptoms, do not take further doses of sildenafil until you have been medically assessed, but continue taking other regular prescribed medications unless advised otherwise by a healthcare professional. You can report any suspected side effects from sildenafil via the MHRA Yellow Card scheme.

Frequently Asked Questions