Does Cialis Affect Eye Pressure and Vision?

Tadalafil, sold as Cialis, can affect both eye pressure and vision, though the risks are lower than those associated with some other erectile dysfunction drugs and serious eye problems remain uncommon at standard doses. The drug’s chemical design gives it a notable advantage in sparing the retinal enzyme most responsible for visual side effects, but it is not entirely off the hook. Large-scale studies have linked its use to modest increases in intraocular pressure, reduced retinal blood vessel density with long-term use, and rare but serious conditions including sudden vision loss from impaired blood flow to the optic nerve.

Why Tadalafil Spares the Retina More Than Sildenafil

All drugs in the PDE5-inhibitor class work by blocking the enzyme phosphodiesterase type 5, which relaxes smooth muscle in blood vessel walls. The trouble is that a closely related enzyme, PDE6, is the workhorse of light detection in the retina’s photoreceptor cells. When a drug meant for PDE5 accidentally blocks PDE6 as well, it can disrupt the normal signaling cascade that converts light into a neural signal, producing the blue-tinged vision, light sensitivity, and blurriness that some users report.

Tadalafil is far more selective for PDE5 over PDE6 than sildenafil or vardenafil. Laboratory measurements show tadalafil has a selectivity ratio of roughly 210-fold for cone PDE6 and 640-fold for rod PDE6, meaning it takes hundreds of times more drug to interfere with the retinal enzyme than with the target enzyme in blood vessels.¹ Molecular modeling puts this selectivity even higher, around 1,020-fold, compared with sildenafil’s poor discrimination between PDE5 and PDE6.² In practical terms, sildenafil’s half-maximal inhibitory concentrations for PDE5 and PDE6 are in a similar range (about 6 and 74 nanomolar, respectively), while tadalafil’s corresponding figures are roughly 5 nanomolar for PDE5 versus 5,100 nanomolar for PDE6.²

This selectivity difference is why sildenafil users commonly report a temporary blue tint to their vision or increased light sensitivity, while those symptoms are unusual with tadalafil. The transient visual disturbances linked to PDE5 inhibitors as a class, including blurred vision and a blue or green color shift, are primarily a PDE6 story. Tadalafil’s chemistry largely sidesteps that particular problem, but as we will see, it introduces other ocular considerations through its effects on blood vessels.

Effects on Intraocular Pressure

Because tadalafil relaxes smooth muscle in blood vessel walls throughout the body, it increases blood flow to vascular beds that include the eye. One consequence is a rise in intraocular pressure (IOP), the fluid pressure inside the eyeball. In an animal study using sheep as a model, both sildenafil and tadalafil raised IOP from a baseline of about 9 millimeters of mercury to around 11 within an hour. What set tadalafil apart was its duration: because the drug stays active in the body far longer than sildenafil, IOP remained 1.6 to 1.9 times higher than normal for at least 48 hours and did not return to baseline for about four days.³ Researchers attributed this to vasodilation allowing more plasma-like fluid into the front chamber of the eye.

A large multinational cohort study published in 2025 looked at whether this pressure effect translates into a real-world glaucoma risk. Among patients taking tadalafil for lower urinary tract symptoms, there was a roughly 22 percent higher risk of developing glaucoma over five years compared with non-users. The elevated risk extended to ocular hypertension (about 32 percent higher) and primary open-angle glaucoma (about 33 percent higher). Interestingly, no increased risk was found for low-tension or primary angle-closure glaucoma, suggesting the mechanism is specifically related to fluid pressure rather than other forms of optic nerve damage.⁴

These are population-level findings, and the absolute risk remains small. But if you already have elevated eye pressure or early-stage glaucoma, the sustained IOP bump from tadalafil’s long half-life is worth discussing with your eye doctor, especially if you take the drug daily rather than as needed.

Changes in Retinal Blood Vessels With Long-Term Use

A prospective study using optical coherence tomography angiography, a high-resolution imaging technique that maps tiny blood vessels in the retina, found measurable differences in long-term tadalafil users compared with matched controls who had never taken the drug. Vessel density in both the shallow and deep layers of the retinal capillary network was significantly reduced in tadalafil users. The same pattern appeared in the radial peripapillary capillary network, the mesh of tiny vessels surrounding the optic nerve head.⁵

This finding is somewhat counterintuitive. Tadalafil is a vasodilator, so you might expect it to increase blood flow. The researchers speculated that chronic vasodilation could lead to vascular remodeling over time, where sustained changes in flow dynamics cause some capillary beds to thin out. Whether these reductions in vessel density lead to functional vision problems is still an open question, and the study did not report that participants had noticeable visual symptoms. Still, the structural changes are real and detectable, and they raise legitimate questions about what years of daily use might do to the retinal microvasculature.

Rare But Serious Vision Threats

The most alarming eye-related side effect linked to PDE5 inhibitors is nonarteritic anterior ischemic optic neuropathy (NAION), a condition in which blood supply to the optic nerve is suddenly compromised, leading to painless but often permanent vision loss in one eye. Case reports have documented this occurring in tadalafil users, including a patient taking 40 milligrams daily for pulmonary arterial hypertension whose vision returned to normal only after the drug was stopped.⁶ Other case reports have similarly described NAION developing after tadalafil use.⁷

A case-control study tried to quantify this risk more rigorously. Overall, men with NAION were not significantly more likely to report having used Viagra or Cialis than similarly aged controls. But when the researchers looked at subgroups, a striking pattern emerged: among men with a history of heart attack, the odds of NAION were roughly 11 times higher in those who had used these drugs. A similar trend appeared in men with high blood pressure, though it fell short of statistical significance.⁸ The implication is that cardiovascular risk factors act as force multipliers for an already rare event.

Beyond NAION, tadalafil has been linked to central serous chorioretinopathy (CSCR), a condition where fluid accumulates under the retina, causing a blister-like detachment at the macula and blurry or distorted central vision. PDE5 inhibition causes vasodilation in choroidal blood vessels behind the retina, increasing both blood flow and vascular permeability, which can allow fluid to leak through.⁹ In one case, a 47-year-old man developed CSCR after taking tadalafil 20 milligrams three times on alternate days; his eye exam just two weeks before was completely normal, strongly implicating the drug.¹⁰ Another case involved a man who unknowingly consumed honey adulterated with tadalafil powder and developed CSCR in one eye, which resolved completely within four weeks of stopping the product.¹¹ The good news with CSCR is that it often resolves once the drug is discontinued, though recovery is not guaranteed in every case.

How Common Are Serious Ocular Events

A large U.S. claims-database study published in JAMA Ophthalmology examined ocular adverse events in men who filled prescriptions for PDE5 inhibitors compared with matched non-users. Among the individual outcomes tracked, serous retinal detachment carried the highest adjusted risk, at about 2.6 times the rate in non-users, while ischemic optic neuropathy was roughly twice as common. Retinal vein occlusion showed a trend toward increased risk but did not reach clear statistical significance.¹² In absolute terms, these events remained rare, with incidence rates in the range of three to nine cases per 10,000 person-years of use.

An analysis of the FDA’s adverse event reporting system also documented retinal vascular occlusions specifically tied to tadalafil. Among over 5,500 adverse event reports for PDE5 inhibitors filed since late 2003, tadalafil was associated with 24 retinal vein occlusions and 10 retinal artery occlusions.¹³ These are voluntary reports, meaning they almost certainly undercount the true number, but they also do not prove causation on their own. They do reinforce that the signal is real and not limited to a single type of ocular event.

Who Faces the Greatest Risk

The evidence consistently points to cardiovascular comorbidities as the major risk amplifier. As noted in the NAION case-control data, men with a history of heart attack had dramatically elevated odds of developing optic neuropathy while using PDE5 inhibitors.⁸ High blood pressure showed a similar trend. This makes physiological sense: NAION occurs when the small arteries feeding the optic nerve head fail to deliver enough blood, and people whose vascular system is already compromised have less margin for the hemodynamic shifts that tadalafil introduces.

Other populations that warrant extra caution include:

People with glaucoma or ocular hypertension: The sustained IOP elevation from tadalafil’s long half-life could accelerate damage in eyes where pressure management is already critical.
People with a crowded optic disc: A small cup-to-disc ratio, sometimes called a “disc at risk,” is an established anatomical risk factor for NAION independent of drug use. Adding a vasodilator to that anatomy may tip the balance.
Patients on higher doses for pulmonary hypertension: Tadalafil is prescribed at 40 milligrams daily for pulmonary arterial hypertension, double the maximum dose used for erectile dysfunction. The case of a 46-year-old woman developing NAION on this regimen illustrates that the dose matters, and non-ED patients may face greater ocular exposure than the typical user realizes.⁶
People taking nitrates: Combining tadalafil with nitroglycerin causes dangerous blood pressure drops, with standing systolic blood pressure falling below 85 millimeters of mercury significantly more often than with placebo for up to 24 hours after a dose.¹⁴ Severe hypotension can impair blood flow to the optic nerve and retina just as effectively as a local vascular problem, compounding ocular risk.

If you have NAION in one eye already, most ophthalmologists will strongly advise against using any PDE5 inhibitor, because the risk of the second eye being affected is not well understood and the consequences are irreversible.

What Happens to Retinal Function Over Time

For users without pre-existing eye disease, the reassuring finding is that standard doses of tadalafil do not appear to cause lasting electrical dysfunction in the retina. In a controlled study of men taking typical daily doses for six months, electroretinography, which measures the retina’s electrical response to light, showed no abnormalities compared to men taking a placebo.¹⁵ This is consistent with the selectivity data: if tadalafil largely avoids PDE6, the photoreceptor signaling machinery should remain intact at normal therapeutic concentrations.

Animal data, however, paint a less benign picture and serve as a caution about extrapolating too far. In a study of rats given tadalafil, researchers found significant thinning of the retina, reduced cell populations in both the inner and outer layers, dilated blood capillaries, and a decline in ganglion cells. Under electron microscopy, the photoreceptors showed spacing of their outer segments and disorganized membrane discs, along with degenerative changes in retinal neurons including shrunken nuclei and disrupted mitochondria.¹⁵ Rat studies use doses and durations that do not map neatly onto human use, so these findings are more of a biological signal than a clinical prediction. But combined with the vessel density reductions seen in the human imaging study, they suggest that the retina is not entirely indifferent to chronic tadalafil exposure.

Tadalafil’s Other Enzyme Target and What It Means for Side Effects

Beyond PDE5 and PDE6, tadalafil has meaningful activity against PDE11, an enzyme found in skeletal muscle, the prostate, and the testes. This cross-reactivity is thought to explain the back pain and muscle aches that some tadalafil users experience, side effects that are less common with sildenafil or vardenafil.¹⁶ PDE11 does not appear to play a role in retinal physiology, so this off-target activity is unrelated to the visual side effects discussed above. But it does underscore a broader point: tadalafil’s long half-life and its reach across multiple enzyme families mean it touches more tissues for longer than shorter-acting alternatives. That extended systemic presence is part of what makes tadalafil convenient for daily dosing but also why its effects on the eye are more prolonged than those of sildenafil, whether measured in IOP, vascular remodeling, or drug interaction windows.

Adulterated Products and Unintentional Exposure

One underappreciated risk involves consuming tadalafil without knowing it. Regulatory agencies around the world have repeatedly flagged “herbal” sexual enhancement supplements and specialty food products that turn out to contain undeclared PDE5 inhibitors, often at unpredictable doses. The CSCR case triggered by honey laced with tadalafil powder is a vivid example: the patient had no idea the product contained a pharmaceutical ingredient, developed fluid under his retina, and recovered only after stopping the honey.¹¹ If you experience sudden visual changes after using an over-the-counter “enhancement” product, mention it to your eye doctor. The visual symptoms can mimic other retinal conditions, and knowing about possible PDE5-inhibitor exposure can speed up the correct diagnosis and avoid unnecessary procedures.

Regulatory authorities in multiple countries have updated product labeling for PDE5 inhibitors to include warnings about visual abnormalities and NAION, reflecting the accumulated weight of the adverse event reports and clinical data. If your prescriber has not specifically asked about your eye history before writing a tadalafil prescription, it is worth volunteering the information, particularly any history of glaucoma, optic nerve problems, or previous episodes of sudden vision loss.

1
Investigative Ophthalmology & Visual Science. Efficacy and Selectivity of Phosphodiesterase-Targeted Drugs in Inhibiting Photoreceptor Phosphodiesterase (PDE6) in Retinal Photoreceptors
2
PubMed. The molecular basis for the selectivity of tadalafil toward phosphodiesterase 5 and 6: a modeling study
3
PubMed Central. Effects of sildenafil and tadalafil on intraocular pressure in sheep: implications for aqueous humor dynamics
4
PubMed. Risk of glaucoma among patients using tadalafil for lower urinary tract symptoms: a multinational cohort study
5
PubMed Central. Retinal and Optic Disc Vascular Changes in Patients Using Long-Term Tadalafil: A Prospective Non-Randomized Matched-Pair Study
6
CHEST. Tadalafil-Induced Nonarteritic Anterior Ischemic Optic Neuropathy in a Patient With Pulmonary Arterial Hypertension
7
PubMed Central. Anterior Ischemic Optic Neuropathy in a Patient with Erectile Dysfunction: Tadalafil as an Offending Medication
8
PubMed Central. Non-arteritic anterior ischaemic optic neuropathy and the treatment of erectile dysfunction
9
PubMed Central. Central Serous Chorioretinopathy Associated with Tadalafil
10
PubMed Central. Case Report of Tadalafil-Induced Central Serous Chorioretinopathy
11
PubMed Central. Central Serous Chorioretinopathy Following Oral Use of Adulterated Honey Mixed with Tadalafil: A Case Report
12
JAMA Ophthalmology. Risk of Ocular Adverse Events Associated With Use of Phosphodiesterase 5 Inhibitors in Men in the US
13
Investigative Ophthalmology & Visual Science. FDA Adverse Event Reports of Retinal Vascular Occlusions Associated with PDE5 Inhibitor Use
14
PubMed Central. Time course of the interaction between tadalafil and nitrates
15
Survey of Ophthalmology. Effects of medications on the human electroretinogram: A comprehensive review
16
PubMed Central. Investigation of PDE5/PDE6 and PDE5/PDE11 selective potent tadalafil-like PDE5 inhibitors using combination of molecular modeling approaches, molecular fingerprint-based virtual screening protocols and structure-based pharmacophore development