Can Cialis or Viagra Affect Your Eyes? What the Evidence Really Shows

Cialis® (tadalafil) and Viagra® (sildenafil) are phosphodiesterase type-5 (PDE-5) inhibitors. They are best known for erectile dysfunction; tadalafil is also used for the urinary symptoms of benign prostatic hyperplasia, and PDE-5 drugs are used in other formulations for pulmonary hypertension. They increase nitric oxide–cGMP signaling and relax smooth muscle. Their eye effects come from systemic blood-flow changes, the eye’s own vascular physiology and — particularly for sildenafil — partial inhibition of retinal PDE-6.

Sildenafil can inhibit PDE-6, an enzyme involved in the retina’s light-sensing chemistry (phototransduction). This can temporarily change blue-green color discrimination, increase sensitivity to light, or blur vision. In fixed-dose Viagra trials, “abnormal vision” was reported by about 1% of patients at 25 mg, 2% at 50 mg and 11% at 100 mg, compared with 1% on placebo. The effects were generally mild and transient.

Tadalafil is more selective. Current tadalafil labeling reports changes in color vision in fewer than 0.1% of patients across its clinical studies. A new fixed dark area, a missing part of the visual field, or marked dimming in one eye should never be dismissed as a benign color effect.

Non-arteritic anterior ischemic optic neuropathy (NAION) is an uncommon condition in which part of the optic nerve is injured after insufficient blood supply. It usually causes sudden, painless vision loss in one eye. U.S. prescribing information for both tadalafil and sildenafil carries a warning about rare postmarketing reports of NAION, and both labels instruct patients to stop the PDE-5 inhibitor and seek medical attention if sudden vision loss occurs. Our neuro-ophthalmology pages cover optic-nerve conditions in more detail.

• Patients who have already had NAION in one eye are at increased risk in the other eye; the labels say PDE-5 inhibitors should be used with caution in these patients, and only when the anticipated benefits outweigh the risks.
• A small or “crowded” optic disc is an anatomic NAION risk factor, but current labeling states that the evidence is insufficient to support screening every prospective user for it.
• Sudden painless loss of vision is an emergency symptom regardless of whether the medication ultimately caused it.

A multinational cohort study published in 2026 compared men aged 40 and older who took tadalafil for lower urinary tract symptoms with matched men who took no PDE-5 inhibitor. It reported a modest association with new glaucoma diagnoses. The numbers deserve to be read carefully.

A separate 2026 multicenter study looked at men with erectile dysfunction and chronic PDE-5 inhibitor exposure. It found fewer glaucoma-suspect diagnoses and less open-angle glaucoma among PDE-5 users. Open-angle glaucoma developed in 2.13% versus 3.22% at one year, 3.00% versus 3.80% at two years, and 3.88% versus 4.28% at three years, and the adjusted hazard ratios stayed below 1.0 (0.76 at one year, 0.79 at two years, 0.84 at three years).

That study does not prove PDE-5 inhibitors prevent glaucoma either. The two studies involved different indications, populations, exposure definitions and follow-up, and both were retrospective. The scientifically correct conclusion in 2026 is that the glaucoma relationship remains unsettled. If you have glaucoma or ocular hypertension, keep your usual glaucoma visits; the 2026 tadalafil study alone is not a reason to stop a prescribed medication.

A 2022 JAMA Ophthalmology insurance-claims study of 213,033 men receiving PDE-5 inhibitors reported associations with a composite of serous retinal detachment, retinal vascular occlusion and ischemic optic neuropathy. The composite incidence was 15.5 per 10,000 person-years, with an adjusted incidence-rate ratio of 1.85. Individually, serous retinal detachment (incidence-rate ratio 2.58, 95% CI 1.55–4.30) and ischemic optic neuropathy (2.02, 95% CI 1.14–3.58) were elevated in that analysis. The retinal vascular occlusion estimate was 1.44, with a 95% confidence interval of 0.98–2.12 that crossed 1.0. Our retina and vitreous pages explain these conditions.

• Anyone with previous NAION, particularly when considering continued or new PDE-5 therapy.
• Patients with substantial vascular risk factors or untreated obstructive sleep apnea.
• Patients with glaucoma or ocular hypertension, who should stay current with their normal glaucoma surveillance; the 2026 tadalafil study alone is not a reason to discontinue therapy.
• Patients with hereditary retinal degenerations such as retinitis pigmentosa: tadalafil clinical trials excluded such patients, and current Cialis labeling does not recommend use in known hereditary degenerative retinal disorders.