Non-Arteritic Anterior Ischemic Optic Neuropathy Associated With the Use of Phosphodiesterase Type 5 Inhibitors: A Literature Review

Abstract

Phosphodiesterase type 5 (PDE5) inhibitors are frequently used for erectile dysfunction (ED) as the first line of treatment. This medication was initially developed to treat muscle spasms and pulmonary hypertension. The United States Food and Drug Administration (FDA) approved its usage for treating ED. Sildenafil, tadalafil, vardenafil, and avanafil are PDE5 inhibitors. The decrease of cyclic guanosine monophosphate (cGMP) in smooth muscle cells caused by sildenafil causes smooth muscle relaxation and penile erection. Vasodilation of the blood vessels reduces perfusion and blood flow to the optic nerve and eye. Several incidences of non-arteritic anterior ischemic optic neuropathy (NAION) have been recorded in sildenafil users, among other ocular complications. The onset of NAION is usually sudden and painless, and it is associated with any pattern of visual field loss. Possible symptoms include poor visual acuity, diminished color vision, a visual field defect, or hemorrhages in the form of flames. Nevertheless, NAION pathogenesis is still a mystery. Most visual effects are reversible weeks after the medication is stopped, and NAION does not seem to cause a permanent blindness. A small cup-to-disc ratio (disc at risk) and underlying systemic illnesses, such as hypertension, increase the risk of developing NAION. An early indicator of cardiovascular disease is ED. NAION diagnosis is challenging due to a lack of confirmatory diagnostic evidences. Normal visual acuity does not exclude NAION from being a possibility. In order to evaluate visual outcomes in NAION, data on both visual acuity (VA) and the full peripheral visual field are needed. Treatment with steroids did not seem to improve visual results.

The erectile and ejaculatory implications of the surgical management of rectal cancer

“…71 Aside from sildenafil, other FDA-approved potent PDE5is include tadalafil, avanafil, and vardenafil, with tadalafil becoming increasingly popular. [71][72][73] Compared to these other approved PDE5is, sildenafil shows increased peak systolic velocity, improving penile circulation long-term. 74 Compounded with libido stimulation, PDE5is may result in better erectile recovery.…”

“…Using a PDE5i increases intracellular cGMP levels and allowing for a prolonged erection 71 . Aside from sildenafil, other FDA‐approved potent PDE5is include tadalafil, avanafil, and vardenafil, with tadalafil becoming increasingly popular 71–73 . Compared to these other approved PDE5is, sildenafil shows increased peak systolic velocity, improving penile circulation long‐term 74 .…”

Risk factors of non-arteritic anterior ischaemic optic neuropathy and central retinal artery occlusion

“…The anatomical structure of the small optic disc, small cup-todisc ratio (C/D), small optic cup, or ignoring cup may be local risk factors for NAION [6][7] . In addition to the above risk factors, NAION is also related to drugs and surgery [8][9] . The clinical manifestations of central retinal artery occlusion (CRAO) are similar to those of NAION, usually characterized by sudden and painless vision loss in one or both eyes.…”