The Association Between Phosphodiesterase Type 5 Inhibitor Use and Risk of Non-Arteritic Anterior Ischemic Optic Neuropathy: A Systematic Review and Meta-Analysis

Changes in Posterior Ocular Structures in Individuals Using Phosphodiesterase 5 Inhibitor

PURPOSE

To examine posterior ocular structures with optical coherence tomography (OCT) in individuals using a phosphodiesterase 5 inhibitor (PDI, tadalafil).

METHOD

This prospective study included 26 eyes of 26 patients who used 1 tablet of 5-mg tadalafil regularly every day for 1 month due to erectile dysfunction. The routine ophthalmological examinations of the participants were performed at the pre-tadalafil and post-tadalafil first-month visits. At both visits, OCT was used to measure the central retinal thickness (CRT), ganglion cell layer + inner plexiform layer (GCL + IPL) thicknesses, and peripapillary retinal nerve fiber layer (pRNFL; average and superior, temporal, inferior, and nasal quadrants) thicknesses. The disc area, rim area, average and vertical cup/disc ratio, and cup volume of the optic disc head were evaluated. Choroidal thickness was measured from five points: the subfoveal area and the nasal and temporal areas 500 and 1500 microns from the fovea. Choroidal vascular area values and choroidal vascular index (CVI) were calculated using a special binarization technique.

RESULTS

The mean age of the patients was 56 ± 8(range 34-72) years. No significant difference was detected in the CRT,GCL + IPL thicknesses,or pRNFL thicknesses in any of the quadrants before and after tadalafil use. The optic disc head measurements and choroidal thickness values measured from five points were similar between the two visits. The luminal choroidal area was 0.15 ± 0.04 mm2 before tadalafil use and 0.17 ± 0.05 mm2 after 1-month tadalafil use, with no statistically significant difference. The remaining choroidal vascular parameters, namely the stromal and total choroidal area and CVI values, were similar between the two visits.

CONCLUSION

This study showed no significant change in the posterior ocular structures in individuals using tadalafil regular daily use for 1 month due to erectile dysfunction.

Predictors of Phosphodiesterase Type 5 Inhibitor Treatment Failure in Patients Diagnosed With Erectile Dysfunction

INTRODUCTION

Erectile dysfunction (ED) is a prevalent condition, especially in aging populations, with significant implications for quality of life. While phosphodiesterase type 5 inhibitors (PDE5Is) are the first-line treatment, a substantial percentage of patients do not respond satisfactorily. This study aimed to identify predictors of PDE5I treatment failure in ED patients.

METHODS

Data from January 2016 to January 2022 was reviewed for patients with ED who either failed PDE5I treatment or had a successful outcome. Demographic, medical, and laboratory data were collected and analyzed. Patients with contraindications or who did not complete the treatment were excluded.

RESULTS

The treatment failure group comprised 288 patients, while 225 age-matched patients formed the control responder group. There were no significant differences in marriage duration, comorbidities, smoking, or BMI. However, HbA1c levels, free testosterone, and SHBG were significantly different between the two groups.

CONCLUSION

This study found that high HbA1c levels, low free testosterone, and high sex hormone-binding globulin (SHBG) were associated with PDE5I treatment failure. Managing high HbA1c levels and addressing hormonal imbalances may enhance PDE5I treatment effectiveness in ED patients. However, further research is needed to explore other factors contributing to treatment outcomes.

[Nonarteritic anterior ischemic optic neuropathy (nAION)]

Nonarteritic anterior ischemic optic neuropathy (nAION) is the second most common degenerative disease of the optic nerve. The pathogenesis remains elusive. A transient ischemia in the short posterior ciliary arteries not triggered by thromboembolic events is suspected. The typical history of a sudden onset of scotoma without associated pain in conjunction with (sectorial) optic disc swelling, an afferent pupillary defect and a visual field defect are of decisive diagnostic importance. The most urgent diagnostic measure is the exclusion of arteritic AION. There are no proven treatment approaches. Frequently used but without clear study results, is the treatment with steroids and secondary prophylaxis with acetylsalicylic acid (ASA). Recurrence in the ipsilateral or contralateral eye is possible.

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

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.

Risk Factors for Non-arteritic Anterior Ischemic Optic Neuropathy: A Large Scale Meta-Analysis

Objective: We conducted a meta-analysis to explore all the potential risk factors for non-arteritic anterior ischemic optic neuropathy (NAION) based on the published literature. Methods: A comprehensive literature search through the online databases was performed to obtain studies concerning the risk factors of NAION up to June 2020. Pooled unadjusted odds ratios (ORs) or rate ratios (RRs) were calculated to evaluate the weight of risk factors. This study was registered in PROSPERO under the number CRD42018084960. Results: Our meta-analysis included 49 original studies comprising of more than 10 million patients. The following risk factors were proved to be significantly associated with NAION: male gender (OR = 1.67, 95% CI: 1.50-1.85, P < 0.00001), hypertension (RR = 1.28, 95% CI: 1.20-1.37, P < 0.00001), hyperlipidemia (RR = 1.43, 95% CI: 1.26-1.62, P < 0.00001), diabetes mellitus (DM) (RR = 1.53, 95% CI: 1.36-1.73, P < 0.00001), coronary heart disease (CHD) (RR = 1.68, 95% CI: 1.24-2.27, P = 0.0008), sleep apnea (RR = 3.28, 95% CI: 2.08-5.17, P < 0.00001), factor V Leiden heterozygous (RR = 2.21, 95% CI: 1.19-4.09, P = 0.01), and medication history of cardiovascular drugs. Conclusion: We concluded that the above risk factors were significantly related to NAION. Better understanding of these risk factors in NAION can help the direct therapeutic approaches.

A p97/Valosin-Containing Protein Inhibitor Drug CB-5083 Has a Potent but Reversible Off-Target Effect on Phosphodiesterase-6

CB-5083 is an inhibitor of p97/valosin-containing protein (VCP), for which phase I trials for cancer were terminated because of adverse effects on vision, such as photophobia and dyschromatopsia. Lower dose CB-5083 could combat inclusion body myopathy with early-onset Paget disease and frontotemporal dementia or multisystem proteinopathy caused by gain-of-function mutations in VCP. We hypothesized that the visual impairment in the cancer trial was due to CB-5083's inhibition of phosphodiesterase (PDE)-6, which mediates signal transduction in photoreceptors. To test our hypothesis, we used in vivo and ex vivo electroretinography (ERG) in mice and a PDE6 activity assay of bovine rod outer segment (ROS) extracts. Additionally, histology and optical coherence tomography were used to assess CB-5083's long-term ocular toxicity. A single administration of CB-5083 led to robust ERG signal deterioration, specifically in photoresponse kinetics. Similar recordings with known PDE inhibitors sildenafil, tadalafil, vardenafil, and zaprinast showed that only vardenafil had as strong an effect on the ERG signal in vivo as did CB-5083. In the biochemical assay, CB-5083 inhibited PDE6 activity with a potency higher than sildenafil but lower than that of vardenafil. Ex vivo ERG revealed a PDE6 inhibition constant of 80 nM for CB-5083, which is 7-fold smaller than that for sildenafil. Finally, we showed that the inhibitory effect of CB-5083 on visual function is reversible, and its chronic administration does not cause permanent retinal anomalies in aged VCP-disease model mice. Our results warrant re-evaluation of CB-5083 as a clinical therapeutic agent. We recommend preclinical ERG recordings as a routine drug safety screen. SIGNIFICANCE STATEMENT: This report supports the use of a valosin-containing protein (VCP) inhibitor drug, CB-5083, for the treatment of neuromuscular VCP disease despite CB-5083's initial clinical failure for cancer treatment due to side effects on vision. The data show that CB-5083 displays a dose-dependent but reversible inhibitory action on phosphodiesterase-6, an essential enzyme in retinal photoreceptor function, but no long-term consequences on retinal function or structure.

Retinal and Optic Disc Vascular Changes in Patients Using Long-Term Tadalafil: A Prospective Non-Randomized Matched-Pair Study

Retinal, choroidal and optic disc vascularity has never been evaluated in patients taking PDE5is long-term. The aim of our study was to evaluate the neurostructural and vascular changes after long-term use of tadalafil, using spectral domain (SD)-optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA). In the present clinical trial, 27 patients who have been taking tadalafil 20 mg on alternate days (OAD) for at least 6 months (Group A) were enrolled. The matched group consisted of 27 healthy men (Group B). Both groups of patients underwent SD-OCT to study ganglion cell complex (GCC), retinal nerve fiber layer (RNFL) and choroidal thickness and OCTA for the evaluation of superficial capillary plexus (SCP), deep capillary plexus (DCP), choriocapillaris (CC) and radial peripapillary capillary (RPC). A reduction in SCP, DCP and RPC vessel density was found in patients using tadalafil long-term. Retinal and optic disc toxicity may be detected using modifications of capillary vessel density. Further studies are needed to investigate the possibility of a causal association.

Visual Side Effects Linked to Sildenafil Consumption: An Update

Phosphodiesterase type 5 (PDE5) inhibitors such as Viagra^® (sildenafil citrate) have demonstrated efficacy in the treatment of erectile dysfunction (ED) by inducing cyclic guanosine monophosphate (cGMP) elevation followed by vasodilation and increased blood flow. It also exerts minor inhibitory action against PDE6, which is present exclusively in rod and cone photoreceptors. The effects of sildenafil on the visual system have been investigated in a wide variety of clinical and preclinical studies due to the fact that a high dose of sildenafil may cause mild and transient visual symptoms in some patients. A literature review was performed using PubMed, Cochrane Library and Clinical Trials databases from 1990 up to 2020, focusing on the pathophysiology of visual disorders induced by sildenafil. The aim of this review was not only to gather and summarize the information available on sildenafil clinical trials (CTs), but also to spot subpopulations with increased risk of developing undesirable visual side effects. This PDE inhibitor has been associated with transient and reversible ocular side effects, including changes in color vision and light perception, blurred vision, photophobia, conjunctival hyperemia and keratitis, and alterations in the electroretinogram (ERG). Sildenafil may induce a reversible increase in intraocular pressure (IOP) and a few case reports suggest it is involved in the development of nonarteritic ischemic optic neuropathy (NAION). Reversible idiopathic serous macular detachment, central serous retinopathy and ERG disturbances have been related to the significant impact of sildenafil on retinal perfusion. So far, sildenafil does not seem to cause permanent toxic effects on chorioretinal tissue and photoreceptors as long as the therapeutic dose is not exceeded and is taken under a physician’s direction to treat a medical condition. However, the recreational use of sildenafil can lead to harmful side effects, including vision changes.

Risk of nonarteritic ischaemic optic neuropathy with phosphodiesterase type 5 inhibitors: a systematic review and meta-analysis

The development of nonarteritic anterior ischaemic optic neuropathy has been described to phosphodiesterase type 5 inhibitors. The aim of this systematic review and meta-analysis was to assess the risk of nonarteritic anterior ischaemic optic neuropathy associated with phosphodiesterase type 5 inhibitors exposure. A literature search was performed at MEDLINE, EMBASE, Toxline and VigiBase. Randomized controlled trials, observational studies, case reports and spontaneous reports describing nonarteritic anterior ischaemic optic neuropathy associated with phosphodiesterase type 5 inhibitors exposure were included. The risk of bias was assessed according to Centre for Reviews and Dissemination's (CRD) guidance. Data were analysed using descriptive statistics and meta-analysis. Four observational studies, 50 case reports and 608 spontaneous reports were identified. All observational studies evaluated males treated for erectile dysfunction. Treatment with phosphodiesterase type 5 inhibitors is not associated with an increased risk of definitive nonarteritic anterior ischaemic optic neuropathy [odds ratio (OR) 1.16; 95% CI 0.89, 1.52, p = 0.046; I²  = 62.6%]. The methodological quality was assessed as good for three studies. Among case reports, 12 (23%) patients did not have risk factors to develop nonarteritic anterior ischaemic optic neuropathy. Thirty-nine (78%) patients were treated for erectile dysfunction. A regular administration of phosphodiesterase type 5 inhibitors was observed in 24 (48%) case reports. All case reports were assessed as higher risk of bias. According to the available evidence, the treatment with phosphodiesterase type 5 inhibitors was not found to be associated with nonarteritic anterior ischaemic optic neuropathy. Further research is needed to study such association, including possible confounding factors.