Effect of sildenafil citrate (Viagra) on the ocular circulation

Central retinal vein and artery occlusion associated with sildenafil: a case report and review of the literature

BACKGROUND

Sildenafil is a selective phosphodiesterase type 5 inhibitor used for the treatment of erectile dysfunction and pulmonary hypertension. It is available over the counter in many countries. While there have been a few reports of retinal vascular occlusion following sildenafil consumption, most cases have other comorbidities as risk factors for the disease, and the exact causal role of this drug in these conditions remains unclear.

CASE PRESENTATION

We present the case of a healthy 32-year-old Iranian man who developed combined central retinal vein occlusion and retinal artery occlusion following sildenafil exposure. The patient underwent a hypercoagulative state workup for possible underlying risk factors. Additionally, we conducted a literature search on PubMed using the keywords: retinal vein occlusion AND Sildenafil OR Viagra, retinal artery occlusion AND Sildenafil OR Viagra, retinal vascular occlusion AND Sildenafil OR Viagra. To obtain more objective results in the reviews, we employed an adverse drug reaction possibility algorithm. The patient was found to be otherwise healthy, and ancillary tests were unremarkable. A literature review identified seven reports of retinal vascular occlusion following sildenafil use. In most of these cases, the role of sildenafil was not clearly established. To the best of our knowledge, our case achieved the highest score based on the algorithm compared with previous reports.

CONCLUSION

Sildenafil may be associated with severe retinal vascular accidents in otherwise healthy young individuals.

The Impact of Systemic Medications on Retinal Function

This study will provide a thorough review of systemic (and select intravitreal) medications, along with illicit drugs that are capable of causing various patterns of retinal toxicity. The diagnosis is established by taking a thorough medication and drug history, and then by pattern recognition of the clinical retinal changes and multimodal imaging features. Examples of all of these types of toxicity will be thoroughly reviewed, including agents that cause retinal pigment epithelial disruption (hydroxychloroquine, thioridazine, pentosan polysulfate sodium, dideoxyinosine), retinal vascular occlusion (quinine, oral contraceptives), cystoid macular edema/retinal edema (nicotinic acid, sulfa-containing medications, taxels, glitazones), crystalline deposition (tamoxifen, canthaxanthin, methoxyflurane), uveitis, miscellaneous, and subjective visual symptoms (digoxin, sildenafil). The impact of newer chemotherapeutics and immunotherapeutics (tyrosine kinase inhibitor, mitogen-activated protein kinase kinase, checkpoint, anaplastic lymphoma kinase, extracellular signal-regulated kinase inhibitors, and others), will also be thoroughly reviewed. The mechanism of action will be explored in detail when known. When applicable, preventive measures will be discussed, and treatment will be reviewed. Illicit drugs (cannabinoids, cocaine, heroin, methamphetamine, alkyl nitrite), will also be reviewed in terms of the potential impact on retinal function.

Effects of systemic drugs on the development and progression of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of severe loss of central vision among people over 50. The pathophysiology of the disease is multifactorial and can be attributed to genetics, aging, inflammation, environmental factors, and lifestyle factors including smoking, diet, obesity, and alcohol consumption. While there is no treatment for dry AMD, the current standard treatment for wet AMD is an intraocular injection of anti-vascular endothelial growth factor-an effective, yet expensive, therapy that requires ongoing treatment. As the aging population continues to grow, and AMD diagnoses continue to rise, new treatments should be explored to reduce vision complications and decrease treatment burdens. Many systemic conditions have progressive pathological changes that may affect AMD, particularly those affecting systemic vasculature like diabetes and cardiovascular status. Consequently, systemic drugs used to treat coexistent systemic diseases may influence some of the pathogenic mechanisms of AMD and lead its progression or delay. In this review we explore the current literature to summarize the findings of the reported effects of antihypertensive, immunosuppressants, cholesterol lowering agents, nonsteroidal anti-inflammatory drugs, dopamine precursors, hypoglycemic agents, and anticoagulants on AMD.

Sildenafil in ophthalmology: An update

Sildenafil citrate, a selective oral phosphodiesterase 5 inhibitor, is a widely used drug for erectile dysfunction that acts by elevating cGMP levels and causing smooth muscle relaxation. It also has 10% activity against PDE6, a key enzyme in phototransduction cascade in the retina. Recent ocular imaging developments have further revealed the influence of sildenafil on ocular hemodynamics, particularly choroidal perfusion. Choroidal thickness is increased, and choroidal perfusion is also enhanced by autoregulatory mechanisms that are further dependent on age and microvascular abnormalities. Studies demonstrating high intraocular pressure via a "parallel pathway" from increased choroidal volume and blood flow to the ciliary body have challenged previous concepts. Another new observation is the effect of sildenafil on bipolar cells and cyclic-nucleotide gated channels. We discuss potential deleterious effects (central serous chorioretinopathy, glaucoma, ischemic optic neuropathy, and risks to recessive carriers of retinitis pigmentosa), potential beneficial effects (ameliorate choroidal ischemia, prevent thickening of Bruch membrane, and promote recovery of the ellipsoid zone) in macular degeneration, as well as potential drug interactions of sildenafil.

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.

Effects of phosphodiesterase type 5 inhibitors on choroid and ocular vasculature: a literature review

To provide information on the effects of phosphodiesterase type 5 (PDE5) inhibitors on choroidal vessels and central serous chorioretinopathy (CSC) and possible implications for development of exudative age-related macular degeneration (AMD). Two independent investigators conducted a qualitative review of PubMed to identify studies on the choroidal effect of PDE5 inhibitors in June 2019. The search used key words that included PDE5 inhibitors, sildenafil, tadalafil, vardenafil, choroid, choroidal flow, choroidal vessels, choroidal thickness, CSC, AMD or a combination. Only studies which assessed choroidal findings were included. Many ocular diseases are related to changes in choroidal thickness and perfusion. Patients with AMD, who have decreased choroidal perfusion, may manifest more severely diminished choroidal ability to deliver oxygen and other metabolites to the retina, leading to growth of neovascular tissue. As a result of this engorgement of the choroidal vasculature, some patients may have leakage across the retinal pigment epithelium (RPE) and accumulation of subretinal fluid, resulting in CSC. Transient visual symptoms, i.e., changes in color perception and increased light sensitivity, are well-known adverse effects, but there have been rare reports of vision-threatening ocular complications in users of PDE5 inhibitors, such as nonarteritic anterior ischemic optic neuropathy and cilioretinal artery occlusion. The choroid is a vascular tissue analogous in many respects to the corpus cavernosum, and PDE5 inhibitors may increase the choroidal thickness and perfusion. While it is intuitively obvious that thickness of the choroid alone does not guarantee better choriocapillaris oxygenation, it is a reasonable step towards ameliorating ischemia. These drugs have numerous physiologic effects on the choroid related to blood flow, such as clinical consequences in CSC and AMD.

MACULAR ATROPHY FINDINGS BY OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY COMPARED WITH FUNDUS AUTOFLUORESCENCE IN TREATED EXUDATIVE AGE-RELATED MACULAR DEGENERATION

The area of choriocapillaris nonperfusion on optical coherence tomography angiography correlated with the area of macular atrophy on fundus autofluorescence in eyes with exudative age-related macular degeneration. Choroidal ischemia might be involved in macular atrophy in treated age-related macular degeneration.

Purpose:

To compare the areas of choriocapillaris (CC) nonperfusion and macular atrophy (MA) in treated exudative age-related macular degeneration.

Methods:

This was a prospective, observational, cross-sectional study. Forty-four eyes exhibiting MA (42 patients with age-related macular degeneration), with a dry macula, underwent fundus autofluorescence and optical coherence tomography angiography. The area of MA detected by fundus autofluorescence and CC nonperfusion detected by optical coherence tomography angiography was measured using image analysis software. The rates of concordance between the MA and CC nonperfusion areas were calculated. We qualitatively and quantitatively compared the areas of MA and CC nonperfusion in age-related macular degeneration eyes.

Results:

The mean areas of MA and CC nonperfusion were 5.95 ± 4.50 mm² and 10.66 ± 7.05 mm², respectively (paired t-test, P < 0.001). In 39 eyes (88.6%), the CC nonperfusion area was larger than the MA area, and the mean CC nonperfusion area was significantly larger than the mean MA area. Fundus autofluorescence matching optical coherence tomography angiography showed that the CC nonperfusion area was almost included in the MA area. The mean concordance rate for the MA area inside the CC nonperfusion area was 87.7 ± 13.9%.

Conclusion:

The MA and CC nonperfusion areas markedly overlapped. The area of CC nonperfusion correlated with the MA area. Choroidal ischemia might be involved in the pathogenesis of MA in treated age-related macular degeneration.

Precautions and Monitoring of Patients Taking Phosphodiesterase Type 5 Inhibitors Who are at Risk of Increased Intraocular Pressure

Phosphodiesterase type 5 inhibitors (PDE5Is) may increase intraocular pressure (IOP) by increasing blood flow to the ciliary body. Although clinical studies of changes in IOP after single and multiple doses of PDE5Is show variable results, most are limited by small sample sizes, absence of control groups and blinding, and use of normal patient volunteers who have no risk factors for glaucoma. However, multiple case reports of glaucoma have been published, and one epidemiologic analysis of the National Health and Nutrition Examination Survey (NHANES) database of US respondents suggested a significant association of prolonged sildenafil use and self-reported glaucoma. With the widespread use of PDE5Is for treatment of erectile dysfunction in males with risk factors for glaucoma, and the potential of PDE5Is to worsen optic nerve damage in patients with glaucoma, we recommend a vision screening exam prior to the initiation of the PDE5I and careful follow-up thereafter, particularly if the patient is taking tadalafil, a long-acting PDE5I, if the patient is taking high doses of a PDE5I daily and persistently, and if the patient has risk factors for glaucoma or if the patient is at risk of worsening glaucoma.

Vascular Response to Sildenafil Citrate in Aging and Age-Related Macular Degeneration

Age-related macular degeneration (AMD) - the leading cause of vision loss in the elderly - share many risks factors as atherosclerosis, which exhibits loss of vascular compliance resulting from aging and oxidative stress. Here, we attempt to explore choroidal and retinal vascular compliance in patients with AMD by evaluating dynamic vascular changes using live ocular imaging following treatment with oral sildenafil citrate, a phosphodiesterase type 5 (PDE5) inhibitor and potent vasodilator. Enhanced-depth imaging optical coherence tomography (EDI-OCT) and OCT angiography (OCT-A) were performed on 46 eyes of 23 subjects, including 15 patients with non-exudative AMD in one eye and exudative AMD in the fellow eye, and 8 age-matched control subjects. Choroidal thickness, choroidal vascularity, and retinal vessel density were measured across the central macula at 1 and 3 hours after a 100 mg oral dose of sildenafil citrate. Baseline choroidal thickness was 172.1 ± 60.0 μm in non-exudative AMD eyes, 196.4 ± 89.8 μm in exudative AMD eyes, and 207.4 ± 77.7 μm in control eyes, with no difference between the 3 groups (P = 0.116). After sildenafil, choroidal thickness increased by 6.0% to 9.0% at 1 and 3 hours in all groups (P = 0.001-0.014). Eyes from older subjects were associated with choroidal thinning at baseline (P = 0.005) and showed less choroidal expansion at 1 hour and 3 hours after sildenafil (P = 0.001) regardless of AMD status (P = 0.666). The choroidal thickening appeared to be primarily attributed to expansion of the stroma rather than luminal component. Retinal vascular density remained unchanged after sildenafil in all 3 groups (P = 0.281-0.587). Together, our studies suggest that vascular response of the choroid to sildenafil decreases with age, but is not affected by the presence of non-exudative or exudative AMD, providing insight into changes in vessel compliance in aging and AMD.

SILDENAFIL CITRATE INDUCED RETINAL TOXICITY-ELECTRORETINOGRAM, OPTICAL COHERENCE TOMOGRAPHY, AND ADAPTIVE OPTICS FINDINGS

BACKGROUND/PURPOSE

To report a case of persistent retinal toxicity associated with a high dose of sildenafil citrate intake.

METHODS

Single retrospective case report.

RESULTS

A 31-year-old white man with no medical history presented with complaints of bilateral multicolored photopsias and erythropsia (red-tinted vision), shortly after taking sildenafil citrate-purchased through the internet. Patient was found to have cone photoreceptor damage, demonstrated using electroretinogram, optical coherence tomography, and adaptive optics imaging. The patient's symptoms and the photoreceptor structural changes persisted for several months.

CONCLUSION

Sildenafil citrate is a widely used erectile dysfunction medication that is typically associated with transient visual symptoms in normal dosage. At high dosage, sildenafil citrate can lead to persistent retinal toxicity in certain individuals.

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

INTRODUCTION

Phosphodiesterase type 5 inhibitors (PDE5-Is) are first-line drugs for erectile dysfunction. Non-arteritic anterior ischemic optic neuropathy (NAION) has been linked with PDE5-I use. However, no meta-analysis or conclusive review has explored the association between NAION and PDE5-I use.

AIM

To investigate the association between PDE5-I use and risk of NAION.

METHODS

A comprehensive literature search was conducted using online databases in October 2017 to obtain studies researching the association between PDE5-I application and occurrence of NAION. Summarized unadjusted risk ratios (RRs) with 95% CIs were calculated for the strength of this association. This study was conducted in accordance to Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines and registered in PROSPERO under number CRD42017080865.

MAIN OUTCOME MEASURES

The strength of association between PDE5-I use and risk of NAION was assessed through pooled unadjusted RRs and 95% CIs.

RESULTS

5 original articles with 6 clinical observations were included in the meta-analysis. No significant higher risk of NAION was observed after the use of PDE5-Is within a 1-month period (RR = 1.16, 95% CI = 0.98-1.39, P = .09). Subgroup analyses indicated 2 PDE5-Is were significantly related to NAION (tadalafil: RR = 2.14, 95% CI = 1.20-3.84, P = .01; sildenafil: RR = 2.25, 95% CI = 1.29-3.94, P = .004).

CONCLUSIONS

Although we found no association between NAION and PDE5-I use, our results should be interpreted cautiously because we included only observational studies and could not control for potential confounders. Because NAION is a rare ocular disease and difficult to diagnose, this association should be confirmed in prospective comparative studies with larger samples and more rigorous designs. Liu B, Zhu L, Zhong J, et al. The Association Between Phosphodiesterase Type 5 Inhibitor Use and Risk of Non-Arteritic Anterior Ischemic Optic Neuropathy: A Systematic Review and Meta-Analysis. Sex Med 2018;6:185-192.

The nitric oxide-guanylate cyclase pathway and glaucoma

Glaucoma is a prevalent optic neuropathy characterized by the progressive dysfunction and loss of retinal ganglion cells (RGCs) and their optic nerve axons, which leads to irreversible visual field loss. Multiple risk factors for the disease have been identified, but elevated intraocular pressure (IOP) remains the primary risk factor amenable to treatment. Reducing IOP however does not always prevent glaucomatous neurodegeneration, and many patients progress with the disease despite having IOP in the normal range. There is increasing evidence that nitric oxide (NO) is a direct regulator of IOP and that dysfunction of the NO-Guanylate Cyclase (GC) pathway is associated with glaucoma incidence. NO has shown promise as a novel therapeutic with targeted effects that: 1) lower IOP; 2) increase ocular blood flow; and 3) confer neuroprotection. The various effects of NO in the eye appear to be mediated through the activation of the GC- guanosine 3:5'-cyclic monophosphate (cGMP) pathway and its effect on downstream targets, such as protein kinases and Ca²⁺ channels. Although NO-donor compounds are promising as therapeutics for IOP regulation, they may not be ideal to harness the neuroprotective potential of NO signaling. Here we review evidence that supports direct targeting of GC as a novel pleiotrophic treatment for the disease, without the need for direct NO application. The identification and targeting of other factors that contribute to glaucoma would be beneficial to patients, particularly those that do not respond well to IOP-dependent interventions.

An immunohistochemical and ultrastructural analysis of the retina in tadalafil (Cialis) treated rats

Tadalafil (Cialis) is one of the most commonly used phosphodiesterase type5 (PDE5) inhibitors. This work aimed to analyze the histological and ultrastructural changes provoked by chronic tadalafil administration in the rat retina, correlate between such changes and PDE5 immunoexpression and to evaluate the possible reversibility of these changes. Thirty Sprague Dawley male rats were randomly distributed into 3 groups. Control group; given 1 ml distilled water daily for 6 weeks. Tadalafil group; given tadalafil in a daily dose of 2.6 mg/kg for 6 weeks. Withdrawal group; given tadalafil 2.6 mg/kg daily for 6 week followed by a withdrawal period of 4 weeks. Retinal specimens were prepared for histological, ultrastructural and immunohistochemical study using anti-PDE5 and anti-Bcl-2 antibodies. Morphometric and statistical studies were performed. Tadalafil group displayed a significant reduction in retinal thickness, diminished cell population of outer and inner nuclear layers, dilated blood capillaries and a significant decline in the number of ganglion cells. Significant reductions of both PDE5 and Bcl-2 immunoexpression were observed. At the ultrastructural level, the photoreceptors showed spacing of outer segments and disorganized membranous discs. Retinal neurons showed ultrastructural degenerative changes in the form of shrunken irregular nuclei, dilated rER, and disrupted mitochondria. Withdrawal group revealed preservation of histological structure and partial restoration of retinal thickness, retinal cells ultrastructure, and PDE5 and Bcl-2 immunoexpressions. In conclusion, chronic use of tadalafil could induce reversible apoptotic and degenerative changes in retinal neurons due to its inhibitory effect on PDE5 expression which affects the metabolism and viability of retinal cells.

Treatment of Macular Degeneration with Sildenafil: Results of a Two-Year Trial

OBJECTIVE

To evaluate PDE5/6 inhibition with sildenafil to reduce choroidal ischemia and treat age-related macular degeneration.

METHODS

Sildenafil was prescribed to treat participants with macular degenerations or macular dystrophies measured by spectral-domain optical coherence tomography, color fundus photography, enhanced depth imaging, and best-corrected visual acuity.

RESULTS

No change in calcified drusen was noted. Vitelliform-type soft drusen were not substantially changed. A participant with Best vitelliform macular dystrophy had a significant improvement in vision as well as in photoreceptor and ellipsoid layers.

CONCLUSIONS

Our research supports sildenafil as a safe treatment for age-related and vitelliform macular degenerations. Thickened Bruch's membrane reduces the beneficial effect of perfusion increase, but all eyes appear to benefit from PDE6. Notably, maintenance or improvement in the photoreceptor layer may be the most significant result of sildenafil and is consistent with PDE6 inhibition. Thus, sil-denafil treatment of macular degeneration offers significant potential for vision retention and recovery.

Erectile Dysfunction Agents and Nonarteritic Anterior Ischemic Optic Neuropathy

Phosphodiesterase-5 inhibitors (PDE5I) are used for treatment of erectile dysfunction and pulmonary arterial hypertension and have been implicated as a causative factor for development of nonarteritic anterior ischemic optic neuropathy (NAION). Controversy remains regarding a cause and effect between PDE5I use and NAION because the mechanism by which NAION occurs is still not well understood. Because neuro-ophthalmologists have accepted that there is a potential relationship between ingestion of the PDE5I class of medications and NAION, the neuro-ophthalmologist should inquire about PDE5I use when evaluating a patient with a new diagnosis of NAION, and counsel patients regarding the implication of continued use of PDE5I.

Effect of topical isopropyl unoprostone on macular atrophy progression in eyes with exudative age-related macular degeneration

BACKGROUND

To evaluate the efficacy and safety of topical isopropyl unoprostone (IU) in treating macular atrophy in age-related macular degeneration (AMD) patients.

METHODS

Fifty-two AMD patients with macular atrophy were included and randomly assigned (1:1) to the treatment (topical 0.15% IU) or placebo group. Subjects used study eye drops 3 times a day for 54 weeks. The macular atrophy was documented on fundus autofluorescence photographs and measured using RegionFinder. The enlargement rate of macular atrophy and the changes in visual acuity were examined statistically between baseline and 54 weeks.

RESULTS

Forty-eight subjects were included in the analyses because 4 subjects withdrew from the study. The differences between the IU and placebo groups in mean and median area of macular atrophy were not statistically significant at baseline. The baseline median lesion size of macular atrophy was 2.33 mm in the IU group and 1.63 mm in the placebo group (P = 0.51). The intergroup difference in the enlargement ratio of macular atrophy (21 ± 15% in the IU group and 111 ± 96% in the placebo group) was statistically significant (P < 0.001). Additionally, visual acuity tended to improve over baseline in the IU group. No serious adverse events were observed.

CONCLUSIONS

Topical IU therapy is safe and effective for treating macular atrophy in AMD patients.

Effect of chronic administration of sildenafil citrate (Viagra) on the histology of the retina and optic nerve of adult male rat

BACKGROUND

Abnormal vision has been reported by 3% of patients treated with sildenafil citrate (Viagra). Although many men use Viagra for an extended period for treatment of erectile dysfunction, the implications of the long term-daily use of it on the retina and optic nerve are unclear.

AIM OF THE WORK

To investigate the effect of chronic daily use of sildenafil citrate in a dose equivalent to men preferred therapeutic dose on the histology of the retina and optic nerve of adult male rat.

MATERIAL & METHODS

Eighteen adult male Wistar rats were equally divided into three groups. Group I: control. Group II: treated with sildenafil citrate orally (10mg/kg/day) for 8 weeks. Group III (withdrawal): treated as group II and then left for 4 weeks without treatment. Specimens from the retina and optic nerve were processed for light and electron microscopy.

RESULTS

In sildenafil citrate treated group, the retina and optic nerve revealed vacuolations and congested blood capillaries with apoptotic endothelial and pericytic cells, and thickened basal lamina. Caspase-3 (apoptotic marker) and CD31 (endothelial marker) expression increased. Glial cells revealed morphological changes: Müller cells lost their processes, activated microglia, astrocytic clasmatodendrosis, degenerated oligodendrocytes surrounded by disintegrated myelin sheathes of the optic nerve fibers. The retina and optic nerve of the withdrawal group revealed less vacuolations and congestion, and partial recovery of the glial cells.

CONCLUSION

Chronic treatment with sildenafil citrate (Viagra) caused toxic effect on the structure of the retina and optic nerve of the rat. Partial recovery was observed after drug withdrawal.

Electroretinography and immunohistochemistry of retina in rabbits treated with sildenafil citrate

Sildenafil citrate is a type-5 phosphodiesterase inhibitor (PDE-5), able to inhibit type-6 phosphodiesterase (PDE-6) as well, providing clinical benefits and paraeffects, some of them potentially related to the retina. The effects of the sildenafil on the retrobulbar and retinal circulation were studied in 27 adult male rabbits of the White New Zealand breed. The electric activity of the retina was evaluated before and at the end of the treatments, and immunohistochemistry studies were conducted. An amplitude increase of the b wave was found in the mixed response of cones and rods after 7 days of treatment with sildenafil citrate. However, in the other evaluations and periods, the values did not differ from the basal ones. Through immunohistochemistry, no significant decrease of the expression of PDE-5 and PDE-6 proteins was observed. Based on the results obtained, it is possible to admit that the sildenafil citrate did not change the expression of PDE-5 and PDE-6, neither the electroretinographic activity of the retina of male rabbits of the White New Zealand breed.

Association between phosphodiesterase-5 inhibitors and nonarteritic anterior ischemic optic neuropathy

BACKGROUND

Use of phosphodiesterase-5 (PDE-5) inhibitors has been reported to be a risk factor for development of nonarteritic anterior ischemic optic neuropathy (NAION) in males, based largely on a number of case reports. The objective of our study was to determine whether men who use this class of medications are more likely than a matched control group to develop NAION.

METHODS

A pharmacoepidemiological nested case-control study was used to examine the above association in a health claims database of physician diagnoses and prescription medication dispensing. Cases of NAION were matched with corresponding controls and correlated with the use of PDE-5 inhibitors. A conditional logistic regression model was used to estimate rate ratios for development of NAION with use of PDE-5 inhibitors.

RESULTS

A total of 1,109 cases of NAION were found and matched to 1,237,290 controls identified within the database. Cases were more likely to have hyperlipidemia, diabetes, hypertension, myocardial infarction, and cerebrovascular accident in the year preceding their NAION. The adjusted rate ratio for any use of PDE-5 inhibitor in the year before the NAION was 1.01 (95% confidence interval [CI], 0.79-1.28); recent use of a PDE-5 inhibitor in the 30 days before the NAION also had no significant association, with an adjusted rate ratio of 0.96 (95% CI, 0.75-1.23). Results for individual PDE-5 inhibitors did not achieve statistical significance.

CONCLUSIONS

Our results do not suggest any association between having a prescription filled for PDE-5 inhibitor medication and receiving a diagnosis code for NAION. This is consistent with other studies in the literature that have failed to elucidate a plausible mechanism by which these drugs might compromise circulation at the optic nerve head.

Comparison of retinal and choriocapillaris thicknesses following sitting to supine transition in healthy individuals and patients with age-related macular degeneration

IMPORTANCE

The effects of position on retinal and choroidal structure are absent from the literature yet may provide insights into disease states such as age-related macular degeneration (AMD).

OBJECTIVE

To evaluate the effect of postural change on retinal and choroidal structures in healthy volunteers and patients with non-neovascular AMD.

DESIGN, SETTING, AND PARTICIPANTS

Prospective observational case series at an academic tertiary care retina service from September 2013 to April 2014 involving 4 unaffected volunteers (8 eyes) and 7 patients (8 eyes) with intermediate AMD. Healthy volunteers selected for the study had no evidence of ocular disease. Patients with AMD were required to have at least 10 intermediate-sized drusen.

EXPOSURES

Spectral-domain optical coherence tomography with enhanced depth imaging in upright (sitting) and supine positions. Stable imaging was achieved using a rotating adjustable mechanical arm that we constructed to allow the optical coherence tomography transducer to rotate 90°. The Iowa Reference Algorithms were used to quantify choroid and choriocapillaris thicknesses.

MAIN OUTCOMES AND MEASURES

Changes in sitting and supine position central macular thickness (in micrometers), total macular volume (in cubic millimeters), choroidal thickness (in micrometers), and choriocapillaris-equivalent thickness (CCET, in micrometers).

RESULTS

Choriocapillaris-equivalent thickness was thinner in healthy participants (9.89 μm; range, 7.15-12.5 μm) compared with patients with intermediate AMD (16.73 μm; range, 10.31-27.38 μm) (P = .02); there was no difference in overall choroidal thickness between the 2 groups (P = .38). There was a 15% CCET reduction among healthy participants when transitioning from a sitting (9.89 μm) to supine (8.4 μm; range, 6.92-10.7 μm) position (P = .02) vs a CCET reduction of 11.1% from sitting (16.73 μm) to supine (14.88 μm; range, 8.76-20.8 μm) positioning (P = .10) in patients with intermediate AMD.

CONCLUSIONS AND RELEVANCE

Intermediate AMD appears to be associated with an increase in CCET and with a lack of positional responses that are observed in the CCET of normal eyes. Our results suggest that although outer portions of the choroid do not appear to be responsive to modest positional or hydrostatic pressure, the choriocapillaris capacity is, and this is measurable in vivo. Whether this physiologic deviation that occurs in AMD is related to atrophy, inflammation, or changes in autoregulatory factors or growth factors remains to be determined.

Ocular surface temperature in age-related macular degeneration

Background. The aim of this study is to investigate the ocular thermographic profiles in age-related macular degeneration (AMD) eyes and age-matched controls to detect possible hemodynamic abnormalities, which could be involved in the pathogenesis of the disease. Methods. 32 eyes with early AMD, 37 eyes with atrophic AMD, 30 eyes affected by untreated neovascular AMD, and 43 eyes with fibrotic AMD were included. The control group consisted of 44 healthy eyes. Exclusion criteria were represented by any other ocular diseases other than AMD, tear film abnormalities, systemic cardiovascular abnormalities, diabetes mellitus, and a body temperature higher than 37.5°C. A total of 186 eyes without pupil dilation were investigated by infrared thermography (FLIR A320). The ocular surface temperature (OST) of three ocular points was calculated by means of an image processing technique from the infrared images. Two-sample t-test and one-way analysis of variance (ANOVA) test were used for statistical analyses. Results. ANOVA analyses showed no significant differences among AMD groups (P value >0.272). OST in AMD patients was significantly lower than in controls (P > 0.05). Conclusions. Considering the possible relationship between ocular blood flow and OST, these findings might support the central role of ischemia in the pathogenesis of AMD.

Sildenafil attenuates vaso-obliteration and neovascularization in a mouse model of retinopathy of prematurity

PURPOSE

We sought to determine the effect of sildenafil on retinal vascular changes in a mouse model of oxygen-induced retinopathy (OIR).

METHODS

Vascular defects in OIR mice were quantified by measuring vaso-obliteration at postnatal days 12 and 17 (P12 and P17) and neovascularization at P17 to compare sildenafil-treated to dextrose-treated OIR mice. Retinal HIF1α protein expression was quantified by Western blotting and normalized to that of β-actin. Right ventricular hypertrophy was measured by Fulton's index as a surrogate for hyperoxia-induced pulmonary hypertension.

RESULTS

At P12, OIR mice treated with sildenafil demonstrated a 24% reduction in vaso-obliteration (P < 0.05), whereas at P17, treated animals showed a 50% reduction in neovascularization (P < 0.05) compared to dextrose-treated controls. Sildenafil-treated OIR mice had stabilization of retinal HIF1α at P12, immediately after hyperoxia. At P17, sildenafil-treated OIR mice had decreased HIF1α relative to untreated mice. OIR mice developed right ventricle hypertrophy that was significant compared to that in room air controls, which was abrogated by sildenafil.

CONCLUSIONS

Sildenafil treatment significantly decreased retinal vaso-obliteration and neovascularization in a mouse OIR model. These effects are likely due to sildenafil-induced HIF1α stabilization during hyperoxia exposure. Furthermore, we confirm disease overlap by showing that OIR mice also develop hyperoxia-induced right ventricular hypertrophy, which is prevented by sildenafil. This study is a first step toward delineating a potential therapeutic role for sildenafil in OIR and further suggests that there may be common pathophysiologic mechanisms underlying hyperoxia-induced retinal and pulmonary vascular disease.

Age-related macular degeneration: choroidal ischaemia?

Aim

Our aim is to use ultrasound to non-invasively detect differences in choroidal microarchitecture possibly related to ischaemia among normal eyes and those with wet and dry age-related macular degeneration (AMD).

Design

Prospective case series of subjects with dry AMD, wet AMD and age-matched controls.

Methods

Digitised 20 MHz B-scan radiofrequency ultrasound data of the region of the macula were segmented to extract the signal from the retina and choroid. This signal was processed by a wavelet transform, and statistical modelling was applied to the wavelet coefficients to examine differences among dry, wet and non-AMD eyes. Receiver operating characteristic (ROC) analysis was used to evaluate a multivariate classifier.

Results

In the 69 eyes of 52 patients, 18 did not have AMD, 23 had dry AMD and 28 had wet AMD. Multivariate models showed statistically significant differences between groups. Multiclass ROC analysis of the best model showed an excellent volume-under-curve of 0.892±0.17. The classifier is consistent with ischaemia in dry AMD.

Conclusions

Wavelet augmented ultrasound is sensitive to the organisational elements of choroidal microarchitecture relating to scatter and fluid tissue boundaries such as seen in ischaemia and inflammation, allowing statistically significant differentiation of dry, wet and non-AMD eyes. This study further supports the association of ischaemia with dry AMD and provides a rationale for treating dry AMD with pharmacological agents to increase choroidal perfusion.

ClinicalTrials.gov registration

NCT00277784.

Does therapeutic dose of sildenafil citrate treatment lead to central serous chorioretinopathy in patients with erectile dysfunction?

The possible effects of sildenafil citrate administration at therapeutic dosage on visual acuity, color vision, intraocular pressure, macular thickness, macular volume, and central serous chorioretinopathy in patients with erectile dysfunction were evaluated. The study consisted of 43 male patients diagnosed as having erectile dysfunction according to the first five question version of International Index of Erectile Function (IIEF-5). All patients were given sildenafil citrate 50 mg po 2 to 3 times/week for a month. The patients were evaluated at the first week and at the end of the treatment. The macular thickness and volume assessments with optic coherence tomography did not differ significantly in foveal, parafoveal areas, parafoveal superior hemisphere, parafoveal inferior hemisphere, parafoveal temporal, superior, nasal, and inferior quadrants. Central serous chorioretinopathy was not found in any of the patients.

Measurement of choroidal perfusion and thickness following systemic sildenafil (Viagra(®) )

PURPOSE

To demonstrate anatomic and physiologic changes in the human choroid following systemic sildenafil citrate (Viagra®) using enhanced depth imaging spectral domain-optical coherence tomography (EDI-OCT) and swept-scan high-frequency digital ultrasound.

METHODS

Seven healthy male subjects (mean age 32.7 years) were evaluated at baseline and 2 hr after ingesting 50 mg of sildenafil. Swept-scan high-frequency digital ultrasound and EDI-OCT were utilized to measure choroidal perfusion and thickness, respectively. Results were read by masked observers. The Wilcoxon signed-rank test and t-test were used to analyse differences in choroidal flow and thickness at baseline and 2 hr after ingestion of sildenafil.

RESULTS

Two hours following sildenafil, increased choroidal perfusion was observed in 11 of 12 eyes measured by swept-scan high-frequency digital ultrasound. The mean increase was 3.46 (±2.00) times baseline with a range of 0.47-7.80 times baseline (p = 0.004). Increased choroidal thickness was observed in 12 of 12 eyes measured with EDI-OCT. The average choroidal thickness increased by 11.6% temporal to the fovea, 9.3% nasal to the fovea and 10.7% underneath the fovea (p < 0.001 for all values).

CONCLUSIONS

Choroidal perfusion and thickness both increase in response to systemic sildenafil. These changes could secondarily affect retinal function, explain previously reported clinical symptoms and potentially be a useful adjunct for treatment of ocular diseases that would benefit from increased choroidal blood flow.

Sildenafil dilates ophthalmic artery in type 2 diabetic patients

Background:

Conflicting reports exist on the effect of sildenafil on ophthalmic artery blood flow; many visual disturbances due to vascular insult were reported with the use of sildenafil in diabetic patients like nonarteritic ischemic optic neuropathy.

Objectives:

The present work aimed to investigate whether sildenafil modulates ophthalmic artery vasoreactivity in patients with type 2 diabetes mellitus. Literature reports on this aspect are lacking.

Methods:

A total of 35 male subjects were enrolled in this study, 18 with type 2 diabetes mellitus matched with 17 normal individuals. Ophthalmic artery was insonated through a transorbital window using colored Doppler equipment with transcranial Doppler facility. Ophthalmic artery reactivity was assessed using breath holding/hyperventilation test, before and after giving 50 mg oral sildenafil.

Results:

It was found that in both normal subjects and diabetic patients, sildenafil increased baseline control of mean flow velocity of ophthalmic artery significantly (p < 0.05), breath holding caused a decrease of MFVopa (p < 0.05), and subsequent hyperventilation caused increase of MFVopa (p < 0.05). There was no statistically significant change in breath holding index and full range of vasodilatation of ophthalmic artery (p > 0.05) after sildenafil, in normal and diabetic groups. There was a significant increase of resistive index of ophthalmic artery flow in diabetic patients compared with that of normal subject (p < 0.05). Sildenafil decreased resistive index of ophthalmic artery flow significantly only in diabetic patients (p < 0.05).

Conclusion:

Sildenafil increased MFVopa, but had no significant effect on vasoreactivity of ophthalmic artery; sildenafil decreased resistive index only in type 2 diabetic patients.

The effects of moxaverine on ocular blood flow in patients with age-related macular degeneration or primary open angle glaucoma and in healthy control subjects

PURPOSE

The phosphodiesterase inhibitor moxaverine has been shown to increase choroidal blood flow (BF) in young healthy subjects. The present study was performed to investigate the effect of intravenously administered moxaverine on ocular BF in patients with age-related macular degeneration (AMD), primary open angle glaucoma (POAG) and in age-matched control subjects.

METHODS

  Twenty patients with AMD, 20 patients with POAG and 20 control subjects were included. Moxaverine 150 mg was applied intravenously over 30 min. BF was measured in the choroid and in the optic nerve head (ONH) using laser-Doppler flowmetry and in retinal vessels combining laser-Doppler velocimetry with retinal vessel analysis before and 30, 60 and 90 min after start of drug administration. BF velocities in the retrobulbar vessels were measured using colour Doppler imaging.

RESULTS

Moxaverine increased choroidal BF by 9 ± 22% (p = 0.012), ONH BF by 13 ± 33% (p = 0.021), mean flow velocity in the ophthalmic artery by 23 ± 34% (p < 0.001) and in the posterior ciliary arteries by 25 ± 35% (p < 0.001). Moxaverine had no significant effect on retinal vessel diameters and retinal BF. There were no significant differences in any of the measured parameters between the three groups.

CONCLUSION

The present study indicates that systemic administration of moxaverine increases choroidal and ONH BF in elderly patients with eye diseases associated with hypoperfusion and in age-matched controls. Further studies in patients are needed to investigate whether long-term treatment with moxaverine is clinically beneficial for patients with ocular diseases.

Ocular safety of sildenafil citrate when administered chronically for pulmonary arterial hypertension: results from phase III, randomised, double masked, placebo controlled trial and open label extension

OBJECTIVE

To assess the ocular effects and safety profile of chronic sildenafil oral dosing in patients with pulmonary arterial hypertension.

DESIGN

12 week, double masked, randomised, placebo controlled, phase III trial with open label extension.

SETTING

53 institutions worldwide.

PARTICIPANTS

277 adults with idiopathic pulmonary arterial hypertension or pulmonary arterial hypertension associated with connective tissue disease or after congenital heart disease repair (mean pulmonary artery pressure ≥25 mm Hg; pulmonary capillary wedge pressure ≤15 mm Hg at rest).

INTERVENTIONS

During the double masked study, oral sildenafil 20 mg, 40 mg, or 80 mg or placebo (1:1:1:1) three times daily for 12 weeks was added to baseline drug treatment. In the extension study, the placebo, 20 mg and 40 mg groups received 40 mg three times daily titrated to 80 mg three times daily at week 6. After unmasking, the dose was titrated according to clinical need.

MAIN OUTCOME MEASURE

Ocular safety (ocular examinations, visual function tests, participants' reports of adverse events, and visual disturbance questionnaire completed by investigators) by treatment group at 12 weeks, 24 weeks, 18 months, and yearly.

RESULTS

Findings of the objective assessments-that is, intraocular pressure and visual function tests (visual acuity, colour vision, and visual field)-were similar across groups (20 mg, n=69; 40 mg, n=67; 80 mg, n=71; placebo, n=70). No clinically significant changes occurred between baseline and 12 weeks, except for an efficacy signal in contrast sensitivity for the sildenafil 40 mg three times daily group. In right eyes, changes in intraocular pressure from baseline to week 12 ranged from a mean of -0.5 (95% confidence interval -1.3 to 0.2) mm Hg with placebo, -0.2 (-0.9 to 0.5) mm Hg with sildenafil 40 mg, and -0.1 (-0.7 to 0.5) mm Hg with 80 mg to 0.3 (-0.4 to 0.9) mm Hg with sildenafil 20 mg (the approved dose for pulmonary arterial hypertension). Mean changes from baseline to week 12 in contrast sensitivity in right eyes were -0.02 (SD 0.12) in the sildenafil 20 mg three times daily group compared with -0.05 (0.18) in the placebo group (P=0.044). Percentages of participants with deterioration in visual acuity (Snellen) from baseline to week 12 ranged from 10% (n=7) in the placebo group to 3% (n=2) in the sildenafil 20 mg three times daily group; the same percentages had visual field changes from normal to abnormal during the period in these two groups. The investigators did not deem any findings on colour vision assessment to be clinically significant. Findings of the objective assessments in the 40 mg and 80 mg three times daily sildenafil treatment groups and in left eyes were not substantially different, nor were any measures different throughout the open label extension compared with week 12. However, objective data were limited after month 18, as most participants had missing data or visual parameters were no longer collected by investigators. Incidence of ocular adverse events reported on the case report forms and assessed by the investigator was low with all doses, but a modest, dose related incidence of chromatopsia, cyanopsia, photophobia, and visual disturbance was reported with 80 mg three times daily consistent with the indicated dosing for erectile dysfunction. Retinal haemorrhages, captured on funduscopy, occurred in 2% (4/207) of sildenafil treated participants and none in the placebo group during the double masked study and in 4% (10/259) during the open label extension.

CONCLUSIONS

Sildenafil dosing up to 80 mg three times daily is safe and well tolerated from an ocular perspective in patients with pulmonary arterial hypertension. Daily chronic dosing in this patient population was not associated with visual change and had no detrimental effect on best corrected visual acuity, contrast sensitivity, colour vision, or visual field, or on slit lamp examinations, funduscopy, or intraocular pressure during the duration of this study.

TRIAL REGISTRATION

Clinical trials NCT00644605 and NCT00159887.

Contrast sensitivity, ocular blood flow and their potential role in assessing ischaemic retinal disease

PURPOSE

To examine the definition, evaluation methodology, association to ocular blood flow and potential clinical value of contrast sensitivity (CS) testing in clinical and research settings, focusing in patients with ischemic retinal disease.

METHODS

A review of the medical literature focusing on CS and ocular blood flow in ischemic retinal disease.

RESULTS

CS may be more sensitive than other methods at detecting subtle defects or improvements in primarily central retinal ganglion cell function early on in a disease process. CS testing attempts to provide spatial detection differences which are not directly assessed with standard visual acuity chart testing. Analyzing all studies that have assessed both CS change and ocular blood flow, it is apparent that both choroidal circulation and retinal circulation may have an important role in influencing CS.

CONCLUSION

The concept that CS is directly influenced by ocular blood flow is supported by reviewing the studies involving both. Although the studies in the literature have not established a direct cause and effect relationship per se, the literature review makes it logical to assume that changes in retinal and choroidal blood flow influence CS. This raises the possibility that a subjective visual characteristic, specifically CS, may be able to be evaluated more objectively by studying blood flow. It appears appropriate to study the relationship between blood flow and CS more extensively to develop improved ways of measuring various aspects of blood flow to the eye and to best quantify early changes in visual function.

Effect of sildenafil citrate on intraocular pressure and blood pressure in human volunteers

Anecdotal reports have suggested that the vasodilator, sildenafil citrate, which evokes its effect via a select inhibition of PDE5, has the potential to increase intraocular pressure (IOP) in some individuals. An ocular hypertensive effect by sildenafil was also recently described in a sheep animal model. In contrast, clinical studies have not found a direct association between sildenafil ingestion (commonly consumed as Viagra) and changes in IOP. However, some such studies also reported no effects of sildenafil on systemic blood pressure (BP) at the time of the IOP determination. Given this surprising result, our purpose was to repeat a study in human volunteers in the city of Corrientes, Argentina to corroborate the effects of sildenafil on human IOP and systemic BP. For the present study, 9 healthy volunteers (male and female, 18-74 years old) were selected as subjects after ophthalmic and cardiovascular evaluation indicated that they exhibited normal parameters for their age. In a masked, placebo-controlled study, the subjects ingested 100 mg sildenafil citrate (provided as Vorst from Laboratorios Bernabo, Argentina) in one session, and a placebo on a second separate occasion. IOP was measured with a Goldman applanation tonometer by an ophthalmologist, and BP by a second physician, neither of whom witnessed the tablet ingestion by the volunteers, nor provided with information on the nature of the test compounds. A third individual administered the tablets. The average baseline IOP of this group of 9 was 13.1 ± 0.6 mm Hg. Subsequent to sildenafil ingestion, IOP increased by 26% to 16.5 ± 0.8 mm Hg 60 min later (P < 0.005, as paired data), and returned to control values within 2 h. Both systolic and diastolic BP were significantly reduced by sildenafil ingestion. At the point of maximal systemic hypotension (90 min), the systolic and diastolic pressures declined by 15% and 13%, respectively. No significant changes in IOP or BP were recorded after ingestion of the placebo. Our results suggest that sildenafil can elicit a transient IOP increase that may be of importance to patients chronically treated with PDE5 inhibitors for various vascular diseases (e.g., pulmonary hypertension). We discuss possible mechanisms by which PDE5 inhibition might lead to a rise in IOP.

The effects of sildenafil citrate on choroidal thickness as determined by enhanced depth imaging optical coherence tomography

PURPOSE

To investigate the effects of the phosphodiesterase-5 inhibitor, sildenafil citrate, on choroidal thickness using eye-tracked enhanced depth imaging spectral-domain optical coherence tomography.

METHODS

In a prospective interventional study, 8 healthy subjects (4 men and 4 women) with no ocular history underwent enhanced depth imaging spectral-domain optical coherence tomography at baseline, 1 hour, and 3 hours after the ingestion of 100 mg of sildenafil citrate. Choroidal thickness measurements for both eyes using enhanced depth imaging spectral-domain optical coherence tomography were taken by 2 masked readers at baseline, 1-hour, and 3-hour time points. Statistical analysis was performed to compare the measurements of choroidal thickness at each of the three intervals.

RESULTS

The mean age of the subjects was 35.9 years (range 30-46 years). Mean choroidal thickness at baseline was 334 μm (± 57 μm). Mean choroidal thickness increased by 12.3% to 375 μm (± 68 μm) at 1 hour after ingestion (P < 0.001). At 3 hours after ingestion, the mean choroidal thickness remained elevated at 372 μm (± 61 μm), 11.6% thicker than baseline (P < 0.001). There was no significant difference in choroidal thickness between the 1-hour and the 3-hour intervals (P = 0.719).

CONCLUSION

Sildenafil citrate appears to increase choroidal thickness as measured by eye-tracked enhanced depth imaging spectral-domain optical coherence tomography measurements in healthy subjects 1 hour and 3 hours after ingestion. These findings may be of relevance given that increased choroidal thickness appears to be a risk factor for central serous chorioretinopathy and that several reports have suggested an association between phosphodiesterase-5 inhibitors and this disorder.

Effects of sildenafil and tadalafil on intraocular pressure in sheep: implications for aqueous humor dynamics

PURPOSE

To determine the effects of vasodilators on intraocular pressure (IOP) and the protein content of sheep aqueous humor (AH), because the vasodilators may increase fluid leakage from the fenestrated capillaries of the ciliary body to the extracellular tissue and directly to the anterior chamber (AC) via the iris, and some senior patients (older than 70) treated with sildenafil have exhibited elevated IOP.

METHODS

Experiments were performed on domestic sheep residing on a ranch in Argentina. These docile and compliant animals readily swallowed tablets of sildenafil (50 and 100 mg) and tadalafil (20 mg). IOP was monitored by Perkins applanation tonometry in 21 normal sheep receiving orally administered drugs. In addition, paracentesis was performed on six sheep to quantify changes in AH protein levels.

RESULTS

Ingestion of both sildenafil and tadalafil increased sheep IOP from normal levels of approximately 9 to 11 mm Hg within 1 hour. The IOP elevation was approximately 1.6-fold with both doses of sildenafil. IOP returned to control values within 4 hours. With the longer-lasting vasodilator tadalafil, IOP remained 1.6- to 1.9-fold higher than normal for at least 48 hours and returned to control levels within 4 days. The AH protein content was approximately 39% higher in sheep given 100 mg sildenafil.

CONCLUSIONS

These data are consistent with a vasodilator-evoked increase in plasma-like fluid in the AC, which likely accounts for the IOP elevation. The results are discussed with a model for AH dynamics that may be of importance to senior individuals treated for vascular diseases with these compounds.

Phosphodiesterase inhibitors and the eye

Phosphodiesterase type 5 (PDE5) inhibitors are effective oral treatments for erectile dysfunction and have become one of the most widely prescribed medications worldwide. The mechanism of action is to reduce the degradation of cyclic GMP (cGMP) potentiating the effect of nitric oxide in the corpus cavernosum and allowing erectile function to occur by consequent relaxation of penile smooth muscle. Because of the presence of PDE5 in choroidal and retinal vessels these medications increase choroidal blood flow and cause vasodilation of the retinal vasculature. The most common symptoms are a blue tinge to vision and an increased sensitivity to light. There have been reports of non-arteritic anterior ischaemic optic neuropathy and serous macular detachment in users of PDE5 inhibitors, although a causal relationship has not been conclusively shown. Despite the role of cGMP in the production and drainage of aqueous humour these medications do not appear to alter intraocular pressure and are safe in patients with glaucoma. All PDE5 inhibitors weakly inhibit PDE6 located in rod and cone photoreceptors resulting in mild and transient visual symptoms that correlate with plasma concentrations. Psychophysical tests reveal no effect on visual acuity, visual fields or contrast sensitivity; however, some studies show a mild and reversible impairment of blue-green colour discrimination. PDE5 inhibitors transiently alter retinal function on electroretinogram testing but do not appear to be retinotoxic. Despite the role of cyclic nucleotides in tear production there is no detrimental effect on tear film quality. Based on the available evidence PDE5 inhibitors have a good ocular safety profile.

Effect of Sildenafil Citrate on Retinal Functions: Preliminary Report on Humphrey Visual Field Analysis

OBJECTIVE

To assess the effect of sildenafil citrate treatment on visual field analysis (VFA) in patients using sildenafil citrate for erectile dysfunction.

MATERIALS AND METHODS

In this prospective study on 18 male volunteers with erectile dysfunction, bilateral VFA was performed using the Humphrey 30-2 central standard threshold test. White-on-white (W/W) and blue-on-yellow (B/Y) protocols were used prior to treatment (baseline VFA) and after treatment (repeat VFA) with sildenafil citrate. W/W and B/Y baseline VFA and repeat VFA mean deviations (MD) were compared.

RESULTS

The baseline MD for W/W and B/Y protocols were -1.34 +/- 1.8 and -2.59 +/- 2.1 dB, respectively, whereas the mean repeat MD for W/W and B/Y protocols were -1.79 +/- 2.21 and -2.83 +/- 3.31 dB, respectively. There was no statistically significant difference between W/W and B/Y baseline and repeat VFA with respect to MD (p > 0.05).

CONCLUSION

Sildenafil citrate causes no significant changes in Humphrey VFA in patients with erectile dysfunction.

Erectile dysfunction drugs and risk of anterior ischaemic optic neuropathy: casual or causal association?

Phosphodiesterase type 5 (PDE5) inhibitor drugs for erectile dysfunction have revolutionised the treatment of male sexual dysfunction and are among the best selling drugs worldwide. Several cases of non-arteritic anterior ischaemic optic neuropathy (NAION) have been reported since 2005 in users of these agents. NAION is a sudden irreversible cause of visual loss with a poorly understood aetiology that affects up to 10 adults per 100,000 each year. Following a series of such case reports, WHO and FDA have labelled the association between use of PDE5 inhibitors and risk of NAION as "possibly" causal. There have been several recent studies of this association, including a rechallenge case report and a large managed care database study. However, the inability to confirm or refute claims of an association between NAION and EDD is generating clinical and regulatory uncertainty. Questions surrounding use of PDE5 inhibitors and risk of NAION highlight weaknesses in current systems used to identify and evaluate uncommon adverse effects of medication use. This paper reviews all the recent evidence on PDE5 inhibitors and the risk of NAION.

Ischemic optic neuropathy in a child

Nonarteritic ischemic optic neuropathy is a rare event in childhood, occurring mostly in the setting of major surgical procedures or hypovolemia. We report on a child who presented with this unusual complication during the course of therapy with sildenafil citrate, which is gaining acceptance as a treatment modality for pulmonary hypertension in the pediatric age group. The ocular complications of this drug have been widely reported in the adult literature, but there are sparse reports, if any, in the pediatric age group. The likely pathophysiology of this condition is reviewed, as are the other ophthalmologic complications of this drug.

Anterior ischemic optic neuropathy and stroke with use of PDE-5 inhibitors for erectile dysfunction: cause or coincidence?

The PDE-5 inhibitors sildenafil (Viagra) vardenafil (Levitra) and tadalafil (Cialis) have been taken by millions of men for erectile dysfunction. Transient visual symptoms are common but there also have been fourteen cases of nonarteritic anterior ischemic optic neuropathy (NAION) described in patients using these drugs as well as a few other vascular events. NAION is a common optic neuropathy in patients in the age group using these drugs and the question arises whether or not PDE-5 inhibitors are causing NAION. One case of NAION occurred after transient visual symptoms occurred with repeated use and one patient experienced a transient ischemic attack after taking a dose followed by a stroke on using the drug again later. Other than these two cases with strong dechallenge-rechallenge data, the evidence to support PDE-5 inhibitors as a cause of NAION or any vascular event is weak. PDE-5 inhibitors probably are a rare cause of a common ischemic disorder of the optic disc. They should be avoided in men who have already experienced NAION in one eye. Patients should be warned to seek medical attention if they have visual field or acuity loss after using PDE-5 inhibitors. Otherwise there is little basis for modifying the current guidelines for the use of these drugs.

Expression of the PDE5 enzyme on human retinal tissue: new aspects of PDE5 inhibitors ocular side effects

OBJECTIVE

We tested the effect of two phosphodiesterase type-5 (PDE5) inhibitors, sildenafil and tadalafil, on ophthalmic artery (OA) blood flow velocity and investigated the presence of the PDE5 enzyme on human retinal tissue in comparison with the PDE6 enzyme localization.

METHODS

Using Colour Doppler ultrasonography (CDU) we investigated, in 30 healthy young subjects (27.8 years of age; range, 24.3-33.7 years), the effects of a single oral dose of sildenafil (100 mg), tadalafil (20 mg), and placebo on OA blood flow velocity. Western blot for PDE6 and PDE5 protein expression was performed on frozen samples of human retina, testis, sperm, skin, and corpus cavernosum. Immunohistochemistry was performed on two ocular globes from dead donors.

RESULTS

CDU showed a relationship between the administration of PDE5 inhibitors and OA blood flow velocity modifications in a time-dependent manner. Western blot and immunohistochemical analysis showed PDE6 and PDE5 presence in human retinal tissue and gave a map of its distribution.

CONCLUSION

We demonstrated that (a) tadalafil and sildenafil are able to modify the OA flux in a time-dependent manner; (b) the PDE5 enzyme is expressed on retinal and choroid vasculature (smooth muscle and endothelial cells), on ganglion and bipolar cells; (c) human retinal tissues express the PDE6 enzyme in the rod and cone photoreceptors; (d) visual side effects after PDE5 inhibitors administration may be linked to a specific effect on the PDE5 enzyme; and (e) the PDE5 enzyme may have a physiologic role on ganglion and bipolar cells that need to be further investigated.

Effect of sildenafil on ocular hemodynamics in 3 months regular use

The aim of this study was to evaluate the effect of sildenafil on ocular hemodynamics in a group of men with erectile dysfunction in 3 months regular use. A total of 15 patients with erectile dysfunction were included in this prospective study. All patients received 50 mg doses of sildenafil (Viagra, Pfizer) two times per week regularly for 3 months. The following examinations were performed on both eyes before and after sildenafil treatment: best-corrected visual acuity (BCVA), intraocular pressure (IOP), color vision, anterior segment, and fundus examination. Using color Doppler imaging, we measured hemodynamic variables in the ophthalmic artery (OA), central retinal artery (CRA), and short posterior ciliary artery (SPCA). No significant changes in BCVA, color vision and IOP were found after sildenafil treatment. The anterior segment and fundus examinations showed no abnormalities. All Doppler parameters of OA, CRA, and SPCA remained nonsignificant for both eyes after sildenafil treatment. Oral sildenafil in 3 months regular use seems to have no effect on ocular hemodynamics.

Effects of Sildenafil Citrate (Viagra®) on Renal Arteries: An Evaluation with Doppler Ultrasound

INTRODUCTION

We aimed to determine hemodynamic alterations in renal arteries that may have resulted from oral intake of sildenafil citrate in healthy volunteers.

MATERIALS AND METHODS

Twelve healthy volunteers were included in our study. Renal Doppler ultrasonography (US) was performed before the drug intake to assess the basal values. Maximum peak systolic velocity, and resistivity and pulsatility indices were measured from the segmental branches of both renal arteries in all the examinations. After the basal measurements 50 mg of sildenafil or placebo were randomly given to the 12 subjects. Renal Doppler US examinations were carried out 1 h after sildenafil or placebo intake. On the following day sildenafil was administered to the subjects who had previously taken placebo or vice versa. Renal Doppler US was repeated after 1 h. The effect of sildenafil on renal vascular hemodynamics was evaluated by comparison of basal values with postplacebo and postsildenafil values.

RESULTS

No statistically significant differences were found between the basal values of bilateral renal arteries and maximum peak systolic velocity, and resistivity and pulsatility index values measured after the placebo or sildenafil intake.

CONCLUSION

We demonstrated that single-dose sildenafil did not cause any significant effect on renal artery hemodynamics in healthy individuals.