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Chlamydia and Blindness

Some time ago, we wrote about the devastating effects of the spread of chlamydia among the vulnerable koala bears of Australia. Since then, Australian scientists have been getting closer to the development of a vaccination for these beautiful marsupials against, what is for them, an extremely dangerous disease, sometimes rendering those infected, blind. Based on the results of a small but successful trial in Brisbane, things might be looking up for the koala bear and maybe even humans alike.

Chlamydia is still one of the most common sexually transmitted infections around today yet rates are generally consistent year after year. Apart from spreading awareness and launching STI health campaigns, there is little else we can do without a vaccine. Part of the problem is that in over 80% of cases, the infection is asymptomatic, and those who carry it spread the infection without even knowing. In koalas, the untreated infection can lead to blindness and infertility. Chlamydia also causes infertility in humans if left untreated. Other complications include pelvic inflammatory disease (PID), which causes infertility, ectopic pregnancy and miscarriage.

In this promising study, 30 out of 60 koalas were vaccinated and the trial group was then observed in its natural surroundings via radio collars thereafter. It was discovered that 7/8 koalas who were suffering from an eye infection at the time of vaccination, showed improvements. In stark contrast, of the koalas who were not vaccinated, 4/6 who were suffering from eye infections, only got worse. Symptoms of the infection in koalas manifest themselves in eye infections but also as infections of the reproductive tract.

Those who were infected with the strain of chlamydia, and who were simultaneously vaccinated, did not go on to experience the full-blown infection. This is a really positive outcome considering the loss of life among this species due, not only to the spread of the chlamydia infection which, in some areas, infection rates are up at 90%, but also down to habitat loss.

Koalas and humans both respond well to antibiotic treatment but in the case of koalas, it is not feasible to treat every koala infected and maintain control over the spread. The vaccine could act as a model for a human vaccine though, a development that has been researched for decades now, but so far, to no avail. If we could use the koala vaccine as a model for the human vaccine, we could prevent the infection across a large portion of the population. The result of this study is good news for the koalas, but it inspires hope for us too.

In the meantime, partner notification, diagnoses, and successful treatments (re-testing), are the key to beating chlamydia and stymieing the spread. Telling partners will directly affect rates of diagnosis, rates that must be consistently maintained in order to gain better control over the spread of infection.  You can find your local testing clinic here. If your are reluctant to attend a clinic then there are online options such as this website.

You can read more about Chlamydia and blindness here.

Does sex really affect your eyesight?

Viagra is used in the treatment of men with erectile dysfunction. Viagra blocks the enzyme known as phosphodiesterase-5 (PDE-5), which leads to smooth muscle relaxation and an increase in blood flow to the penis, and thus to an erection.

Clinical trials have shown that Viagra is well tolerated but, like all medicines, it may cause side effects. One effect that has attracted particular attention is visual disturbance, sometimes referred to as ‘blue vision’. It happens more frequently when high doses of Viagra are taken or in cases of drug abuse. It may occur because Viagra also blocks PDE-6 (although to a much lesser degree than PDE-5), which is involved in converting light into electrical signals in the light-sensitive cells of the eye.

Changes in blue/green colour discrimination were found in some men given single Viagra doses of 100 mg (the maximum recommended dose). Effects were mild and temporary, seen at one hour after dosing and disappearing after two hours. Viagra did not affect visual acuity (clearness) or contrast sensitivity in this study. Another study demonstrated that Viagra had no clinically relevant effects on the vision of patients with early age-related macular degeneration (an eye disorder resulting in loss of central vision).

In clinical trials where Viagra was taken when needed and at the recommended dose, 3% of men reported abnormal vision, which was mainly colour tinge to vision, increased sensitivity to light or blurred vision. The number of events increased with dose and with doses above the recommended dose range.

Men should be advised to stop taking Viagra and notify a doctor if they experience visual defects. They should also avoid driving as it may reduce their concentration. These side effects are usually mild to moderate in severity and temporary, disappearing as the effects of the drug wear off.

Rarely, in post-marketing studies, non-arteritic anterior ischemic optic neuropathy or NAION that causes reduced vision has also been associated with use of PDE5 inhibitors, including Viagra. However, it is not certain that these medicines caused NAION as these men also had other risk factors (such as diabetes, coronary artery disease, and high blood pressure) for this condition. As a precaution, Viagra is not recommended for men who have NAION and loss of vision in one eye. It is also not advised for use by men with a genetic degenerative condition of the retina (such as retinitis pigmentosa) because the effects of the drug in these people are unknown.

So where does this leave us? None of this indicates that taking Viagra is likely to seriously affect eye sight. However, as with all medications, it does indicate that it is preferable to seek advice before taking Viagra and to take the dose recommended by your doctor. It would appear that doctors are agreed that there is no risk here and some of the claims being made against Pfizer are opportunistic to say the least.