Long term use of inhaled steroids to prevent asthma symptoms may increase the risk of cataracts, research suggests.
Inhalers help to control asthma
Scientists at the London School of Hygiene and Tropical Medicine examined data on almost 31,000 people.
Inhaled steroids had been used by 11.5% of those with cataracts, but only 7.5% without the eye condition.
Writing in the British Journal of Ophthalmology, the researchers say doses of inhaled steroids should be kept to a minimum.
Previous research has indicated that some forms of steroids increase the risk of cataracts - but whether the inhaled variety also carries a risk has not been known.
The latest study found that the higher the dose of inhaled steroids, the higher the risk of cataracts.
People taking the lowest daily dose - up to 400ug - seemed to have little or no raised risk.
However, those taking doses greater than 1,600 ug a day, had an increased risk of around 70%.
Risk also rose according to how long patients had been taking their treatment.
Nearly one in 10 people over the age of 65 has asthma or chronic obstructive pulmonary disease, most of whom are prescribed an inhaled steroid at some point.
Lead researcher Dr Liam Smeeth told BBC News Online: "Inhaled steroids are an important and very effective treatment for asthma and for some people with chronic bronchitis.
"The large therapeutic benefits need to be balanced against the relatively small risks. The increased risk was largely confined to he very highest doses and to long duration of use.
'Risk versus benefit'
"My advice would be that if people are concerned they should discuss this with the doctor who manages their medication.
"There is certainly no reason to rush into any changes, and stopping inhaled steroids abruptly should be avoided."
Professor Martyn Partridge, chief medical advisor to the National Asthma Campaign, said a previous study had produced similar findings.
"It is very much a risk versus benefit argument, but what should be clearly understood is that the risk is negligible and the benefit is great if everybody is treated according to the guidelines, with the lowest dose of inhaled steroid that controls their condition.
"Unfortunately, there is evidence that the stepping down of inhaled steroids when asthma is controlled in a guided fashion does not always take place, and those with asthma remain on unnecessarily high doses.
"Nowadays we should be able to control asthma with much smaller doses of inhaled steroids by combining the steroid with a long acting inhaled bronchodilator such as Formoterol or Salmeterol"
Most asthmatics use two types of medication. A preventative inhaler, which includes steroids, and a bronochodiator, which relieves symptoms, and does not.