Evidence
Alert

The glaucoma patients most at risk of sight loss were identified in a new study

People with glaucoma in both eyes, high pressure in the eyes and small amounts of bleeding in the eye (disc haemorrhages) have an increased risk of sight loss. These risk factors for sight loss were revealed in new analysis of study data.

Glaucoma is a common eye condition in which the optic nerve connecting the eye to the brain is damaged. The United Kingdom Glaucoma Treatment Study (UKGTS) followed more than 500 people with glaucoma over two years. It compared latanoprost eyedrops with drops that contained no medication (placebo).

The study found that treatment with latanoprost (a medicine which decreases pressure in the eye) reduced the risk of sight loss by more than half in people with glaucoma. And, unlike in previous studies, older age was not associated with increased risk of blindness.

There are many health risks associated with smoking including other eye conditions that cause sight loss such as age-related macular degeneration. But in this study, people who had ever smoked were at lower risk of sight loss from glaucoma than those who had never smoked. This finding must be interpreted carefully and more research into the possible effects of smoking on vision is needed.

The findings support current treatment guidelines to use latanoprost to treat glaucoma.

What’s the issue?

Glaucoma is the leading cause of irreversible blindness worldwide. If left untreated, the condition gets worse over time, causing gradual loss of vision or blind spots in the eye.

Current glaucoma treatments lower the pressure inside the eye using eye drops. But although these medications are recommended, until recently they had not been tested against dummy eye drops (placebo) to check they really do reduce the risk of vision loss in glaucoma.

Between 2006 and 2010, researchers at Moorfields Eye Hospital conducted the first trial comparing a medicine called latanoprost with placebo. This was the United Kingdom Glaucoma Treatment study (UKGTS). It looked at how long it would take for people with the condition to experience measurable sight loss.

In 2015, the trial researchers published evidence that latanoprost could preserve vision in people with the condition. People who were not taking latanoprost experienced sight loss earlier than those not taking the medication. In this current study, researchers used data from the trial to identify factors that affect the risk of sight loss in glaucoma, including the use of latanoprost.

What’s new?

The UKGTS included 516 patients with untreated glaucoma. Half were given latanoprost eye drops, while the others were given drops that contained no medication. Neither participants nor researchers knew which treatment had been given. Patients were assessed regularly for two years and underwent vision tests and eye pressure measurements.

They found that:

  • treatment with latanoprost more than halved the risk of sight loss in glaucoma (reduced by 58%)
  • glaucoma in both eyes, increased eye pressure, and disc haemorrhage (small areas of bleeding in the eye) at any visit were associated with an increased risk of vision loss
  • older age was not associated with an increased risk of vision loss
  • people who had ever smoked were less likely to experience sight loss with glaucoma than non-smokers.

Why is this important?

The UKGTS results are strong evidence that reducing eye pressure can preserve vision. It supports findings from similar trials and NICE recommendations to offer eye drop treatments such as latanoprost, and possibly tafluprost and travoprost which also reduce pressure in the eye.

In this study, the researchers found several possible risk factors for vision loss, such as elevated eye pressure, disc haemorrhage and glaucoma in both eyes. These findings are useful for doctors and might help them identify patients at risk of vision loss earlier. Treating the condition as early as possible will give patients the best chance of maintaining their sight.

The association between the history of smoking and reduced risk of vision loss requires careful interpretation but might help scientists better understand why glaucoma occurs. It is possible that certain chemicals in tobacco smoke such as nicotine might prevent sight loss, but more research is needed to understand the biochemical mechanism behind this potential protective effect. The researchers note that there were few current smokers in this study and the protective effect was mostly seen in former smokers. It is possible that stopping smoking is related to the decision to adopt a healthier lifestyle with protective effects on vision.

What’s next?

The surprising association between smoking and vision loss should be explored further. Research that looks at potential mechanisms for a protective effect of smoking - such as nicotine or other compounds in tobacco smoke - could help us understand the disease better and help scientists find other treatments for glaucoma.

The researchers of this study are conducting further research to see if there are other predictors of susceptibility to eye pressure. This includes mitochondrial function (mitochondria are the energy-producing elements of cells) and whether taking medications that affect the whole body (for example for high blood pressure, other cardiovascular conditions and diabetes) may increase or decrease the risk of vision loss in glaucoma.

You may be interested to read

The full paper: Founti P, and others. Risk Factors for Visual Field Deterioration in the United Kingdom Glaucoma Treatment StudyOphthalmology. 2020. doi: 10.1016/j.ophtha.2020.06.009

A previous study on eye pressure and sight loss with glaucoma: Heijl A, and others. Reduction of intraocular pressure and glaucoma progression: results from the Early Manifest Glaucoma Trial. Arch Ophthalmol. 2002;120:1268-1279

The earlier paper from The UKGTS showing the protective effect of latanoprost in glaucoma: Garway-Heath DF, and others. Latanoprost for open-angle glaucoma (UKGTS): a randomised, multicentre, placebo-controlled trial. The Lancet. 2015;385:1295-1304

A study looking at how smoking affects the eye: Tamaki Y, and others. Acute effects of cigarette smoking on tissue circulation in human optic nerve head and choroid-retina. Ophthalmology. 1999;106:564-569

 

Funding: The trial was supported by Pfizer, Moorfields Eye Hospital NHS Foundation Trust, the NIHR Biomedical Research Centre at Moorfields Eye Hospital and UCL Institute of Ophthalmology.

Conflicts of Interest: Several authors have received fees and funding from various pharmaceutical companies.

Disclaimer: NIHR Alerts are not a substitute for professional medical advice. They provide information about research which is funded or supported by the NIHR. Please note that views expressed in NIHR Alerts are those of the author(s) and reviewer(s) and not necessarily those of the NHS, the NIHR or the Department of Health and Social Care.

Commentaries

Study author

There was no evidence for an association between older age and sight loss which is contradictory to previously published data. We believe this may be due to differences in the UKGTS patients compared with other trials. Healthier older patients may have been more likely to take part in UKGTS than other studies due to the high commitment and number of follow up appointments required for this trial.

The inverse association between smoking and sight loss seems counter-intuitive, given the many harmful effects of tobacco smoke on the eyes. This finding requires careful interpretation but previous studies have suggested that smoking might protect against neurodegeneration, including glaucoma.

Panayiota Founti, Consultant Ophthalmic Surgeon, Moorfields Eye Hospital, London

Researcher

The finding that sight was preserved for significantly longer with a prostaglandin analogue (eye drops) validates the current NICE guidance. This primary outcome of the landmark United Kingdom Glaucoma Treatment Study was first reported in the Lancet in 2015. The current report extends the analysis to identify specific risk factors associated with visual field deterioration. Most of these factors have been previously reported as increasing the risk of disease progression in glaucoma; the lack of association between older age and field deterioration is surprising. The results of this research may help clinicians to identify those at greatest risk of sight loss.

The finding that a positive smoking history appeared to be protective against field loss needs to be interpreted with caution. Smoking has other adverse effects in the eye (such as increased risk of cataract and age-related macular degeneration), but other research suggests nicotine might have a protective effect on optic nerve circulation. This is clearly an area for further research.

John Lawrenson, Professor of Clinical Visual Science, City University of London