FUNCTIONAL BURDEN

Glaucoma is not only widely under-diagnosed, it also directly limits the quality of life and life expectancy of affected individuals, according to Roger Hitchings MD, who gave a keynote lecture at the 2013 Congress of the European Society of Ophthalmology. “In looking at the functional burden of glaucoma we see that it is under-diagnosed, has a significant effect on quality of life, is extremely costly to treat, especially if it presents late, and results in a significant reduction in social status as well as a reduction in life expectancy," said Prof Hitchings, an honorary consultant ophthalmologist at Moorfields Eye Hospital, London, and Professor Emeritus in Glaucoma and Allied studies at the University of London.

The impact of the disease is particularly deleterious in poorer regions, said Prof Hitchings. “When someone becomes blind, and particularly with late presentation, and especially in the so-called developing world, they cannot work. Their life expectancy falls and they experience a loss of social standing. Women who have lost vision as a result of chronic glaucoma suffer a loss of authority in their households because they are now dependent on others,” he said. Looking at the epidemiological data from 39 countries, Prof Hitchings said that an estimated 285 million people are visually impaired in the world, with 39 million classified as legally blind. Of those blind patients, 43 per cent are due to uncorrected refractive errors, 33 per cent due to cataract, and 12.3 per cent due to glaucoma. “This makes it the commonest irreversible cause of blindness in the world today,” he said.

The majority of patients in the major population studies were unaware that they had glaucoma when the condition was diagnosed, said Prof Hitchings. This figure was as high as 90 per cent in the Aravind Eye Study in India, and around 50 per cent or so in the Rotterdam and Blue Mountains eye studies. “No matter which study we look at, the message to emerge is how common it is for glaucoma patients in population screening to be discovered when they were unaware of the problem, so late presentation is a major problem,” he said.

Socioeconomic status plays a major role in late presentation, with those from poorer backgrounds, living in rental accommodation, with no access to a car and who left full-time occupation at a young age more likely to present late. In the UK, the time to the last visit to an optometrist was identified as a factor, while other studies identified the failure of the optometrist to diagnose glaucoma and a negative family history of glaucoma as also playing a role in late presentation. There are also other less apparent reasons for late presentation, said Prof Hitchings.

“Glaucoma tends to occur in the elderly who think that declining eyesight is part of growing old and so ignore it. The elderly also have other systemic and social problems which are to them more important,” he said, Late presentation also results in increasing costs to the health system, said Prof Hitchings, with at least two studies showing that the more the disease progresses the more costly it is to society. Looking at possible reasons why glaucoma patients do not notice the visual loss, Prof Hitchings said that binocular field loss seems to be one of the most critical factors involved. “If binocular field loss is a disability, we need to ask what effect it has on a patient’s quality of life. We can use a range of questionnaires – generic health related, vision-specific or glaucoma specific – and the patient’s response gives us an idea of how we can assess the effect on the patient’s quality of life,” he said.

Glaucoma has the potential to negatively affect many aspects of a patient’s quality of life, said Prof Hitchings, with one composite analysis of several quality of life studies showing that binocular field loss had a negative impact on activities such as reading, routine household tasks, mobility and driving. “A study by Haymes et al showed that glaucoma patients had a threefold increase in the risk of falls over the previous 12-month period and a sixfold increase in the risk of car accidents over the previous five years compared to agematched controls,” he said.

Another study cited by Prof Hitchings showed that automated visual field screening of 10,000 volunteers showed the incidence of visual field loss was three per cent to 3.5 per cent for persons aged 16 to 60 but was approximately 13 per cent for those older than 65 years. The most common causes of visual field loss were glaucoma, retinal disorders and cataracts. “Drivers with binocular visual field loss had accident and conviction rates twice as high as those with normal visual fields, whereas drivers with monocular visual field loss had accident and conviction rates equivalent to those of a control group,” he said.

A study by Keltner and Johnson in 1983 showed that half of the people with abnormal visual fields were previously unaware of any problem with peripheral vision. “This is probably due to a combination of factors such as denial, a function of the slow rate of change, and also perhaps a compensatory function in the brain,” concluded Prof Hitchings.