RISK FACTORS

Knowledge of risk factors for primary open-angle glaucoma onset and progression can be helpful when deciding on a management strategy in individual patients, according to some noted glaucoma experts who spoke at the 11th European Glaucoma Society Congress in Nice.

“Knowing the risk factors for glaucoma onset won’t tell us with certainty which individual will one day develop glaucoma, however it can help you estimate the possibility,” said Anne L Coleman MD, PhD, Fran and Ray Stark Professor of Ophthalmology, Vice Chair of Academic Affairs in Ophthalmology and Professor of Epidemiology, University of California, Los Angeles, US.

Intraocular pressure (IOP) is the most well-established risk factor for the onset of glaucoma and it is the only risk factor that current therapies attempt to modify, Dr Coleman said. Population-based studies, as well as large prospective and retrospective studies, have shown that patients with a higher IOP have a higher incidence
of glaucoma.

IOP also appears to be closely linked to glaucoma’s pathological mechanisms. For example, it is a common clinical observation that, in patients with asymmetric disease, it is the eye with higher IOP that will progress more rapidly. Moreover, in non-human primates, artificially increasing the IOP causes damage to the optic nerve that is very similar to that which occurs in glaucoma.

Other risk factors identified in the literature include many that are not modifiable, such as age, race, certain genes, family history, central corneal thickness and myopia. However, some of the other identified risk factors are potentially modifiable. They include lower socio-economic status, high body mass index, low intake of antioxidants and high intake of fats, poor exercise habits and sleep apnoea.

“It is important to emphasise that a lot of the risk factors are chosen from statistical analyses. Therefore, a risk factor may cause or induce glaucoma, but it could also be that the glaucoma is inducing the risk factor. In addition, it could be that the risk factor and glaucoma are related to another underlying condition and really have nothing to do with each other,” Dr Coleman added.

Progression

In eyes with established primary open-angle glaucoma, progression of the disease has its own set of risk factors, each with its own fairly well-defined impact on the likely outcome in a particular patient, said Anders Heijl MD, Skåne University Hospital Malmö, Sweden.

“In patients with risk factors we may need to modify our management strategy. For example we may need to aim for a lower target IOP. And more importantly, patients with risk factors for progression need to be followed more frequently,” Dr Heijl said.

He noted that many factors which figure strongly in glaucoma onset appear to have no influence on disease progression. Evidence is weak for any association between glaucoma progression and central corneal thickness, refractive error, and ocular perfusion pressure, although there is good evidence for all those factors and glaucoma onset.

Elevated IOP is a risk factor for both onset and progression. Several large randomised trials, including the Early Manifest Glaucoma Treatment study (EMGT) and the Advanced Glaucoma Intervention Study (AGIS) have shown a clear association between elevated IOP and disease progression. In contrast, there is no evidence that broad IOP fluctuation is an independent risk factor for glaucoma progression.

Advanced age is another risk factor shown in the studies. In the EMGT it doubled the risk of progression. Disc haemorrhage is also a clear marker for increased risk glaucoma progression in eyes with established disease, but an even better marker in suspect glaucoma. The strongest predictor of future progression is the amount of progression occurring in previous years.

He added that, apart from adhering to their IOP-lowering regimens, there unfortunately does not appear to be a lot that glaucoma patients themselves can do to reduce their risk of glaucoma progression, Dr Heijl said.

“There is no evidence that any lifestyle factors influence the risk of glaucoma progression. General health factors are often discussed in the literature, but there’s really no clear-cut scientific evidence,”
he added.

Treatment has its own risks

Among the many factors to keep in mind when assessing how to treat a patient who presents with glaucoma is the patient’s own view of whether the risks of treatment outweigh the risks of non-treatment, said Norbert Pfeiffer MD, University of
Mainz, Germany.

For example, topical medications carry the risk of side effects, such as hyperemia and allergic reactions. In addition, in certain rare instances, patients can have a severe cardiovascular reaction to topical beta blockers.

Surgical treatments, for their part, carry the risk of complications that can have an immediate effect on vision, Prof Pfeiffer noted. Even successful and uncomplicated surgery can leave a patient unhappy, as was the case with a patient of his who became very self-conscious when a partially visible bleb formed at the junction the limbus.

“You have to keep weighing the risks, and please keep in mind that your risk assessment may be greatly different from your patient's risk assessment and their quality-of-life is not ours,” he concluded.

Anne L Coleman: colemana@ucla.edu

Anders Heijl: anders.heijl@med.lu.se

Norbert Pfeiffer:
pfeiffer@Augen.klinik.uni-mainz.de