By 2010, glaucoma will affect 60 million people worldwide and cause blindness in more than 8 million.1 Despite the availability of effective treatments that delay or halt progression of the disease, an unacceptable number of
people with glaucoma remain undiagnosed and untreated. Strategies for achieving earlier and more accurate diagnosis of glaucoma
are therefore urgently needed to combat the rising burden of this disease in an ageing European population.
Fotis Topouzis, MD
The challenge of early glaucoma detection
Studies in industrialized countries, including the recent Thessaloniki Eye Study, a population-based study in Greece,2 have consistently shown that as many as 50% of glaucoma cases are undiagnosed.3-5 There are several reasons for this:
- Glaucoma is silent and asymptomatic in nature, particularly during the early stages of the disease.
- Elevated intraocular pressure (IOP), despite being a hallmark of glaucoma, is not present in a high proportion of patients
at the time of diagnosis.2,5
- Visual function may not deteriorate significantly until advanced stages of the disease, by which point significant and irreversible
damage to the optic nerve has already occurred.
- Even in the advanced stages of disease, glaucoma can still be missed depending on the frequency of patients' visits to the
eye care specialist and the thoroughness of the ophthalmic examination.6
- Recent evidence suggests that a small cup-to-disc ratio is strongly associated with an increased risk of undiagnosed glaucoma.6 A possible explanation could be that ophthalmologists being trained in focusing their optic disc assessment on the cup-to-disc
ratio, ovelook and miss specific glaucomatous changes (rim thinning, rim notching) when the cup-to-disc ratio is small.
From an economic point of view, recent data have shown that the costs of treating glaucoma in Europe and the US rise as the
severity of disease increases.7,8 For example, Lee and colleagues estimated that the annual cost of glaucoma treatment increases from €2,365 to €3,544 per
patient between stage 0 (ocular hypertension) and stage 5 (end-stage) glaucoma. Early detection of glaucoma is therefore essential
in seeking to maximize the benefits of treatment for patients and minimize the economic burden of glaucoma on society.
Current screening methods are ineffective
As with all diseases, the key to delaying or halting disease progression can be found in effective screening and early intervention.
An ideal strategy for glaucoma screening has yet to be identified, hence there is considerable scope for improved screening
in everyday clinical practice.
In the Thessaloniki Eye Study, for example, glaucoma patients who had not seen an eye care specialist during the previous
year had a six-fold increase in the odds of being undiagnosed compared with patients who had visited an eye care specialist
during the previous year. In addition, the Visual Impairment Project, a population-based study in Australia, found that a
high proportion of individuals had undiagnosed glaucoma despite having seen an ophthalmologist (33%), optometrist (53%), or
both (14%) in the preceding year.9 It is therefore clear that, in addition to publicizing the benefits of regular eye checks to the public, improved training
of eye care professionals and standardization of examination protocols are essential in order to enhance glaucoma detection
Increasingly, detection of early structural changes to the optic disc and retinal nerve fibre layer, which may precede subsequent
visual field abnormalities, is also seen as a key strategy in achieving earlier and more accurate diagnosis of glaucoma. Current
approaches to structural assessment are often reliant on examination and photography of the optic disc. Whilst an essential
component of the ophthalmic examination, these methods sometimes lack the sensitivity, objectivity and reproducibility needed
to detect the subtle structural changes that occur in early stage glaucoma.