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Session Title: Cornea Medical
Session Date/Time: Monday 07/10/2013 | 08:00-10:00
Paper Time: 09:10
Venue: Elicium 1 (First Floor)
First Author: : S.Serghiou UK
Co Author(s): : P. Koay
We aim to identify the known risk factors of pterygium, assess their importance and explore their utility in the context of medical practice. We also propose a “framework of guidelines” to assist further research in the aetiology of pterygium and solve the long-standing problem of its origin.
Pterygium is macroscopically a wing-shaped encroachment of conjunctival tissue onto the cornea and microscopically a centripetal migration of limbal stem cells with degeneration of the underlying corneal epithelium and Bowman’s layer. Even though not as common in Europe, it can affect almost a third of certain populations, such as Kumejima islanders in Japan, and cause an annual burden of €2.2 million in Australia. Nevertheless, the environmental risk factors for pterygium and their relative importance are currently elusive. As a result (1) no specific measures can be taken to reduce the burden of disease and its recurrence and (2) important clues for better research in its pathophysiology and management are missing.
This is a systematic review and meta-analysis of the risk factors of pterygium from the year 2000 onwards. We searched MEDLINE and Cochrane Library with the medical subject heading (MeSH) “pterygium” in combination to the subheadings: epidemiology, ethnology, aetiology, microbiology, veterinary and virology. This search produced 293 results, after which, year of publication, type of publication and relevance criteria were employed to produce a sample of 63 papers. The papers were then reviewed against our eligibility criteria to produce the final sample of 15 papers, from which relevant information was extracted and analysed using random and fixed-effects models on the statistical programming language R.
The statistically significant risk factors for pterygium in order of strength (based on their pooled odds ratio [OR] and confidence interval [CI]) are: rural residence (OR 4.27, 95% CI 3.49-5.23), old age (OR 2.68, 95% CI 1.51-4.74), poor education (OR 2.23, 95% CI 1.68-2.96), sunlight exposure (OR 1.92, 95% CI 1.26-2.93), light skin colour (OR 1.49, 95% CI 1.03-2.17), manual occupation (OR 1.46, 95% CI 1.20-1.78), low income (OR 1.31, 95% CI 1.10-1.55), dry eye symptoms (OR 1.29, 95% CI 1.11-1.50), total cholesterol (OR 1.2, 95% CI 1.01-1.43) and refractive error (OR 1.08, 95% CI 1.03-1.13). Risk factors implicated in the literature but ineligible for further analysis due to our eligibility criteria were: eye fixation, family history, shiny landscape, G6PD (Glucose-6-Phosphate Dehydrogenase) deficiency, lower intraocular pressure, eye protrusion, sightedness and ocular viral infections (e.g. Human Papillomavirus). Pterygium has been reported as a risk factor for late (OR 3.30, 95% CI 1.1-10.3) and early (OR 1.80, 95% CI 1.1-2.9) age-related maculopathy (ARM) but ARM is not a risk factor for pterygium (OR 1.05, 95% CI 0.30-3.66) Factors without statistically significant effect on pterygium were: gender, altitude, marital status, cataracts, central corneal thickness, iris colour, use of eye drops, smoking, diabetes mellitus, blood pressure, obesity, height, alcohol consumption, allergy and rosacea. A protective effect has been reported for the use of prescription spectacles (OR 0.66, 95% CI 0.55-0.80), but the use of a hat or sunglasses did not produce any significant results in the currently available literature (hat: OR 1.02, 95% CI 0.82- 1.27; sunglasses: OR 0.56, 95% CI 0.27-1.17).
far as we know, this is the first comprehensive list of the risk factors of pterygium and the first attempt to quantify their effect. It is clear that sunlight and related factors can increase the risk of pterygium substantially, whereas protective equipment such as prescription spectacles can reduce it. However, there is a significant research bias towards the traditional concepts of pterygium, such as sunlight, with almost no research in conceptually important risk factors, such as mechanical microtrauma. Furthermore, the majority of the reviewed epidemiologic studies suffer from important methodological pitfalls, leading to questionable inferences and thus failing to make a contribution to eliciting the risk factors and pathophysiology of pterygium. We propose a framework of guidelines to improve the reliability and effective quality of future studies in the aetiology of pterygium. We predict that, on the basis of these guidelines we will obtain concrete evidence about the risk factors of pterygium, their effect and the potential of possible interventions to prevent the occurrence of pterygium. We particularly advocate the importance of quantitative data in experimental variables such as sunlight exposure, the combination of population-studies to lab work and the need for prospective cohort and randomised control trials in pterygium prevention. This study has the potential to: (1) aid research in pterygium pathogenesis, (2) highlight areas for effective interventions, (3) clarify the importance of occupational health in pterygium, (4) the potential of prevention and (5) improve the comprehensive management of pterygium.
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