Pterygium in Indonesia: prevalence, severity and risk factors. (World View).

Aim: To determine prevalence rates, severity, and risk factors far pterygium in adults in provincial Indonesia and to validate a clinical grading scheme in a population based setting.

Methods: A population based prevalence survey of 1210 adults aged 21 years and above was conducted in five rural villages and one provincial town in Riau province, Sumatra, Indonesia, an area near to the equator. A one stage household cluster sampling procedure was employed: 100 households were randomly selected from each village or town. Pterygia were graded for severity (T1 to T3, by visibility of episcleral vessels) and the basal and apical extent measured by an ophthalmologist (GG) with a hand held slit lamp. Refraction was measured by hand held autorefractor (Retinomax). Face to face household interviews assessed outdoor activity, occupation, and smoking. The participation rate was 96.7%.

Results: The mean age was 36.6 years (SD 13.1), 612 were male. The age adjusted prevalence rate of any pterygium was 10.0% (95% confidence intervals (CI) 8.2 to 11 .7) and of bilateral pterygia was 4.1% (95% CI 2.9 to 5.3). There was a significant dose-response relation with age (2.9% (95% CI 0.4 to 5.8) for 21-29 years versus 17.3% (95% CI 10.4 to 24.2) 50 years and above; p for trend <0.001) and occupations with more time outdoors (p for trend = 0.02). This was true for both sexes, all grades of lesion (T1 to T3), and bilateral disease. A multivariate logistic regression model showed pterygium was independently related to increasing age and outdoor activity 10 years earlier. The mean basal diameter = 3.3 mm (SD 1.51, range 0.1-9.5) and extent from limbus = 1.4 mm (SD 1.18, range 0.1-8.0). Higher grade pterygia were larger for basal and apical extent (p for trend <0.001). The presence of pterygium was associated with astigmatism (defined as cylinder at least -0.5 dioptres (D); p <0.001). This association inc reased with increasing grade of lesion (p for trend <0.001). Median cylinder for those with pterygium (-0.50 D) was greater than for those without (-0.25D), (p <0.001), and increased with higher grade of lesion (p for trend <0.001). For eyes with pterygia, magnitude of astigmatism was associated with greatest extent from the limbus, (p = 0.03), but not basal width (p = 0.99).

Conclusions: There is a high prevalence rate of pterygia in provincial Sumatra. The independent increase with age and past outdoor activity (a surrogate for sun exposure) is consistent with previous findings. Clinical grading of pterygium morphology by the opacity of the lesion was a useful additional marker of severity.

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Pterygium is a disfiguring and potentially blinding disease that in the advanced stages can require complex surgery for full visual rehabilitation. (1) Insights into risk factors, causes, and the distribution of the disease may be useful in guiding appropriate strategies for preventive measures. (2) The prevalence rates of pterygium obtained for a number of populations vary widely, (3-7) from 1.2% in urban, temperate white people (8) to 23.4% in the black population of tropical Barbados. (2) These study populations differ in race, latitude, and sun exposure, but generally prevalence rates in the tropics are higher than at temperate latitudes. Theories of the pathogenesis of pterygium have implicated ultraviolet light exposure as a major causative factor. Evidence for sunlight exposure as one of the prime aetiological agents derives both from case-control studies (9) and prevalence surveys. (4 8 10-13)

As with theories of pathogenesis, techniques of treatment for pterygia have advanced in recent years. Alongside recognition of mechanisms of disordered cell growth (14-19) has been the development of techniques for conjunctival (20 21) and amniotic membrane (1) transplantation to reduce recurrence after surgery. It has been further shown, in a randomised control trial comparing bare sclera excision with conjunctival autografting, that simple clinical grading of pterygium morphology can usefully predict the likelihood of recurrence. (20)

We report the findings of a prevalence study from equatorial Indonesia and the application of this same morphological grading scheme to this population based sample. Ours is the first study, to our knowledge, to examine the Malay/Indonesian racial group.

METHODS

A population based prevalence survey in five rural villages and one provincial town of Riau province, Sumatra, Indonesia, was conducted from April to June 2001 as part of a large general village health survey. The region is tropical with secondary forests, near the Kampar River, one degree north of the equator, and the nearest large city is the capital of the Riau province, Pekan Baru. A random sample of all household members living in five villages (Kuala Terusan Baru, Pelalawan, Delik, SP7, and Segati) and the nearby provincial town, Kerinci was assessed. Villages were variously situated in forest (Segati), near logging roads (Kuala Terusan Baru, Delik), alongside the Kampar River (Pelalawan), and close to a paper and pulp mill (SP7). All houses in each village were individually mapped and assigned a number by an enumeration team. A one stage cluster sampling procedure was conducted whereby 100 households were randomly selected from a sampling frame of the total number of households in each village (as ther e were only 60 households in Delik all 60 were assessed). Membership of a household was defined as the habitual occupation of that dwelling with a presence in the house for at least 2 of the preceding 4 weeks.

Among the randomly selected 1251 adult villagers 21 years and above, examinations were performed on 1210, an initial participation rate of 96.7%. There were 216 subjects recruited from Kerinci, 231 subjects from Kuala Terusan Baru, 229 from Pelalawan, 120 from Delik, 233 from SP7 and 181 from Segati. Of these, 297 were described as possible positives in the initial screening survey and 248 were re-examined (a secondary participation rate of 83.5%). The unexamined subjects were considered as negative cases for the purpose of this analysis. Non-participants included non-contactables and refusals. Non-contactables were defined as individuals who were not contactable on three separate occasions and refusals defined as individuals who declined to participate in the study. The median age of the participants (33.0 years, n = 1210) and non-participants (31.0 years, n = 41) was not different (p = 0.64, rank sum test).

Sample size …