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Statistical Analysis Statistical data analysis was performed with SPSS 17.0. Comparisons of recurrance rate between groups were made useing Chisquare test.P<0.05 was considered statistically significant.
RESULTS
Out of 93 pterygium operated, a total of 7 (7.5%) recurrences were observed. Patients were grouped according to recurrencerelated factors including gender, age and therapy history. 41 patients (48 pterygium) were men and 38 patients(45 pterygium) were women. The patients mean age was 47.9±14.7 years, 45 patients (53 pterygium) were more than 40 years old and the rest 34 patients (40 pterygium) were less than 40 years old. In 64 patients (74 eyes) the pterygium was primary; in the remaining 15 patients (19 eyes) there was history of surgical treatment. There was no significant difference between male and female (P=0.485); the gender did not affect recurrence rate. The recurrence rate was significantly higher in the younger age group (6/40 vs 1/53,P=0.048) and in the recurrence lesions group (4/19 vs 3/74,P=0.044) that had previously been treated by surgery.
Side effects of postoperative 90Sr βirradiation were modest during the period of followup. A few patients were observed with local pain, conjunctivitis, photophobia or an increase in tear flow. None of the patients showed severe side effects related to 90Sr βirradiation viz scleral necrosis and radiation cataract.
DISCUSSION
The treatment of pterygium is still quite controversial, with various treatments being advocated in the scientific literature. The various treatments for pterygium aim at reducing recurrence of the lesion. Bare sclera technique excision of a pterygium without adjuvant treatment has an unacceptably high recurrence rate and therefore should not be used. Bunching of conjunctiva and formation of parallel loops of vessels at the limbus usually denotes a conjunctival recurrence. Recent findings suggested that pterygium was not just a degenerative lesion, but could be a result of uncontrolled cell proliferation [7,8]. Radiation prevents the proliferation of fibroblasts and further angiogenesis, thus reducing its recurrence[9]. In the early of 1970s, it is reported that radiation has been shown to inhibit corneal wound healing, with prominent effect on fibroblast proliferation. It is demonstrated that dosedependent inhibition of human tenons fibroblast proliferation up to a plateau at exposures of 1000cGy [10]. In the treatment of pterygium, initially a high dose of βirradiation was applied without surgical excision, the aim being to induce regression of the lesion. Administration of βirradiation after surgery, particularly for recurrent pterygium, was widely adopted, with subsequent reports indicating a low recurrence rate. It is suggested that postoperative βirradiation of 3 weekly 800cGy fractions reduces the likelihood for pterygium recurrence. When the βirradiation is fractionated, satisfactory results can be achieved with low morbidity. Smith et al [5] reported a very satisfactory result with immediate postoperative βirradiation of 2500cGy in 5 fractions for prevention of recurrence. Isohashi
et al[11] showed recurrence of the pterygium after postoperative 90Sr βirradiation to be 7.7% (97 of 1253 cases). Mourits et al[12] compared longterm effects of patients with primary pterygium treated with bare sclera excision technique followed by 90Sr βirradiation or by sham irradiation. They reported the usage of 2500cGy singledose postoperative 90Sr βirradiation is an effective treatment with lasting results that reduces the risk of primary pterygium recurrence and very few complications. Doses administered varied considerably in different studies. Typical doses have been of the order of 20006000cGy [13], frequently given in fractions. Kal et al[14] demonstrated for pterygium recurrence after bare sclera surgery and 90Sr βirradiation, a biologically effective dose of about 3000cGy seems to be sufficient to reduce the recurrence rate to less than 10%. We chosen 2400cGy in 3 fractions in order to get expected result and minimize the side effects.
There are some safety issues to be considered when using postoperative 90Sr βirradiation. First of all, the eyeball should be fixed during the radiotherapy. Eye fixation can reduce the incidence of scleral necrosis. The second safety issue is that the cornea should be protected, when the affected area is covered with the 90Sr applicator. Third, the dosage of 90Sr βirradiation and treatment time should be precise. The last but not the least, the patient should be examined everyday carefully for 10 days in order to avoid occurrence of serious side effects. If the patient has feeling of pain or chemosis, we should be extremely cautious to carry out the treatment.
In this study, we also analyzed the factors related to local recurrence of the pterygium, after surgery and 90Sr βirradiation. The reason for high recurrence rate of pterygium in younger patients (<40 years) could be that younger persons have more opportunity to exposure to ultraviolet radiation and stronger ability of fibroblast proliferation. The healthy Bowmans membrane seems to act as a barrier to the in growth of conjunctival tissues. In patients of recurrent pterygium with previous history of surgery, the cause for recurrence could be the destruction of normal limbal structure and the changes in the tear film. There were some reports suggesting a high recurrence in males[11]. In contrast, our data didnt show statistically difference between male and female. However, our study is a retrospective analysis, and prospective studies are required to overcome the selection bias and prove this point.
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