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Abstract: Purpose: To report a case of conjunctival squamous metaplasia associated with oral carbamazepine use. Methods: Following completion of an ocular comfort questionnaire, biomicroscopy and a phenol red thread test, impression cytology from the inter-palpebral zone (nasal) of the bulbar conjunctival surface was undertaken using a Millcell®-CM filter after topical anaesthesia with oxybuprocaine 0.4%. The filter was stained with Giemsa and colour images taken at 400× magnification by light microscopy. The images were graded and also a 35mm was prepared. From the projected image, an overlay method was used to outline the borders such that the cell and nucleus area, and the longest and shortest dimensions could be measured by planimetry. Results: A male subject, added 22 years, presented with slight conjunctival injection but no substantial symptoms and only slight surface staining with fluorescein. The subject reported use of oral carbamazepine (200mg, b.d.s.). Impression cytology showed large sheets of squamous cells (grade 2–3) with few goblet cells. The average cell area was 1509μm2, the long:short dimension ration averaged 1.42 and the average nucleus/cytoplasm (N/C) value was just 0.092 (or 1:11.5 as a ratio). Conclusions: Since the drug has been reported to be excreted in the tear film, and with no other risk factors (such as contact lens wear, smoking or dry eye disease), the squamous metaplasia is attributed to the use of carbamazepine. [Copyright &y& Elsevier]