The preterm infant is deficient in vitamin A (retinol) and this has been implicated in the pathogenesis of chronic lung disease of prematurity. Conjunctival impression cytology (CIC) has been used in adults to assess retinol status. We aimed to assess the feasibility of performing CIC in the preterm infant and to determine the significance of abnormal CIC findings. CIC samples were collected during routine retinopathy screening, and classified as inadequate, normal, borderline normal or abnormal. Ninety preterm infants were studied. Seventy-four (82%) CIC specimens produced a positive yield, whereas 16 (18%) were inadequate. Of the 74 adequate samples, 61 (82%) were normal or borderline normal and 13 (18%) abnormal. Seventy-three CIC specimens were assessed by a second histopathologist with complete agreement on 64 (88%) samples and disagreement on 9 (12%) samples. Ten sets of conjunctival impressions, taken from both eyes, gave identical results in all adequate samples. Birth weight was significantly lower in this abnormal group. Four infants (32%) in the abnormal group required treatment for retinopathy compared to two (3%) in the normal/borderline normal group, (P < 0.01).
Conclusion: Conjunctival impression cytology is simple and reproducible technique which maybe easily applied to the preterm infant. Abnormal CIC is associated with retinopathy of prematurity requiring treatment.