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Conjunctival Impression Cytology

The conjunctival impression cytology test is based on the lack of normal goblet cells and the presence of enlarged epithelial cells in the conjunctiva of vitamin-A deficient people. Cells are transferred from the conjunctiva to filter paper, where they are stained and examined under a microscope.

Rapid Dark Adaptation Test

This test is based on measurements of the time of occurrence of the Purkinje shift. This refers to the peak wavelength sensitivity of the retina shifting from red to the blue end of the spectrum during the transition from day vision to night vision. The test has high sensitivity and specificity.

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