Which staining technique is used to show punctate staining when the ocular surface is damaged by tear film instability?

• A. Fluorescein
• B. Rose Bengal
• C. Lissamine Green
• D. Tetracaine

Answer: (A)

Punctate staining from tear film instability is best demonstrated with fluorescein because it penetrates and highlights corneal epithelial breaks. When the tear film is unstable, tiny defects in the corneal epithelium form and fluorescein readily enters these gaps, pooling in them and producing bright green punctate spots under cobalt blue light. This pattern directly reveals epithelial compromise related to tear film breakup and helps assess the extent of damage. Other dyes like rose Bengal or lissamine green stain devitalized cells and mucins on the ocular surface and can indicate surface dryness, but they are less specific for pinpoint corneal epithelial defects caused by tear film instability. Tetracaine is an anesthetic, not a staining agent, so it does not reveal surface damage.