The ophthalmological equivalent of the 'Seidel test' uses 2% fluorescein under cobalt blue illumination. In a penetrating ocular injury, a positive Seidel sign (streaming dilution of fluorescein) indicates:

• A Blood-staining of aqueous causing relative quenching of fluorescein fluorescence
• B Vitreous prolapse through the scleral wound detectable by its different refractive index
• C Aqueous humor flow through a corneal or scleral laceration, with the wound stream producing a green rivulet in the dark orange dye ✓
• D Hypotony causing reduced corneal light reflex with fluorescein pooling at the wound edge

Explanation

The Seidel test involves painting 2% fluorescein on the suspected wound area and observing under cobalt blue light. In a wound leak, aqueous humor (which contains no fluorescein) flows through the opening and dilutes the dark orange concentrated dye, producing a characteristic lighter-green streaming rivulet flowing away from the wound — a positive Seidel. This confirms a full-thickness wound breach with active aqueous leak. A positive Seidel mandates urgent surgical wound closure to prevent endophthalmitis and further uveal prolapse. The test is also used to check integrity of bleb wounds post-trabeculectomy (bleb-related leaks). The concentrated 2% fluorescein appears dark orange-red; aqueous dilution produces a bright green stream.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.