How to administer tetracaine (anesthetic) eye drops followed by fluorescein (dye)?

Administration of Tetracaine Followed by Fluorescein Eye Drops

Administer one drop of tetracaine 0.5% topically to the eye, wait approximately 1-2 minutes for adequate anesthesia to develop, then apply fluorescein using a saline-moistened strip to the inferior tarsal conjunctiva, and examine the ocular surface with a biomicroscope using cobalt blue filter within 1-2 minutes of fluorescein application for optimal visualization. 1, 2, 3

Step-by-Step Administration Protocol

Tetracaine Application

• Instill one drop of tetracaine hydrochloride 0.5% topically to the eye as needed for procedures requiring rapid, short-acting topical anesthesia 3
• The anesthetic effect begins within a few minutes and typically lasts 10-15 minutes, though duration can extend to 55-58 minutes depending on the procedure 4, 5
• Discard any unused portion after single-use application to maintain sterility 3

Timing Considerations

• Wait 1-2 minutes after tetracaine instillation before proceeding with fluorescein application to allow adequate corneal anesthesia to develop 1
• The mean ligand residence time (tau) for tetracaine is approximately 41.7 minutes, with a half-life of 28.89 minutes 5

Fluorescein Application Technique

• Use a saline-moistened fluorescein strip rather than fluorescein-anesthetic combination drops, as anesthetics may affect test results 2
• Apply the strip to the inferior tarsal conjunctiva using proper technique 2
• Avoid manipulating the eyelids before evaluation to prevent false-positive results 2

Examination Protocol

• Examine the ocular surface through a biomicroscope using a cobalt blue filter immediately after fluorescein application 1
• Optimal visualization occurs 1-2 minutes after fluorescein application, as staining may become more apparent during this timeframe 1, 2
• Use a yellow filter in conjunction with cobalt blue light for enhanced visualization of corneal staining patterns 1, 2

Critical Safety Warnings

Tetracaine-Specific Precautions

• Never use tetracaine intracamerally as it may lead to permanent damage of corneal endothelial cells 3
• Prolonged or repeated use may cause corneal epithelial toxicity, manifesting as epithelial defects that can progress to permanent corneal damage 3, 6
• Patients should not touch the eye for at least 10-20 minutes after tetracaine application due to corneal insensitivity and risk of accidental injury 3
• Tetracaine should only be administered under direct supervision of a healthcare provider and is not intended for patient self-administration 3

Adjunct Antibiotic Considerations

• Avoid combining tetracaine with topical antibiotics when possible, as this combination has additive negative effects on corneal wound healing parameters, reducing fibroblast viability, proliferation, and migration 6
• If antibiotics are necessary, be aware that regular-strength proparacaine (0.5%) with antibiotics shows the most pronounced negative effects on corneal healing 6

Interpretation of Fluorescein Staining

Normal vs. Pathological Findings

• Mild fluorescein staining can occur in normal eyes, particularly in the morning, and should not automatically indicate pathology 1, 2
• Dry eye typically presents with exposure-zone (interpalpebral) punctate or blotchy staining of the cornea and bulbar conjunctiva 1, 2
• Viral keratoconjunctivitis shows diffuse corneal and conjunctival staining patterns 1
• Inferior corneal and bulbar conjunctival staining suggests staphylococcal blepharitis, meibomian gland dysfunction, lagophthalmos, or exposure keratopathy 1

Visualization Advantages

• Fluorescein is more easily visualized on the cornea than conjunctiva and causes significantly less ocular irritation compared to rose bengal dye 1, 2
• Fluorescein specifically stains areas where corneal epithelial intercellular junctions are disrupted, allowing dye penetration into tissue 1, 2

Common Pitfalls to Avoid

• Do not use fluorescein-anesthetic combination drops as the anesthetic component may interfere with diagnostic accuracy 2
• Do not perform fluorescein staining after instilling other eye drops, as this can affect staining patterns and interpretation 2
• Avoid blind sweeping of the fornices with cotton buds or glass rods when performing ocular hygiene after anesthetic application, as this may cause corneal damage 1
• Do not assume all staining is pathological - recurrent tear break-up in the same area may simply indicate localized anterior basement-membrane abnormalities rather than acute injury 2