In order to perform Goldmann Tonometry, a topical anaesthetic must be used, along with the dye fluorescein. These drugs come in various forms. It is important to remember to check for allergies before instilling any sort of eye drop. All topical anaesthetics sting – don’t forget to warn your patients! Upon instilling the drops, make a note of the drug used on the record card, along with its expiry.
- Minims Lidocaine Hydrochloride 4% and Fluorescein Sodium 0.25% (recommended): This is the only anaesthetic and fluorescein sodium combined minim available.* To use, insert one drop into each eye and ask the patient to gently ‘dab’ their eyes, being careful not to wipe the drop out of the eye. The time it takes you to set up the Goldmann tonometer should be sufficient for the drop to take effect.
- Minims Proxymetacaine Hydrochloride 0.5% and Fluorescein Sodium Impregnated Strips (e.g. Bio Fluoro): You may prefer to use proxymetacaine as it stings the least of the topical anaesthetics. To use for tonometry there are two methods:
- Put one drop of anaesthetic into each eye. Then, using the rest of the minim, wet the fluoroscein strip over a tissue. Instil the fluorescein into each eye onto the conjunctiva. (Recommended method)
- Open the packet of proxymetacaine and squeeze the contents of the minim into it. Dye the anaesthetic with the fluorescein strip. Using the empty minim, squeeze the tube touching the yellow anaesthetic, and let go – the liquid will be sucked back into the minim. Now instil one drop into each eye.
- Minims Oxybuprocaine Hydrochloride 0.4% and Fluorescein Sodium Impregnated strips (e.g. Bio Fluoro): Use as per instructions for Proxymetacaine.
- Minims Tetracaine Hydrochloride 1% and Fluorescein Sodium Impregnated Strips (e.g. Bio Fluoro): Tetracaine can be used for tonometry but as it is the most potent anaesthetic, it is usually reserved for procedures such as corneal foreign body removal.
- Minims Fluorescein Sodium: As an alternative to impregnated strips, you may with to use minims of fluorescein. These come in 2 strengths, 1% and 2%. For tonometry, it is best to use the lower strength. I would suggest always instilling your anaesthetic first, then fluorescein second, as per the method for using fluorescein strips.
* You may have used proxymetacaine and fluorescein combined minims in the past. These are no longer available.
