Question 53 of 100

(demo test)

Fluorescein dye can permanently stain soft contact lenses, so the lenses come out before the dye goes in. Soft lenses are made of a water-loving plastic. They soak up the dye and hold it. The green-yellow stain does not wash out, and the lens is ruined. After tonometry you should rinse the eye with irrigating solution before she puts the lenses back on. Rinsing washes out the leftover dye so the fresh lens does not pick it up.

Fluorescein is a dye that glows bright yellow-green under cobalt-blue light. Goldmann tonometry needs it. The dye outlines the ring of tear film where the tonometer tip flattens the cornea. In the eyepieces that ring looks like two semicircles, one above and one below a line. You turn the force knob until the inner edges of the semicircles just touch. Without dye you cannot see the semicircles, so you cannot set the endpoint. The routine is simple: anesthetic drop, then fluorescein, and some offices use one solution that holds both. Soft lenses must be off the eye for all of it. Give the lenses a clean case while they wait, and keep them labeled right and left.

The take-home rule is short. No fluorescein over a soft contact lens, ever. Ask every patient about lenses before you reach for the bottle. A ruined pair of lenses costs the patient money and costs your office trust, and both are easy to avoid. Rinse the eye before the lenses go back in. Protecting a patient's lenses and eyes during dye use is part of the COA content area of eye pressure measurement, or tonometry.

Incorrect Answers

• A. This is not the concern. The drop still reaches the eye surface with a lens in place, and lens wear is not the reason the anesthetic is given.
• B. The dial is not affected by lenses. Its reading is always multiplied by 10 to give mm Hg, whatever the patient wears.
• D. Scleral rigidity is the resistance of the eye wall to stretching. It matters for Schiøtz indentation readings, and a contact lens does not change it.

Testing Pearls

• Remove soft contact lenses before instilling fluorescein; the stain is permanent.
• Rinse the eye with irrigating solution before the lenses are reinserted.
• Fluorescein glows yellow-green in cobalt-blue light.
• Goldmann endpoint: the inner edges of the two semicircles just touch, never overlap.
• Standard order is anesthetic first, then dye, unless one combined solution is used.

References

1. American Academy of Ophthalmology. Ophthalmic Medical Assisting: An Independent Study Course. Chapter 8, Comprehensive Medical Eye Examination.