How would you expect the mires to appear if you instill too much fluorescein prior to Goldmann tonometry?

When using fluorescein in preparation for Goldmann tonometry, the appearance of the mires is crucial for accurately measuring intraocular pressure. If too much fluorescein is instilled, it can cause the mires—that is, the illuminated images created by the tonometer in the tear film—to appear thick.

An excess of fluorescein can create an overly dense layer on the surface of the cornea. This makes it difficult to differentiate the mires clearly, potentially leading to inaccuracies in the measurement. Ideally, a balanced amount of fluorescein is required to ensure that the mires are neither too thick nor too thin, allowing for precise alignment and measurement during the tonometry process.

The other options, while they could describe different outcomes of fluorescein application, do not reflect the specific consequence of using too much fluorescein. Too dark would imply inadequate illumination or concentration, too thin would refer to insufficient stain distribution, and completely clear would indicate a lack of fluorescein which wouldn't provide the needed contrast for accurate tonometry.