An official website of the United States government
Here's how you know
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Laser interface display of a single excimer laser system. Note that the “@” symbol is used to denote axis on one screen (A) and meridian on another (B). The “^” symbol replaces the sign for plus or minus cylinder on a third screen (C).