A two-dimensional scanning ocular fluorophotometer.

For certain studies of the dynamics of fluorescein in the anterior segment of the eye it would be advantageous to measure fluorescent intensity from several anatomic regions of the cornea and anterior chamber simultaneously or in rapid succession. In the present paper we describe a device called a two-dimensional scanning ocular fluorophotometer that we have designed and built to measure fluorescein concentration in a horizontal section through the cornea and anterior chamber. The 488-nm wavelength beam of an argon laser is mechanically scanned through the target area (70 microW total power at the eye) and fluorescent light is measured with a photon-counting photomultiplier tube. A single anterior-posterior scan requires 100 msec and is divided into 33 sample time periods of 3 msec each. Thirty anterior-posterior scans are made within 3 sec. A two-dimensional array of fluorescein concentration is reconstructed from the data. Concentrations ranging from 3 X 10(-10) gm/ml to 3 X 10(-6) g/ml are measured in a single scan. Examples of scans through the anterior chamber and cornea after topical and systemic administration of fluorescein are presented. These scans illustrate how this instrument can be used to measure two types of regional differences in fluorescein concentration, the "pupillary aqueous bubble" following topical administration and the radial concentration gradient in the cornea following systemic administration.