Abstract:
For the purpose of vision screening, we develop an eye
fixation monitor that detects the fovea by its unique radial orientation
of birefringent Henle fibers. Polarized near-infrared light is reflected
from the foveal area in a bow-tie pattern of polarization states, similar
to the Haidinger brush phenomenon. In contrast to previous devices
that used scanning systems, this instrument uses no moving parts. It
rather utilizes four spots of linearly polarized light—two aligned with
the “bright” arms and two aligned with the “dark” arms—of the bow-
tie pattern surrounding the fovea. The light reflected from the fundus
is imaged onto a quadrant photodetector, whereby the circular polar-
ization component of the polarization state of each reflected patch of
light is measured. The signals from the four photodetectors are ampli-
fied, digitized, and analyzed. A normalized differential signal is com-
puted to detect central fixation. The algorithm is tested on a computer
model, and the apparatus is tested on human subjects. This work
demonstrates the feasibility of a fixation monitor with no moving
parts.
