A machine vision method for automated alignment of fundus imaging systems.
OBJECTIVE
To report a method to track the pupil in three axes simultaneously prior to imaging the fundus.


METHODS
The system is based on parallax optical alignment to detect the center of the pupil. The system consists of two cameras acquiring pupil images from two distinct directions and an operator-supervised algorithm to derive the coordinates of the pupil center and output of commands to drive a three-axes computer-controlled stage. The system was tested in a cohort of 45 individuals 61 ± 15 years of age, 26 with and 19 without glaucoma. The tracking was performed without pharmacologic pupil dilation.


RESULTS
The variability of the pupil center determination (assessed by the standard deviation) was ± 0.19 and ± 0.33 mm for the vertical and horizontal directions, respectively. The processing time of the algorithm was 0.75 msec. The tracking converged to within a preset tolerance of ± 0.5 mm in 45 of the 45 eyes.


CONCLUSIONS
Image acquisition and processing of pupil images can be used to align fundus imaging systems rapidly, accurately, and with minimal operator intervention.
Moscaritolo
Michele
M
Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore, MD, USA.
Knezevich
Frederick P
FP
Zimmer-Galler
Ingrid
I
Jampel
Henry
H
Zeimer
Ran
R
D000368:Aged; D000465:Algorithms; D001331:Automation; D015331:Cohort Studies; D005260:Female; D005654:Fundus Oculi; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods* / Q000592:standards; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011680:Pupil; D013997:Time Factors