An Automated Method for Assessing Visual Acuity in Infants and Toddlers Using an Eye-Tracking System

This novel automated method called the automated acuity card procedure or AACP, can evaluate visual acuity in young children. The procedure is useful for infancy and the younger children who have not yet acquired sufficient communication skills. The AACP procedure uses a webcam instead of a remote eye tracker.

A two-choice looking test automatically recognizes the child's watching behaviors when the child watches the visual stimuli on a digital display screen. Cartoon images are presented in the center of the screen as visual rewards during the testing procedure. It reduces the misstatement of the procedure caused by the infant's eye gets shifting to the side.

In the future, by changing the types of visual stimulation, the AACP may be used to evaluate other visual information processing functions early in children's development. Begin by obtaining informed consent from the parents of the child to be tested with an eye-tracking calibration system, and describe the study format to them. Position the child to be tested at 55 centimeters from the display monitor in the parent's lap.

Adjust the position of the lifting table to place it with the monitor so that the screen is perpendicular to the child's eyes. Adjust the webcam's position to ensure that the child's face is visible in the recording system and to avoid capturing faces other than the child's. Before starting the procedure, inform the child that they will watch the screen.

Instruct the parent to prompt the child to look at the screen when the child is not paying attention. Then open the automated acuity card procedure or AACP software and type the child's information, including name, sex, and age into the software. Click on the start button to calibrate the procedure.

A graphics interchange format or GIF image appears against a white background in the center of the screen for at least three seconds. The analysis system simultaneously determines whether the child's line of sight is fixated on the image by showing green dot on the screen. If the gaze data is not available within a minute, the screen presents another cartoon GIF image.

When gaze coordinates are detected within this region, the test procedure starts without the tester's action and runs automatically. To begin the visual acuity assessment, present the initial grading on the computer, depending on the child's age and as per the teller acuity cards II or TAC II Test. Present the initial grading ranging from 0.33 to 30.0 cycles per degree in one by two octave steps for 1, 000 milliseconds, which is the length of a trial before presenting a blank screen for 200 milliseconds.

Present the same stimulus again, followed by a blank screen. Present the grading of the same spatial frequency set, three times. During the execution of the procedure, let the webcam record the facial pictures for analyzing the child's watching behavior.

The vision testing program checks the eye movement responses with the criteria to determine whether the stimulus has been seen. Let the testing result processing program present the subsequent stimulus according to the protocol. After every three trials, present a GIF image with background music as a visual reward to maintain the child's interest.

Stop the test if no gaze data are usable due to the child turning around or closing their eyes within one minute of the GIF image presentation. Once the test is complete, analyze the grading acuity results for the child outputted by the software programs. The AACP was applied to a group of 155 normally developing infants and toddlers from five to 36 months old.

The grading acuity measured by the AACP gradually increased with the infants age. In infants of six to 12 months, the grading acuity increased by 0.5 octaves. The grading acuity was increased by one octave in the age group, 12 to 24 months.

An increase of 1.5 octaves was observed in toddlers of 24 to 36 months. The trend of acuity development in this study was consistent with the acuity development measured by TAC II in the same group of infants.