Purpose:
To develop a novel system employing eye tracking technology for performing automated static perimetry (ASP) in children, and to assess its feasibility as a diagnostic technique.
Methods:
The system comprises a personal computer, display screen and an eye tracking device to detect a child’s gaze point in real time when a stimulus is presented in their visual field. The reflexive saccadic eye movement to fixate on the stimulus if seen can be detected and measured. Repeating the process allows a visual field map to be built up.The eye tracking device (Tobii X50, Tobii Technology) requires nothing fixed to the child’s head allowing free head movement. It also supplies real time data on the position of the child’s eyes thus allowing the calculation of the appropriate position and size of the next visual field point stimulus.Subjects were recruited to assess the viability of the technique. These included 6 children with suspected visual field loss, 8 adults with known visual field defect and 11 normal subjects. Subjects performed tests designed to replicate the Humphrey Field Analyser’s C-40 suprathreshold screening test with stimulus size Goldmann III and intensity 20dB in each eye. Binocular testing was also carried out in the children. Adults performed the equivalent Humphrey test for comparison.
Results:
In healthy eyes of all subjects over 98% of points agreed with a normal visual field (including blind spot). Good agreement was also found between tests performed by adults with field defects performing both the eye tracking test and Humphrey C-40 screening test.In children, as well as confirming full fields in healthy eyes, visual field defects were identified. The figure shows the binocular visual field result from the eye tracking system of a 4 year old with clinically suspected left homonymous hemianopia.
Keywords: perimetry • infant vision • visual fields