Current automated system models
A number of automated systems for the measurement of eye misalignment
have been described in the literature, and they have mainly been used
for screening or detecting strabismus in adults or
children.3 Different eye tracker systems allow for the
accurate detection of eye position.11 Although good
for detecting the latent components of strabismus they cannot be used in
patients with nystagmus or high refractive error (nanophtalmos or
pathological myopia).12 Binocular optical Coherence
Tomography calculates eye position by using the measurement of corneal
vertex reflection in the fixating eye (draws line between pupil margins
at the posterior epithelium of the iris of both eyes). This allows for
the detection of subtle differences in the size of the strabismus, not
visible to the naked eye; it is however incapable of differentiating
between heterophoria and heterotropia.13 Finally, some
systems simply use a camera mounted directly in front of the patient on
a laptop linked to eye-tracking image analysis software to film the
eyes. The advantage of such a setup is its portability and ease of use.
It is, however, incapable of measuring the exact angle of the
strabismus14 and such an integrated system would not
be convenient for bedside testing.
In order to test for skew, the eyes have to be occluded in an
alternating manner; this can be done either manually or automatically.
Some systems such as the video-Goggle Hess Screen Test use an automated
LCD shutter, which occludes the vision in an alternate manner between
the left and right eye, thus allowing for the measurement, if needed, of
latent strabismus and skew.15 Other semi-automated
systems need a manual mouse/trigger indicating the alternating
frequency.16 Our device
(EyeSeeCamTM), however, used a synchronized trigger on
a tablet system that provided an automated alternating color stimulus in
order to allow monocular alternating vision by color filters. Eye
tracking systems adapted for vestibular testing such as the GN
OtometricsTM or the EyeSeeCamTMsystems use goggles with a single, highspeed, infrared
camera.16 These multipurpose devices allow a
comprehensive and integrated battery for bedside vestibular testing
including static and dynamic vestibular tests.