Measurement of the pupillary response using high-velocity videoculography and conventional videoculography

Abstract

The study of eye movements is an important technique to identify and evaluate disorders. For a complete understanding of the consequences of eye movements is necessary to measure the horizontal movements, vertical movements and torsional components. Regarding the biodynamics of the pupil and iris, it is required to quantify the functional variations in its expansion and contraction as well as the shapes and contours, due to natural and evoked visual stimulation. Conventional methods of oculography such as electro-oculography or photo-electro-oculography are complex, time consuming, and their accuracy is not appropriate. This is why videooculography is preferred since it is a non-invasive method to record eye movements and components. Video recordings can be done at a studio and can be analyzed later. One of the earliest tests to monitor and evaluate the pupillary changes was the technique of direct observation using lenses and scales. The photographic technique used by Lowenstein and Loewenfeld used infrared light-sensitive film at a rate of 10–50 frames per second, which was manually analyzed to measure the pupil. The technique based on video obtains images of the pupil to analyze the dynamic pupillary changes based on reflective differences between the iris and the pupil. This technique has recently been used in clinical situations with a video camera of CCD or CMOS technology for detecting and observing the slow movements of the eye. At 250 frames per second the results of the velocity of nystagmus are different from those recorded with traditional cameras. HS-VOG (High Speed Video Oculography) demonstrates that conventional low-speed VOG (30 frames per second) is not sufficient to detect the complete bandwidth of eye biomechanics. The HS-VOG approach allows study and analysis of the dynamic behavior of the eye, with the aim of influencing neuro ophthalmologic diagnosis and the development of new methodologies.