Abstract:

BACKGROUND: Recent methods for diopter measurement utilize the infrared LED light emitting diode as the light source. The infrared light passes through the cornea, the aqueous, the lens, the vitreous and the retina, and causes the uneven reflection image. The edge determination error is inevitable, and affects the measurement results.
OBJECTIVE: To design a new measurement system of eye diopter based on image processing to improve precision of diopter measurement.
METHODS: The infrared image of six dots was emitted in retina, and it was displayed on CCD through optical system. First, the binary image was divided up with adaptive multi-threshold method. Subsequently, the center coordinate was calculated by centroid method. Finally, the parameter of diopter was acquired by least-squares fitting. The standard analogue eye was used for testing, and the testing results were compared with that of the refractor made in Japan TPCON.
RESULTS AND CONCLUSION: The precision of diopter measurement can meet the requirement of ±0.25 m^-1 which is prescribed by National Metrology Bureau, and the error which caused by uneven image on CCD can be avoided. The structure of system is simple, and the light energy can meet the requirement. The experiment shows that the precision of diopter parameter can be increased, and the prototype has been made. In the hospital, the technology can be used in quick clinical examination and vision screening. However, the structure is too simple, and may lead to the error in large diopter measurement. The coaxial requirement of the light source and the optical system is high, which should be improved in future.