Mr. Cassius Riul Profile

Cassius Riul

at Univ de São Paulo

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Proceedings Article | 5 March 2007 Paper

Automatic keratometry in slit lamps

Liliane Ventura, Cassius Riul, Jean-Jacques De Groote, Sidney Sousa, Gunter Dablas de Oliveira

Proceedings Volume 6426, 64261S (2007) https://doi.org/10.1117/12.697061

KEYWORDS: Cornea, Lamps, Eye, Optical spheres, Calibration, Monochromatic aberrations, Image processing, Spherical lenses, Light emitting diodes, Infrared radiation

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We have developed an automatic keratometer module for slit lamp that provides automatic measurements of the radii of the corneal curvature. The system projects 72 light spots displayed in a precise circle at the examined cornea. The displacement and deformation of the reflected image of these light spots are analyzed providing the keratometry. Measurements in the range of 26,8D - 75D can be obtained and a self-calibration system has been specially designed in order to keep the system calibrated. Infrared leds indicate automatically which eye is being examined. Volunteer patients (492) have been submitted to the system and the results show that our system has a high correlation factor with the commercially available manual keratometers and the keratometry measurements from a topographer. Our developed system is 95% in agreement with the corneal topographer (Humphrey - Atlas 995 CZM) and the manual keratometer (Topcon OM-4). The system's nominal precision is 0,05mm for the radii of curvature and 1^o for the associated axis.

Proceedings Article | 5 March 2007 Paper

Prototype for measuring pupil size changes

Liliane Ventura, Fernando Pergoraro Silva, Giuliano Rossi, Cassius Riul

Proceedings Volume 6426, 64261U (2007) https://doi.org/10.1117/12.701129

KEYWORDS: Eye, Surgery, Prototyping, Image processing, Infrared radiation, Infrared imaging, Mirrors, Infrared cameras, Visualization, Eyeglasses

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The neurological control of the visual process is extremely complex and the pupil movement plays an important role. It controls the intensity of light entering the eye, is responsible for focusing depth and avoiding undesired paracentral rays. As such factors vary along the day for each patient individually, allied to the individual answer to determined light stimulation, it is not possible to predict the pupilar size change along the day, leading to undetermined image quality of the patient for a pre-existent condition. Among the clinical and surgical procedures in order to enhance the quality of the visual system of the patient, wave-front based surgeries are performed and its efficiency is strongly dependent on the pupilar position as well as the area to be ablated. In order to predict the individual behavior of the pupil change during an ordinary routine of the patient we have been developing a system to provide means for the personal refractive surgery to be the most efficient as possible. This work presents a method for monitoring the dynamics of the pupil. The methodology presented in this work provides measurements of the patient's pupil sizes along an entire day with light intensity conditioned to the one that the patient is exposed. A prototype has been developed using an eyeglass frame, where a dichroic mirror (70% transmittance) is attached to the frame, as well as a CMOS camera and an infrared illumination system. The image of the pupil is acquired every 4 minutes, its transferring is done by wireless serial communication (RS-232) and saved in a flash memory. Image processing and pupil size determination are done later separately from monitoring. The system is under preliminary tests.

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