Astigmatism Research Today is a free monthly online journal that collates and summarizes the latest research about Astigmatism, including details on cornea, retina, treatment, types, signs, tests.

Corneal astigmatism measuring module for slit lamps.

Ventura L, Riul C, Sousa SJ, De Groote JG, Rosa Filho AB, Oliveira GC

Laboratório de Instrumentação Oftálmica, Department of Electrical Engineering-EESC, Universidade de São Paulo, Av. Trabalhador Sãocarlense 400, 13566-590 São Carlos-SP, Brazil. liliane@sel.eesc.usp.br

We have developed an automatic keratometer module for slit lamps 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 analysed providing the keratometry. Measurements in the range of 26.8-75 D 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 0.05 mm for the radii of curvature and 1 degree for the associated axis.

Published 7 June 2006 in Phys Med Biol, 51(12): 3085-98.
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