Corneal astigmatism measuring module for slit lamps

• Published in: Physics in medicine & biology Vol. 51; no. 12; p. 3085
• Main Authors: Ventura, L, Riul, C, Sousa, S J F, De Groote, J G S, Rosa Filho, A B, Oliveira, G C D
• Format: Journal Article
• Language: English
• Published: England 21-06-2006
• Subjects: Astigmatism - diagnosis; Corneal Topography - instrumentation; Corneal Topography - methods; Diagnosis, Computer-Assisted - instrumentation; Diagnosis, Computer-Assisted - methods; Equipment Design; Equipment Failure Analysis; Humans; Lighting - instrumentation; Reproducibility of Results; Sensitivity and Specificity
• ISSN: 0031-9155
• DOI: 10.1088/0031-9155/51/12/006

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.