Quantitative Analysis of the Effect of Optical Probe Positioning on the Measurements of Flattened Diameter of Ocular Cornea for Applanation Tonometry

The precise positioning of optical probe is an attractive technique in application to an accurate assessment of intraocular pressure (IOP) during applanation tonometry. Based on a mathematical model, the influence of the optical probe positioning on the measurements of the flattened diameter of the ocular cornea is analyzed. The measurements of the flattened diameter are evaluated for two cases. One is that the flattened circle's center is concentric with the corneal apex, located in the visual axis of the eyeball, and the other is that the flattened circle's center is offset from the corneal apex. Experimental results show that the present optical probe is position sensitive and only for case one the measured diameter has good agreement with the real diameter. The research results are very valuable for the improvement of an applanation tonometer.