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Karol M. Karnowski, David Alonso-Caneiro, Bartlomiej J. Kaluzny, Maciej Szkulmowski, Andrzej Kowalczyk, Maciej Wojtkowski; Measuring Corneal Biomechanical Properties And Intraocular Pressure With Swept Source Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1755.
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© ARVO (1962-2015); The Authors (2016-present)
To demonstrate the applicability of swept source Optical Coherence Tomography (ssOCT) combined with an air-puff system to non-contact measurement of the biomechanics of the cornea and the intraocular pressure in vivo.
An air-puff system similar to that used in non contact tonometers is incorporated with ultrahigh speed swept source OCT laboratory set-up. The air-puff is used to deform the cornea into a slight concavity. Shortly after the applanation, air pump shuts off and the pressure declines in a smooth manner. As the pressure decreases, the cornea returns to its normal configuration. This process is simultaneously monitored with ultrahigh speed OCT signals along the line perpendicular to the surface in the centre of the corneal flatting. A purposely build prototype ssOCT t 1300nm was combined with an air-puff system from commercially available tonometer to acquire axial scans for the applanated cornea. Instrument provides 50,000 axial lines per second with 9 um resolution. Software was used to extract the information from the axial scans. The data analysis procedure contains: automated layers segmentation, calculation of distance between layers and temporal evolution of each layer during applanation. Healthy subjects as well as patients with keratoconus and after laser refractive surgery were examined with the prototype. Intraocular pressure was verified with Goldmann and Pascal tonometry.
Preliminary measurements in human eyes show the viability of this technique to study corneal biomechanics and measure intraocular pressure during of non-contact air-puff applanation. The comparison of the results acquired from different groups of patients shows suitability of such a system to enhance current biomechanical measurements. Different characteristics of temporal evolution of the corneal surface position during applanation were observed for particular intraocular pressure levels.
Combined ssOCT- air-puff r system is demonstrated. The current prototype enables data acquisition for the studies of corneal changes during non-contact applanation with an air-puff. The system has potential of providing additional information on corneal biomechanics and may be used as an alternative method of intraocular pressure measurement.
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