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B. Grajciar, M. Pircher, C. K. Hitzenberger, A. F. Fercher; Measurement of Intraocular Distances of the Human Eye in vivo With High Sensitive Fourier Domain Low Coherence Interferometry. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3704.
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© ARVO (1962-2015); The Authors (2016-present)
To measure intraocular distances of the human eye in vivo with high sensitivity using Fourier domain low coherence interferometry (FD-LCI).
Currently, the depth range of FD-LCI systems is limited to only a few mm. To measure larger distances (e.g. human eye length) we implemented two separate reference arms with different arm lengths into the interferometer. Each reference arm length corresponds to a different depth position within the sample (e.g. cornea and retina). Therefore two different depth sections, each with a depth range of a few mm can be imaged simultaneously.
With the new system the maximum detectable optical distance is limited only by the travel range of the translation stage plus the spectrometer depth range. Motion artifacts are suppressed due to the high acquisition speed of 20,000 depth profiles per second. Axial distances are measured with a precision of 8µm. The system performance was tested on 9 patients with cataract and the results are compared with those obtained with the IOL Master. Every tested patient was measured on the first attempt without the need of repetition. Our system was able to measure the length of the eye of cataract patients even if the IOL Master failed due to a low signal-to-noise ratio. Each measurement includes several recordings consisting of typically 100 A-scans which can be averaged to further increase of the sensitivity. The average measurement including alignment procedure for both eyes took around 5 minutes. In addition we have performed intraocular distances measurements of the anterior segment on 10 healthy subjects.
The FD-LCI method provides important sensitivity and acquisition speed enhancements in comparison with commercially available time-domain LCI based systems. Our system was able to measure all eye lengths of cataract patients out of an arbitrary sequence of 9 clinical patients. The correlation between measurements with FD-LCI system and IOL Master was excellent. Extended length measurements within the anterior segment of the eye on 10 healthy subjects have proven capability of the system for measurement of all important intraocular distances. The designed FD system has potential to become a useful clinical method for biometric eye length measurements before cataract surgery.
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