Biometric measurements inside the model eye using a two wavelengths Fourier domain low coherence interferometer

Abstract

We present a setup to measure biometric data of the eye using Fourier domain interferometry. The measuring depth of a Fourier domain system is basically limited owing to the spectral resolution. Combining two spectral domain interferometers with different wavelength ranges creates two measurement sections and allows for a simultaneous biometric measurement in terms of corneal thickness, anterior chamber depth, and axial length. The necessary offset between both sections in the combined setup was calibrated with a known reference object. The setup was tested by measuring a self-constructed model eye. All biometric data of the model eye can be detected simultaneously. This system has a precision of 13 μm (standard deviation) and a trueness of 46 μm. The signal-to-noise ratio was 98 dB for the anterior part and 76 dB for the posterior part. In contrast to time domain interferometry, this setup does not need any mechanically moving parts. Owing to the short time frame of the biometric measurement, potential eye movements should have no influence on the result. In addition to the fast measurement, this setup provides the possibility to adjust the laser power of both sections independently. This could help in the case of dense cataract.

Opto-Mechanical Eye Models, a Review on Human Vision Applications and Perspectives for Use in Industry

“…Regarding biometry applications, some examples were found. Birkner et al [ 39 ] created an eye model to evaluate biometric measurements inside the model eye using a two-wavelength Fourier domain low-coherence interferometer. The test subject was a model eye, including a rigid polymethylmethacrylate (PMMA) contact lens (CL) as the cornea, a commercial biconvex lens as the crystalline lens, and a reflecting surface as the retina.…”

“…One of the first cornea models was made of two thin glass shells, the space between filled with a liquid of index 1.377 [ 3 ]. There have also been reports where rigid and scleral contact lenses (CLs) were used as cornea models [ 11 , 39 , 45 , 67 ], while soft CLs were also mentioned [ 45 ].…”

“…Wet-cells can simply change the thickness of the cuvette, or change the relative positions between optical components on the optical bench. Some other models have specific mechanisms to vary the distance between these components, but they usually require disassembling the device to apply the modifications [ 39 , 46 , 52 , 73 , 74 , 76 ], or building alternative embodiments of the model [ 12 , 52 ].…”