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Mihai State, Jan-Willem M Beenakker, Denis P Shamonin, Marrie Van der Mooren, Berend C Stoel, Andrew G Webb, Gregorius P M Luyten, Patricia A Piers; Retinal shape assessment in young phakic eyes by a combined partial coherence interferometry - magnetic resonance imaging approach. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2958.
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© ARVO (1962-2015); The Authors (2016-present)
The current study proposes a comparative partial coherence interferometry (PCI) - magnetic resonance imaging (MRI) quantitative assessment of the retinal shape enabling an individualized description of the image plane usable for constructing ray-tracing model eyes valid for both on and off-axis evaluations.
The on and off-axis axial lengths of 16 left eyes of healthy volunteers were measured using a Lenstar LS900 (Haag-Streit AG) PCI. The on-axis axial length varied between 22.59 and 25.99 mm with an average of 23.74 mm. The measurements were performed along the 0 degrees horizontal meridian and within a -30 to +30 degrees field angle range with an angular step of 10 degrees. To enable the off-axis measurements, a wide-angle LED gazing system was fabricated and fixed to the interferometer head. With the addition of the measured anterior corneal geometry on-axis, an algorithm was created to geometrically reconstruct the retinal shape. Subsequently, the retinal shape was quantified by a parameterized elliptical fit algorithm using a linear least square method with a trace constraint. Concurrently, the volunteers left eyes were scanned with a custom-made dedicated 3-channel receive eye-coil combined with a volume transmit coil (Nova Medical) in a Philips Achieva 7 T whole body MR scanner. The retinal shape was segmented from the acquired images by the means of an automatic algorithm.
For the entire data set, the PCI fitted vertex radius varied between 10.31 and 12.26 mm. When compared on-axis, there is a strong correlation (R2 = 0.9923) between the PCI reconstructed and MRI segmented centre of the lens-retina distances with a systematic error of 0.083 mm and a reproducibility of 0.132 mm. The 95% confidence interval limits are between -0.176 and 0.341 mm. These values are inferior to the spatial resolution of the MRI (0.5 x 0.5 x 1.0 mm3). For 30 degrees field of view, the correlation coefficient is R2= 0.9424, the systematic error is 0.160 mm and the reproducibility 0.244 mm. The 95% confidence interval is between -0.319 and 0.639 mm.
The comparative analysis between the PCI and MRI reconstructed retinal shapes demonstrated a strong correlation for both on and off-axis values thus enabling the construction of individual eye models with an anatomical image plane geometry.
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