May 2004
Volume 45, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2004
A PURKINJE IMAGING SYSTEM FOR IN VIVO MEASUREMENT OF CURVATURES, TILT AND DECENTRATION OF THE CRYSTALLINE LENS
Author Affiliations & Notes
  • P. Rosales
    Instituto de Optica, Instituto de Optica, CSIC, Madrid, Spain
  • S. Barbero
    Instituto de Optica, Instituto de Optica, CSIC, Madrid, Spain
  • S. Marcos
    Instituto de Optica, Instituto de Optica, CSIC, Madrid, Spain
  • Footnotes
    Commercial Relationships  P. Rosales, None; S. Barbero, None; S. Marcos, None.
  • Footnotes
    Support  MCyT BFM2002–02638 & CAM08.7/004.1/2003 to SM, MCyT Predoctoral Fellowship to PR, and MECyD to SB
Investigative Ophthalmology & Visual Science May 2004, Vol.45, 1722. doi:
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      P. Rosales, S. Barbero, S. Marcos; A PURKINJE IMAGING SYSTEM FOR IN VIVO MEASUREMENT OF CURVATURES, TILT AND DECENTRATION OF THE CRYSTALLINE LENS . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1722.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Abstract: : Purpose: The optical quality of the eye is determined by the contributions of corneal and internal aberrations. Internal aberrations depend primarily on the crystalline lens geometry, position and refractive index distribution. We have developed a system, based on recordings of Purkinje images I, III and IV to measure curvatures, tilts and decentrations of the crystalline lens in vivo. Methods: The system consists on two illuminating channels (from ultrabright LEDs): 1) double LED at an angle of 20 deg, and 2) collimated light from a single LED at 14 deg; 3) an imaging channel with an IR–enhanced CCD camera, with a telecentric lens, collinear with the ocular line of sight; and 4) a fixation channel with targets displayed on a monitor. Routines written in Matlab detect automatically the Purkinje images. The heights of double PIII and PIV images relative to PI were used to estimate the anterior and posterior lens radii of curvature, using both the equivalent mirror and iterative methods. The procedures were tested using eye models in an optical design program (Zemax). Lens tilt and decentration were estimated assuming that the positions of PI, PIII and PIV are linearly dependent on eye rotation, lens tilt, and decentration. Zemax was used to test this assumption, to generate the weighting coefficients for each individual eye (using the estimated lens curvatures and measured anterior chamber depths), and to validate the procedure. The system was tested on 9 young eyes (25–32 years) moderately myopic eyes (–0.5 to –6 D). Results: Simulations using Zemax showed that the iterative method to calculate the radii of curvature provided better estimates (∼8%) than equivalent mirror method and that lens tilt and decentration estimates were not very sensitive (differences of 0.06 deg and 0.05 mm respectively) to the lens model used (spherical vs aspheric surfaces). The anterior lens radii measured experimentally in vivo ranged from 7.5 to 11.6 mm, and the posterior lens radii from –4.9 to –6.8 mm across eyes. Lens tilt ranged from –2.2 to –14 deg and lens decentration from –0.03 to +0.29 mm. Experimental variability was 1.3 deg and 0.06 mm for lens tilt and decentration, respectively. Conclusions:We have developed, validated and tested an experimental system to measure crystalline lens shape and position. Correlations of those properties to internal aberrations may provide relevant information of their impact on optical quality in individual eyes. The system can alternatively be used to measure intraocular lens properties in vivo.

Keywords: optical properties • anterior chamber 
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