• PURPOSE: To compare biometry performed by an enhanced version of dual beam partial coherence interferometry and applanation ultrasound in a prospective study of 85 cataract eyes to improve refractive outcome of cataract surgery due to a more accurate calculation of intraocular lens power. • METHODS: The SRK II formula using ultrasound biometry data was employed. Three months after surgery, partial coherence interferometry biometry was repeated and refractive outcome was determined. Preoperative partial coherence interferometry biometry data were used to determine the refractive power of the intraocular lenses retrospectively and to calculate the possible refractive outcome. • RESULT: Precision of partial coherence interferometry biometry was more than 10 times better than that of ultrasound. Therefore, the possible mean absolute error for postoperative refraction achieved with partial coherence interferometry biometry was 0.49 diopters (compared with 0.67 diopters with ultrasound biometry), resulting in an improvement of 27%. Axial eye length measured with the two techniques differed by a mean of 460 μm. The difference in lens thickness measured with partial coherence interferometry and ultra-sound significantly correlated with cataract grade. A mean shortening of 120 μm of axial eye length following cataract surgery was also detected by partial coherence interferometry. • CONCLUSIONS: The enhanced version of partial coherence interferometry offers biometry with un, precedented precision (<10 μm) and resolution (~12 μm), therefore improving the refractive outcome in cataract surgery. This noninvasive technique provides a high degree of comfort for the patient, with no need for local anesthesia or pupil dilation and minimized risk of corneal infection.

Partial Coherence Interferometry: A Novel Approach to Biometry in Cataract Surgery

Optical Engineering Core 28 hours CPE 112 3 Intro To Computer Programming MA 113, MA 115, or Level III placement FSM EE 307 3 Electricity and Magnetism EE 300 FSM EE 313 3 Electrical Circuits II Preor co-requisite: EE 307 FSM EE 447 3 Electromagnetic Waves EE 313 S OPE 453 3 Laser Systems EE 307 F OPE 455 2 Optical Engineering Laboratory PH 113, OPT 342, EE 382 or OPT 442 S OPE 459 3 Optical Engineering Design ISE 321, Senior standing S OPT 341 3 Geometrical Optics PH 113 F OPT 342 3 Physical Optics OPT 341 S OPT 411 2 Geometrical Optics Laboratory PH 116, OPT 341, OPE 441 suggested co-requisite F

海外文献紹介 Optical Engineering

Further development of the objective version of the Howland and Howland [(1976) Science, 193, 580-582; (1977) Journal of the Optical Society of America, 67, 1508-1518 aberroscope technique for measuring ocular aberrations is described. Compensation for refractive corrections and calibration is discussed. The technique was used to investigate the effect of accommodation upon the monochromatic aberrations of the right eyes of 15 subjects. Coma and coma-like aberrations were the dominant aberrations for most people at different accommodation levels, thus confirming previous findings.

Variations in aberrations were considerable between subjects. About half the subjects showed the classical trend towards negative spherical aberration with accommodation. Changes in spherical aberration with accommodation in this study were less than that found in previous studies where all monochromatic aberration was considered to be spherical aberration.

Measurement of Monochromatic Ocular Aberrations of Human Eyes as a Function of Accommodation by the Howland Aberroscope Technique

Presbyopia: Effectiveness of correction strategies

Purpose. To demonstrate the feasibility of measuring the anterior structures of the human eye by partial coherence interferometry and to determine its precision for eyes under normal and cycloplegic conditions. Methods. The dual-beam version of partial coherence interferometry, a recently developed noninvasive optical ranging technique, enables high resolution measurements of several intraocular distances with unprecedented precision. A modified, more sensitive scanning version of this technique was used to assess the central and peripheral corneal thickness, the anterior chamber depth, and the lens thickness of 20 healthy, emmetropic to moderately myopic eyes. Furthermore the anterior structures of three eyes were measured under cycloplegia (1% cyclopentolate) to investigate the influence on the precision of this technique after suppression of residual accommodations. Results. The mean geometric precision (standard deviation) of the measurement of the central corneal thickness was 0.29 μm (range, 0.22 μm to 0.38 μm) and 0.43 μm (range, 0.27 μm to 0.56 μm) for the peripheral corneal thickness at a distance 2 mm from its apex. The precision for measuring the anterior chamber depth and the lens thickness for fixation at infinity was 8.7 μm (range, 3.9 μm to 16.8 μm) and 8.9 μm (range, 2.9 μm to 14.4 μm) for noncycloplegic eyes and 1.9 μm (range, 1.7 μm to 2 μm) and 1.4 μm (range, 0.7 μm to 1.8 μm) for cycloplegic eyes, respectively. Conclusions. The dual-beam partial coherence interferometry enables fast, noninvasive, submicrometer precision biometry of the anterior segment of the eye. The precision of determining the anterior chamber depth and the lens thickness is more than one order of magnitude better than that of the currently used ultrasound and optical techniques, and it can be improved by a factor of 5 by using cycloplegia.

Submicrometer Precision Biometry of the Anterior Segment of the Human Eye

In vivo three-dimensional (3-D) anterior segment biometry before and after cataract surgery was analyzed by using custom high-resolution high-speed anterior segment spectral domain Optical Coherence Tomography (OCT). The system was provided with custom algorithms for denoising, segmentation, full distortion correction (fan and optical) and merging of the anterior segment volumes (cornea, iris, and crystalline lens or IOL), to provide fully quantitative data of the anterior segment of the eye. The method was tested on an in vitro artificial eye with known surfaces geometry at different orientations and demonstrated on an aging cataract patient in vivo. Biometric parameters CCT, ACD/ILP, CLT/ILT Tilt and decentration are retrieved with a very high degree of accuracy. IOL was placed 400 μm behind the natural crystalline lens, The IOL was aligned with a similar orientation of the natural lens (2.47 deg superiorly), but slightly lower amounts (0.77 deg superiorly). The IOL was decentered superiorly (0.39 mm) and nasally (0.26 mm).

/pdf/full-oct-anterior-segment-biometry-an-application-in-594ld51gvv.pdf

Full OCT anterior segment biometry: an application in cataract surgery

PURPOSE. To estimate changes in surface shape and gradient refractive index (GRIN) profile in primate lenses as a function of accommodation. To quantify the contribution of surface shape and GRIN to spherical aberration changes with accommodation. METHODS. Crystalline lenses from 15 cynomolgus monkeys were studied in vitro under different levels of accommodation produced by a stretching system. Lens shape was obtained from optical coherence tomography (OCT) cross-sectional images. The GRIN was reconstructed with a search algorithm using the optical path measured from OCT images and the measured back focal length. The spherical aberration of the lens was estimated as a function of accommodation using the reconstructed GRIN and a homogeneous refractive index. RESULTS. The lens anterior and posterior radii of curvature decreased with increasing lens power. Both surfaces exhibited negative asphericities in the unaccommodated state. The anterior surface conic constant shifted toward less negative values with accommodation, while the value of the posterior remained constant. GRIN parameters remained constant with accommodation. The lens spherical aberration with GRIN distribution was negative and higher in magnitude than that with a homogeneous equivalent refractive index (by 29% and 53% in the unaccommodated and fully accommodated states, respectively). Spherical aberration with the equivalent refractive index shifted with accommodation toward negative values (� 0.070 lm/diopter [D]), but the reconstructed GRIN shifted it farther (� 0.124 lm/ D). CONCLUSIONS. When compared with the lens with the homogeneous equivalent refractive index, the reconstructed GRIN lens has more negative spherical aberration and a larger shift toward more negative values with accommodation.

/pdf/influence-of-shape-and-gradient-refractive-index-in-the-4t75zt1uko.pdf

Influence of shape and gradient refractive index in the accommodative changes of spherical aberration in nonhuman primate crystalline lenses.

http://www.vision.csic.es/Publications/Articles/Three-Dimensional%20Evaluation%20of%20Accommodating%20Intraocular%20Lens%20Shift%20and%20Alignment%20In%20Vivo.pdf

Three-Dimensional Evaluation of Accommodating Intraocular Lens Shift and Alignment In Vivo

Contribution of the gradient refractive index and shape to the crystalline lens spherical aberration and astigmatism.

Supported by Spanish Government Grant FIS2011-25637 (SM); European Research Council ERC-AdG-294099 (SM); Consejo Superior de Investigaciones Cient´ificas Junta de Ampliacion de ´ Estudios (CSIC JAE)-Pre Program (JB); CSIC i-LINKþ 2012, iLINKþ0609 (SM). The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007- 2013)/ERC Grant Agreement 294099.

Judith Birkenfeld

Papers

Full OCT anterior segment biometry: an application in cataract surgery

Influence of shape and gradient refractive index in the accommodative changes of spherical aberration in nonhuman primate crystalline lenses.

Three-Dimensional Evaluation of Accommodating Intraocular Lens Shift and Alignment In Vivo

Contribution of the gradient refractive index and shape to the crystalline lens spherical aberration and astigmatism.

Contribution of Shape and Gradient Refractive Index to the Spherical Aberration of Isolated Human Lenses