Wavefront-Guided Programmable Spectacles Related Metrics

Transcription

1 Wavefront-Guided Programmable Spectacles Related Metrics Lawrence Sverdrup, Sean Sigarlaki, Jeffrey Chomyn, Jagdish Jethmalani, Andreas Dreher Ophthonix, Inc. 23rd February 2007

2 Outline Background on Ophthonix Technology and Metrics for Wavefront Correction Accuracy Wavefront Candidacy, a Metric for izon Lens Preference Chromatic Aberration Reduction and the Effective Abbe Value Metric

3 Ophthonix Inc. Technology Z-View Wavefront Aberrometer izon Wavefront-Guided Spectacle Lens

4 Z-View Wavefront Aberrometer Diffractive Talbot sensor Less expensive than Shack-Hartmann devices Higher spatial resolution than SH devices Binocular Viewing Specifies Prescription

5 izon Lens Configuration Lens blank (sphere cylinder, axis in surface) Cover izonik polymer

6 izon Lens Technology (Ophthalmic Technologies XVII, SPIE vol. 6426A, Jan 2007) Target Fringes Recorded Fringes 0.20µm Z 4, µm Z 5mm

7 Example of izon Lens Capability Lens Blank Error 6 mm Diameter Target Fringes 4.4 mm Diameter Erase Lens Blank Error 6 mm Diameter Programmed Fringes 4.4 mm Diameter

8 Metrics for Wavefront Correction Accuracy (Ophthalmic Technologies XVII, SPIE vol. 6426A, Jan 2007) Correction Factor = Z P P Purity ZP ZG P = = cos( θ ) = Z Z Z P G G RMS Accuracy = 1 ( Z Z ) ( Z Z ) G P G P 2 Z G Z G = Zernike vector programming goal Z P = Zernike vector actually programmed

9 Zernike RMS Accuracy of 89.5% (Ophthalmic Technologies XVII, SPIE vol. 6426A, Jan 2007) Target 4.57mm Fringes Measured in Lens

10 Wavefront Candidacy, a Metric for izon Spectacle Lens Preference

11 Subjective Preference Study izon lens prescribed by the Z-View vs. a conventional lens prescribed by an optometrist via manifest refraction. Both lenses based on 1.6 index plastic and have identical AR coatings. 67 patients from 7 independent practices. Sites and tester double masked. Subjects wore each pair for 7 days and the order of wear was randomized. Subjects filled out a lifestyle questionnaire after wearing each pair. Data from the questionnaires was analyzed.

12 Neural Network Training Back-propagation network with one hidden layer High-order aberration measurements were used as input parameters Output: Value of 1 = izon lens preferred Value of 0 = Conventional lens preferred

13 Results: Neural Network Profiling Dependence of Patient Preference on Amount of Spherical Aberration Rel. Preference Weight Average Physiological Level Spherical Aberration [ D/mm^2 ]

14 Results: Neural Network Profiling Rel. Preference Weight Dependence of Patient Preference on Amount of Trefoil Average Trefoil Magnitude Trefoil [ D/mm ]

15 Results: Neural Network Profiling Rel. Preference Weight Dependence of Patient Preference on Amount of Coma Average Coma Magnitude Coma [ D/mm ]

16 Patient Profiling in Z-View Software Z-View Aberrometer software incorporates the neural network algorithm which automatically identifies patients who would benefit from izon lens correction.

17 Reduction of Chromatic Aberration in Spectacle Lenses

18 Threshold for Obvious TCA Blur TCA = d mm Threshold 10 V 1 P diopter : 0.1 Measurable Degradation well before Threshold Distance from Optical Center (mm) Threshold for Obvious TCA Blur Abbe Value = 42 1 Mo Jalie Ophthalmic Lenses & Dispensing Power (diopters)

19 Study Involving Polycarbonate 1 VA of 40 eyes with an average acuity of 20/13 VA reduced linearly to 20/31 through 16 diopters of prism P = d mm P diopters 10 1 Hampton et al., JAOA, Volume 62, No. 19 (1991) pp

20 Programmable Layer has Chromatic Effects Two requirements for chromatic effects: Optical Power Different Abbe Values

21 Effective Abbe Number P + P = P 1 2 by Design P V P + = V P1 P2 P + = V V V 1 2 effective

22 Effective Photopic Abbe Value Laser Displacement Measurements P TCA = V V P photopic V effective photopic P 1 39r + 12r =... = TCA 170 r r ( ) ( )

23 Chromatic Aberration Measurement Set-Up Beam Steering Device Laser Variable Attenuator Spatial Filter Aperture Beam Forming Aperture Test Lens Camera Parameter Spatial Filter Aperture Diameter Beam Forming Aperture (BFA) Diameter Distance Between Apertures Distance from Lens to Camera Distance from BFA to Lens Value 10 µm 500 µm 50 cm 50 cm 2.5 cm

24 Pure Lens Materials 70 Effective Abbe Value Measurements 60 Effective Abbe Value Polycarbonate Ave CR39 Ave 1.6 Plastic Ave Distance from the Optical Center (mm)

25 Composite izon Lens Effective Abbe Value for a Composite izon Lens 4 Effective Abbe Value Relative to Base Plastic Radius 1 Radius 2 Radius 3 Radius Radial Distance from Optical Center (mm)

26 Conclusions Wavefront profiles have been successfully used to predict patient preference for wavefront-guided lenses using a neural net based metric A new metric, the effective photopic Abbe value, has been used to characterize the chromatic quality of ophthalmic lenses, including composite lenses. Measurements demonstrate that the izon lens has a significantly elevated effective Abbe value and chromatic quality in the lens periphery (where TCA is important) as compared to that of the base plastic.

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