Biomedical subjects

Daniel R Neal

Publications and source records attributed to Daniel R Neal.

4 recordsLinked to original sources

PubMed2004

Optimized and wavefront guided corneal refractive surgery using the Carl Zeiss Meditec platform: the WASCA aberrometer, CRS-Master, and MEL80 excimer laser.

The Carl Zeiss Meditec platform for custom ablation incorporates a suite of technology integrating high-resolution wavefront aberrometry (WASCA), corneal surface shape data (TOSCA), energy stabilized excimer laser delivery (MEL80), and surgeon-controlled individualization of the ablation profile (CRS-Master). Together, these components deliver increasingly higher accuracy and sophistication in treatment planning for corneal refractive surgery.

Cornea↗

PubMed2002

Direct photolithographic deforming of organomodified siloxane films for micro-optics fabrication.

Direct photolithographic deforming of hybrid glass films is used to fabricate optical structures. The structure is fabricated in polyethylene-oxide-acrylate modified hybrid glass films with (1) binary and gray-scale photomasks using a mercury UV-lamp exposure and (2) maskless UV-laser patterning. Fabrication of isolated lenslets, lens arrays, and gratings is presented, including the associated exposure patterns. The hybrid glass material yields light-induced deformation peak-to-valley (p.v.) heights up to 12.8 microm with mercury UV-lamp exposure and p.v. deformation heights up to 6.8 microm with 365-nm UV-laser exposure. The fabricated lenslets' surface data are presented as Zernike-polynomial fit coefficients. Material synthesis and processing-related aspects are examined to understand and control the material's deformation under exposure. The hybrid glass material exhibits a maximum spectral extinction coefficient of 1.6 x 10(-3) microm(-1) at wavelengths ranging from 450 to 2,200 nm and has a refractive index of 1.52 at 632.8 nm. The fabricated structures exhibit rms surface roughness between 1 and 5 nm.

Journal Article↗

PubMedDate not supplied

Errors in Zernike transformations and non-modal reconstruction methods.

PURPOSE: Wavefront aberrometers often represent the wavefront in terms of Zernike polynomials. The fit coefficients for these polynomials are pupil-size dependent; hence it is desirable to be able to calculate polynomial coefficients at a different pupil size from the initial measurement. METHODS: We developed a method for scaling the Zernike fit coefficients for different sized pupils and compared them to the coefficients calculated by reanalyzing the original data. We evaluated cases where the initial set of Zernike coefficients was an accurate representation of the data as well as cases where the Zernike polynomials fit the data poorly. RESULTS: The rescaling methods work well in all cases with a good original fit (as measured by the gradient root-mean-square [RMS] fit error). Rescaling and reanalyzing also agree well over a small scaling range. However, if the original fit was poor, large errors result if the rescaling is more than approximately 25%. CONCLUSIONS: Rescaling works well and is useful as long as the RMS fit error can be evaluated. The RMS difference between the zonal reconstruction and the Zernike fit is useful for determining this fit error.

Adult↗

PubMedDate not supplied

Zonal matrix iterative method for wavefront reconstruction from gradient measurements.

PURPOSE: To present an alternate method to Zemike decomposition (modal) of wavefront reconstruction using iterative implicit solution to the finite difference equations (zonal). METHODS: Different reconstruction methods, modal and zonal, were compared and the advantages of each method were analyzed. RESULTS: Although the modal or Zemike method allows for quantitative interpretation of some of the aberrations, it is cumbersome for use with fine details and may lead to errors for eyes with keratoconus or other rapidly varying aberration. The zonal method produces a very high-resolution map that can be used for identifying irregular structures. CONCLUSIONS: The distinction between the two methods is useful to maintain, and the solution methods are generally different. In practice, both methods are useful and, with modern computers, both zonal and lower-order modal may be calculated rapidly. The difference between the wavefronts derived from the two methods may provide useful insight or interpretation of the infornation.

Cornea↗