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You searched for subject:(Ophthalmic Instruments). Showing records 1 – 2 of 2 total matches.

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University of Houston

1. Chen, Dong. Safety Evaluation of Light Levels in Ophthalmic Instruments and Devices.

Degree: Optometry, College of, 2016, University of Houston

PURPOSE: There is an absence of information regarding safe levels of light exposure in present ophthalmic devices, and data on the highest continuous usage of these devices is unavailable. Studies that explored similar safety parameters were last conducted over 35 years ago using the American National Standard Institute (ANSI) Z136.1-1976 Standard. The maximum permissible exposure (MPE) identified in the Standard has been periodically updated based on new findings in studies examining light safety and damage thresholds in the eye. Furthermore, evolving imaging techniques have given rise to a number of new ophthalmic devices that did not exist previously, such as optical coherence tomography (OCT). The purposes of this research were to assess the light exposure levels of current ophthalmic devices and to provide a quantitative safety time limit for each instrument using the most recent ANSI Z136.1-2014 American National Standard for Safe Use of Lasers. METHODS: The spectral distribution, radiant power, pulse characteristic, and visual angle of the light emitted from 15 different ophthalmic devices at the University Eye Institute were measured using a spectroradiometer and a calibrated power meter. The examined instruments included optical biometers, corneal topographers, autorefractors, wavefront aberrometers, OCT instruments, fundus cameras, slit lamps, and binocular indirect ophthalmoscopes. A combination of a custom MATLAB program and an Excel Spreadsheet with Excel Visual Basic for Applications (VBA) was developed based on the guidelines written in the 2014 ANSI standard and used to analyze all measurements. Spectral weighting functions were applied following an adjustment guideline for using the ANSI Standards to estimate the weighted MPEs of ophthalmic devices with broadband sources. RESULTS: The ophthalmic instruments and devices evaluated were measured to be safe for typical, clinically relevant usage times. Instruments that were calculated to have the shortest exposure times before exceeding the MPEs were slit lamps when used for direct illumination (~100-400 seconds for continuous usage). Exposure times were much less hazardous when using a condensing lens with a slit lamp for indirect illumination of a larger retinal area. CONCLUSIONS: All examined instruments were calculated to be light safe for normal eyes using our methods. However, caution should be exercised when using slit lamps for direct illumination as exposure levels for these devices can most quickly reach the MPEs within achievable durations. In particular, caution should be exercised when practicing with and training in the use of these instruments, as longer exposure times are expected compared with a typical clinical examination. The reason that slit lamps with direct illumination more quickly reached the MPEs is the visual angle subtended by the source is much smaller. The reason that slit lamps and BIOs with LED sources more quickly reach the MPE limits could be due to the presence of large amounts of short wavelength light in their… Advisors/Committee Members: Porter, Jason (committee member), Stevenson, Scott B. (committee member), Patel, Nimesh B. (committee member).

Subjects/Keywords: Light Safety; Ophthalmic Instruments

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Chen, D. (2016). Safety Evaluation of Light Levels in Ophthalmic Instruments and Devices. (Thesis). University of Houston. Retrieved from http://hdl.handle.net/10657/3233

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Chen, Dong. “Safety Evaluation of Light Levels in Ophthalmic Instruments and Devices.” 2016. Thesis, University of Houston. Accessed November 18, 2019. http://hdl.handle.net/10657/3233.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Chen, Dong. “Safety Evaluation of Light Levels in Ophthalmic Instruments and Devices.” 2016. Web. 18 Nov 2019.

Vancouver:

Chen D. Safety Evaluation of Light Levels in Ophthalmic Instruments and Devices. [Internet] [Thesis]. University of Houston; 2016. [cited 2019 Nov 18]. Available from: http://hdl.handle.net/10657/3233.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Chen D. Safety Evaluation of Light Levels in Ophthalmic Instruments and Devices. [Thesis]. University of Houston; 2016. Available from: http://hdl.handle.net/10657/3233

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Vanderbilt University

2. Shaver, Jesse Hart. Optical measurement techniques for clinical assessment of corneal physiology.

Degree: PhD, Molecular Physiology and Biophysics, 2012, Vanderbilt University

A refined wavelength-dependent biophysical model of the relationship between corneal thickness, refractive index, and tissue hydration is presented in this dissertation. This model provides a more accurate description of the observed relationship between corneal hydration and refractive index, and highlights the need for accurate model input parameters. Particular attention is paid to the parameter for solvent refractive index, as well as the need to account for the dispersive nature of optical media in Gladstone-Dale models. In order to verify the model, a new instrument was developed to measure the thickness of the cornea during dehydration using a low-cost confocal optical system. This system has shown good performance and may be suitable for eventual clinical use. A second instrument was also designed to enable direct measurement of tissue hydration by ratiometric Raman spectroscopy at a safe laser excitation power level. This system employs a new variation of optical chopping and lock-in detection. While the system was able to measure hydration using a safe power level, the time required to make the measurement is impractical for clinical use without further development. Advisors/Committee Members: Dr. Albert H. Beth (chair), Dr. Hassane S. Mchaourab (committee member), Dr. David H. Wasserman (committee member), Dr. Frederick R. Haselton (committee member), Dr. Paul Sternberg (committee member).

Subjects/Keywords: signal recovery; ophthalmic instruments; optical chopping; pachymetry; corneal biophysics; lock-in amplification

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Shaver, J. H. (2012). Optical measurement techniques for clinical assessment of corneal physiology. (Doctoral Dissertation). Vanderbilt University. Retrieved from http://etd.library.vanderbilt.edu//available/etd-12072007-142102/ ;

Chicago Manual of Style (16th Edition):

Shaver, Jesse Hart. “Optical measurement techniques for clinical assessment of corneal physiology.” 2012. Doctoral Dissertation, Vanderbilt University. Accessed November 18, 2019. http://etd.library.vanderbilt.edu//available/etd-12072007-142102/ ;.

MLA Handbook (7th Edition):

Shaver, Jesse Hart. “Optical measurement techniques for clinical assessment of corneal physiology.” 2012. Web. 18 Nov 2019.

Vancouver:

Shaver JH. Optical measurement techniques for clinical assessment of corneal physiology. [Internet] [Doctoral dissertation]. Vanderbilt University; 2012. [cited 2019 Nov 18]. Available from: http://etd.library.vanderbilt.edu//available/etd-12072007-142102/ ;.

Council of Science Editors:

Shaver JH. Optical measurement techniques for clinical assessment of corneal physiology. [Doctoral Dissertation]. Vanderbilt University; 2012. Available from: http://etd.library.vanderbilt.edu//available/etd-12072007-142102/ ;

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