Dynamic measurement of the corneal tear film with a Twyman-Green interferometer

Micali, Jason D.; Greivenkamp, John E.; Primeau, Brian

doi:10.1117/1.jbo.20.5.055007

Cited by 4 publications

(11 citation statements)

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“…A more detailed discussion of phase unwrapping and the methods used are discussed in the TFI reference 62 but are briefly reviewed in this section. Measured interferometric data can only be recovered by a modulo of 2π.…”

Section: Phase Unwrappingmentioning

confidence: 99%

“…This led to the second phase, the development of the tear film interferometer (TFI) for in vivo measurements of the tear film surface on the human cornea. 61,62 The successful demonstration of the TFI has led to the third phase, an interferometer for measuring the dynamic corneal topography of the in vivo eye that is described in this paper.…”

Section: Research Background and Historymentioning

confidence: 99%

“…Temporal surface measurements (e.g., topographic movies) are possible with this system and has been previously demonstrated with tear film measurements. 62 Static data (i.e., single-frame snapshots) are presented here to focus on the absolute surface reconstruction capabilities of the system. Comparisons to the Keratron Piccolo are also presented.…”

Section: Human Subjects Testingmentioning

confidence: 99%

“…The original TFI system had an external fixation assembly and required an additional step of aligning the fixation system to the subject before the interferometer system could be aligned. 62 The second issue with an external fixation system was that to test both of the subject's eyes during a test, either two fixation assemblies were required, or one had to be removed and placed on the other side. A second advantage of placing the fixation assembly in-line with the interferometer systems has to do with the placement of the aperture stop for the imaging system.…”

Section: Fixationmentioning

confidence: 99%

“…75,76 The combination of eye motion, anatomical variation, and tear film dynamics results in an average of 100 μm of measured surface error and can exceed the dynamic range of the surface interferometer which is 265 μm. 62 If the absolute surface topography is to be recovered with any accuracy, retrace error has to be corrected. The process for retrace error correction that is used with this system is documented in a separate publication, 77 but is briefly summarized in this section.…”

Section: Surface Reconstructionmentioning

confidence: 99%

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Dual interferometer for dynamic measurement of corneal topography

Micali

Greivenkamp

2016

J. Biomed. Opt

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Abstract. The cornea is the anterior most surface of the eye and plays a critical role in vision. A thin fluid layer, the tear film, coats the outer surface of the cornea and serves to protect, nourish, and lubricate the cornea. At the same time, the tear film is responsible for creating a smooth continuous surface, where the majority of refraction takes place in the eye. A significant component of vision quality is determined by the shape of the cornea and stability of the tear film. A dual interferometer system for measuring the dynamic corneal topography is designed, built, verified, and qualified by testing on human subjects. The system consists of two coaligned simultaneous phase-shifting polarization-splitting Twyman-Green interferometers. The primary interferometer measures the surface of the tear film while the secondary interferometer tracks the absolute position of the cornea, which provides enough information to reconstruct the absolute shape of the cornea. The results are high-resolution and high-accuracy surface topography measurements of the in vivo tear film and cornea that are captured at standard camera frame rates.

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Section: Phase Unwrappingmentioning

confidence: 99%

Section: Research Background and Historymentioning

confidence: 99%

Section: Human Subjects Testingmentioning

confidence: 99%

Section: Fixationmentioning

confidence: 99%

Section: Surface Reconstructionmentioning

confidence: 99%

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Dual interferometer for dynamic measurement of corneal topography

Micali

Greivenkamp

2016

J. Biomed. Opt

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Mechanisms, imaging and structure of tear film breakup

2018

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Tear film breakup (BU) is an important aspect of dry eye disease, as a cause of ocular aberrations, irritation and ocular surface inflammation and disorder. Additionally, measurement of breakup time (BUT) is a common clinical test for dry eye. The current definition of BUT is subjective; here, a more objective concept of "touchdown" - the moment when the lipid layer touches down on the corneal surface - is proposed as an aid to understanding processes in early and late stages of BU development. Models of BU have generally been based on the assumption that a single mechanism is involved. In this review, it is emphasized that BU does not have a single explanation but it is the end result of multiple processes. A three-way classification of BU is proposed - "immediate," "lid-associated," and "evaporative." Five different types of imaging systems are described, which have been used to help elucidate the processes involved in BU and BUT; a new method, "high resolution chromaticity images," is presented. Three directions of tear flow - evaporation, osmotic flow out of the ocular surface, and "tangential flow" along the ocular surface - determine tear film thinning between blinks, leading to BU. Ten factors involved in BU and BUT, both before and after touchdown, are discussed. Future directions of research on BU are proposed.

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Wire grid polarizer based in-line laser interferometer for macroscopic and microscopic phase estimation of transmissive and reflective phase samples

Sengupta

Bhattacharya

2023

Phys. Scr.

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This work describes a full-field and near-common-path in-line laser interferometer and interferometric microscope utilizing a wire-grid polarizer (WGP) placed normally on the laser beam illuminating the sample. The WGP serves the dual purpose of a beam splitter and a polarization separator where the reference and sample beams reflected and transmitted from it respectively are orthogonally polarized so that, unlike other conventional interferometers, polarization phase shifting is inherent in its architecture. This arrangement presents experimental results showing quantitative phase analysis of transparent and reflecting phase samples

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Dynamic measurement of the corneal tear film with a Twyman-Green interferometer

Cited by 4 publications

References 50 publications

Dual interferometer for dynamic measurement of corneal topography

Dual interferometer for dynamic measurement of corneal topography

Mechanisms, imaging and structure of tear film breakup

Wire grid polarizer based in-line laser interferometer for macroscopic and microscopic phase estimation of transmissive and reflective phase samples

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