The Stability of Corneal Topography in the Post-Blink Interval

Buehren, Tobias F.; Collins, Michael J.; Iskander, D. Robert; Davis, Brett A.; Lingelbach, Bernd

doi:10.1097/00003226-200111000-00010

Cited by 80 publications

(51 citation statements)

References 31 publications

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“…The correlation was -0.45, which was reported previously (10,21) . It occurs probably due to changes in the cornea caused by less eyelid tension (22)(23) . In children, the main factor influencing horizontal ocular coma was the cornea and in older ages the main factor was the lens.…”

Section: Discussionmentioning

confidence: 99%

Study of ocular aberrations with age

Athaide¹,

Campos²,

Costa³

2009

Arq. Bras. Oftalmol.

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20/25, emmetropia or spherical equivalent < 3.50 SD, refractive astigmatism < 1.75 CD on cycloplegic refraction, normal ophthalmologic exam and no previous ocular surgeries. This protocol was approved by Federal University of São Paulo Institutional Review Board. Total optical aberrations were measured by H-S sensor LadarWave® Custom Cornea Wavefront System (Alcon Laboratories Inc, Orlando, FLA, USA) and were statistically analysed. Corneal aberrations were calculated using CT-View software Version 6.89 (Sarver and Associates, Celebration, FL, USA). Lens aberrations were calculated by subtraction. RESULTS: High-order (0.32 e 0.48 µm) and ocular spherical aberrations (0.02 e 0.26 µm) increased respectively in child and middle age groups. High order (0.27 µm) and corneal spherical aberrations (0.05 µm) did not show changes with age. Lens showed a statistically significant spherical aberration increase (from -0.02 to 0.22 µm). Vertical (from 0.10 to -0.07 µm) and horizontal coma (from 0.01 to -0.12 µm) presented progressively negative values with aging. CONCLUSION: High-order and spherical aberrations increased with age due to lens contribution. The cornea did not affect significantly changes observed on ocular aberrations.]]>

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Section: Discussionmentioning

confidence: 99%

Study of ocular aberrations with age

Athaide¹,

Campos²,

Costa³

2009

Arq. Bras. Oftalmol.

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“…Although the instruments provide precise data [4], the cornea and the tear film change their properties with time [5][6][7][8][9]. Therefore, in some cases a sequence of images is needed to observe or measure variations of 30 the corneal topography in time.…”

Section: Introductionmentioning

confidence: 99%

“…Although their innovative proposal allows accurate exploration of the corneal dynamics, no full access to 70 the CCD parameters -gain, frame rate, resolution -is assured and the topography reconstruction is still done through the Medmont software. [1][2][3][4][5][6][7][8][9] {TANDF_FPP}TMOP/TMOP_A_405267.3d (TMOP) [FPP Stage] It may be interesting for many researchers to apply their own elevation algorithms for measuring optical 75 surfaces. Algorithms for reconstructing the corneal topography from the shape of reflected Placido ring images are available in the literature [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Custom designed dynamic videokeratometer

Mas¹,

Kowalska²,

Espinosa³

et al. 2010

Journal of Modern Optics

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Human eye is a complex dynamic system that undergoes fine rotations and deformations. Usually information about the eye globe deformation and micromovements are averaged and lost when using commercial measuring devices, although they provide important information about the eye's physiology and the visual process. We have constructed a dynamic topographer from an existing Placido projection head and a video camera. The algorithms 10 of calibration, data processing and topographic reconstruction are also explained in this paper. With our system, the CCD parameters and the algorithms can be controlled offering many possibilities for eye researchers.Obtained results show that the system is reliable for measuring eye dynamics. Some applications of the device are also outlined.

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“…In this technique, a set of concentric rings formed in a cone or a bowl is projected on the anterior cornea and their reflection imaged on a CCD. The technique requires minimal reflections from eyelashes, minimal movements of the measured eye [1], [2], and a high quality of the overlying tear film to produce accurate estimates of the underlying corneal topography [3]- [5]. These requirements make it apparent that the estimators of corneal topography strongly depend on the interference from the eyelashes and that they are conditioned by the quality of tear film.…”

Section: Introductionmentioning

confidence: 99%

Estimating Corneal Surface Topography in Videokeratoscopy in the Presence of Strong Signal Interference

Alonso‐Caneiro

Iskander

Collins

2008

IEEE Trans. Biomed. Eng.

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Abstract-Videokeratoscopy techniques rely on a number of factors in order to achieve accurate estimates of corneal surface topography. Good tear film quality, minimal reflections from eyelashes, and minimal eye movements are essential for corneal topography estimates to be reliable. However, in practice, these ideal conditions may not always be fulfilled, especially in cases of subjects diagnosed with dry eye syndrome, having narrow palpebral apertures, long eyelashes, or nystagmus (uncontrolled eye movements). Such non-optimal conditions of image acquisition result in poorer estimates of corneal topography. The aim of this work was to devise a technique that would provide more accurate estimation of corneal topography in such situations and particularly when the source of signal interference is strong. This was achieved by developing a set of algorithms that extract the interference from the acquired raw videokeratoscopic image and filter the topography according to the interference location. The experiments carried out with test surfaces and real corneas showed that this new technique leads to a significant improvement in the topography estimator. Additionally, it is an interference indication procedure that, in the future, could be used for the purpose of tear film quality estimation.

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The Stability of Corneal Topography in the Post-Blink Interval

Abstract: For normal eyes, the central regions of videokeratographs show high stability in the inter-blink period. However, the upper and lower edges of 8-mm diameter maps show statistically significant variability, which appears to be related to the effects of eyelid pressure.

Cited by 80 publications

References 31 publications

Study of ocular aberrations with age

Study of ocular aberrations with age

Custom designed dynamic videokeratometer

Estimating Corneal Surface Topography in Videokeratoscopy in the Presence of Strong Signal Interference

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