Scheimpflug and high-resolution magnetic resonance imaging of the anterior segment: a comparative study

Abstract

High-resolution imaging with a camera system built on the Scheimpflug principle has been used to characterize the geometry of the anterior segment of the adult human eye as a function of aging and accommodative state but is critically dependent on algorithms for correction of distortion. High-resolution magnetic resonance imaging (MRI), in contrast, provides lower-resolution information about the adult eye but is undistorted. To test the accuracy of the Scheimpflug correction methods used by Cook and Koretz [J. Opt. Soc. Am. A 15, 1473 (1998)]; [Appl. Opt. 30, 2088 (1991)], data on anterior chamber and segment lengths, as well as lens thickness and anterior and posterior curvatures, were compared with corresponding MRI data for adults aged 18-50 at 0 diopter accommodation. Excellent statistical agreement was found between the MRI and the Scheimpflug data sets with the exception of the posterior lens radius of curvature, which is less well defined than the other measurements in the Scheimpflug images. The considerable agreement between data obtained with MR and Scheimpflug imaging, two different yet complementary in vivo imaging techniques, validates the Scheimpflug correction algorithms of Cook and Koretz and suggests the capability of directly integrating information from both. A third, equivalent, data set obtained with a Scheimpflug-style camera system differs considerably from both Scheimpflug and MRI results in magnitude and age dependence, with negative implications for this alternative method and its correction procedures.

Quantification of the ciliary muscle and crystalline lens interaction during accommodation with synchronous OCT imaging

“…The crystalline lens and/or the ciliary muscle have been imaged at static accommodation states using MRI [4][5][6][7][8], ultrasound [9][10][11], Scheimpflug imaging [12][13][14][15][16][17][18] and transscleral imaging with commercial time-domain (TD) OCT systems operating at wavelengths around 1300 nm [19][20][21][22][23][24]. These longer wavelengths enhance light penetration through the sclera and improve the visibility of the ciliary muscle in the OCT images.…”

Inverse Optical Design and Its Applications

“…Distortion due to the geometry of the Scheimpflug camera can be corrected analytically with relative ease, but correction of distortion due to refraction at intermediate ocular surfaces is much less approachable. Measurements of a particular surface are subjected to refraction at all successive surfaces (Dubbelman & Van der Heijde, 2001;Koretz, Strenk, Strenk, & Semmlow, 2004;Rosales et al, 2006a) and traversal through media of individually varying thickness and curvature. Hence, arbitrary quantification errors in one surface are propagated throughout the system (Dubbelman, Weeber, Van der Heijde, & Völker-Dieben, 2002).…”

“…Hence, arbitrary quantification errors in one surface are propagated throughout the system (Dubbelman, Weeber, Van der Heijde, & Völker-Dieben, 2002). Conversely, magnetic resonance imaging has recently been used for in vivo visualization of structures in the anterior segment, which eliminates the distortion dilemma (Koretz et al, 2004), but suffers from low resolution, signal-to-noise ratio (SNR) constraints, and eye motion artifacts due to longer acquisition times (Strenk et al, 1999). On the other hand, corneal topography is a rapidly developing technique that provides very detailed and reliable measurements regarding corneal curvature (Schwiegerling, Greivenkamp, & Miller, 1995;Navarro, González, & Hernández, 2006;Zhou, Hong, Miller, Thibos, & Bradley, 2004;Guirao & Artal, 2000), including astigmatism and surface irregularities, although it does not provide information about the remaining ocular surfaces.…”

Inverse optical design of the human eye using likelihood methods and wavefront sensing

“…Distortion due to the geometry of the Scheimpflug camera can be corrected analytically with relative ease, but correction of distortion due to refraction at intermediate ocular surfaces is much less approachable. Measurements of a particular surface are subjected to refraction at all successive surfaces [3,10,21] and traversal through media of individually varying thickness and curvature. Hence, arbitrary quantification errors in one surface are propagated throughout the system [22].…”

“…Hence, arbitrary quantification errors in one surface are propagated throughout the system [22]. Conversely, magnetic resonance imaging has recently been used for in vivo visualization of structures in the anterior segment, which eliminates the distortion dilemma [21], but suffers from low resolution, signal-to-noise ratio (SNR) constraints, and eye motion artifacts due to longer acquisition times [23]. On the other hand, corneal topography is a rapidly developing technique that provides very detailed and reliable measurements regarding corneal curvature [24][25][26][27], including astigmatism and surface irregularities, although it does not provide information about the remaining ocular surfaces.…”